Fading Multipath Reduction via FLL-aided Code Tracking in GPS

Sai K. Kalyanaraman and Michael S. Braasch

Abstract:	Pseudorange multipath is a major error component in GPS. Multiple techniques have been devised to mitigate pseudorange multipath at the antenna and receiver levels. Previous research has demonstrated that multipath with a non-zero phase-rate (relative to the direct signal) contributes to a lesser overall pseudorange error than static multipath, given sufficiently narrow code loop bandwidth. The reduction in pseudorange error due to fading multipath is made possible by the utilization of a carrier aided code-tracking loop. The focus of this research effort is to examine the implementation of a FLL (Frequency Locked Loop) aided code-tracking loop and compare it to the conventional PLL (Phase Locked Loop) aided code- tracking loop. The FLL aided code tracking loop will provide the GPS receiver with inherently higher resistance to interference while providing frequency estimates to the code-tracking loop, which are comparable to that from the PLL. It will be shown that significant reduction in pseudorange error due to fading multipath can be obtained even with the standard/wide correlator (1.0 chip spacing) architecture. The paper will present the appropriate background and theory. Bench test data will be provided to validate the theory.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	655 - 665
Cite this article:	Kalyanaraman, Sai K., Braasch, Michael S., "Fading Multipath Reduction via FLL-aided Code Tracking in GPS," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 655-665.
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