Synchronization in a Direct Sequence Receiver Aided by LMS Adaptive Filtering

Least-mean-squared (LMS) adaptive filtering has been shown to be an effective technique for suppressing narrow-band jamming in a direct sequence spread spectrum receiver. Most investigations have assumed that perfect synchronization is available to the adaptive filter, i.e., synchronization is obtained prior to the jammer suppression. Unfortunately, this synchronization may be difficult or impossible to obtain due to the effects of the jamming. This paper presents a receiver structure which allows synchronization to be obtained after the adaptive jammer suppression and fed back to the suppression filter. Bit-error-rate results are shown which domonstrate the performance of a delay-lock loop in conjunction with the adaptive filter in tone jamming. These performance results are compared to those for the adaptive filter with perfect synchronization.