Mitigation of Adaptive Antenna-Induced Biases in GNSS Receivers

Andrey J. O'Brien and Inder J. Gupta

Abstract:	Antenna arrays equipped with adaptive processing allow global navigation satellite system (GNSS) receivers to operate in environments with harsh interference. However, since these antennas utilize spatial and temporal filters, they have the potential to introduce significant bias errors into the delay and carrier phase measurements made by GNSS receivers. For precision navigation applications, these biases must be mitigated. However, since the antenna pattern is adaptive, the biases will vary based on the incident signal scenario, and it follows that these biases must be predicted at runtime in order to correct for them. This paper describes a novel bias prediction and correction technique in which additional logic is added to the receiver which provides runtime compensations for these biases. The technique is general in the sense that it can be applied to a wide variety of adaptive antennas and tracking loop implementations. It utilizes a computationally efficient bias prediction equation that incorporates the stored antenna data, the adaptive filter weights, and the receiver discriminator function. The bias correction via additional receiver logic is applied in either the navigation processor or in the tracking loop. Simulations demonstrate centimeter-level bias correction accuracy for a variety of GPS signals using an adaptive antenna in environments both with and without interference.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	177 - 185
Cite this article:	O'Brien, Andrey J., Gupta, Inder J., "Mitigation of Adaptive Antenna-Induced Biases in GNSS Receivers," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 177-185.
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