Research Article A Fully Reconfigurable Polarimetric ...

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Research Article A Fully Reconfigurable Polarimetric Phased Array Antenna Testbed Sudantha Perera, 1 Yu Pan, 1 Yan Zhang, 1 Xining Yu, 1 Dusan Zrnic, 2 and Richard Doviak 2 1 Advanced Radar Research Center (ARRC) and Department of Electrical and Computer Engineering, University of Oklahoma, Norman, OK, USA 2 National Severe Storms Laboratory (NSSL), National Oceanic and Atmospheric Administration (NOAA), Norman, OK, USA Correspondence should be addressed to Yan Zhang; [email protected] Received 7 January 2014; Accepted 26 May 2014; Published 6 August 2014 Academic Editor: Stefano Selleri Copyright © 2014 Sudantha Perera et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e configurable phased array demonstrator (CPAD) is a low-cost, reconfigurable, small-scale testbed for the dual-polarized array antenna and radar prototype. It is based on the concept that individual transmit and receive (TR) modules and radiating elements can be configured in different ways to study the impact of various array manifolds on radiation pattern performance. For example, CPAD is configured as (a) a 4 × 4 planar array, (b) a planar array with mirror configuration, and (c) a circular array to support the multifunctional phased array radar (MPAR) system risk reduction studies. System descriptions are given in detail, and measurements are made and results are analyzed. 1. Introduction Risk mitigation of a large-scale, multifunctional phased array radar (MPAR) usually involves [1] designing, fabricating, and testing small-scale subarray panels and [2] scaling up to larger array systems. Oſten these subarrays are based on assump- tions about the linear or planar array manifold. However, there have been other options for the array manifold, such as the cylindrical array [3] and the sparse array [4]. Although theoretical analysis has claimed unique advantages for each of the different array manifold options, testing the different design options with full-scale systems built for each option is expensive and time consuming. A laboratory scale testbed that can be instrumented for fair, quantitative, and precise design comparisons is needed. Because the main focus of our investigation is how the array manifold configurations affect the polarimetric array radiation pattern, a configurable phased array demonstrator (CPAD) is developed based on integrating the radiating ele- ment with the individual T/R module. e array manifold, as well as the beamforming and control circuitry, can be rapidly reconfigured (Figure 1), as in the case of the planar subarray (Figure 2(a)) and the circular/conformal array (Figure 2(b)). Multiple circular structures can be stacked together to analyze the performance of manifolds on scalable and complicated curvature surfaces. It is shown that a simple measurement procedure can be developed, and accurate measurement data for the scalable validation of candidate array antenna system designs can be provided with this concept. is paper is organized as follows. In Sections 2 and 3, basic system architecture and CPAD TR module designs are discussed. Section 4 introduces CPAD configuration for both planar and circular arrays. Sections 5 and 6 describe the measurement method and procedures, as well as detailed measurement results. Discussion and conclusions are found in Section 7. 2. Instrumentation Components 2.1. Front End. e individual TR modules of the CPAD have independent antennas and control signals so that they can easily fit into different manifold structures. Various antenna element designs can be attached to the TR modules as long as they are within the maximal allowable dimensions (3 ×3 for the current configuration). With this architecture, the Hindawi Publishing Corporation International Journal of Antennas and Propagation Volume 2014, Article ID 439606, 14 pages http://dx.doi.org/10.1155/2014/439606

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Research ArticleA Fully Reconfigurable Polarimetric PhasedArray Antenna Testbed

Sudantha Perera1 Yu Pan1 Yan Zhang1 Xining Yu1 Dusan Zrnic2 and Richard Doviak2

1 Advanced Radar Research Center (ARRC) and Department of Electrical and Computer Engineering University of OklahomaNorman OK USA

2National Severe Storms Laboratory (NSSL) National Oceanic and Atmospheric Administration (NOAA) Norman OK USA

Correspondence should be addressed to Yan Zhang rockeeouedu

Received 7 January 2014 Accepted 26 May 2014 Published 6 August 2014

Academic Editor Stefano Selleri

Copyright copy 2014 Sudantha Perera et alThis is an open access article distributed under theCreativeCommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The configurable phased array demonstrator (CPAD) is a low-cost reconfigurable small-scale testbed for the dual-polarizedarray antenna and radar prototype It is based on the concept that individual transmit and receive (TR) modules and radiatingelements can be configured in different ways to study the impact of various array manifolds on radiation pattern performance Forexample CPAD is configured as (a) a 4 times 4 planar array (b) a planar array with mirror configuration and (c) a circular array tosupport the multifunctional phased array radar (MPAR) system risk reduction studies System descriptions are given in detail andmeasurements are made and results are analyzed

1 Introduction

Risk mitigation of a large-scale multifunctional phased arrayradar (MPAR) usually involves [1] designing fabricating andtesting small-scale subarray panels and [2] scaling up to largerarray systems Often these subarrays are based on assump-tions about the linear or planar array manifold Howeverthere have been other options for the array manifold suchas the cylindrical array [3] and the sparse array [4] Althoughtheoretical analysis has claimed unique advantages for eachof the different array manifold options testing the differentdesign options with full-scale systems built for each optionis expensive and time consuming A laboratory scale testbedthat can be instrumented for fair quantitative and precisedesign comparisons is needed

Because the main focus of our investigation is how thearray manifold configurations affect the polarimetric arrayradiation pattern a configurable phased array demonstrator(CPAD) is developed based on integrating the radiating ele-ment with the individual TR moduleThe array manifold aswell as the beamforming and control circuitry can be rapidlyreconfigured (Figure 1) as in the case of the planar subarray(Figure 2(a)) and the circularconformal array (Figure 2(b))

Multiple circular structures can be stacked together to analyzethe performance of manifolds on scalable and complicatedcurvature surfaces It is shown that a simple measurementprocedure can be developed and accurate measurement datafor the scalable validation of candidate array antenna systemdesigns can be provided with this concept

This paper is organized as follows In Sections 2 and3 basic system architecture and CPAD TR module designsare discussed Section 4 introduces CPAD configuration forboth planar and circular arrays Sections 5 and 6 describethe measurement method and procedures as well as detailedmeasurement results Discussion and conclusions are foundin Section 7

2 Instrumentation Components

21 Front End The individual TRmodules of the CPAD haveindependent antennas and control signals so that they caneasily fit into different manifold structures Various antennaelement designs can be attached to the TRmodules as long asthey are within the maximal allowable dimensions (310158401015840 times 310158401015840for the current configuration) With this architecture the

Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2014 Article ID 439606 14 pageshttpdxdoiorg1011552014439606

2 International Journal of Antennas and Propagation

Backend controllers

Reconfigurable array manifolds

∙ TRM with radiating elements

Figure 1 The CPAD concept

(a) An example of a polarimetric planar array config-uration

(b) An example of a polarimetric circular array con-figuration

Figure 2 3D model of example CPAD configurations

CPADcan function as a subarray in a large-scale array systemor it can be reconfigured to study the performance of differentarray manifold designs for the risk mitigation missionsincluding the cost and performance of large systems Aninitial demonstration of the CPAD is developed with 16radiating elements (4 times 4) which are separated by 07120582spacingThe operating frequency is 2705GHzThe front-endcircuitry is shown in Figure 3

22 TR Modules An introduction of the development of theTR module was presented earlier in [5] The structure of theCPAD TR module is depicted in Figure 3 The CPAD TRmodules are designed to have all the required circuit elementsin a typical modern phased array radar with self-containedfeatures that is the individual antenna elements are attacheddirectly to the TR modules and the microcontroller unit(MCU) in each TR module can store its own program tocontrol the phase shift and attenuation of each polarimetricchannel At the same time a master MCU board can com-municate with the MCUs within all the TR modules througha serial peripheral interface (SPI) for program loading syn-chronizing and so forth TR modules have the same external

global triggeringcontrol signal which can have a 5 dutycycle without overloading the high power amplifier (HPA)This triggering signal is used to control the TR switcheswhich enable sharing the same phased shifter (PS) and atten-uator (ATT) for both transmission and reception signals asin Figure 3 The amplifiers in TRMs (LNA preamplifier andHPA) can operate in both continuous wave (CW) and pulsedmodes In laboratory measurements low-power continuoustransmission is more appropriate because it avoids possibleelectromagnetic hazards for equipment and people and it issimpler to implement For field demonstrations the higherpower pulsed mode is necessary since high peak power isimportant for effective range performance When operatingin pulse mode the amplifiers in all the TR modules aresynchronized with the same triggering signal

Each TR module consists of LNA preamp HPA phaseshifter attenuator and polarized microstrip patch radiatingelements The power dividersplitters in the CPAD are com-mon components of the beamformer for both transmissionand reception The same architecture is used for both hori-zontal and vertical polarizations Images of individual TRMsare shown in Figure 4 Each TR module contains four PCB

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Figure 3 An example of CPAD front-end system architecture for planar array demo

boards as well as the microstrip patch antenna As shownin Figure 4(a) the RF transceiver and controller board havebeen assembled with TR switches a phased shifter LNAattenuator and limiter The MCU board is attached to theback of the RF transceiver and controller board For the highpower version the power amplifier boards for the H and Vchannels are identical Figure 4(c) shows a GaN HPA boardfor one channel For low-power HPA only the preamplifiersare used and the two channels are integrated on the sameboard All the TRMs are carefully tested to ensure theiroperational stability before installing them into the arraysystem

3 CPAD Integration

31 Planar Array An initial demonstration of the CPADis via a simple planar subarray system which is shown inFigure 5(a) 16 TR modules are mounted on the 30 cm times30 cm aluminum plate of the CPAD structure to constructa 4 times 4 polarimetric antenna array In this demonstrationthe radiation elements can be either arranged normally (allin the same orientation) or in a mirror configuration [6] (theorientation in Figure 12) if cross-polarization levels need to

be suppressed at broadsideThe arraymanifold in Figure 5(a)also shows three layers of electronics (1) the power dividercombiner and cabling (2) the TR module and antennas and(3) the master MCU for the subarray and power suppliers(110 V AC to 28V DC converters) which are mounted onthe third plate At the subarray level the master MCU cancommunicate with a computer through a USB port andtransfer the phaseattenuation codes of all the TRMs

A LabVIEW program runs on the computer with asimple graphic user interface (GUI) The antenna elementsare divided into three regions labeled as 1 2 and 3 ona 4 times 4 array (Table 1) The first region has four elementsnear the center The second region has elements at the fourcorners The third region has the remaining eight elementsBy adjusting the relative power to elements in each of theregions we can optimize the amplitude tapering The userinterface accepts specified phase shifts and attenuations tosteer and form the beam

32 Circular Array The circular array (or ring array) hasmany applications in communication radar and directionalfinding systems [7] It is also an important candidate forthe polarimetric MPAR manifold [2] The CPAD has been

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SW SW HPA Block Limiter

Attenuator Phase shifter LNA Power SW

(a) A close look of V channel RF circuit (b) A completed TRmodule with RF boardtwo 40 dBm HPAsRf board and a dual-polarized patch antenna

(c) The GaN HPAboard NPT25015 tran-sistor from NITRONEXis used

Figure 4 TR module

(a) Planar subarray manifold to study the polarimetric arraypattern variation with different scanning angles (1) is thebeamformer (2) is the RF board and (3) is power supply

(b) 4-element circular array mani-fold to study the polarimetric arraypattern variation with different scan-ning angles

Figure 5 The CPAD being integrated

Table 1 Three regions of the antenna elements distribution on the4 times 4 array

Region Element labels (refer to Figure 8) Attenuation1 (1 1) (1 2) (2 1) and (2 2) 0 dB2 (0 0) (0 3) (3 0) and (3 3) 15 dB

3 (0 1) (0 2) (1 0) (2 0) and (3 1) 5 dB(3 2) (1 3) and (2 3)

configured as a 16-element circular array for the initial con-formal array demonstration During pattern measurementsthe CPAD was configured as either a 4-element (depictedin Figure 5(b)) or an 8-element circular array Integration of

the circular array is identical to the planar CPAD except forthe antenna manifold on top of the RF system

4 Measurement Method

The initial measurements of the planar CPAD were made inan anechoic chamber at the University of Oklahoma usinga vector network analyzer (VNA) (Agilent E8364B PNAnetwork analyzer is used) The tests performed were for thereceive-mode array and the low power transmit-mode array(the HPAs were not activated)

Antenna measurement setup is shown in Figure 6 TheCPAD test antenna array was mounted on a positioningsystem consisting of an azimuth rotary stage (soloist single-axis digital servo controller is used to control the azimuth

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CPAD

Source antenna

Rotary stage

Control and data signal

Agilent PNA network analyzer

Coaxial cable

Coaxial cable

USBRotary stage

controller

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Figure 6 Block diagram of H-H H-V V-V or V-H pattern measurements

(a) Planar array (b) Circular array

Figure 7 The CPAD is mounted on the rotary stage for antenna positioning

(AZ) angle of the positioning system) as shown in Figures7(a) and 7(b) The dual-polarized KOUN (KOUN is aprototype dual-pol WSR-88D radar system) feed-horn wasused as the source antenna which was connected to thetransmitting signal generating port of the PNAThe transmitpower was 9 dBm The PNA collects via the coaxial cablethe received signals from the antenna array it controls thepositioning system simultaneously The network analyzeris programmed to collect 200 samples of received signalsbetween 2700MHz and 2710MHz The software invokes ascript to increment a one-degree angle in AZ each time thescript is executed Then the VNA software collects the datafrom the test antenna and saves the data as a text file witha unique name This simple setup can collect measurements

over a 180-degree azimuth angle range for the CPAD withone-degree resolution Measurements with antenna taperingare done by changing the attenuation of regions 2 and 3of the antenna elements listed in Table 1 while maintainingzero attenuation in the elements of Region 1 The optimalamplitude tapering for achieving a minimum sidelobe levelfor the 4 times 4 array was computed using the particle swarmoptimization method [8 9] and the attenuation factors usedin the measurements are shown in Figure 8

5 Planar Array Radiation Patterns

The pattern function can be derived using Fourier seriesmethods as in [10]

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(0 0) (0 1) (0 2) (0 3)

(1 3)(1 2)(1 1)(1 0)

(2 0) (2 1) (2 2) (2 3)

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15dB 15dB5dB5dB

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Figure 8 Attenuation map for each element for optimum tapering in theory

51 Receive Array Beam Steering without Amplitude TaperingFigure 9 presents the measurement results of polarimetricplanar antenna array patterns for different azimuth scan-ning angles No amplitude tapering was applied Measuredcopolarization (Co) and cross-polarization (X) patterns arebased on vertical (V) or horizontal (H) polarizations ofthe sourcetransmit horn (according to the nature of themeasurement method definition 3 of cross-polarization [11]is used) The simulated co- and cross-polarization patternsare based on an open-source finite-difference time-domain(FDTD) EM solver [12] A good agreement between themeasurement and simulation radiation patterns of the copo-larization and the power level of the cross-polarizationpatterns are observed for most of the steering angles

Note that as the array scans electronically the cross-polarization pattern also varies and a cross-polarization peakappears in a similar direction as the main beam steers off-broadside At broadside the full-wave simulation pattern hasa deep null while the measurement pattern results generallydo not show this null This is mainly due to the KOUNhorn itself having a peak (about minus35 dB) in the cross-polarization pattern Considering that the antennas used inthis configuration were simple probe-fed patched antennasthese initial results help general studies of planar array cross-polarization pattern evolution with different steering angleswhile the power level of the cross-polarization pattern maybe further suppressed if the radiating elements are replacedby more sophisticated designs

52 Receive Array Beam Steering with Optimal AmplitudeTapering Amplitude tapering is a common technology to

reduce the array pattern sidelobes (eg to below minus20 dBin this experiment) at the cost of a broader beamwidthAs mentioned in Section 4 Figure 8 an amplitude taperingtechnique based on a nonlinear optimization procedure wasused in the demonstrative experiment The measurementresults and comparison with the simulations are again shownin Figure 10 Minor adjustments to the tapering factors wereapplied to the theoretical values during the measurements(Figure 11) to take account of the attenuator quantizationeffects In the measurement results shown in Figure 10the copolarized V and cross-polarized H patterns match thesimulation results very well The H copolarized pattern hasnoticeable distortion at small positive steering angles whichis possibly due to some interference by the H polarizationwithin the chamber setup

53 Transmit Array Mirror Configuration for Reducing Cross-Polarization Levels The mirror array configuration [13] hasbeen introduced in previous studies as a possible methodfor reducing cross-polarization levels The CPAD enablesresearchers to configure the planar array with a differentmirror manifold and different numbers of antenna elementsThe pattern of mirror configuration is easy to obtain withtransmit arrays Figure 12 shows a simple 2 times 2 mirrorconfiguration as an example A comparison of the measuredtransmit array pattern for the mirror and nonmirror con-figurations is illustrated in Figure 13 As is seen the mirrorconfiguration indeed reduces the cross-polarization powerlevelsThemost significant improvement however is aroundbroadside Measurements are also performed for the mirrorconfiguration and array beam steering to off-broadside and

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Figure 9Measured polarimetric 4times 4 planar array patterns and comparisonwith simulations Beam-steering angle 120601 is in azimuth directionSimulations are performed using FDTD

here the cross-polarization isolation performance degradesquickly which indicates that a mirror configuration designedfor broadside cross-polarization cancellation may not beappropriate for off-broadside arrays

54 Transmit Array 3D Amplitude and Phase Patterns Thetransmit radiation pattern of the CPAD can be characterizedusing near-field measurement techniques (the low-cost near-field measurement tool EMSCAN was used for the mea-surements) Figure 14 depicts the 3D amplitude and phasepattern measurement results The basic profiles of thesepatterns match the corresponding simulation results The 3D

pattern (including phase) characterization is an importantstep in obtaining complete knowledge about polarimetricarray radiations and how to achieve good calibrations It isshown that the CPAD enables such measurements

6 Circular Array Radiation Patterns

In this study we provided electronic beam steering resultsfor a circular array mainly to demonstrate the capability ofthe testbed and to investigate the fundamental properties ofa conformal array manifold and currently not to comparepatterns using electronic beam steering of the planar array

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Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

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Figure 13 Measured radiation patterns for the 2 times 2 arrays

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Figure 15 Configuration of a 4-element circular array

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Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

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(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

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Shock and Vibration

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International Journal of

Page 2: Research Article A Fully Reconfigurable Polarimetric ...

2 International Journal of Antennas and Propagation

Backend controllers

Reconfigurable array manifolds

∙ TRM with radiating elements

Figure 1 The CPAD concept

(a) An example of a polarimetric planar array config-uration

(b) An example of a polarimetric circular array con-figuration

Figure 2 3D model of example CPAD configurations

CPADcan function as a subarray in a large-scale array systemor it can be reconfigured to study the performance of differentarray manifold designs for the risk mitigation missionsincluding the cost and performance of large systems Aninitial demonstration of the CPAD is developed with 16radiating elements (4 times 4) which are separated by 07120582spacingThe operating frequency is 2705GHzThe front-endcircuitry is shown in Figure 3

22 TR Modules An introduction of the development of theTR module was presented earlier in [5] The structure of theCPAD TR module is depicted in Figure 3 The CPAD TRmodules are designed to have all the required circuit elementsin a typical modern phased array radar with self-containedfeatures that is the individual antenna elements are attacheddirectly to the TR modules and the microcontroller unit(MCU) in each TR module can store its own program tocontrol the phase shift and attenuation of each polarimetricchannel At the same time a master MCU board can com-municate with the MCUs within all the TR modules througha serial peripheral interface (SPI) for program loading syn-chronizing and so forth TR modules have the same external

global triggeringcontrol signal which can have a 5 dutycycle without overloading the high power amplifier (HPA)This triggering signal is used to control the TR switcheswhich enable sharing the same phased shifter (PS) and atten-uator (ATT) for both transmission and reception signals asin Figure 3 The amplifiers in TRMs (LNA preamplifier andHPA) can operate in both continuous wave (CW) and pulsedmodes In laboratory measurements low-power continuoustransmission is more appropriate because it avoids possibleelectromagnetic hazards for equipment and people and it issimpler to implement For field demonstrations the higherpower pulsed mode is necessary since high peak power isimportant for effective range performance When operatingin pulse mode the amplifiers in all the TR modules aresynchronized with the same triggering signal

Each TR module consists of LNA preamp HPA phaseshifter attenuator and polarized microstrip patch radiatingelements The power dividersplitters in the CPAD are com-mon components of the beamformer for both transmissionand reception The same architecture is used for both hori-zontal and vertical polarizations Images of individual TRMsare shown in Figure 4 Each TR module contains four PCB

International Journal of Antennas and Propagation 3

V(0)

V(15)

0123456789

101112131415

SW

SW

TRSW

Preamp HPA

SW

Limiter

LNA

H(0)PS

ATT

SW

SWPreamp HPA

SW

Limiter

LNA

H(15)PS

ATT

H

V

Pow

er co

mbi

ner

pow

er sp

litte

rTR

TRTR

TR

TR

TRSWTR

Figure 3 An example of CPAD front-end system architecture for planar array demo

boards as well as the microstrip patch antenna As shownin Figure 4(a) the RF transceiver and controller board havebeen assembled with TR switches a phased shifter LNAattenuator and limiter The MCU board is attached to theback of the RF transceiver and controller board For the highpower version the power amplifier boards for the H and Vchannels are identical Figure 4(c) shows a GaN HPA boardfor one channel For low-power HPA only the preamplifiersare used and the two channels are integrated on the sameboard All the TRMs are carefully tested to ensure theiroperational stability before installing them into the arraysystem

3 CPAD Integration

31 Planar Array An initial demonstration of the CPADis via a simple planar subarray system which is shown inFigure 5(a) 16 TR modules are mounted on the 30 cm times30 cm aluminum plate of the CPAD structure to constructa 4 times 4 polarimetric antenna array In this demonstrationthe radiation elements can be either arranged normally (allin the same orientation) or in a mirror configuration [6] (theorientation in Figure 12) if cross-polarization levels need to

be suppressed at broadsideThe arraymanifold in Figure 5(a)also shows three layers of electronics (1) the power dividercombiner and cabling (2) the TR module and antennas and(3) the master MCU for the subarray and power suppliers(110 V AC to 28V DC converters) which are mounted onthe third plate At the subarray level the master MCU cancommunicate with a computer through a USB port andtransfer the phaseattenuation codes of all the TRMs

A LabVIEW program runs on the computer with asimple graphic user interface (GUI) The antenna elementsare divided into three regions labeled as 1 2 and 3 ona 4 times 4 array (Table 1) The first region has four elementsnear the center The second region has elements at the fourcorners The third region has the remaining eight elementsBy adjusting the relative power to elements in each of theregions we can optimize the amplitude tapering The userinterface accepts specified phase shifts and attenuations tosteer and form the beam

32 Circular Array The circular array (or ring array) hasmany applications in communication radar and directionalfinding systems [7] It is also an important candidate forthe polarimetric MPAR manifold [2] The CPAD has been

4 International Journal of Antennas and Propagation

SW SW HPA Block Limiter

Attenuator Phase shifter LNA Power SW

(a) A close look of V channel RF circuit (b) A completed TRmodule with RF boardtwo 40 dBm HPAsRf board and a dual-polarized patch antenna

(c) The GaN HPAboard NPT25015 tran-sistor from NITRONEXis used

Figure 4 TR module

(a) Planar subarray manifold to study the polarimetric arraypattern variation with different scanning angles (1) is thebeamformer (2) is the RF board and (3) is power supply

(b) 4-element circular array mani-fold to study the polarimetric arraypattern variation with different scan-ning angles

Figure 5 The CPAD being integrated

Table 1 Three regions of the antenna elements distribution on the4 times 4 array

Region Element labels (refer to Figure 8) Attenuation1 (1 1) (1 2) (2 1) and (2 2) 0 dB2 (0 0) (0 3) (3 0) and (3 3) 15 dB

3 (0 1) (0 2) (1 0) (2 0) and (3 1) 5 dB(3 2) (1 3) and (2 3)

configured as a 16-element circular array for the initial con-formal array demonstration During pattern measurementsthe CPAD was configured as either a 4-element (depictedin Figure 5(b)) or an 8-element circular array Integration of

the circular array is identical to the planar CPAD except forthe antenna manifold on top of the RF system

4 Measurement Method

The initial measurements of the planar CPAD were made inan anechoic chamber at the University of Oklahoma usinga vector network analyzer (VNA) (Agilent E8364B PNAnetwork analyzer is used) The tests performed were for thereceive-mode array and the low power transmit-mode array(the HPAs were not activated)

Antenna measurement setup is shown in Figure 6 TheCPAD test antenna array was mounted on a positioningsystem consisting of an azimuth rotary stage (soloist single-axis digital servo controller is used to control the azimuth

International Journal of Antennas and Propagation 5

CPAD

Source antenna

Rotary stage

Control and data signal

Agilent PNA network analyzer

Coaxial cable

Coaxial cable

USBRotary stage

controller

120601

Figure 6 Block diagram of H-H H-V V-V or V-H pattern measurements

(a) Planar array (b) Circular array

Figure 7 The CPAD is mounted on the rotary stage for antenna positioning

(AZ) angle of the positioning system) as shown in Figures7(a) and 7(b) The dual-polarized KOUN (KOUN is aprototype dual-pol WSR-88D radar system) feed-horn wasused as the source antenna which was connected to thetransmitting signal generating port of the PNAThe transmitpower was 9 dBm The PNA collects via the coaxial cablethe received signals from the antenna array it controls thepositioning system simultaneously The network analyzeris programmed to collect 200 samples of received signalsbetween 2700MHz and 2710MHz The software invokes ascript to increment a one-degree angle in AZ each time thescript is executed Then the VNA software collects the datafrom the test antenna and saves the data as a text file witha unique name This simple setup can collect measurements

over a 180-degree azimuth angle range for the CPAD withone-degree resolution Measurements with antenna taperingare done by changing the attenuation of regions 2 and 3of the antenna elements listed in Table 1 while maintainingzero attenuation in the elements of Region 1 The optimalamplitude tapering for achieving a minimum sidelobe levelfor the 4 times 4 array was computed using the particle swarmoptimization method [8 9] and the attenuation factors usedin the measurements are shown in Figure 8

5 Planar Array Radiation Patterns

The pattern function can be derived using Fourier seriesmethods as in [10]

6 International Journal of Antennas and Propagation

(0 0) (0 1) (0 2) (0 3)

(1 3)(1 2)(1 1)(1 0)

(2 0) (2 1) (2 2) (2 3)

(3 3)(3 2)(3 1)(3 0)

15dB 15dB5dB5dB

5dB

5dB

5dB 5dB

0dB 0dB

0dB 0dB 5dB

5dB

15dB15dB

76

mm

76mm

Figure 8 Attenuation map for each element for optimum tapering in theory

51 Receive Array Beam Steering without Amplitude TaperingFigure 9 presents the measurement results of polarimetricplanar antenna array patterns for different azimuth scan-ning angles No amplitude tapering was applied Measuredcopolarization (Co) and cross-polarization (X) patterns arebased on vertical (V) or horizontal (H) polarizations ofthe sourcetransmit horn (according to the nature of themeasurement method definition 3 of cross-polarization [11]is used) The simulated co- and cross-polarization patternsare based on an open-source finite-difference time-domain(FDTD) EM solver [12] A good agreement between themeasurement and simulation radiation patterns of the copo-larization and the power level of the cross-polarizationpatterns are observed for most of the steering angles

Note that as the array scans electronically the cross-polarization pattern also varies and a cross-polarization peakappears in a similar direction as the main beam steers off-broadside At broadside the full-wave simulation pattern hasa deep null while the measurement pattern results generallydo not show this null This is mainly due to the KOUNhorn itself having a peak (about minus35 dB) in the cross-polarization pattern Considering that the antennas used inthis configuration were simple probe-fed patched antennasthese initial results help general studies of planar array cross-polarization pattern evolution with different steering angleswhile the power level of the cross-polarization pattern maybe further suppressed if the radiating elements are replacedby more sophisticated designs

52 Receive Array Beam Steering with Optimal AmplitudeTapering Amplitude tapering is a common technology to

reduce the array pattern sidelobes (eg to below minus20 dBin this experiment) at the cost of a broader beamwidthAs mentioned in Section 4 Figure 8 an amplitude taperingtechnique based on a nonlinear optimization procedure wasused in the demonstrative experiment The measurementresults and comparison with the simulations are again shownin Figure 10 Minor adjustments to the tapering factors wereapplied to the theoretical values during the measurements(Figure 11) to take account of the attenuator quantizationeffects In the measurement results shown in Figure 10the copolarized V and cross-polarized H patterns match thesimulation results very well The H copolarized pattern hasnoticeable distortion at small positive steering angles whichis possibly due to some interference by the H polarizationwithin the chamber setup

53 Transmit Array Mirror Configuration for Reducing Cross-Polarization Levels The mirror array configuration [13] hasbeen introduced in previous studies as a possible methodfor reducing cross-polarization levels The CPAD enablesresearchers to configure the planar array with a differentmirror manifold and different numbers of antenna elementsThe pattern of mirror configuration is easy to obtain withtransmit arrays Figure 12 shows a simple 2 times 2 mirrorconfiguration as an example A comparison of the measuredtransmit array pattern for the mirror and nonmirror con-figurations is illustrated in Figure 13 As is seen the mirrorconfiguration indeed reduces the cross-polarization powerlevelsThemost significant improvement however is aroundbroadside Measurements are also performed for the mirrorconfiguration and array beam steering to off-broadside and

International Journal of Antennas and Propagation 7

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(b) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(c) 120601 = 20∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(d) 120601 = 30∘

Figure 9Measured polarimetric 4times 4 planar array patterns and comparisonwith simulations Beam-steering angle 120601 is in azimuth directionSimulations are performed using FDTD

here the cross-polarization isolation performance degradesquickly which indicates that a mirror configuration designedfor broadside cross-polarization cancellation may not beappropriate for off-broadside arrays

54 Transmit Array 3D Amplitude and Phase Patterns Thetransmit radiation pattern of the CPAD can be characterizedusing near-field measurement techniques (the low-cost near-field measurement tool EMSCAN was used for the mea-surements) Figure 14 depicts the 3D amplitude and phasepattern measurement results The basic profiles of thesepatterns match the corresponding simulation results The 3D

pattern (including phase) characterization is an importantstep in obtaining complete knowledge about polarimetricarray radiations and how to achieve good calibrations It isshown that the CPAD enables such measurements

6 Circular Array Radiation Patterns

In this study we provided electronic beam steering resultsfor a circular array mainly to demonstrate the capability ofthe testbed and to investigate the fundamental properties ofa conformal array manifold and currently not to comparepatterns using electronic beam steering of the planar array

8 International Journal of Antennas and Propagation

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus60

minus50

120579 (deg)

(b) 120601 = 5∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(c) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(d) 120601 = 15∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(e) 120601 = 20∘

Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

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Shock and Vibration

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Acoustics and VibrationAdvances in

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International Journal of

Page 3: Research Article A Fully Reconfigurable Polarimetric ...

International Journal of Antennas and Propagation 3

V(0)

V(15)

0123456789

101112131415

SW

SW

TRSW

Preamp HPA

SW

Limiter

LNA

H(0)PS

ATT

SW

SWPreamp HPA

SW

Limiter

LNA

H(15)PS

ATT

H

V

Pow

er co

mbi

ner

pow

er sp

litte

rTR

TRTR

TR

TR

TRSWTR

Figure 3 An example of CPAD front-end system architecture for planar array demo

boards as well as the microstrip patch antenna As shownin Figure 4(a) the RF transceiver and controller board havebeen assembled with TR switches a phased shifter LNAattenuator and limiter The MCU board is attached to theback of the RF transceiver and controller board For the highpower version the power amplifier boards for the H and Vchannels are identical Figure 4(c) shows a GaN HPA boardfor one channel For low-power HPA only the preamplifiersare used and the two channels are integrated on the sameboard All the TRMs are carefully tested to ensure theiroperational stability before installing them into the arraysystem

3 CPAD Integration

31 Planar Array An initial demonstration of the CPADis via a simple planar subarray system which is shown inFigure 5(a) 16 TR modules are mounted on the 30 cm times30 cm aluminum plate of the CPAD structure to constructa 4 times 4 polarimetric antenna array In this demonstrationthe radiation elements can be either arranged normally (allin the same orientation) or in a mirror configuration [6] (theorientation in Figure 12) if cross-polarization levels need to

be suppressed at broadsideThe arraymanifold in Figure 5(a)also shows three layers of electronics (1) the power dividercombiner and cabling (2) the TR module and antennas and(3) the master MCU for the subarray and power suppliers(110 V AC to 28V DC converters) which are mounted onthe third plate At the subarray level the master MCU cancommunicate with a computer through a USB port andtransfer the phaseattenuation codes of all the TRMs

A LabVIEW program runs on the computer with asimple graphic user interface (GUI) The antenna elementsare divided into three regions labeled as 1 2 and 3 ona 4 times 4 array (Table 1) The first region has four elementsnear the center The second region has elements at the fourcorners The third region has the remaining eight elementsBy adjusting the relative power to elements in each of theregions we can optimize the amplitude tapering The userinterface accepts specified phase shifts and attenuations tosteer and form the beam

32 Circular Array The circular array (or ring array) hasmany applications in communication radar and directionalfinding systems [7] It is also an important candidate forthe polarimetric MPAR manifold [2] The CPAD has been

4 International Journal of Antennas and Propagation

SW SW HPA Block Limiter

Attenuator Phase shifter LNA Power SW

(a) A close look of V channel RF circuit (b) A completed TRmodule with RF boardtwo 40 dBm HPAsRf board and a dual-polarized patch antenna

(c) The GaN HPAboard NPT25015 tran-sistor from NITRONEXis used

Figure 4 TR module

(a) Planar subarray manifold to study the polarimetric arraypattern variation with different scanning angles (1) is thebeamformer (2) is the RF board and (3) is power supply

(b) 4-element circular array mani-fold to study the polarimetric arraypattern variation with different scan-ning angles

Figure 5 The CPAD being integrated

Table 1 Three regions of the antenna elements distribution on the4 times 4 array

Region Element labels (refer to Figure 8) Attenuation1 (1 1) (1 2) (2 1) and (2 2) 0 dB2 (0 0) (0 3) (3 0) and (3 3) 15 dB

3 (0 1) (0 2) (1 0) (2 0) and (3 1) 5 dB(3 2) (1 3) and (2 3)

configured as a 16-element circular array for the initial con-formal array demonstration During pattern measurementsthe CPAD was configured as either a 4-element (depictedin Figure 5(b)) or an 8-element circular array Integration of

the circular array is identical to the planar CPAD except forthe antenna manifold on top of the RF system

4 Measurement Method

The initial measurements of the planar CPAD were made inan anechoic chamber at the University of Oklahoma usinga vector network analyzer (VNA) (Agilent E8364B PNAnetwork analyzer is used) The tests performed were for thereceive-mode array and the low power transmit-mode array(the HPAs were not activated)

Antenna measurement setup is shown in Figure 6 TheCPAD test antenna array was mounted on a positioningsystem consisting of an azimuth rotary stage (soloist single-axis digital servo controller is used to control the azimuth

International Journal of Antennas and Propagation 5

CPAD

Source antenna

Rotary stage

Control and data signal

Agilent PNA network analyzer

Coaxial cable

Coaxial cable

USBRotary stage

controller

120601

Figure 6 Block diagram of H-H H-V V-V or V-H pattern measurements

(a) Planar array (b) Circular array

Figure 7 The CPAD is mounted on the rotary stage for antenna positioning

(AZ) angle of the positioning system) as shown in Figures7(a) and 7(b) The dual-polarized KOUN (KOUN is aprototype dual-pol WSR-88D radar system) feed-horn wasused as the source antenna which was connected to thetransmitting signal generating port of the PNAThe transmitpower was 9 dBm The PNA collects via the coaxial cablethe received signals from the antenna array it controls thepositioning system simultaneously The network analyzeris programmed to collect 200 samples of received signalsbetween 2700MHz and 2710MHz The software invokes ascript to increment a one-degree angle in AZ each time thescript is executed Then the VNA software collects the datafrom the test antenna and saves the data as a text file witha unique name This simple setup can collect measurements

over a 180-degree azimuth angle range for the CPAD withone-degree resolution Measurements with antenna taperingare done by changing the attenuation of regions 2 and 3of the antenna elements listed in Table 1 while maintainingzero attenuation in the elements of Region 1 The optimalamplitude tapering for achieving a minimum sidelobe levelfor the 4 times 4 array was computed using the particle swarmoptimization method [8 9] and the attenuation factors usedin the measurements are shown in Figure 8

5 Planar Array Radiation Patterns

The pattern function can be derived using Fourier seriesmethods as in [10]

6 International Journal of Antennas and Propagation

(0 0) (0 1) (0 2) (0 3)

(1 3)(1 2)(1 1)(1 0)

(2 0) (2 1) (2 2) (2 3)

(3 3)(3 2)(3 1)(3 0)

15dB 15dB5dB5dB

5dB

5dB

5dB 5dB

0dB 0dB

0dB 0dB 5dB

5dB

15dB15dB

76

mm

76mm

Figure 8 Attenuation map for each element for optimum tapering in theory

51 Receive Array Beam Steering without Amplitude TaperingFigure 9 presents the measurement results of polarimetricplanar antenna array patterns for different azimuth scan-ning angles No amplitude tapering was applied Measuredcopolarization (Co) and cross-polarization (X) patterns arebased on vertical (V) or horizontal (H) polarizations ofthe sourcetransmit horn (according to the nature of themeasurement method definition 3 of cross-polarization [11]is used) The simulated co- and cross-polarization patternsare based on an open-source finite-difference time-domain(FDTD) EM solver [12] A good agreement between themeasurement and simulation radiation patterns of the copo-larization and the power level of the cross-polarizationpatterns are observed for most of the steering angles

Note that as the array scans electronically the cross-polarization pattern also varies and a cross-polarization peakappears in a similar direction as the main beam steers off-broadside At broadside the full-wave simulation pattern hasa deep null while the measurement pattern results generallydo not show this null This is mainly due to the KOUNhorn itself having a peak (about minus35 dB) in the cross-polarization pattern Considering that the antennas used inthis configuration were simple probe-fed patched antennasthese initial results help general studies of planar array cross-polarization pattern evolution with different steering angleswhile the power level of the cross-polarization pattern maybe further suppressed if the radiating elements are replacedby more sophisticated designs

52 Receive Array Beam Steering with Optimal AmplitudeTapering Amplitude tapering is a common technology to

reduce the array pattern sidelobes (eg to below minus20 dBin this experiment) at the cost of a broader beamwidthAs mentioned in Section 4 Figure 8 an amplitude taperingtechnique based on a nonlinear optimization procedure wasused in the demonstrative experiment The measurementresults and comparison with the simulations are again shownin Figure 10 Minor adjustments to the tapering factors wereapplied to the theoretical values during the measurements(Figure 11) to take account of the attenuator quantizationeffects In the measurement results shown in Figure 10the copolarized V and cross-polarized H patterns match thesimulation results very well The H copolarized pattern hasnoticeable distortion at small positive steering angles whichis possibly due to some interference by the H polarizationwithin the chamber setup

53 Transmit Array Mirror Configuration for Reducing Cross-Polarization Levels The mirror array configuration [13] hasbeen introduced in previous studies as a possible methodfor reducing cross-polarization levels The CPAD enablesresearchers to configure the planar array with a differentmirror manifold and different numbers of antenna elementsThe pattern of mirror configuration is easy to obtain withtransmit arrays Figure 12 shows a simple 2 times 2 mirrorconfiguration as an example A comparison of the measuredtransmit array pattern for the mirror and nonmirror con-figurations is illustrated in Figure 13 As is seen the mirrorconfiguration indeed reduces the cross-polarization powerlevelsThemost significant improvement however is aroundbroadside Measurements are also performed for the mirrorconfiguration and array beam steering to off-broadside and

International Journal of Antennas and Propagation 7

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(b) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(c) 120601 = 20∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(d) 120601 = 30∘

Figure 9Measured polarimetric 4times 4 planar array patterns and comparisonwith simulations Beam-steering angle 120601 is in azimuth directionSimulations are performed using FDTD

here the cross-polarization isolation performance degradesquickly which indicates that a mirror configuration designedfor broadside cross-polarization cancellation may not beappropriate for off-broadside arrays

54 Transmit Array 3D Amplitude and Phase Patterns Thetransmit radiation pattern of the CPAD can be characterizedusing near-field measurement techniques (the low-cost near-field measurement tool EMSCAN was used for the mea-surements) Figure 14 depicts the 3D amplitude and phasepattern measurement results The basic profiles of thesepatterns match the corresponding simulation results The 3D

pattern (including phase) characterization is an importantstep in obtaining complete knowledge about polarimetricarray radiations and how to achieve good calibrations It isshown that the CPAD enables such measurements

6 Circular Array Radiation Patterns

In this study we provided electronic beam steering resultsfor a circular array mainly to demonstrate the capability ofthe testbed and to investigate the fundamental properties ofa conformal array manifold and currently not to comparepatterns using electronic beam steering of the planar array

8 International Journal of Antennas and Propagation

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus60

minus50

120579 (deg)

(b) 120601 = 5∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(c) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(d) 120601 = 15∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(e) 120601 = 20∘

Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

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Page 4: Research Article A Fully Reconfigurable Polarimetric ...

4 International Journal of Antennas and Propagation

SW SW HPA Block Limiter

Attenuator Phase shifter LNA Power SW

(a) A close look of V channel RF circuit (b) A completed TRmodule with RF boardtwo 40 dBm HPAsRf board and a dual-polarized patch antenna

(c) The GaN HPAboard NPT25015 tran-sistor from NITRONEXis used

Figure 4 TR module

(a) Planar subarray manifold to study the polarimetric arraypattern variation with different scanning angles (1) is thebeamformer (2) is the RF board and (3) is power supply

(b) 4-element circular array mani-fold to study the polarimetric arraypattern variation with different scan-ning angles

Figure 5 The CPAD being integrated

Table 1 Three regions of the antenna elements distribution on the4 times 4 array

Region Element labels (refer to Figure 8) Attenuation1 (1 1) (1 2) (2 1) and (2 2) 0 dB2 (0 0) (0 3) (3 0) and (3 3) 15 dB

3 (0 1) (0 2) (1 0) (2 0) and (3 1) 5 dB(3 2) (1 3) and (2 3)

configured as a 16-element circular array for the initial con-formal array demonstration During pattern measurementsthe CPAD was configured as either a 4-element (depictedin Figure 5(b)) or an 8-element circular array Integration of

the circular array is identical to the planar CPAD except forthe antenna manifold on top of the RF system

4 Measurement Method

The initial measurements of the planar CPAD were made inan anechoic chamber at the University of Oklahoma usinga vector network analyzer (VNA) (Agilent E8364B PNAnetwork analyzer is used) The tests performed were for thereceive-mode array and the low power transmit-mode array(the HPAs were not activated)

Antenna measurement setup is shown in Figure 6 TheCPAD test antenna array was mounted on a positioningsystem consisting of an azimuth rotary stage (soloist single-axis digital servo controller is used to control the azimuth

International Journal of Antennas and Propagation 5

CPAD

Source antenna

Rotary stage

Control and data signal

Agilent PNA network analyzer

Coaxial cable

Coaxial cable

USBRotary stage

controller

120601

Figure 6 Block diagram of H-H H-V V-V or V-H pattern measurements

(a) Planar array (b) Circular array

Figure 7 The CPAD is mounted on the rotary stage for antenna positioning

(AZ) angle of the positioning system) as shown in Figures7(a) and 7(b) The dual-polarized KOUN (KOUN is aprototype dual-pol WSR-88D radar system) feed-horn wasused as the source antenna which was connected to thetransmitting signal generating port of the PNAThe transmitpower was 9 dBm The PNA collects via the coaxial cablethe received signals from the antenna array it controls thepositioning system simultaneously The network analyzeris programmed to collect 200 samples of received signalsbetween 2700MHz and 2710MHz The software invokes ascript to increment a one-degree angle in AZ each time thescript is executed Then the VNA software collects the datafrom the test antenna and saves the data as a text file witha unique name This simple setup can collect measurements

over a 180-degree azimuth angle range for the CPAD withone-degree resolution Measurements with antenna taperingare done by changing the attenuation of regions 2 and 3of the antenna elements listed in Table 1 while maintainingzero attenuation in the elements of Region 1 The optimalamplitude tapering for achieving a minimum sidelobe levelfor the 4 times 4 array was computed using the particle swarmoptimization method [8 9] and the attenuation factors usedin the measurements are shown in Figure 8

5 Planar Array Radiation Patterns

The pattern function can be derived using Fourier seriesmethods as in [10]

6 International Journal of Antennas and Propagation

(0 0) (0 1) (0 2) (0 3)

(1 3)(1 2)(1 1)(1 0)

(2 0) (2 1) (2 2) (2 3)

(3 3)(3 2)(3 1)(3 0)

15dB 15dB5dB5dB

5dB

5dB

5dB 5dB

0dB 0dB

0dB 0dB 5dB

5dB

15dB15dB

76

mm

76mm

Figure 8 Attenuation map for each element for optimum tapering in theory

51 Receive Array Beam Steering without Amplitude TaperingFigure 9 presents the measurement results of polarimetricplanar antenna array patterns for different azimuth scan-ning angles No amplitude tapering was applied Measuredcopolarization (Co) and cross-polarization (X) patterns arebased on vertical (V) or horizontal (H) polarizations ofthe sourcetransmit horn (according to the nature of themeasurement method definition 3 of cross-polarization [11]is used) The simulated co- and cross-polarization patternsare based on an open-source finite-difference time-domain(FDTD) EM solver [12] A good agreement between themeasurement and simulation radiation patterns of the copo-larization and the power level of the cross-polarizationpatterns are observed for most of the steering angles

Note that as the array scans electronically the cross-polarization pattern also varies and a cross-polarization peakappears in a similar direction as the main beam steers off-broadside At broadside the full-wave simulation pattern hasa deep null while the measurement pattern results generallydo not show this null This is mainly due to the KOUNhorn itself having a peak (about minus35 dB) in the cross-polarization pattern Considering that the antennas used inthis configuration were simple probe-fed patched antennasthese initial results help general studies of planar array cross-polarization pattern evolution with different steering angleswhile the power level of the cross-polarization pattern maybe further suppressed if the radiating elements are replacedby more sophisticated designs

52 Receive Array Beam Steering with Optimal AmplitudeTapering Amplitude tapering is a common technology to

reduce the array pattern sidelobes (eg to below minus20 dBin this experiment) at the cost of a broader beamwidthAs mentioned in Section 4 Figure 8 an amplitude taperingtechnique based on a nonlinear optimization procedure wasused in the demonstrative experiment The measurementresults and comparison with the simulations are again shownin Figure 10 Minor adjustments to the tapering factors wereapplied to the theoretical values during the measurements(Figure 11) to take account of the attenuator quantizationeffects In the measurement results shown in Figure 10the copolarized V and cross-polarized H patterns match thesimulation results very well The H copolarized pattern hasnoticeable distortion at small positive steering angles whichis possibly due to some interference by the H polarizationwithin the chamber setup

53 Transmit Array Mirror Configuration for Reducing Cross-Polarization Levels The mirror array configuration [13] hasbeen introduced in previous studies as a possible methodfor reducing cross-polarization levels The CPAD enablesresearchers to configure the planar array with a differentmirror manifold and different numbers of antenna elementsThe pattern of mirror configuration is easy to obtain withtransmit arrays Figure 12 shows a simple 2 times 2 mirrorconfiguration as an example A comparison of the measuredtransmit array pattern for the mirror and nonmirror con-figurations is illustrated in Figure 13 As is seen the mirrorconfiguration indeed reduces the cross-polarization powerlevelsThemost significant improvement however is aroundbroadside Measurements are also performed for the mirrorconfiguration and array beam steering to off-broadside and

International Journal of Antennas and Propagation 7

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(b) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(c) 120601 = 20∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(d) 120601 = 30∘

Figure 9Measured polarimetric 4times 4 planar array patterns and comparisonwith simulations Beam-steering angle 120601 is in azimuth directionSimulations are performed using FDTD

here the cross-polarization isolation performance degradesquickly which indicates that a mirror configuration designedfor broadside cross-polarization cancellation may not beappropriate for off-broadside arrays

54 Transmit Array 3D Amplitude and Phase Patterns Thetransmit radiation pattern of the CPAD can be characterizedusing near-field measurement techniques (the low-cost near-field measurement tool EMSCAN was used for the mea-surements) Figure 14 depicts the 3D amplitude and phasepattern measurement results The basic profiles of thesepatterns match the corresponding simulation results The 3D

pattern (including phase) characterization is an importantstep in obtaining complete knowledge about polarimetricarray radiations and how to achieve good calibrations It isshown that the CPAD enables such measurements

6 Circular Array Radiation Patterns

In this study we provided electronic beam steering resultsfor a circular array mainly to demonstrate the capability ofthe testbed and to investigate the fundamental properties ofa conformal array manifold and currently not to comparepatterns using electronic beam steering of the planar array

8 International Journal of Antennas and Propagation

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus60

minus50

120579 (deg)

(b) 120601 = 5∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(c) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(d) 120601 = 15∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(e) 120601 = 20∘

Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 5: Research Article A Fully Reconfigurable Polarimetric ...

International Journal of Antennas and Propagation 5

CPAD

Source antenna

Rotary stage

Control and data signal

Agilent PNA network analyzer

Coaxial cable

Coaxial cable

USBRotary stage

controller

120601

Figure 6 Block diagram of H-H H-V V-V or V-H pattern measurements

(a) Planar array (b) Circular array

Figure 7 The CPAD is mounted on the rotary stage for antenna positioning

(AZ) angle of the positioning system) as shown in Figures7(a) and 7(b) The dual-polarized KOUN (KOUN is aprototype dual-pol WSR-88D radar system) feed-horn wasused as the source antenna which was connected to thetransmitting signal generating port of the PNAThe transmitpower was 9 dBm The PNA collects via the coaxial cablethe received signals from the antenna array it controls thepositioning system simultaneously The network analyzeris programmed to collect 200 samples of received signalsbetween 2700MHz and 2710MHz The software invokes ascript to increment a one-degree angle in AZ each time thescript is executed Then the VNA software collects the datafrom the test antenna and saves the data as a text file witha unique name This simple setup can collect measurements

over a 180-degree azimuth angle range for the CPAD withone-degree resolution Measurements with antenna taperingare done by changing the attenuation of regions 2 and 3of the antenna elements listed in Table 1 while maintainingzero attenuation in the elements of Region 1 The optimalamplitude tapering for achieving a minimum sidelobe levelfor the 4 times 4 array was computed using the particle swarmoptimization method [8 9] and the attenuation factors usedin the measurements are shown in Figure 8

5 Planar Array Radiation Patterns

The pattern function can be derived using Fourier seriesmethods as in [10]

6 International Journal of Antennas and Propagation

(0 0) (0 1) (0 2) (0 3)

(1 3)(1 2)(1 1)(1 0)

(2 0) (2 1) (2 2) (2 3)

(3 3)(3 2)(3 1)(3 0)

15dB 15dB5dB5dB

5dB

5dB

5dB 5dB

0dB 0dB

0dB 0dB 5dB

5dB

15dB15dB

76

mm

76mm

Figure 8 Attenuation map for each element for optimum tapering in theory

51 Receive Array Beam Steering without Amplitude TaperingFigure 9 presents the measurement results of polarimetricplanar antenna array patterns for different azimuth scan-ning angles No amplitude tapering was applied Measuredcopolarization (Co) and cross-polarization (X) patterns arebased on vertical (V) or horizontal (H) polarizations ofthe sourcetransmit horn (according to the nature of themeasurement method definition 3 of cross-polarization [11]is used) The simulated co- and cross-polarization patternsare based on an open-source finite-difference time-domain(FDTD) EM solver [12] A good agreement between themeasurement and simulation radiation patterns of the copo-larization and the power level of the cross-polarizationpatterns are observed for most of the steering angles

Note that as the array scans electronically the cross-polarization pattern also varies and a cross-polarization peakappears in a similar direction as the main beam steers off-broadside At broadside the full-wave simulation pattern hasa deep null while the measurement pattern results generallydo not show this null This is mainly due to the KOUNhorn itself having a peak (about minus35 dB) in the cross-polarization pattern Considering that the antennas used inthis configuration were simple probe-fed patched antennasthese initial results help general studies of planar array cross-polarization pattern evolution with different steering angleswhile the power level of the cross-polarization pattern maybe further suppressed if the radiating elements are replacedby more sophisticated designs

52 Receive Array Beam Steering with Optimal AmplitudeTapering Amplitude tapering is a common technology to

reduce the array pattern sidelobes (eg to below minus20 dBin this experiment) at the cost of a broader beamwidthAs mentioned in Section 4 Figure 8 an amplitude taperingtechnique based on a nonlinear optimization procedure wasused in the demonstrative experiment The measurementresults and comparison with the simulations are again shownin Figure 10 Minor adjustments to the tapering factors wereapplied to the theoretical values during the measurements(Figure 11) to take account of the attenuator quantizationeffects In the measurement results shown in Figure 10the copolarized V and cross-polarized H patterns match thesimulation results very well The H copolarized pattern hasnoticeable distortion at small positive steering angles whichis possibly due to some interference by the H polarizationwithin the chamber setup

53 Transmit Array Mirror Configuration for Reducing Cross-Polarization Levels The mirror array configuration [13] hasbeen introduced in previous studies as a possible methodfor reducing cross-polarization levels The CPAD enablesresearchers to configure the planar array with a differentmirror manifold and different numbers of antenna elementsThe pattern of mirror configuration is easy to obtain withtransmit arrays Figure 12 shows a simple 2 times 2 mirrorconfiguration as an example A comparison of the measuredtransmit array pattern for the mirror and nonmirror con-figurations is illustrated in Figure 13 As is seen the mirrorconfiguration indeed reduces the cross-polarization powerlevelsThemost significant improvement however is aroundbroadside Measurements are also performed for the mirrorconfiguration and array beam steering to off-broadside and

International Journal of Antennas and Propagation 7

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(b) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(c) 120601 = 20∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(d) 120601 = 30∘

Figure 9Measured polarimetric 4times 4 planar array patterns and comparisonwith simulations Beam-steering angle 120601 is in azimuth directionSimulations are performed using FDTD

here the cross-polarization isolation performance degradesquickly which indicates that a mirror configuration designedfor broadside cross-polarization cancellation may not beappropriate for off-broadside arrays

54 Transmit Array 3D Amplitude and Phase Patterns Thetransmit radiation pattern of the CPAD can be characterizedusing near-field measurement techniques (the low-cost near-field measurement tool EMSCAN was used for the mea-surements) Figure 14 depicts the 3D amplitude and phasepattern measurement results The basic profiles of thesepatterns match the corresponding simulation results The 3D

pattern (including phase) characterization is an importantstep in obtaining complete knowledge about polarimetricarray radiations and how to achieve good calibrations It isshown that the CPAD enables such measurements

6 Circular Array Radiation Patterns

In this study we provided electronic beam steering resultsfor a circular array mainly to demonstrate the capability ofthe testbed and to investigate the fundamental properties ofa conformal array manifold and currently not to comparepatterns using electronic beam steering of the planar array

8 International Journal of Antennas and Propagation

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus60

minus50

120579 (deg)

(b) 120601 = 5∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(c) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(d) 120601 = 15∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(e) 120601 = 20∘

Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 6: Research Article A Fully Reconfigurable Polarimetric ...

6 International Journal of Antennas and Propagation

(0 0) (0 1) (0 2) (0 3)

(1 3)(1 2)(1 1)(1 0)

(2 0) (2 1) (2 2) (2 3)

(3 3)(3 2)(3 1)(3 0)

15dB 15dB5dB5dB

5dB

5dB

5dB 5dB

0dB 0dB

0dB 0dB 5dB

5dB

15dB15dB

76

mm

76mm

Figure 8 Attenuation map for each element for optimum tapering in theory

51 Receive Array Beam Steering without Amplitude TaperingFigure 9 presents the measurement results of polarimetricplanar antenna array patterns for different azimuth scan-ning angles No amplitude tapering was applied Measuredcopolarization (Co) and cross-polarization (X) patterns arebased on vertical (V) or horizontal (H) polarizations ofthe sourcetransmit horn (according to the nature of themeasurement method definition 3 of cross-polarization [11]is used) The simulated co- and cross-polarization patternsare based on an open-source finite-difference time-domain(FDTD) EM solver [12] A good agreement between themeasurement and simulation radiation patterns of the copo-larization and the power level of the cross-polarizationpatterns are observed for most of the steering angles

Note that as the array scans electronically the cross-polarization pattern also varies and a cross-polarization peakappears in a similar direction as the main beam steers off-broadside At broadside the full-wave simulation pattern hasa deep null while the measurement pattern results generallydo not show this null This is mainly due to the KOUNhorn itself having a peak (about minus35 dB) in the cross-polarization pattern Considering that the antennas used inthis configuration were simple probe-fed patched antennasthese initial results help general studies of planar array cross-polarization pattern evolution with different steering angleswhile the power level of the cross-polarization pattern maybe further suppressed if the radiating elements are replacedby more sophisticated designs

52 Receive Array Beam Steering with Optimal AmplitudeTapering Amplitude tapering is a common technology to

reduce the array pattern sidelobes (eg to below minus20 dBin this experiment) at the cost of a broader beamwidthAs mentioned in Section 4 Figure 8 an amplitude taperingtechnique based on a nonlinear optimization procedure wasused in the demonstrative experiment The measurementresults and comparison with the simulations are again shownin Figure 10 Minor adjustments to the tapering factors wereapplied to the theoretical values during the measurements(Figure 11) to take account of the attenuator quantizationeffects In the measurement results shown in Figure 10the copolarized V and cross-polarized H patterns match thesimulation results very well The H copolarized pattern hasnoticeable distortion at small positive steering angles whichis possibly due to some interference by the H polarizationwithin the chamber setup

53 Transmit Array Mirror Configuration for Reducing Cross-Polarization Levels The mirror array configuration [13] hasbeen introduced in previous studies as a possible methodfor reducing cross-polarization levels The CPAD enablesresearchers to configure the planar array with a differentmirror manifold and different numbers of antenna elementsThe pattern of mirror configuration is easy to obtain withtransmit arrays Figure 12 shows a simple 2 times 2 mirrorconfiguration as an example A comparison of the measuredtransmit array pattern for the mirror and nonmirror con-figurations is illustrated in Figure 13 As is seen the mirrorconfiguration indeed reduces the cross-polarization powerlevelsThemost significant improvement however is aroundbroadside Measurements are also performed for the mirrorconfiguration and array beam steering to off-broadside and

International Journal of Antennas and Propagation 7

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(b) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(c) 120601 = 20∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(d) 120601 = 30∘

Figure 9Measured polarimetric 4times 4 planar array patterns and comparisonwith simulations Beam-steering angle 120601 is in azimuth directionSimulations are performed using FDTD

here the cross-polarization isolation performance degradesquickly which indicates that a mirror configuration designedfor broadside cross-polarization cancellation may not beappropriate for off-broadside arrays

54 Transmit Array 3D Amplitude and Phase Patterns Thetransmit radiation pattern of the CPAD can be characterizedusing near-field measurement techniques (the low-cost near-field measurement tool EMSCAN was used for the mea-surements) Figure 14 depicts the 3D amplitude and phasepattern measurement results The basic profiles of thesepatterns match the corresponding simulation results The 3D

pattern (including phase) characterization is an importantstep in obtaining complete knowledge about polarimetricarray radiations and how to achieve good calibrations It isshown that the CPAD enables such measurements

6 Circular Array Radiation Patterns

In this study we provided electronic beam steering resultsfor a circular array mainly to demonstrate the capability ofthe testbed and to investigate the fundamental properties ofa conformal array manifold and currently not to comparepatterns using electronic beam steering of the planar array

8 International Journal of Antennas and Propagation

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus60

minus50

120579 (deg)

(b) 120601 = 5∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(c) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(d) 120601 = 15∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(e) 120601 = 20∘

Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

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Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 7: Research Article A Fully Reconfigurable Polarimetric ...

International Journal of Antennas and Propagation 7

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(b) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(c) 120601 = 20∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(d) 120601 = 30∘

Figure 9Measured polarimetric 4times 4 planar array patterns and comparisonwith simulations Beam-steering angle 120601 is in azimuth directionSimulations are performed using FDTD

here the cross-polarization isolation performance degradesquickly which indicates that a mirror configuration designedfor broadside cross-polarization cancellation may not beappropriate for off-broadside arrays

54 Transmit Array 3D Amplitude and Phase Patterns Thetransmit radiation pattern of the CPAD can be characterizedusing near-field measurement techniques (the low-cost near-field measurement tool EMSCAN was used for the mea-surements) Figure 14 depicts the 3D amplitude and phasepattern measurement results The basic profiles of thesepatterns match the corresponding simulation results The 3D

pattern (including phase) characterization is an importantstep in obtaining complete knowledge about polarimetricarray radiations and how to achieve good calibrations It isshown that the CPAD enables such measurements

6 Circular Array Radiation Patterns

In this study we provided electronic beam steering resultsfor a circular array mainly to demonstrate the capability ofthe testbed and to investigate the fundamental properties ofa conformal array manifold and currently not to comparepatterns using electronic beam steering of the planar array

8 International Journal of Antennas and Propagation

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus60

minus50

120579 (deg)

(b) 120601 = 5∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(c) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(d) 120601 = 15∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(e) 120601 = 20∘

Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 8: Research Article A Fully Reconfigurable Polarimetric ...

8 International Journal of Antennas and Propagation

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

50

minus60

120579 (deg)

(a) 120601 = 0∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus60

minus50

120579 (deg)

(b) 120601 = 5∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(c) 120601 = 10∘

Nor

mal

ized

pow

er (d

B)

minus80 minus60 minus40 minus20 0 20 40 60 80

0

minus10

minus20

minus30

minus40

minus50

minus60

120579 (deg)

(d) 120601 = 15∘

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

minus60minus80 minus60 minus40 minus20 0 20 40 60 80

Measured Co (V)Measured X (V)Measured Co (H)

Measured X (H)Simulated CoSimulated X

120579 (deg)

(e) 120601 = 20∘

Figure 10 Measured polarimetric array patterns with actual amplitude tapering Beam-steering angle 120601 is in azimuth direction Simulationsare performed using FDTD

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 9: Research Article A Fully Reconfigurable Polarimetric ...

International Journal of Antennas and Propagation 9

01887 01887

0188701887

0551 0551

05510551

0551 0551

0551 0551

11

11

(a) Theoretical

0562

0562 0562

0562

0562

05620562

0562

01778

1 1

1 1

0177801778

01778

(b) Actual

Figure 11 Theoretical and actual amplitude tapering values (linear scale values are displayed here in order to compare the configurations)

H∙+V∙+

H∙minus

+ V∙

H∙minus

+ V∙

H∙+V∙+

Figure 12 A simple 2 times 2 mirror array configuration of the CPAD

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 V-port fed elevation

(a) Vertical polarization pattern

minus80 minus60 minus40 minus20 0 20 40 60 80

Angle (∘)

Co-pol nonmirrorX-pol nonmirror

Co-pol mirrorX-pol mirror

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

Nor

mal

ized

pow

er (d

B)

2 times 2 H-port fed elevation

(b) Horizontal polarization pattern

Figure 13 Measured radiation patterns for the 2 times 2 arrays

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 10: Research Article A Fully Reconfigurable Polarimetric ...

10 International Journal of Antennas and Propagation

minus1 minus05 0

0

05 1

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of Ecombined (dB)

(a) |119864120579+ 119864120601|

1

1

08

08

06

06

04

04

02

02

0

0

minus02

minus02

minus04

minus04

minus06

minus06

minus08

minus08minus1minus1

y=

sin(120579)s

in(120601)

minus10

minus20

minus30

minus40

minus50

minus60

minus70

X = sin(120579)cos(120601)

Amplitude of E120579 (dB)

(b) |119864120579|

minus1minus1

minus05

minus05

0

0

05

05

1

1

minus10

minus20

minus30

minus40

minus50

minus60

X = sin(120579)cos(120601)

y=

sin(120579)s

in(120601)

Amplitude of E120601 (dB)

(c) |119864120601|

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08minus1

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120579 (deg)

(d) ang119864120579

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1

y=

sinsin

(120579)

(120601)

1080604020minus02minus04minus06minus08

X = sin(120579)cos(120601)

150

100

50

0

minus50

minus100

minus150

Phase of E120601 (deg)

(e) ang119864120601

1

08

06

04

02

0

minus02

minus04

minus06

minus08

minus1minus1 minus05 0 05 1

X = sin(120579)cos(120601)

300

200

100

0

minus100

minus200

minus300

Phase of E phase of E120579 minus 120601 (deg)

y=

sinsin

(120579)

(120601)

(f) ang119864120579minus ang119864120601

Figure 14 Measured 3D transmitting pattern of the planar 4 times 4 (nonmirror) CPAD configuration

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 11: Research Article A Fully Reconfigurable Polarimetric ...

International Journal of Antennas and Propagation 11

Broadside Focused beam direction

1

2

34

Referenceplane

120579 = 45∘ 55∘Δ120601

Δ120601Δ120601

= 1125∘

120579

65∘ and 75∘

(a) Element arrangement

Element1 852 110 141 189 -1073 110 98 106 1314 151 116 100

minus157 minus89 minus8

minus157

0∘ 10∘ 20∘ 30∘120579 minus 45∘

(b) Phase taper (in degrees) for a focused beam

Figure 15 Configuration of a 4-element circular array

Broadside

θ

Focused beam direction

Referenceplane

1

2

345

6

7

8Δ120601Δ120601

120579 = 90∘ 95∘Δ120601 = 1125∘

65∘ and 100∘

(a) Element arrangement

Element12 15 61 10734 110 123 1405 110 102 996 175 1527 158 137

minus121

minus157

minus157

minus125

minus68

minus68

minus91

minus16

minus121 minus174

minus29

0∘ 5∘ 10∘120579 minus 90∘

(b) Phase taper (in degrees) for a focusedbeam

Figure 16 Configuration of an 8-element circular array

with that obtained using the commutative beam steering ofthe circular array

The phase mode excitation [14] technique is used to formthe focused beam for a circular arrayThe excitation of the 119899thelement 119891(119899) can be expressed as follows

119891 (119899) = exp 119895119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (1)

Then the phase taper of the radiating elements can becalculated as follows

120595 (119899) = minus119896119877 cos [120579 minus (2119899 minus 1) Δ120601] (2)

In (1) and (2) 119899 is the reference number of the radiatingelement 120595(119899) is the phase taper of the 119899th element 119896 is thepropagation constant 119877 is the radius of the circular array120579 is the steering angle of the focused beam and Δ120601 is theelement projected angle at the center of the circular arrayFor the CPAD the radius 119877 is 1736120582 and 120582 is 110mmand Figures 15(a) and 16(a) show the geometries for thecalculation of the phase taper values for 4-element and

8-element arrays respectively The horizontal axis in thesefigures is the reference plane for all the angles For the4-element circular array Figure 15(b) lists the phase tapervalues calculated for 0∘ 10∘ 20∘ and 30∘ beam steering using(2) Figure 17 shows the simulated and measured radiationpatterns For this case the measured radiation patterns havesidelobes lower than minus10 dB and a cross-polarization level ofless thanminus25 dB both ofwhich are comparable to the patternsof a planar array with a similar aperture dimension

For the 8-element circular array Figure 16(b) lists thephase taper values calculated for 0∘ 5∘ and 10∘ beam steeringusing (2) The measured sidelobes in this case are lower thanminus15 dB and the cross-polarization is lower than minus22 dB asshown in Figure 18

7 Conclusion

The development of a large-scale phased array radar systemsuch as the futureMPARwill need amethod for cost-effectiveriskmitigation Simulations are not sufficient for determiningthe precise performance and building large-scale arrays for

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 12: Research Article A Fully Reconfigurable Polarimetric ...

12 International Journal of Antennas and Propagation

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(a) 120579119887= 0∘

Azimuth angle (deg)N

orm

aliz

ed p

ower

(dB)

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(b) 120579119887= 10∘

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50minus80 minus60 minus40 minus20 0 20 40 60 80

(c) 120579119887= 20∘

Azimuth angle (deg)

Co-pol measurementX-pol measurement

Co-pol simulationX-pol simulation

minus80 minus60 minus40 minus20 0 20 40 60 80

Nor

mal

ized

pow

er (d

B)0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

minus45

minus50

(d) 120579119887= 30∘

Figure 17 Measured 4-element circular array patterns Beam-steering angle 120579119887is in azimuth direction Simulations are performed using CST

each new manifold idea is not realistic Also an educationaltool is needed in the community to allow researchers toquickly acquire related knowledge The CPAD provides ascalable reconfigurable and low-cost platform for testing andevaluating polarimetric phased array antennas and subarraysfor radar systems The comparative studies using simulationand measurements of different array manifolds demonstratethe effectiveness of the CPAD concept and its reconfigurationcapabilities

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work is supported by NOAANSSL through Grant noNA080AR4320904

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 13: Research Article A Fully Reconfigurable Polarimetric ...

International Journal of Antennas and Propagation 13

Azimuth angle (deg)

Nor

mal

ized

pow

er (d

B)0

minus10

minus20

minus30

minus40

minus50minus50 0 50

(a) 120579119887= 0∘

Nor

mal

ized

pow

er (d

B)

Azimuth angle (deg)minus50 0 50

0

minus10

minus20

minus30

minus40

minus50

(b) 120579119887= 5∘

Azimuth angle (deg)minus50 0 50

Nor

mal

ized

pow

er (d

B)

0

minus10

minus20

minus30

minus40

minus50

Co-pol measurementX-pol measurement

(c) 120579119887= 10∘

Figure 18 Measured 8-element circular array patterns Beam-steering angle 120579119887is in azimuth direction

References

[1] J Herd S Duffy M Weber G Brigham C Weigand and DCursio ldquoAdvanced architecture for a low cost MultifunctionPhased Array Radarrdquo in Proceedings of the IEEEMTT-S Interna-tional Microwave Symposium (MTT rsquo10) pp 676ndash679 usa May2010

[2] MIT Lincoln Laboratory ldquoMultifunction phased array radar(MPAR) government proof of concept demonstratorrdquo in DualPolarization Patterns Extracted from Final Test Report Gen1Panel Evaluation MIT Lincoln Laboratory Lexington MassUSA 2012

[3] G Zhang R J Doviak D S Zrnic R Palmer L Lei and YAl-Rashid ldquoPolarimetric phased-array radar for weather meas-urement a planar or cylindrical configurationrdquo Journal of

Atmospheric and Oceanic Technology vol 28 no 1 pp 63ndash732011

[4] E Brookner ldquoMimo radar demystifiedrdquo Microwave Journal2013

[5] Y Zhang Y Pan S Wang Q Zhao D Zrnic and R JDoviak ldquoReconfigurable and scalable array element design forpolarimetric multifunctional PARrdquo in Proceedings of the IEEERadar Conference In the Eye of the Storm (Radar rsquo11) pp 175ndash179 May 2011

[6] Y Rahmat-Samii K S Kona M Manteghi et al ldquoA novel light-weight dual-frequency dual-polarized sixteen-element stackedpatch microstrip array antenna for soil-moisture and sea-surface-salinity missionsrdquo IEEE Antennas and PropagationMagazine vol 48 no 6 pp 33ndash46 2006

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 14: Research Article A Fully Reconfigurable Polarimetric ...

14 International Journal of Antennas and Propagation

[7] P Gething ldquoHigh-frequency direction findingrdquo Proceedings ofthe Institution of Electrical Engineers vol 113 no 1 pp 49ndash611996

[8] J Robinson andY Rahmat-Samii ldquoParticle swarmoptimizationin electromagneticsrdquo IEEE Transactions on Antennas and Prop-agation vol 52 no 2 pp 397ndash407 2004

[9] M Benedetti R Azaro D Franceschini and A Massa ldquoPSO-based real-time control of planar uniform circular arraysrdquo IEEEAntennas andWireless Propagation Letters vol 5 no 1 pp 545ndash548 2006

[10] R J Mailloux Phased Array Antenna Handbook Artech HouseBoston Mass USA 2005

[11] A Ludwig ldquoThe definition of cross polarizationrdquo IEEE Trans-actions on Antennas and Propagation vol 21 no 1 pp 116ndash1191973

[12] T Liebig ldquoopenEMSmdashopen electromagnetic field solverrdquo Gen-eral andTheoretical Electrical Engineering (ATE) University ofDuisburg-Essen httpopenemsdestartindexphp

[13] KWoelders and J Granholm ldquoCross-polarization and sidelobesuppression in dual linear polarization antenna arraysrdquo IEEETransactions on Antennas and Propagation vol 45 no 12 pp1727ndash1740 1997

[14] A W Rudge The Handbook of Antenna Design vol 16 of IET1983

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 15: Research Article A Fully Reconfigurable Polarimetric ...

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of


Fully polarimetric W-band ISAR imagery of scale … Polari w isar_tcm18...Fully polarimetric W-band ISAR imagery of scale-model tactical targets using a 1.56THz compact range Thomas

Fully polarimetric W-band ISAR imagery of scale … Polari w isar_tcm18...Fully polarimetric W-band ISAR imagery of scale-model tactical targets using a 1.56THz compact range Thomas

Reconfigurable Radio Design Reconfigurable Architecture –Reconfigurable Chip design example –Hardware Reconfiguration Introduction to Software RADIO.

Reconfigurable Radio Design Reconfigurable Architecture –Reconfigurable Chip design example –Hardware Reconfiguration Introduction to Software RADIO.

Reconfigurable Computing Reconfigurable Architectures ... · Reconfigurable Computing Reconfigurable Architectures Chapter 3.2 ... is usually an 8-bit, 16-bit or 32-bit tiny ALU ...

Reconfigurable Computing Reconfigurable Architectures ... · Reconfigurable Computing Reconfigurable Architectures Chapter 3.2 ... is usually an 8-bit, 16-bit or 32-bit tiny ALU ...

Polarimetric SAR Interferometry (PolInSAR) and … APRS Tutorial...Polarimetric SAR Interferometry (PolInSAR) and Inversion Modelling Shashi Kumar & Unmesh Govind Khati Polarimetric

Polarimetric SAR Interferometry (PolInSAR) and … APRS Tutorial...Polarimetric SAR Interferometry (PolInSAR) and Inversion Modelling Shashi Kumar & Unmesh Govind Khati Polarimetric

Polarimetric characterisation of two

Polarimetric characterisation of two

Fully Polarimetric Analysis of Weather Radar Signatures ... · EEC Enterprise Electronics Corporation IF Intermediate Frequency ... Fig. 5.1 Case study 1, convective event, RHIs 80

Fully Polarimetric Analysis of Weather Radar Signatures ... · EEC Enterprise Electronics Corporation IF Intermediate Frequency ... Fig. 5.1 Case study 1, convective event, RHIs 80

TU1.L09.3 - Fully Polarimetric TerraSAR-X Data: Data Quality and Scientific Analysis

TU1.L09.3 - Fully Polarimetric TerraSAR-X Data: Data Quality and Scientific Analysis

Polarimetric SAR

Polarimetric SAR

A Novel Reconfigurable GaN Based Fully Solid-State ...

A Novel Reconfigurable GaN Based Fully Solid-State ...

Optimizing polarimetric parameter estimation in the ... · Optimizing polarimetric parameter estimation in the presence of detector and shot noise. 1 Why a polarimetric imager ? Décamouflage

Optimizing polarimetric parameter estimation in the ... · Optimizing polarimetric parameter estimation in the presence of detector and shot noise. 1 Why a polarimetric imager ? Décamouflage

A calibration method for fully polarimetric microwave radiometers …lib.tkk.fi/Diss/2003/isbn9512268140/article1.pdf · 2003-12-02 · Microwave Radiometers Janne Lahtinen, Student

A calibration method for fully polarimetric microwave radiometers …lib.tkk.fi/Diss/2003/isbn9512268140/article1.pdf · 2003-12-02 · Microwave Radiometers Janne Lahtinen, Student

Compact Reconfigurable Avionics – Reconfigurable Data ...

Compact Reconfigurable Avionics – Reconfigurable Data ...

Polarimetric Characteristics of Fully Polarization SAR Image Observed by Ground-Based SAR System

Polarimetric Characteristics of Fully Polarization SAR Image Observed by Ground-Based SAR System

SENTINEL-1 Toolbox Polarimetric Tutorial Polarimetry...Polarimetric Tutorial 2 Polarimetric Tutorial The goal of this tutorial is to provide novice and experienced remote sensing users

SENTINEL-1 Toolbox Polarimetric Tutorial Polarimetry...Polarimetric Tutorial 2 Polarimetric Tutorial The goal of this tutorial is to provide novice and experienced remote sensing users

A fully reconfigurable photonic integrated signal processor

A fully reconfigurable photonic integrated signal processor

A fully reconfigurable photonic integrated signal processor€¦ ·  · 2017-10-14A fully reconfigurable photonic integrated signal processor ... Photonic signal processing has been

A fully reconfigurable photonic integrated signal processor€¦ ·  · 2017-10-14A fully reconfigurable photonic integrated signal processor ... Photonic signal processing has been

POLARIMETRIC CHARACTERISTICS OF FULLY POLARIZATION …sar.kangwon.ac.kr/paper/isrs09_kang.pdf · SAR polarimetry technique is concerned with control of the polarimetric properties

POLARIMETRIC CHARACTERISTICS OF FULLY POLARIZATION …sar.kangwon.ac.kr/paper/isrs09_kang.pdf · SAR polarimetry technique is concerned with control of the polarimetric properties

DOCUMENT OVERVIEW Title: Fully Polarimetric Airborne SAR and ERS SAR Observations of Snow: Implications For Selection of ENVISAT ASAR Modes Journal: International.

DOCUMENT OVERVIEW Title: Fully Polarimetric Airborne SAR and ERS SAR Observations of Snow: Implications For Selection of ENVISAT ASAR Modes Journal: International.

ENG3050 Embedded Reconfigurable Computing Systems Introduction to Reconfigurable Computing Introduction to Reconfigurable Computing.

ENG3050 Embedded Reconfigurable Computing Systems Introduction to Reconfigurable Computing Introduction to Reconfigurable Computing.

Thomas.boerner@dlr.de, slide 1 German Aerospace CenterMicrowaves and Radar Institute Methodology for obtaining physical parameters from fully polarimetric.

[email protected], slide 1 German Aerospace CenterMicrowaves and Radar Institute Methodology for obtaining physical parameters from fully polarimetric.