Fast Code Acquisition with FFT and Its Sampling Schemes

Chun Yang

Abstract:	There has been a growing interest in the application of frequency-domain signal processing techniques to GPS receiver design, not only in fast code acquisition offered by FFT-implemented correlation but also in narrowband interference suppression based on power spectral analysis. The top efficiency of FFT is attained only when the data length is factorable. With GPS C/A code, however, its length is neither in a power of two nor highly cornpositive. To make efficient use of FFT, the incoming signal may be sampled at a rate being a power of two (not proportional to the chipping rate) or zeros are added to the sampled sequence to make it a power of two. In both cases, the signal and reference codes are not the same sequence circularly shifted relative to each other any more; the resulting correlation function is no longer in a triangular form; and the calculated correlation peak’s position may not necessarily correspond to the correct code shift. This paper investigates this problem aspect in order to search. for a better implementation scheme. In addition, it also discusses the effects of commensurability ratio between sampling rate and chipping rate on correlation resolution and code-matching accuracy as well as the roles of FFT beyond open-loop code acquisition.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	1729 - 1734
Cite this article:	Yang, Chun, "Fast Code Acquisition with FFT and Its Sampling Schemes," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 1729-1734.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In