Multipath Mitigation with Gated Signal Technique

Sunil M. Kanekal, Michael S. Braasch

Abstract:	The effect of multipath in a GPS receiver is to cause an error in tracking the code phase and the carrier phase of the incoming signal. The new technique proposed here reduces the error in tracking the code phase significantly. In the generic early-late delay-lock-loop with a correlator spacing of one chip, error in tracking the code phase exists for a multipath signal delayed upto 1.5 chips. The maximum range error in such a delay-lock-loop could be as much as 85 meters, in the presence of a multipath signal with an amplitude of half of that of the direct signal. Multipath signals are the largest source of error in DGPS applications. The new technique (henceforth referred to as the Gated Correlator) proposed here reduces the magnitude of the range error to the order of about 1 meter, in the presence of short delay multipath with a strength of one-half of the direct. In addition, the range error becomes insignificant for a multipath signal delayed by more than 0.075 chips. Theoretically, these parameters can be reduced even further. The extent of improvement is limited by hardware complexities and by the amount of signal power that we are ready to trade off. The technique is realized by obtaining a discriminator function, which is less susceptible to multipath contamination. This is achieved by a judicious combination of multiple correlators.
Published in:	Proceedings of the 54th Annual Meeting of The Institute of Navigation (1998) June 1 - 3, 1998 The Adams Mark Hotel Denver, CO
Pages:	535 - 542
Cite this article:	Kanekal, Sunil M., Braasch, Michael S., "Multipath Mitigation with Gated Signal Technique," Proceedings of the 54th Annual Meeting of The Institute of Navigation (1998), Denver, CO, June 1998, pp. 535-542.
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