Robust Mismatched Filter for Off-Grid Target

In this letter, we consider the robustness of the mismatched filter in presence of off-grid target. Since for an off-grid target, the received sampled signal differs from the on-grid signal, the mismatched filter as optimized in the literature is not optimal anymore, and in particular may present a deteriorated sidelobe level. We propose here a general optimization program enabling to get an optimal mismatched filter-with respect to the integrated sidelobe level (ISL)-within the resolution cell. We detail then the resulting solution in two particular radar cases, namely a Doppler steering vector and a linear chirp signal. In both cases, the proposed solution involves the discrete prolate spheroidal sequences. Simulation results show that this solution indeed provides the best ISL in the resolution cell.