GPS Anti- Jam Enhancement Techniques

Joseph Przyjemski, Edmund Balboni, and John Dowdle

Abstract:	Two Electronic Counter Countermeasures (ECCM) developed to improve Global Positioning System anti-jam performance are Amplitude Domain Processing and Extended Range Adaptive Tracking. Both signal processing techniques can be efficiently implemented in low cost VLSI. Their combination together can extend the GPS receiver jamming threshold from 54dB to as high as 120dB J/S under tactical-strike aircraft scenarios. Amplitude Domain Processing (ADP) is a nonlinear precorrelation processing technique that exploits the statistical properties of non-Gaussian jammers to achieve a signal-to-interference ratio improvement. ADP is fully adaptive in that it responds to changing jamming conditions by direct measurement of the jamming statistics. ADP performance has been demonstrated in hardware against a number of jamming formats. As much as 45dB of improvement in receiver tracking threshold has been measured. The second technique, Extended Range Adaptive Tracking, is a correlation processor that adapts to changing jamming and dynamic conditions to provide optimal GPS code tracking. Extended Range Adaptive Tracking optimally adjusts the code tracking loop bandwidth and multiple correlator weights to minimize the receiver error in response to instantaneous jamming and dynamic conditions. Analysis and simulation have shown that Extended Range Adaptive Tracking can extend the receiver tracking threshold by an additional 26dB under conditions of high user dynamics and jamming associated with strike aircraft scenarios. Improvement is independent of the jamming waveform and, consequently, applies to a broadband Gaussian jammer. This paper will present detailed description and performance data for both a time domain and frequency domain implementation of ADP and for aided, Extended Range-Adaptive Tracking.
Published in:	Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993) June 21 - 23, 1993 Royal Sonesta Hotel Cambridge, MA
Pages:	41 - 50
Cite this article:	Przyjemski, Joseph, Balboni, Edmund, Dowdle, John, "GPS Anti- Jam Enhancement Techniques," Proceedings of the 49th Annual Meeting of The Institute of Navigation (1993), Cambridge, MA, June 1993, pp. 41-50.
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