Broadband X-band circularly polarized microstrip antenna with elliptical patch ring-slotted for airborne sar system

A broadband circularly polarized (CP) microstrip antenna with elliptical patch ring-slotted is presented. The proposed antenna is unit element of microstrip array antenna for X-band circularly polarized synthetic aperture radar (CP-SAR) onboard airborne. The antenna is designed in double-stage substrate structure, low weight, low profile, and single feeding. Basically circularly polarized of the antenna is generated by conventional square patch which have diagonally circle-chamfered that printed in the middle layer of antenna structure. To increase the quality of axial ratio, elliptical patch with circle-slotted is placed on upper layer as a parasitic element. The measured 10-dB impedance bandwidth and 3-dB axial ratio bandwidth are obtained 1.9 GHz or 20.5% (8.5-10.4 GHz) and 1.1 GHz or 11.2% (9.1-10.2 GHz), respectively.