Passive target motion analysis using multipath differential time-delay and differential Doppler shifts

Target motion analysis (TMA) is a basic function in passive sonar, generally using bearings only or bearings and frequency measurements. But due to the use of arrays whose aperture are practically negligible considering the target range, and even if the platform moves itself to yield a "synthetic array", the classical TMA methods take minutes to give an acceptable solution. Hence, this paper presents an enhanced TMA estimator using jointly the bearings and multipath parameters: the differential time-delays and their Doppler shifts. The Cramer-Rao lower bounds are studied for two cases of sound propagation: a constant celerity profile and a bilinear one. They both exhibit advantages in terms of a shorter time to get a given precision of the target parameters: its range, depth, and speed vector.