BROAD-BAND MATCHED-FIELD PROCESSING

Acoustic energy in the ocean propagates from a source to an array of s ensors via multiple pathways. Conventional time-delay-and-sum beamform ing does not utilize energy contained in the multipath arrivals. In th is paper, a generalized beamformer is presented which coherently recom bines the multipaths to provide enhanced detectability of broadband tr ansients as well as range and depth localization of the source. Modeli ng of the wave field at the array due to a broadband source is accompl ished with a normal mode model using 1.0-Hz increments across the 1- t o 100-Hz band. These results are combined to yield the impulse respons e from a specified source location to each of the array elements. The set of calculated impulse responses is used in the generalized beamfor mer to coherently recombine energy arriving along multipaths that exis t from that source range and depth to the array. The location of a sou rce is determined by examining the beamformer output at a number of ca ndidate range/depth cells; a peak in the output gives the location of the source. Experimental data, consisting of multiple arrivals at a hy drophone array from an explosive source at mid-depth in 2800 m of wate r, are processed using the generalized-beamformer.