An Architecture for Capturing the Nonlinear Distortion of Analog Self-Interference Cancellers in Full-Duplex Radios

Analog self-interference (SI) cancellation is a key process to enable full-duplex wireless communications, which generates a cancelling signal (a copy of the SI) at the local receiver and subtracts from the received signal to cancel the SI imposed by the local transmitter. However, due to the inherent nonlinearities of analog canceller (AC), the SI cancellation performance is often restricted by introducing extra nonlinear distortion to the receiver. In this letter, an observation architecture is proposed to capture the AC nonlinear distortion by deploying an auxiliary chain identical to the AC and a linear cancellation approach. The captured nonlinear distortion could be used as a reference in the digital domain to mitigate the AC-induced nonlinear interference at the receiver. Experiments verify that the proposed architecture is capable of capturing the weak AC-induced distortion and suppressing it to close the receiver noise floor.