Adaptive array processing for wideband nulling in GPS systems

Military GPS systems must operate in the presence of hostile jamming. Vast power differences between nearby jammers and distant satellite sources makes the spread-spectrum gain of the GPS signal inadequate for anti-jamming (A/J) protection. Adaptive antenna nulling systems have been proposed for additional A/J protection, but current systems, such as the AE-1, fail to address the near-field multipath associated with arrays mounted on a real aircraft. We examine the design of a space-time-adaptive (STAP) beamformer for GPS nulling, including the effects the STAP processor has on the GPS position calculation via the time-difference-of-arrival (TDOA) measurements from different satellites. Two novel architectures are proposed, and their performance quantified via a simulation driven by measurements taken on a 1/4 scale F-16.