Enhanced Time Domain Interference Suppression Techniques

摘要

Many methods have been proposed for suppressing interference in a direct sequence spread spectrum signal and a number of these utilize adaptive transversal suppression filters to remove a large portion of the interference prior to despreading. This report investigates the performance of predictive and two-sided adaptive filtering systems and presents a method to improve the performance of the predictive filter by compensating for the distortion introduced into the desired direct sequence signal during the adaptive filtering process. It is shown that the predictive filter acts as a pre-whitener and the two-sided filter acts as a power inverter. Additionally, the two-sided adaptive filter automatically performs the same function as the compensated predictive filter. The performance of the adaptive systems is also studied when there is multipath propagation and it is shown that the presence of multipath allows the filters to partially suppress the desired direct sequence signal, resulting in performance loss. A combination of simulation and analysis was used to perform this study. Simulations were performed using the Signal Processing Work System (SPW) from Alta Group of Cadence Design Systems, Inc.