An efficient high‐resolution method of source localization processing in mode space

The matched‐field processing proposed by Bucker [J. Acoust. Soc. Am. 59, 368–373 (1976)] can be performed in phone space (matching the total field received by each phone of an array) or in mode space (matching a subset of modes resolved from the array data). For a stratified waveguide, processing in mode space can be more efficient and more robust. However, the method processing in mode space previously proposed as the ‘‘modal beamforming’’ method has the drawback of less inherent resolution. In this paper, the high‐resolution modal matching (HRMM) method has been proposed instead of the ‘‘modal beamforming’’ technique. One of the advantages of the HRMM method is that high resolution can be achieved even when only a few modes are available; for depth estimation especially, the first two modes are good enough. Some numerical examples are presented.