Two Stage Beamformer for GNSS Receiver Antenna Arrays

Ying Chieh (Jay) Chuang and Inder J. Gupta

Abstract:	A new approach to suppress strong interference signals in the first stage of two stage adaptive antenna systems is presented. In two stage adaptive antenna systems, interference suppression is carried out in the first stage followed by beamforming in the second stage. The current two stage adaptive systems use subspace orthogonal projection for the suppression of the interfering signals. The performance of these systems depends on the appropriate threshold selection. Also, as will be shown in this paper, for strong wideband interfering signals these systems do not lead to optimum performance. The proposed approach carries out simple power minimization in the first stage. Power minimization is carried out by selecting one of the antenna elements as the reference (weight fixed to be unity). Multiple outputs are generated by selecting various antenna elements as the reference element. These multiple outputs are combined in the second stage to maximize carrier to noise ratio (C/N0). It is shown that the proposed approach is free of all the problems associated with the current state-of-the-art two stage adaptive systems. Also, if desired, one can apply Space-Time Adaptive Processing (STAP) in the first stage to increase interference suppression capability in the first stage followed by space-only beamforming in the second stage. This leads to efficient implementation in the presence of multiple weak desired signals in that individual beams can be steered along the various desired signals without applying STAP for each incident desired signal. Results are presented to demonstrate that with the proposed approach (STAP followed by space only beamforming) also leads to near-optimal C/N0 (obtained from a single stage STAP based adaptive antenna arrays for each incident desired signal).
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	2277 - 2285
Cite this article:	Chuang, Ying Chieh (Jay), Gupta, Inder J., "Two Stage Beamformer for GNSS Receiver Antenna Arrays," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 2277-2285.
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