Constrained Optimization for Joint Estimation of Channel Biases and Angles of Arrival for Small GPS Antenna Arrays

Chun Yang and David M. Lin

Abstract:	Array antennas have been applied to GPS for signal enhancement, multipath mitigation, jamming suppression, interference location, and attitude determination among others. The mismatches among multiple antenna/receiver channels have been a problem of less importance to those GPS applications that utilize power minimization (e.g., jammer suppression) or maximization (e.g., signal enhancement). However, they are more critical to carrier phase-related applications and particularly for digital beamforming-based applications. Array calibration is usually conducted in an anechoic chamber or in an outdoor test facility with specialized equipment. However, such an off-line once-for-all calibration may not suffice and an on-line frequent calibration thus becomes necessary. It is therefore highly desired to be able to calibrate the array antennas while making use of the same signal for the intended applications. This naturally leads to the problem of joint calibration will be first reviewed. The focus will then be placed on the phase-domain approach, which can be formulated in the array frame, the local frame, and the ECEF frame. Of particular interest in this paper is the constrained optimization formulated in the ECEF frame for the joint estimation of channel biases and GPS signal’s AOA. A singular value decomposition (SVD)- based solution is obtained for this nonlinear least-squares problem. Field tests were conducted with real GPS signals and the processing results of the joint channel bias and AOA estimation will be presented to show the performance of the present approach. The use of the calibrated array in digital beamforming monopulse for GPS attitude determination will also be outlined.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	548 - 559
Cite this article:	Yang, Chun, Lin, David M., "Constrained Optimization for Joint Estimation of Channel Biases and Angles of Arrival for Small GPS Antenna Arrays," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 548-559.
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