Use of comb filters in GPS L1 receivers

Comb filters can be designed by replacing single delays in digital filters by multiple delays. These filters are “periodic” in the sense that their frequency response repeats itself at fixed intervals. They are thus well suited to a signal such as GPS L1 which has a spectrum made up of lines separated by the code repetition frequency of 1 kHz. In this paper we examine how periodic filters can be used in a conventional GPS L1 receiver. We find that comb filters assist with acquisition of weak signals, and can improve code-tracking performance.