Subspace Rejection for Matching Pursuit in the Presence of Unresolved Targets

Unresolved scatterers (separated by less than a 3-dB matched filter main lobe width) are known to degrade the matching pursuit performances in radar: It tends to generate spurious detection or miss weaker targets, hidden in strong sidelobes. In this paper, we propose a new matching pursuit algorithm performing a subspace radar resolution cell rejection. The philosophy is the following: As it is usually not possible to distinguish several unresolved scatterers, we do not try to distinguish them, but when a scatterer is detected, then every contribution in the corresponding resolution cell should be cleaned. For that, the continuous cell interval is approximated by a subspace and the corresponding orthogonal projector is build. The projector basis is chosen so that it minimizes the projection residue inside the interval and a method is proposed to select its dimension according to the rejected target SNR. We show that it enables to control the sidelobe level after rejection (orthogonal projection) so that the sidelobe detection probability can be maintained low. It allows matching pursuit to work well even if the target parameter distribution differs from a delta Dirac distribution inside the matched filter resolution cell.