Results and trade-off of self-interference cancellation in a full-duplex radio front-end

This paper reports experimental results of self-interference cancellation of a full-duplex radio front-end using two techniques, which are antenna cancellation and RF circuit cancellation. Transmitting signals are fed to two identical antennas through a rat race coupler for 180° phase difference, resulting in the antenna cancellation at a receiving antenna equally apart from transmitting antennas. The coupled transmitting signals are adjusted by RF cancellation circuits (attenuator, phase shifter and true time delay) and coupled back to the receiving antenna to achieve the RF circuit cancellation. After optimizing RF cancellation circuits, experimental result shows 60-dB cancellation over 20-MHz bandwidth in a noisy indoor environment. Also, practical difficulties of SIC in RF domain due to transmit and receive path losses and power budget are discussed.