A Full-Duplex Transceiver With Two-Stage Analog Cancellations for Multipath Self-Interference

In this paper, a full-duplex transceiver with a two-stage analog interference cancellation architecture is proposed for the prevailing wireless full-duplex communication, which enables simultaneous transmission and reception on the same frequency. This two-stage cancellation architecture jointly combines the structures of two typical analog self-interference (SI) cancellation approaches, i.e., the radio frequency (RF)-tapping and the baseband-tapping approaches, and mitigates the SI signal in two steps to provide an improved analog cancellation performance with reduced restrictions on the RF components required to build the cancellation architecture. The stage-I cancellation uses a dual-tap analog canceling circuit to mitigate only the direct leakage and one refection component within the SI signal to yield a residual multipath SI of reduced dynamic range. In the stage-II cancellation, a nonlinear model is particularly designed to build a multipath canceling signal in digital domain, which is capable of characterizing the joint effect of the multipath SI propagation channel, the transmitter nonlinearity, and the receiver nonlinearity of high accuracy. The digital canceling signal is then transmitted through an auxiliary transmit chain to cancel the residual SI from the stage-I cancellation to further improve the overall analog cancellation performance. Simulations are explicitly performed on a variety of wideband signals to verify cancellation capability of the proposed full-duplex transceiver. For proof-of-concept verification, experiments are also performed on our self-designed testbed to validate the cancellation performances of each cancellation stage.