Elliptical microstrip antenna for circularly polarized synthetic aperture radar

We propose a new circularly polarized elliptical microstrip antenna intended for use in circularly polarized synthetic aperture radar (CP-SAR) systems operated in L-Band (1.27 GHz). The design and fabrication process aim to fulfill the challenging specification for our CP-SAR onboard unmanned aerial vehicle (UAV). We apply the proximity-coupled, single feeding method by a microstrip line positioned 45° counterclockwise to the semi-major axis of the ellipse to generate the left-handed circularly polarized wave radiating from the patch. Both simulated and measured results are presented. For a single-element model, the simulation gives an axial ratio bandwidth (<3dB) of about 0.85% (10.8 MHz), which is consistent with the bandwidth measured for the measured fabricated model of 0.82% (10.4 MHz) and 0.91% (11.6 MHz) simulated for an antenna array model. These results satisfy the specification for our CP-SAR sensor onboard UAV.