IEEE 2007 International Symposium on Microwave, Antenna, Propagation, and EMC Technologies For Wireless Communications

Design of Broad-Band Circularly Polarized Microstrip PatchAntenna Array

Dong TaoSatellite Application System Department,China Academy of Space Technology,Beijing 100086,China

Email:dongtaoandy@sohu.com

Abstract: A Broadband circularly polarized microstripantenna array is presented in this paper. This array

has 8X8 elements and a parallel feed networks. The

whole size of this X band array is 190mm X 190mm X

0. 787mm. The measurement of the bandwidth of this array

is 7. 32%(VSWR<2), the gain is about 24dB and the axial

ratio is less than 3dB in the operating band. This

single layer microstrip antenna array is promising in

application because of its compact size and excellent

characteristics.

Index Terms: microstrip array, circularly polarized,broad-band, single layer

characteristics is realized by the truncated corner of the

square patch method. The gain of the element is about7dBi and the axial ratio is ldB.

1 Introduction

Microstrip patch antenna array is widely used in

radar, communication and other electronic systemsbecause of its compact size, low cost, easymanufacture and excellent characteristics. In this paper,a single layer circularly polarized microstrip patchantenna array is proposed. This array has compact sizeand excellent characteristics, such as broadband, highgain and good circularly polarized axial ratio.

2 Design and Simulation

2.1 circularly polarized patch element designThe circularly polarized microstrip patch element

is optimized by Ansoft Designer. The optimizationgoals are resonant frequency, gain and axial. Theelement planar EM model is shown in Fig.l.Thesubstrate is RT/duriod 5880 (sr = 2.2,tan 8 = 0.0009)with a thickness of 0.787mm. The circularly polarized

1-4244-1044-4/07/S25.00 ©2007 IEEE.

Fig.l microstrip pach element2.2 parallel feed networks design

This antenna array was formed by 2 X 2 elements,the layout of 2 X 2 feed networks is also optimized byAnsoft Designer. The optimization goals are resonant

frequency, transmission and reflection coefficients. Thesimulation circuit model is shown in Fig.2, and the

planar EM model is shown in Fig.3.

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Fig.2 layout of 2 X 2 feed networks(circuit model)

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IEEE 2007 International Symposium on Microwave, Antenna, Propagation, and EMC Technologies For Wireless Communications

-160 -120 -80 -40 0 40

angle(DEG)

Fig.3 layout of 2 X 2 feed networks(planar EM model)2.3 whole size patch array simulation

The whole size 8X8 elements array is shown Fig.4,which is simulated by Ansoft HFSS. It can be seen

that the array is parallel fed, each element has equalamplitude and phase excitation. The spacing between

two elements is 0.7 A0 in two dimensions. The whole

size of this X band array is 190mm X 190mm X0.787mm.The radiation pattern of simulation in the

principal plane is shown in Fig.5.

Fig.4 simulation model

Fig.5 radiation pattern(simulation)

3 Measurement and Results

A prototype of the antenna is shown in Fig. 6. TheVSWR is measurement by using Agilent 8757D scalarnetwork analyzer. The measurement results andsimulation results(by Ansoft Designer and HFSS) are

compared in Fig. 7. We can see that they are good in

agreement. The bandwidth(VSWR<2)of the antenna

array is 7.32%(8.56GHz~9.21GHz) .The radiation

pattern, gain and axial of this single layer antenna

array are measured in the anechoic chamber. Circular

polarization gain and axial ratio are measured by usinga spinning horn and a gain comparison method. Theradiation pattern in the central frequency is presentedin Fig. 8. It can be seen that the gain is about 24.5dBiand the SLL is about -12dB.

Fig.6(a) Prototype ofproposed antenna(top)

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IEEE 2007 International Symposium on Microwave, Antenna, Propagation, and EMC Technologies For Wireless Communications

Fig.6(a) Prototype of proposed antenna(bottom)

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5.0-

4.5

4.0-

3.5

3.0

2.5

2.0

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-HFSS_simDesigner_sim

-test

8.9 9.0 9.1 9.2 9.3 9.4

frequency(GHz)

Fig.7 measurement ofVSWR

v -10J

120 160 200 240

angle(DEG)

Fig.8 radiation pattern(measurement)

4 ConclusionsThis paper presents a high-performance single

layer 8X8 elements circularly polarized microstrippatch array antenna. The measurement of thebandwidth of this array is 7.32%(VSWR<2),the gain isabout 24dB and the axial ratio is less than 3dB in the

operating band.References

[l]Kwok L. Chung,'A circularly polarized stacked

electromagnetically coupled patch antenna," IEEE

Trans.Antennas Propaga.,Vol.52(5),ppl365-1370, 2004.

[2]Hao Wang,'A compact single layer monopulse microstripantenna array," IEEE Trans.Antennas

Propaga.,Vol.54(2),pp503-509,2006[3]S.Holzworth, "planar antenna design at 60 GHz for high date

rate point-to-point connections," Antennas and PropagationSociety International Symposium, IEEE , 2005

[4] M. L. Oberhart, Y. T. Lo, and R. Q. H. Lee, "New simplefeed network of an array module of four microstrip elements,"Electron. Lett., vol. 23,no. 9, pp. 436-437, 1987.

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