Abstract:

Several approaches to passive broadband matched-field processing have been proposed. In most cases, an incoherent average over a narrow band is quite successful in driving down unwanted sidelobes. The ability of coherent broadband techniques to out perform this simple approach may require additional phase information about the source that, in general, may not be available. In this paper, a fully coherent method that can out perform an incoherent average is derived, although its practical application is problematic. In other words, the simple incoherent average may be the most efficient approach. These ideas are demonstrated using data from the SWellEx-96 experiment. Given the environmental conditions under which these data were taken, the new coherent approach has some physical advantages over other broadband methods since it more efficiently uses variations of range dependence exhibited by the different frequency components of the signal. The net result is that the range, depth, and azimuth ambiguities have comparable spatial extent.