A Single-Antenna Full-Duplex Subsystem With High Isolation and High Gain

In this paper, a single-antenna full-duplex subsystem is proposed, consisting of a high isolation network and a stacked patch antenna with reflector. The employed patch antenna is fed by two ports with very similar input impedances to make the reflected signals identical. The high isolation network composed of two hybrids and two circulators plays a crucial part in achieving high transmitting to receiving (Tx-Rx) isolation. It is able to cancel out the inevitable reflected signals from the antenna ports and the leakage signals from the circulators. The theoretical analysis is presented and the subsystem is also fabricated and measured. According to the measurement results, across the operation band from 2.018 to 2.12 GHz, the subsystem has VSWR <1.55, Tx-Rx isolation > 50 dB, axial ratio <2.4, and gain >10.2 dBic. Compared with the state-of-art single-antenna full-duplex subsystems, the proposed design features high Tx-Rx isolation level and high gain, which is suitable for microwave radio relay communication and satellite detection application.