Asymptotic maximum likelihood estimation of multiple radar targets

This work deals with the problem of jointly estimating complex amplitudes, directions of arrival (DOAs) and Doppler frequencies of multiple radar targets present in the same range-azimuth resolution cell. We derive the conditional maximum likelihood (CML) and the asymptotic (large sample size) ML (AML) estimators. We propose as well an efficient way to implement the AML algorithm based on a RELAXation method. RELAX allows us to decouple the problem of jointly estimating the parameters of the signal components into a sequence of simpler problems, in which we estimate separately and iteratively the parameters of each component. Performance of the AML estimator is investigated through Monte Carlo simulation and compared with the Cramer-Rao lower bound in the case of target model mismatch. The AML estimator has been derived, in fact, in the case of deterministic amplitude, but here, the performance of the estimator is evaluated in the case of random target amplitudes.