Performance of a New Adaptive Filter for Digital Communications

摘要

The improvement in performance of a digital communications receiver preceded by an adaptive filter using the soft-constraint Least Mean Square algorithm is found. This algorithm has previously only been used in conjunction with adaptive antenna arrays. The fundamentals of adaptive filters and the spread spectrum technique are presented. A computer model is developed which simulated a 19 tap adaptive filter and spread spectrum receiver combination in the baseband region. The filter is shown to adapt well to hopping jammers and dual jammers. Plots of the filter's transfer function show notch depths ranging from -34 dB to -77 dB over iterations ranging from 15 to 5000 for the case of a 20 db sinusoid jammer. The improvement gained by adjusting the softness of the constraints is presented. The computer program and recommendation for further study are included as well as a 44 item bibliography.