Code Range and Carrier Phase Multipath Mitigation Using SNR, Range and Phase Measurements in a Multi-Antenna System

J.K. Ray, P. Fenton

Abstract:	Multipath is a major source of error in high precision GPS static and kinematic differential positioning. It is a major concern in reference stations such as in Local Area Augmentation Systems (LAAS), whereby corrections generated by a reference station which are based on multipath corrupted measurements, can significantly influence the position accuracy of differential users. Code range, carrier phase and signal-to-noise (SNR) measurements are all affected by multipath, and is spatially correlated within a small area. In order to estimate and remove code and carrier phase multipath, a system comprising of a cluster of five GPS receivers and antennas is used at a reference station location. The spatial correlation of the receiver data, and the known geometry among the antennas, are exploited to estimate multipath for each satellite in each antenna in the system. The paper analyzes generic receiver code and carrier tracking loop discriminator functions, and formulates relationships between receiver data, such as code range, carrier phase and SNR measurements and relates them to various multipath parameters. A Kalman filter is described which uses a combination of the available information from the antennas (receivers) in the multi-antenna cluster to estimate various multipath parameters. From the multipath parameters, the code range and carrier phase multipath is estimated and compensated. The technique is first tested on simulated data in a controlled multipath environment. Results are then presented using field data and show a significant reduction in multipath error.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	713 - 726
Cite this article:	Ray, J.K., Fenton, P., "Code Range and Carrier Phase Multipath Mitigation Using SNR, Range and Phase Measurements in a Multi-Antenna System," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 713-726.
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