A modified recursive least squares adaptive lattice filter for narrowband interference rejection

Abstract

A modified recursive least squares (MRLS) lattice filter has been developed for co-channel narrowband interference rejection in high frequency (HF) serial tone waveforms. Co-channel interference of this nature can severely limit the performance of the HF modem (John M. Goodman 1992). For nonstationary narrowband interference signals, conventional adaptive lattice filtering techniques have been to have poor transient response behavior in the presence of large interference signals. To address this problem, we have developed a modified recursive least squares (MRLS) lattice filter that mitigates the transient error typical of the more conventional interference rejection techniques. The MRLS technique is compared against standard lattice filters such as the recursive least-squares (RLS) adaptive lattice filter and the simpler gradient adaptive lattice (GAL) filter.