Spectral estimation of migrating targets in wideband radar
Low pulse repetition frequency radars aimed at detecting moving targets are faced with the problem of blind velocities, since Doppler ambiguous targets have to compete with clutter and possibly the sidelobes of strong targets. On the other hand, wideband radars offer high range resolution, and hence fast moving targets, in contrast to clutter or non moving targets, are likely to migrate during the coherent processing interval. Moreover, range migration is different between two Doppler ambiguous targets. These properties can be used to remove Doppler ambiguities and detect targets which fall in the clutter or targets sidelobes. In this paper, we derive new spectral estimators (and detectors accordingly) that can take into account range migration to improve detectability of Doppler ambiguous targets. The new techniques are based on an extension of Capon method to the wideband case, and take into account the non-stationarity of the covariance matrix of the targets. Numerical simulations show that the new estimators significantly reduce clutter and target sidelobes compared to previous proposed schemes.