A Concurrently Dual-Polarized, Simultaneous Transmit and Receive (STAR) Antenna

A concurrently dual-polarized, simultaneous transmit and receive (STAR) antenna system with high transmit (TX)-receive (RX) isolation is presented. The STAR antenna consists of four dual-polarized patches, two for TX and two for RX. The radiators are fed using a network consisting of four 90 degrees hybrids and four 180 degrees hybrids. The input ports of the feed network constitute the inputs/outputs of the STAR antenna system. The system supports concurrent transmission and reception of waves with both right- and left-hand circular polarization. Due to the phase cancellation and geometrical symmetry of the antenna, the TX/RX coupling between ports with the same polarization is canceled using the feed network. In addition, four right-angle slots are inserted in the ground plane and a cross-shaped, high-impedance surface is inserted between the radiating patches to further suppress the coupling between the differently polarized TX and RX ports. Simulation and measurement results of a fabricated prototype show good agreement and demonstrate TX/RX isolation levels greater than 38 dB for all polarization combinations over a 6.5% bandwidth (6.0-6.4 GHz). Moreover, the fabricated prototype provides broadside axial ratios below 2.5 dB and realized gains above 7.8 dBic for all TX and RX modes, demonstrating good, concurrent-dual-polarization performance.