Antijam Spread Spectrum Receiver using LMS Adaptive Filtering Techniques

Abstract

Analytical results have shown that least-mean-squared (LMS) adaptive filtering techniques are useful for narrowband jammer suppression in a direct sequence spread spectrum receiver. Recently, a Widrow-Hoff LMS adaptive filter has been implemented in digital form using a burst processing technique to provide a simplified hardware structure. This paper presents experimental results obtained using this digital LMS adaptive filter as a jammer suppressor for a 7-chip pseudo-noise (PN) spread spectrum system. Actual probability of error results are presented and compared to results obtained earlier on an analog version of the same type of adaptive processor. In addition, a new two stage adaptive processor comprised of a jammer estimator followed by an adaptive filter is introduced and discussed. This new system will provide improved probability of error performance by increasing the jammer cancellation while reducing the code distortion.