Dual-Stage Co-Site RF Interference Canceller for Wideband Direct-Conversion Receivers Using Reduced Observation Chain

Abstract

In this paper, a dual stage interference cancellation architecture is proposed to cancel the wideband interference for direct-conversion receiver in co-site radio environment. A single tap all-analog canceller and a reduced observation chain (ROC) based digital canceller are deployed at the radio frequency stage and digital stage, respectively. First, in order to avoid the saturation of the receiver, the all-analog canceller that contains an analog vector modulator and an analog correlator is used to cancel the direct coupling interference with low hardware complexity. Then, the ROC-based digital canceller is employed to cancel the multipath components. In the digital canceller, the ROC is used to obtain a digital domain copy of the transmitted signal with a reduced sampling rate. Furthermore, a parallel interference coupling model which jointly considers multipath wireless channel, nonlinearity and in-phase/quadrature (I/Q) imbalance of the direct-conversion receiver, as well as a widely linear least mean squares-based coefficients estimation algorithm are developed to track the time-varying interference coupling channel. Simulation and experimental results confirm that the proposed scheme can effectively suppress the co-site interference under multipath, nonlinearity, and I/Q imbalance effect, and significantly reduce the implementation complexity at the cost of tiny interference cancellation performance loss.