Subband approach for wideband self-interference cancellation in full-duplex transceiver

A specific characteristic for the isolator circuits used in small form-factor in-band full-duplex transceivers, used to attenuate the leakage of the transmit signal to the receive path (self-interference), is nonuniform performance over the wide frequency band as these circuits must tune at the operating frequency. Moreover active cancellation circuits are required in addition to the isolation circuit to attenuate the self-interference further. In this work an RF self-interference cancellation is proposed to attenuate further the remaining self-interference, on the top of achieved isolation, uniformly over the wide band. This approach divides the wideband signal into a number of narrower subbands and then self-interference cancellation is performed at each subband separately. This is an alternate approach to the previously proposed delay and attenuation network active RF self-interference cancellation. Simulation results indicate significant improvements in uniformly self-interference cancellation and system performance which is achieved in the expense of moderate extra loss.