Space-Time Adaptive Processing for Mitigation of Platform Generated Multipath

Andrew J. O'Brien, Inder J. Gupta, C.J. Reddy, Frederick S. Werrell

Abstract:	GNSS signals received by antennas mounted on airborne platforms undergo multipath from aircraft structures such as wings, stabilizers and engines. The effects of this platform multipath on the GNSS receiver’s code delay and carrier phase measurements can represent a significant source of error in precision GNSS applications. It has been proposed that antenna arrays could reduce the effects of platform multipath. When the array performs beamforming, it is expected that multipath signals will be automatically de-emphasized; however, these claims have not previously been investigated. In this paper, we present the results of a detailed study regarding suppression of aircraft platform multipath using GNSS antenna arrays. Simulation results of an array on a simple aircraft model show that traditional beamforming does not provide sufficient multipath suppression for array aperture sizes commonly used today. It is shown that, even if one adjusts the array pattern to suppress multipath, the trade-off in directpath signal strength is prohibitive for low-elevation angles near aircraft structures. Therefore, we conclude that altering the array pattern is not a practical solution for mitigating aircraft platform multipath effects. Rather, an alternative solution is to adjust the array to coherently combine the multipath with the direct-path signal. This can be performed using space-time adaptive processing (STAP) techniques that have previously been developed, and it is shown that, provided the in-situ antenna array manifold, the effects of platform multipath can be mitigated.
Published in:	Proceedings of the 2010 International Technical Meeting of The Institute of Navigation January 25 - 27, 2010 Catamaran Resort Hotel San Diego, CA
Pages:	646 - 656
Cite this article:	O'Brien, Andrew J., Gupta, Inder J., Reddy, C.J., Werrell, Frederick S., "Space-Time Adaptive Processing for Mitigation of Platform Generated Multipath," Proceedings of the 2010 International Technical Meeting of The Institute of Navigation, San Diego, CA, January 2010, pp. 646-656.
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