We have developed an array antenna consisting of 12 elements of simple square-shaped, corner-truncated patches for circularly polarized synthetic aperture radar (CP-SAR) operated in the L-band. The corporate feed design concept is implemented by combining a split-T and a 3-way circular-sector-shape power divider to excite circularly polarized radiation. The fabricated antenna based on the simulation using moment method gives a good circular polarization at the center frequency of 1.27 GHz with an impedance bandwidth of 6.1% and 3-dB axial ratio bandwidth of 1.0%, satisfying the specification for our circularly polarized synthetic aperture radar intended for use onboard an unmanned aerial vehicle and a small satellite.

Abstract-An equilateral triangular microstrip antenna is proposed for circularly-polarized synthetic aperture radar (CP-SAR) systems operated in L-Band (1.27 GHz). For airborne application, a prototype antenna patch is designed, fabricated and tested. Electromagneticallycoupled, dual-feeding method is applied to generate the circularlypolarized wave radiating from the patch. The fabricated patch exhibits an axial ratio bandwidth (< 3 dB) of about 0.58% (7.4 MHz), which is consistent with the value of 0.57% (7.24 MHz) from the simulation.

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Abstract-We have investigated elliptical annular ring microstrip antennas having a sine wave periphery both theoretically and experimentally. The proposed antenna gives a good circular polarization at the center frequency of 1.285 GHz, with measured 3 dB axial ratio bandwidth of about 0.73% (9.5 MHz) and impedance bandwidth of about 1.7% (22.0 MHz). Input and radiation characteristics are also examined for different sine wave amplitudes applied to the periphery of elliptical ring patch antenna.