Mismatched Filter Effects on Synthetic Aperture Radar Image Quality Metrics

Detection of targets across a wide dynamic range is an enduring challenge in radar. This work formulates a modified least-squares mismatched filter that greatly reduces these sidelobes in order to enable the detection of small radar cross section targets in the presence of considerably larger scatterers, increasing the dynamic range. Unlike previous mismatched filters, the proposed filter is applicable to noisy, oversampled signals with no requirements on signal structure. Range profiles and images are presented to demonstrate the superior sidelobe suppression of the modified least-squares mismatched filter in comparison to the commonly employed matched filter. Various weighting vectors are introduced to further increase sidelobe suppression for particular scene geometries. The modified mismatched filter created with the addition of a noise compensation term is shown to have superior sidelobe suppression to that of the matched filter across all signal-to-noise ratios, coming at the relatively low expense of a small degree of mainlobe energy loss and widening, as well as increased processing time