Dual circularly polarized aperture-coupled metasurface antennas with high-isolation for X-band synthetic aperture radars

This paper describes a dual circularly polarized (CP) antenna with high isolation and its 2 x 2 element array for the X-band synthetic aperture radars. The antenna is an aperture-coupled metasurface of 4 x 4 periodic corner-truncated patches, which is fed by two orthogonal microstrip-lines to generate the dual-CP radiation. A novel asymmetric fence-shaped slot is utilized as the coupled aperture of the antenna to enhance the port-to-port isolation. To achieve a more robust dual-CP radiation, the 2 x 2 element array of the aperture-coupled metasurface antenna is designed, fabricated, and tested. Both simulation and measurement indicate that the array prototype achieves an excellent dual-CP radiation at 9.6 GHz, i.e., isolation of >= 30 dB, axial ratio <= 1-dB, radiation efficiency >= 80%, realized gain of 14.0 dBic, and cross-polarized level <= -20 dB at the broadside.