Wideband direction finding via shielded gradient beamspace techniques
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Monopulse techniques have been used for over 50 years in the radar community to estimate the direction of arrival (DOA) of incoming echoes. In recent years, a variant of the monopulse technique has been developed, termed the shielded gradient technique which allows DOA estimation for signals of arbitrary bandwidth. In its simplest from, the technique involves the formation of two beam outputs which may be combined to produce a single DOA estimate. The technique may be extended to generate multiple beam outputs, any pair of which may be used for DOA estimation. These multiple beam outputs may also be combined using a model similar to the signal subspace model underlying the narrowband MUSIC algorithm, in order to estimate the DOA of multiple echoes arriving simultaneously. The work presented here describes the shielded gradient beamspace model, and develops wideband DOA estimation algorithms analogous to the narrowband MUSIC, root-MUSIC, and ESPRIT algorithms. The performance of these newalgorithms is studied through simulation and application to measured sonar data, and they are compared to existing wideband DOA estimation algorithms.