A Low Cost Variable Butler Matrix Design for Controlled Reception Pattern Antenna System Testing

Larry D. Smith and Charles D. Ormsby

Abstract:	Current military technologies use controlled reception pattern antenna (CRPA) systems as a primary means for Global Positioning System (GPS) interference suppression. Considering this, a method must be devised for testing the end-to-end system including the multi-element CRPA, the antenna electronics unit, and the GPS receiver. In the past this testing has relied on field methods. The high cost and risk associated with field testing drives a need for test organizations to possess a capability to test CRPA systems in a simulation laboratory environment. As a result, the 746 th Test Squadron, Holloman AFB, NM has designed a low cost Variable Butler Matrix (VBM) for use in end-to-end testing of GPS systems utilizing a CRPA. The VBM is designed to provide jamming/interference signals to the antenna electronics unit, modeling each element of the CRPA. The design incorporates software controlled variable phase shifters and variable attenuators. The software accounts for geometry between the jammers and the CRPA to set the variable phase shifters and attenuators to produce appropriate interference signals for each CRPA element. The design is flexible enough to allow for easy modification to test a CRPA-based system with any number of antenna elements. This paper presents the design of the VBM including design assumptions, prototype testing performed and initial results. Additionally, the paper presents a concept for using the VBM in conjunction with a multi-output GPS simulator for full dynamic GPS jamming simulation test capability, and a brief cost analysis for building a VBM.
Published in:	Proceedings of the 2000 National Technical Meeting of The Institute of Navigation January 26 - 28, 2000 Pacific Hotel Disneyland Anaheim, CA
Pages:	679 - 683
Cite this article:	Smith, Larry D., Ormsby, Charles D., "A Low Cost Variable Butler Matrix Design for Controlled Reception Pattern Antenna System Testing," Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2000, pp. 679-683.
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