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26 November 2001 Vulnerability of recent GPS adaptive antenna processing (and all STAP/SLC) to statistically nonstationary jammer threats
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We alert the reader here to an apparent vulnerability in recent adaptive antenna processing that claims increased GPS jammer resistance via use of lucrative new approaches to adaptive beamforming and/or null-steering, but unfortunately, presumes only simplistic unsophisticated wideband barrage WGN jammers as threats. When jammers are less cooperative by being statistically non-stationary (e.g., by exhibiting time-varying means or biases, by being synchronized blinking jammer pairs, or by varying the total power output with time), then statistics on the jammers can apparently no longer be successfully extracted fro the time-averages (even in post-processing mode using long blocks of received data that was saved) because ergodicity of the underlying intermediate covariance estimate is lost. This unpleasant situation arises or exists for abstracted, idealized STAP or SLC algorithms making use of the, by now, familiar fundamental STAP-related equation: R-1υ, where this necessary intermediate covariance estimate R=R1+R2+R3 has the three indicated constituent components due to thermal/environmental noise, clutter, and jammers, respectively. Without an ability to accurately estimate R3, the appropriate jammer nullings apparently can no longer be activated successfully. Such systems susceptible to jamming can be revealed by in-situ tests with simple equipment. Topics herein include updates to PRN generation, updates to statistical tests in general and to CLT in particular and all three updates being new to most engineers.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Thomas Henderson Kerr III "Vulnerability of recent GPS adaptive antenna processing (and all STAP/SLC) to statistically nonstationary jammer threats", Proc. SPIE 4473, Signal and Data Processing of Small Targets 2001, (26 November 2001);

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