Broadband adaptive matched field processing with modal filtering

Abstract

This paper will demonstrate 3D localization of a moving, broadband source in a shallow water channel using adaptive matched field processing (AMFP) with modal filtering. The adaptation is desirable to mitigate the high sidelobes of the conventional processor, but it also introduces the requirement for long observation times, which can be difficult to satisfy for moving sources. Rank reduction can be achieved through modal preprocessing by exploiting the sparsity of propagating modes. In addition, the modal decomposition provides a mechanism for filtering the signatures of surface interferers from those of a submerged source. Results will be presented that demonstrate rejection of surface interference as well as quantifying the relationship between localization accuracy and the size of the modal subspace. The acoustic data was obtained during the Santa Barbara Channel Experiment (SBCX) which employed a 150-hydrophone volumetric array consisting of five vertical line arrays (VLAs) instrumented for element localization. The VLAs fully spanned the 209-m water column and allowed accurate modal decomposition. The MFP results will be presented for exercises involving a research vessel, the Acoustic Explorer (AX), towing an acoustic source. The results of broadband AMFP show accurate localization of both the towed source and towship.