A low sidelobe level of circularly polarized microstrip array antenna for CP-SAR sensor

Abstract

In this paper, an elliptical microstrip array antenna with a low sidelobe level for circularly polarized synthetic aperture radar (CP-SAR) sensor is investigated. The low sidelobe level is obtained by implementing the Chebyshev synthesis method to distribute the power unevenly to each element of the patch. A Method of Moment is employed for optimizing the design and achieving a good circular polarization at the working frequency (L-Band). The simulated axial ratio (AR) bandwidth (<3 dB) for the five elements elliptical array antenna is around 11.2 MHz (0.88%), which is consistent with the measured value of 13.3 MHz (1.05%). The maximum sidelobe level of the proposed antenna is 23.3 and 21.4 dB for measured and simulated value, respectively. The simulated and measured results considerably agree with the theoretical design calculated using Chebyshev polynomial of 20 dB. The low sidelobe level and reasonable AR values indicate that the proposed antenna satisfies the specifications of the CP-SAR sensor.

Acknowledgments

The author would like to thank Takafumi Kawai and Takahiro Miyazaki for assisting in antenna development, Egyptian Ministry of Higher Education and State for Scientific research for a grant to travel and stay in Japan during this research. The authors would like also to thank professor Josaphat Tetuko Sri Sumantyo for permitting to use of the facilities available in his laboratory to carry out this research.