Use of Anti-Jam Equipment in Location of Interference Sources

Kenneth Falcone

Abstract:	The use of GPS in aircraft applications provides a necessary update for landing systems, but the low power levels used in GPS leave aircraft susceptible to unintentional interference in the GPS frequency bands. Determining the location of unintentional interference sources and removing them is becoming important for both civilian and military aircraft. The focus of the research and development work described in this paper is to use COTS anti-jam hardware instead of expensive custom equipment to perform the direction finding task. In addition to providing the information necessary to determine the direction of arrival of the interference source, the anti-jam equipment will also protect a GPS receiver from the interference. Position information from this GPS receiver can then be used in combination with the direction of arrival information to locate the interference source. Our objective is to use analysis, simulation, and laboratory testing to show that direction finding can be performed using a four element digital adaptive spatial filter. Direction finding performance was measured using simulations to compare square and triangular antenna array geometries, and direction finding algorithms. Direction finding algorithms include: (1) searching for nulls based on the ASF weights, (2) a monopulse technique, and (3) a simplified MUSIC (MUltiple SIgnal Classification) technique. Results show that the ease of implementation as well as performance is determined by the combination of array geometry and algorithm. A triangular antenna geometry works better with weight based techniques, while a simplified version of the MUSIC algorithm is easier to implement on a square array. The results presented in this paper suggest that an angle of arrival accuracy of ±2 degrees with COTS hardware employing these algorithms can be obtained.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	904 - 911
Cite this article:	Falcone, Kenneth, "Use of Anti-Jam Equipment in Location of Interference Sources," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 904-911.
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