Space-time adaptive processing with sum and multiple difference beams for airborne radars

This paper describes some new results on a signal processing approach for airborne surveillance radars. This is a spacetime adaptive processing (STAP) technique that simultaneously processes temporal data from sum and difference (Sigma Delta) beams to suppress clutter returns. The approach also includes employing spatial adaptive pre-suppression (SAPS) to suppress wideband noise jammers in a two-stage processor. Previous work on Sigma Delta-STAP with SAPS has concentrated on the case with one difference beam. This has shown to be effective in suppressing strong clutter and jamming when the number of wideband noise jammers does not exceed the number of auxiliary channels used for SAPS. Additional difference beams, which are orthogonal to these two beams and to each other, can be available on most radar systems. This work analyzes the performance of the Sigma Delta-STAP with SAPS processor, which utilizes these additional difference beams. It is shown to be effective with either one or two additional beams when the number of jammers exceeds the number of auxiliary channels by one. This occurs even though the jammers are in the nulls of the additional beams. Additional results show that the performance can improve when the jammers move from the nulls and that the clutter entering through the auxiliary has little impact.