Time-varying filtering using full spectral information for soft-cancellation of FM interference in spread spectrum communications

Abstract

Time-varying notch filters have been applied to reject FM interference in direct-sequence spread spectrum communications. The time-varying notch filter was formed using instantaneous frequency estimation of the interference regardless of its power or other spectral information. Consequently, when the interference is moderate or weak, the notch filter may cancel more signal than interference, and hence yield a deteriorating system performance. We propose a time-varying filter for soft-cancellation of interference that uses full spectral information about the interference and the desired signal and aims at minimum signal distortion. We model the received signal with a time-varying autoregressive model and form the filter based on the Wiener solution. Simulations reveal its performance improvement over the notch filter based hard-cancellation.