Single antenna full duplex cancellation network for ISM band

Abstract

Full-Duplex (FD) communications can double wireless capacity by simultaneously transmitting and receiving (STAR) on the same frequency channel. In this paper, a single antenna solution is proposed using a hybrid coupler to isolate transmit and receive paths. The fourth port of the hybrid coupler is terminated with a variable impedance (ZV) to improve self-interference cancellation (SiC). The ZV consists of two cascaded commercially available integrated circuits (IC): a variable attenuator and a variable phase shifter, with a short circuit. This implementation resulted in 45.0 dB average SiC over a 20 MHz bandwidth in the 2.45 GHz Industrial, Medical and Scientific (ISM) band.