Doppler Frequency Geolocation of Uncooperative Radars

Passive geolocation of uncooperative radar emitters remains an important problem in radar electronic warfare. Several location estimation techniques have been investigated in the past. In this paper, we present a passive geolocation technique for radar emitters using Doppler frequency measurements. For uncooperative sources, neither the emitter location, nor its transmitted frequency is known a priori. The relationship between these unknowns and the measured Doppler frequencies is non-linear. In the special case where the moving receiver measures frequencies along a straight path at constant speed, the relationship becomes linear in the Cartesian location coordinates. A simple 1-D discrete search for the transmitted frequency is followed by a least squares (LS) estimator to provide a coarse estimate of the emitter coordinates. This is followed by Newton's algorithm to provide a maximum likelihood (ML) estimation. The simulation results demonstrate that the resulting ML estimator approximately meets the Cramer-Rao lower bound (CRLB).