Overcoming the Limitations of the Phase Multipath Mitigation Window

D. Bétaille, J. Maenpa, H-J. Euler, P. Cross

Abstract:	Array antennas and antenna electronics have undergone significant improvement in performance, size, weight, power consumption, and affordability. GPS applications have benefited from adaptive array spatial processing in jammer suppression, signal enhancement, and multipath rejection among others. A new development along this line is the recent use of digital beamforming monopulse technique for attitude determination with GPS signals. Monopulse is a mature technique widely used in tracking and surveillance radar. For each angular dimension, a pair of sum and difference beams are formed digitally from individual array element outputs. The ratio of the sum beam over the difference beam provides an angular offset measurement of the incident wavefront off the array boresight. This therefore provides an alternative to the interferometric technique that has so far been used predominantly in GPS attitude determination. A definite advantage of the digital beamforming monopulse technique over the interferometric technique is the ability to incorporate an interference suppression capability. Indeed, the directions of unknown interference sources can be learned adaptively from the array antenna data in which the corresponding nulls are placed in the antenna gain pattern. For monopulse angular measurements, however, nulls have to be placed onto both the sum and difference beams simultaneously, while maintaining the monopulse ratio slope. For this purpose, a constrained adaptive monopulse technique is presented in this paper in conjunction with an adaptive nulling GPS receiver to ensure the proper timing, positioning, and attitude determination in a jamming environment. In this paper, the system concept will be first described with the enabling techniques discussed. The jam suppression and attitude determination performance will then be analyzed and illustrated with computer simulation results.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	2102 - 2111
Cite this article:	Bétaille, D., Maenpa, J., Euler, H-J., Cross, P., "Overcoming the Limitations of the Phase Multipath Mitigation Window," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 2102-2111.
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