On the use of energy concentrating beamformers and filters for detection of wideband angularly spread signals

Slepian described the filter that maximizes the in- band energy while minimizing the out-of-band energy. Claus, Kadota and Romain applied Slepian´s results to spatially filter out angularly distributed interference. An important benefit of this approach is that both coherent and incoherent interference can be accommodated. The approach discussed here extends their work by defining matrix filters capable of filtering for a fixed angular sector, [thetas₁,thetas₂], over a range of frequencies. A detector of scattered broadband signals arriving within [thetas₁,thetas₂] is then specified. The detector is shown to possess important invariances and approximate optimality properties related to Scharf´s Constant False Alarm Rate (CFAR) matched subspace detector.