A Digital-Domain Controlled Nonlinear RF Interference Cancellation Scheme for Co-Site Wideband Radios

In this paper, a digital-domain reconstruction based radio-frequency (RF) interference cancellation scheme is proposed to cancel the nonlinear wideband self-interference (SI) signal in co-site radio systems. First, an auxiliary cancellation chain is employed to reconstruct and suppress the SI signal received at the receiver chain. Then, in order to generate the SI replica more accurately, we derive two nonlinear models to predicate the coupling characteristics for the nonlinear wideband SI signal. The proposed models combine the transmit chain and wireless SI channel characteristics, and employ both the Hammerstein model and Wiener model for the transmit chain, respectively. Next, the coefficients of each linear and nonlinear component in the SI chain are integrated into a coefficient vector, which is linear with respect to the output samples, with the proposed models. Based on the linearity, a dynamic least-squares (LS) type algorithm is developed to efficiently estimate and update the coefficients of the proposed models. Finally, experimental results obtained from a FPGA-based testbed have validated that the proposed scheme has a superior interference cancellation performance for nonlinear wideband SI.