Bounding Multipath Errors Induced by Electronic Components in Receiver Hardware

James P. Keith

Abstract:	The front end of a GPS receiver can introduce multipath errors due to impedance mismatch between electronic components causing reflections of the input signals. If multiple signals of the same tlequency are input into a circuit, then all of the multipath signals caused by reflections within the circuit have the same delay. Therefore, all the correlator flmctions will have the same multipath error, which will be treated by the receiver as a clock offset. Thk is only tme for reflections occurring within a circuit, for input signals of the same flequency. If the input signals are at different ilequencies, then the reflected signals no longer have the same delay. The multipath error in the correlator fimction will be different for each input signal, hence introducing a multipath tracking error in the final solution. This multipath tracking error due to differences in the input fiwquencies is referred to as a ‘relative’ multipath tracking error. This paper investigates the relative multipath tracking errors created in the front end of a GPS receiver. The nature of some electronic devices makes it very difftcult to measure the delay of a reflected signal which is required to calculate the relative multipath tracking error. Determining the bounds of the relative multipath tracking error, on the other hand, is readily obtained. This paper derives a technique to bound the relative multipath error through circuit design. The magnitude of the relative multipath tracking error is influenced by the relative frequency of the input signals, Small frequency differences in input signals due to Doppler shifts as well as large frequency differences such as in GLONASS and off frequency pseudolite signals are considered in this paper.
Published in:	Proceedings of the 1999 National Technical Meeting of The Institute of Navigation January 25 - 27, 1999 Catamaran Resort Hotel San Diego, CA
Pages:	165 - 172
Cite this article:	Keith, James P., "Bounding Multipath Errors Induced by Electronic Components in Receiver Hardware," Proceedings of the 1999 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1999, pp. 165-172.
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