SIFTER: Signal inversion for target extraction and registration

Abstract

Signal inversion for target extraction and registration (SIFTER) is a technique for enhanced radar target detection and coordinate registration (CR). The technique is currently being developed for over‐the‐horizon radar (OTHR). The power received by a radar as a function of radar coordinates and Doppler shift may be expressed as an integral operator applied to the field of backscatter cross section (FBC) per unit area of the illuminated region. The FBC is a function of the geographic position and the velocity vector of the scattering point. The kernel of the integral operator is treated as a known function that is determined by the model of the propagation channel, antenna patterns, and the radar signal processing parameters. The relationship between the FBC and the received power is treated as an integral equation to be resolved with respect to the FBC. This inversion is accomplished using techniques for ill‐posed problems. The obtained FBC is subsequently analyzed for peaks. The location of a peak provides an estimate for actual ground coordinates and velocity vector of the target. Gain in sensitivity and CR is achieved by introducing a continuity equation, which evolves the FBC between radar revisit cycles. The evolved FBC is corrected using data from each subsequent revisit. Two versions of the SIFTER algorithm are presented. One is based on Tikhonov’s method, and the other is based on the Kalman filter method. SIFTER concepts and performance are demonstrated using modeled data.