Range estimation of a broadband moving source using the cross-correlated field

The field differencing method, based on the cross-correlation of pressure fields at adjacent ranges, has been proposed as a model-independent approach for passive source localization. While this method has been widely studied for narrowband sources, its application to broadband signals has received comparatively less attention. Shallow-water environments present greater multipath complexity compared to deep water, leading to distortions in the cross-correlated field that produce multiple ambiguous velocity estimates that degrade range estimation accuracy. This study proposes a method to accurately estimate the source range by applying a two-dimensional Fourier transform (2-D-FT) to the cross-correlated field. The approach enhances the separation of source-related information from multipath-induced ambiguity, particularly in shallow-water environments where path separability is limited. The method is validated with experimental data from the SAVEX15 experiment. Results confirm that the proposed 2-D-FT-based technique enables reliable extraction of the true velocity of a broadband moving source using a single hydrophone. [Work supported by the Korea Research Institute for Defense Technology Planning and Advancement (KRIT)—grant funded by the Korean government (DAPA, Defense Acquisition Program Administration) (No. KRIT-CT-23-026, Integrated Underwater Surveillance Research Center for Adapting Future Technologies, 2025.]