Study of the Impact of False Lock Points in Subcarrier Modulated Ranging Signals and Recommended Mitigation Approaches

V.S. Lin, P.A. Dafesh, A. Wu, C.R. Cahn

Abstract:	In this paper we compare two different techniques to eliminate incorrect delay-lock code tracking of the GPS M code. The current proposed technique to eliminate incorrect tracking of the M code signal is to determine whether or not the peak being tracked is the correct one. The algorithm compares the power of the punctual correlation with the power of correlations at the incorrect peaks by implementing very-early and very-late correlations. To make the detection of incorrect tracking very reliable at a low C/No, a long smoothing time is required for these correlations. In order to improve tracking performance of binary offset carrier (BOC) signals, an alternative technique of eliminating incorrect tracking is proposed in this paper. This alternative uses an additional restoring force derived by noncoherently combining the separate correlations to the individual sidebands that have been isolated by the narrow filters. The new scheme uses the summation of two different restoring forces; one derived from coherent combining of the sidebands and the other derived from noncoherent combining of the sidebands. It will be shown that the alternative technique of tracking BOC(10,5) by the summation restoring force performs better than the current proposed technique at low C/No.
Published in:	Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003) June 23 - 25, 2003 Hyatt Regency Hotel Albuquerque, NM
Pages:	156 - 165
Cite this article:	Lin, V.S., Dafesh, P.A., Wu, A., Cahn, C.R., "Study of the Impact of False Lock Points in Subcarrier Modulated Ranging Signals and Recommended Mitigation Approaches," Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003), Albuquerque, NM, June 2003, pp. 156-165.
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