A T/R antenna pair with polarization-based reconfigurable wideband self-interference cancellation for simultaneous transmit and receive

This paper proposes a transmit and receive (T/R) antenna pair with a novel wideband self-interference cancellation (SIC) feature for simultaneous transmit and receive (STAR) or full-duplex applications. The T/R antennas have orthogonal linear polarizations and an auxiliary port which is cross-polarized with the receive port is introduced on the receive antenna. Introduction of a reconfigurable reflective termination on the auxiliary port reflects the coupled signal to cancel the self interference at the RX port. The reconfigurable termination mimics the required conductance and susceptance across a wide frequency range to achieve wideband SIC. When SIC is activated, isolation between the T/R antenna pair is higher than 50 dB over 300MHz centered at 4.6 GHz. The proposed cancellation technique provides 20 dB improvement in the T/R isolation over 400 MHz. It can be reconfigured in the presence of environmental changes and reflections to recover the degradation in the cancellation. The antenna pair is also employed in a transceiver built using off the shelf components and 70 dB total SIC is achieved in conjunction with digital cancellation.