Rejection of Frequency Sweeping Signal in DS Spread Spectrum Systems Using Complex Adaptive Filters

It is already known that the performance of narrowband interference adaptive filtering in DS spread spectrum systems is additionally degraded in the presence of frequency hopped jamming signal compared to the case with CW interference. Even so, the adaptive filter can be rather efficient because during the hopping interval, while the jamming signal parameters are constant, filter adjusts its weights; and if the hopping rate is not too high, there are time periods when the interfering signal is suppressed. In order to have better insight into the performance of these systems, we analyze DS spread spectrum receiver behavior, when the jamming signal frequency is continuously changed (chirp signal). We find that this is the reasonable step for the jammer trying to be more efficient. In such a case, two-sided filter structure shows worse overall performances than prediction error structure. As the jamming frequency sweeping rate or bandwidth are increased, the system performance is more and more degraded. The analysis provides insight into how much the system performance will be degraded as a function of the interfering (frequency sweeping) signal parameters.