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.