Electromagnetic matched-field processing for target height finding with over-the-horizon radar

The refraction of over-the-horizon skywave radar signals by the ionosphere facilitates wide-area surveillance. While current systems measure target ground range, azimuth, and velocity they do not estimate target altitude, which is important for classi cation purposes. In this paper, a method akin to matchedeld processing in underwater acoustics is proposed for target heightnding. The approach exploits the delay-Doppler di erences between direct and surface-re ected multipath returns from the target. In particular, the coherent sum of these multipath returns can be matched in the complex delay-Doppler space for a single dwell to estimate target altitude, ground range, and radial velocity. In this paper, a maximum likelihood estimate (MLE) of these target coordinates is developed without requiring knowledge of the target backscatter reection coe cients. The performance of the MLE is evaluated through simulation for an uncertain quasi-parabolic ionosphere and compared to the Cramer-Rao lower bound (CRLB).