Flight Trials of a Novel Dual-Patch Anti-Jam GPS Antenna

F.N. Bauregger, T. Walter, D. Akos, P. Enge

Abstract:	This paper presents .ight test results of a novel dualpatch recon.gurable anti-jam GPS antenna (DPRA) for airborne applications. The anti-jam antenna employs two modes of operation. A wide-angle mode is selected for GPS navigation when no radio frequency interference (RFI) is present. If interference is detected, the antenna may be placed in anti-jam mode. The anti-jam mode rejects ground-based RFI, while enhancing signals from high elevation satellites. Since the anti-jam mode reduces the signal strengths of low elevation satellites, use of the wide-angle mode is recommended when no interference is present. Mode switching is accomplished by means of a DC control signal on the feedline. This antenna does not require an external processing unit, typically used with adaptive anti-jam arrays. Switching may be performed manually or automatically by a smart GPS receiver that is able to detect the presence of RFI. This antenna is only slightly larger than conventional aviation GPS patch antennas, and may replace existing antennas with no modi.cation to the fuselage. The dual-patch anti-jam antenna has been built and tested in .ight. To simulate a ground based jamming signal, a pulsed pseudolite transmitter was placed at the approach end of the runway. The test aircraft, a Cessna Caravan, .ew numerous low approaches over the pseudolite. The signal strengths of the pseudolite and all visible GPS satellites were recorded during these approaches. With the anti-jam mode selected, the antenna suppressed the ground-based simulated jammer by 15 dB, compared to the wide-angle mode. The .ight test data also showed that the anti-jam mode improves the J/S ratio by 20 dB for high elevation satellites.
Published in:	Proceedings of the 2003 National Technical Meeting of The Institute of Navigation January 22 - 24, 2003 Disneyland Paradise Pier Hotel Anaheim, CA
Pages:	794 - 799
Cite this article:	Bauregger, F.N., Walter, T., Akos, D., Enge, P., "Flight Trials of a Novel Dual-Patch Anti-Jam GPS Antenna," Proceedings of the 2003 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2003, pp. 794-799.
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