REJECTION OF FREQUENCY SWEEPING SIGNAL IN DS SPREAD-SPECTRUM SYSTEMS USING COMPLEX ADAPTIVE FILTERS

It is already known that the performance of narrowband interference ad aptive filtering in DS spread spectrum systems is additionally degrade d in the presence of frequency hopped jamming signal compared to the c ase with CW interference. Even so, the adaptive filter can be rather e fficient because during the hopping interval, while the jamming signal parameters are constant, filter adjusts its weights; and if the hoppi ng rate is not too high, there are time periods when the interfering s ignal is suppressed. In order to have better insight into the performa nce of these systems, we analyze DS spread spectrum receiver behavior, when the jamming signal frequency is continuously changed (chirp sign al). 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 w orse overall performances than prediction error structure. As the jamm ing frequency sweeping rate or bandwidth are increased, the system per formance 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.