How Comb Filters can be used in GNSS Receivers

This is a non-refereed presentation that examines the use of comb filters in GNSS receivers, reviewing some of the discussion recently presented in [1]. Because the GPS L1 C/A code signal has a spectrum made up of lines regularly spaced at 1kHz intervals, the use of comb filters, which have regularly spaced passor stop-bands, would on the face of it seem a logical step. It is shown, however, that each satellite channel would require its own comb filter, and that it can help with the speed of acquisition of weak signals in a sequential acquisition algorithm. It may also assist in the code tracking loop. There are some applications, such as search engines and FFT acquisition, where comb filters give little or no benefit.