A Compact Printed Van Atta Array with Zero-Phase CRLH ...braaten/APS_2015_2.pdf · A Compact...
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A Compact Printed Van Atta Array with Zero-Phase CRLH Transmission Lines Benjamin D. Braaten * , Sajid Asif, Saeed Khan, Jared Hansen and Daniel L. Ewert Electrical and Computer Engineering Department North Dakota State University Fargo, ND 58108-6050, USA Email: [email protected] Abstract—A key component in the design of a printed Van Array is the requirement of the transmission line (TL) inter- connects between the elements to be a factor of the operating wavelength. This results in interconnects that introduce a 2π phase shift. Traditionally, meander-lines have been used to design these interconnects; however, one drawback is the large space required for the layout. In this paper, a more compact Van Atta array that uses zero-phase composite right/left-handed TLs instead of meander-lines is presented. The result is a Van Array array that is 34.0% smaller at the operating frequency of 2.43 GHz. For validation, simulations are compared to measurements of several prototypes. Index Terms—Van Atta array and CRLH Transmission Lines I. INTRODUCTION Electromagnetic reflectors, such as a Van Atta array [1], have been used to improve the performance of navigation systems [2] and wireless power harvesting [3]. The authors of these papers have shown that a printed Van Atta array can be used to create a surface that reflects an incoming electromagnetic wave in a direction back towards the source and that wireless power harvesting from various directions can be greatly improved. The operation of a 1X4 Van Atta array is shown in Fig. 1(a). There are four elements interconnected with transmission lines that are a factor of the operating wavelength long. When the wavefront of the incident wave arrives at antenna element 1, denoted as A 1 , a voltage is induced on the port, denoted as V + 1 . This voltage then propagates down the interconnect and drives element A 4 and is denoted as V + 4 . If the interconnect is a factor of the operating wavelength, the voltage arrives at A 4 with the same phase induced at A 1 or the phase of V + 1 = V + 4 . Then, the field radiated by A 4 has the same phase as the field arriving at A 1 . A similar interaction is occurring between elements A 2 and A 3 . The overall result is a field radiated from the array back in the direction of the incident wave. Historically, these interconnects were designed with printed meander-lines and the length of each line was chosen such that L = Nλ (N = 1, 2, ...). This ensured that the phase of the voltages on both ends of the meander-lines were the same. However, one drawback of a meander-line interconnect network is the layout space required. Therefore, the objective of this paper is to present the more compact Van Atta array design in Fig. 1(b) that uses composite right/left- handed transmission lines (CRLH-TLs) [4] to reduce the Via to ground Via to ground Via to ground a b c d g h m X Y n p q Scattered wave Incident wave Incident wave front -3Δ -2Δ -Δ 0 Receive phase θ -3Δ -2Δ -Δ 0 Transmit phase zero-phase transmission line interconnects A1 A4 A3 A2 (a) (b) x y Fig. 1. (a) Illustration of the scattering from a 1X4 Van Atta array and (b) drawing of the proposed compact Van Atta array with zero- phase CRLH interconnects (a = 2.9 mm, b = 16.1 mm, c = 2.48 mm, d = 2.86 mm, g = 1.33 mm, h = 4.33 mm, m = 9.2 mm, n = 10.0 mm, p = 4.2 mm, q = 3.48 mm, X = 110.1 mm and Y = 44.3 mm). overall layout size. The layout of the CRLH-TLs were chosen such that the zero-phase frequency and the operating frequency of the patches were the same, then, the CRLH-TLs had a similar phase behavior to the meander-lines with L = Nλ. II. DESIGN OF THE VAN ATTA ARRAY WITH ZERO-PHASE CRLH INTERCONNECTS The prototype array was designed on a grounded 1.52 mm thick Rogers TMM4 substrate with ε r = 4.5 and tan δ = 0.002 [5]. First, the CRLH-TL interconnects were designed in ADS [6] using an iterative approach and the design guidelines 1856 978-1-4799-7815-1/15/$31.00 ©2015 IEEE AP-S 2015
Transcript of A Compact Printed Van Atta Array with Zero-Phase CRLH ...braaten/APS_2015_2.pdf · A Compact...
A Compact Printed Van Atta Array with Zero-PhaseCRLH Transmission Lines
Benjamin D. Braaten∗, Sajid Asif, Saeed Khan, Jared Hansen and Daniel L. EwertElectrical and Computer Engineering Department
North Dakota State UniversityFargo, ND 58108-6050, USAEmail: [email protected]
Abstract—A key component in the design of a printed VanArray is the requirement of the transmission line (TL) inter-connects between the elements to be a factor of the operatingwavelength. This results in interconnects that introduce a 2πphase shift. Traditionally, meander-lines have been used to designthese interconnects; however, one drawback is the large spacerequired for the layout. In this paper, a more compact VanAtta array that uses zero-phase composite right/left-handed TLsinstead of meander-lines is presented. The result is a Van Arrayarray that is 34.0% smaller at the operating frequency of 2.43GHz. For validation, simulations are compared to measurementsof several prototypes.
Index Terms—Van Atta array and CRLH Transmission Lines
I. INTRODUCTIONElectromagnetic reflectors, such as a Van Atta array [1],
have been used to improve the performance of navigationsystems [2] and wireless power harvesting [3]. The authorsof these papers have shown that a printed Van Atta arraycan be used to create a surface that reflects an incomingelectromagnetic wave in a direction back towards the sourceand that wireless power harvesting from various directions canbe greatly improved.
The operation of a 1X4 Van Atta array is shown in Fig. 1(a).There are four elements interconnected with transmission linesthat are a factor of the operating wavelength long. When thewavefront of the incident wave arrives at antenna element 1,denoted as A1, a voltage is induced on the port, denoted asV +1 . This voltage then propagates down the interconnect and
drives element A4 and is denoted as V +4 . If the interconnect
is a factor of the operating wavelength, the voltage arrivesat A4 with the same phase induced at A1 or the phase ofV +1 = V +
4 . Then, the field radiated by A4 has the samephase as the field arriving at A1. A similar interaction isoccurring between elements A2 and A3. The overall resultis a field radiated from the array back in the direction of theincident wave. Historically, these interconnects were designedwith printed meander-lines and the length of each line waschosen such that L = Nλ (N = 1, 2, ...). This ensured thatthe phase of the voltages on both ends of the meander-lineswere the same. However, one drawback of a meander-lineinterconnect network is the layout space required. Therefore,the objective of this paper is to present the more compact VanAtta array design in Fig. 1(b) that uses composite right/left-handed transmission lines (CRLH-TLs) [4] to reduce the
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Fig. 1. (a) Illustration of the scattering from a 1X4 Van Atta arrayand (b) drawing of the proposed compact Van Atta array with zero-phase CRLH interconnects (a = 2.9 mm, b = 16.1 mm, c = 2.48 mm,d = 2.86 mm, g = 1.33 mm, h = 4.33 mm, m = 9.2 mm, n = 10.0mm, p = 4.2 mm, q = 3.48 mm, X = 110.1 mm and Y = 44.3 mm).
overall layout size. The layout of the CRLH-TLs were chosensuch that the zero-phase frequency and the operating frequencyof the patches were the same, then, the CRLH-TLs had asimilar phase behavior to the meander-lines with L = Nλ.
II. DESIGN OF THE VAN ATTA ARRAY WITHZERO-PHASE CRLH INTERCONNECTS
The prototype array was designed on a grounded 1.52 mmthick Rogers TMM4 substrate with εr = 4.5 and tan δ =0.002 [5]. First, the CRLH-TL interconnects were designed inADS [6] using an iterative approach and the design guidelines
1856978-1-4799-7815-1/15/$31.00 ©2015 IEEE AP-S 2015
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Fig. 2. (a) Photograph of the prototype Van Atta array with the zero-phase CRLH interconnects; (b) photograph of the zero-phase CRLHinterconnects for testing and (c) photograph of the prototype Van Attaarray with meander-line interconnecting microstrip transmission linesthat have an electrical length of Nλ where N = 1, 2, ... .
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Fig. 3. Measured and simulated angle introduced by the CRLHinterconnects.
summarized in [4] for a zero-phase frequency of 2.45 GHz.Then, a microstrip patch with the same operating frequencywas designed in ADS and interconnected to form the Van Attaarray shown in Fig. 1(b).
III. MEASUREMENT AND SIMULATION RESULTS
A prototype was then manufactured and is shown in Fig.2(a). Along with the prototype array, the CRLH-TL intercon-nects were individually manufactured (shown in Fig. 2(b)).This was done to measure the zero-phase frequency. Themeasured results are compared to simulation results in Fig.3. The measured zero-phase frequency for the short line was2.47 GHz and for the long line was 2.4 GHz, which arereasonably close to simulated results. Next, the scattering fromthe prototype array was measured using two horn antennas ina full anechoic chamber in the x-z plane. One antenna wasused to provide an incident field (Eθ) on the array and theother antenna was used to measure the scattered field (Eθ)with respect to angle. The horn providing the incident field
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Fig. 4. Normalized scattering from the prototype Van Atta array(a) with the CRLH-TL interconnects and a plate, and (b) with themeander-line interconnects and a plate at 2.43 GHz.
was connected to port 1 of the network analyzer and the hornmeasuring the scattered field was connected to port 2 of theanalyzer. The normalized results (in terms of S-parameters) areshown in Fig. 4(a) for 2.43 Ghz and a -5 dB scattering angle of94.0◦ was measured. To illustrate the wider scattering that ischaracteristic of a Van Atta array, the -5 dB scattering anglefrom a plate the same size as the ground plane on the VanAtta array is also shown for comparison and was determinedto be 40.0◦. Much wider scattering from the prototype arrayis shown.
Next, to show the size reduction of the CRLH-TL intercon-nect approach, the prototype Van Atta array with the meander-line interconnects shown in Fig. 2(c) was manufactured andtested. The results are shown in Fig. 4(b) for 2.43 Ghz. The -5dB scattering angle for the array was 49.0◦ and for the platewas 33.0◦. Again, a much wider scattering from the meander-line design was observed. Finally, the overall size of the designwith the CRLH-TL interconnects was 34.0% smaller than thedesign with the meander-lines.
IV. CONCLUSION
A compact printed Van Atta array that uses zero-phase com-posite right/left-handed transmission line (CRLH-TL) inter-connects was presented in this paper. Additionally, a Van Attaarray designed with traditional meander-lines was presentedand compared to the design with the zero-phase CRLH-TLs.An overall size reduction of 34.0% was successfully shownwith measurements at 2.43 GHz.
REFERENCES
[1] L. C. Van Atta, “Electromagnetic Reflector,” U.S. Patent 2,908,002, SN514040, Oct. 6 1959.
[2] M. Cohn, “A Millimeter Wave Retrodirective Transponder for Colli-sion/Obstical Avoidance and Navigation/Location, Proc. IEEE - IEEVehicle Nav. and Info. Sys. Conf. Ottawa, ONT., Oct. 12 - 15, 1993,pp. 534-538
[3] Y.-J. Ren and K. Chang, “New 5.8 GHz Circularly Polarized Retrodi-rective Arrays for Wireless Power Transmission,” IEEE Trans. Microw.Theory Tech., vol. 54, no. 7, Jul. 2006, pp. 2970 - 2976.
[4] C. Caloz and T. Itoh, Electromagnetic Metamaterials, Piscataway-Hoboken, NJ: Wiley-IEEE Press, 2005.
[5] Rogers Corporation, [online] www.rogerscorp.com.[6] Advanced Design System (ADS) by Agilent Technologies, [online]
www.agilent.com.
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