A new post-correlation anti-jamming technique for GPS receivers

Interference has destructive impacts on all signals, but due to the weakness of the global positioning system (GPS) signals, even low-power interference has a significant destructive effect. Mitigation of that effect is a challenging issue for GPS receivers. We investigate the performance of the acquisition in the presence of the most effective and common interferences in use, such as single-tone continuous wave interference (CWI), multi-tone CWI, and chirp jamming. Our purpose is not to mitigate or completely remove the interference signal, but by using a signal processing method after the correlation, a receiver can acquire weak signals in the presence of interference with a jammer-to-signal ratio up to 60 dB. The main idea is derived from image processing filters so that by applying proper filters to the values of the cross-ambiguity function in the search space, the interference signal contribution decreases without any need for prior knowledge of its specific characteristics. Accordingly, even weak GPS signals can be easily acquired, and the number of acquired satellites increases significantly compared to the usual anti-jamming methods. Moreover, signals can be acquired even at twice the normal decision threshold value.