Theory and Performance of Narrow Correlator Spacing in a GPS Receiver

A. J. Van Dierendonck, Pat Fenton and Tom Ford

Abstract:	Historically, conventional GPS receivers use one chip early-late correlator spacing in the implementa- tion of delay lock loops (DLLs). More than any other reason for this may have been that designers had assumed this was the way to design DLLs. How- ever, there are distinct advantages to narrowing this spacing, especially in C/A Code tracking applica- tions. These advantages are the reduction of track- ing errors in both the presence of noise and multi- path. The primary disadvantage is that a wider pre-correlation bandwidth is required, coupled with higher sample rates and higher digital signal pro- cessing rates. However, with current CMOS tech- nology, this is easily achievable and well worth the price. Noise reduction is achieved with narrower spacing because the noise components of the early and late signals are correlated and tend to cancel, provided that early and late processing is simultaneous (not dithered). Multipath effects are reduced because the noncoherent DLL discriminator is less distorted by the delayed multipath signal. In this paper, we will present the derivation of these improvements followed by both simulated and tested performance.
Published in:	Proceedings of the 1992 National Technical Meeting of The Institute of Navigation January 27 - 29, 1992 Catamaran Resort Hotel San Diego, CA
Pages:	115 - 124
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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