Wideband Decoupling Techniques for Dual-Polarized Bi-Static Simultaneous Transmit and Receive Antenna Subsystem

A wideband, bistatic, and dual-polarized simultaneous transmit and receive antenna subsystem with isolation >60 dB over 6-19 GHz band is demonstrated. The proposed configuration employs two quad-ridge horns fed by a ridge waveguide ortho-mode transducer (OMT) as transmitting (TX) and receiving (RX) antennas. The OMT enables dual-polarized high-power operation for the TX antenna over the entire bandwidth. The TX/RX antennas are flush mounted in a flat ground plane and oriented in D-plane to achieve similar isolation for both polarizations. Different decoupling techniques for increasing isolation between TX/RX antennas are investigated. Specifically, a high capacitive reactance bed of nails is designed to suppress TM polarized surface waves on the metallic ground plane. Moreover, a wideband planar and low-profile high-impedance surface is developed and performance thereof is compared to that of the other considered surfaces. Effect of recessing the RX antenna in an absorber is also discussed. Computational and experimental studies are conducted to demonstrate and validate the performance of the proposed antenna subsystem. Good impedance match, excellent radiation characteristics, and high isolation are achieved.