Multistatic broadband sonar (MSBA): Principles and measurements

Abstract

Shallow-water (SW) coastal areas with depths between 40 and 200 m with bottom sediment layers (<25 m) formed by deposition and sea level variations are known to have frequency-dependent sound transmission and reverberation characteristics especially under the adverse conditions of downward refraction. Coastal ocean-dynamics complicates these environments by coupling the surface, volume, and bottom characteristics and can dramatically affect the temporal and spatial coherency of the signal. The broad-band signal and processing smear these frequency-dependent effects as well as signal excess fluctuations. Furthermore, recent experiments have shown that despite these complexities, explosive sources coupled with directional receivers have the capability to detect, localize, and classify sonar targets in the presence of clutter most likely due to bottom features, fish schools, and sunken objects. Active search sonar operations in SW are typically reverberation limited and experiments have shown that MSBA sonar when employed in bistatic source-receiver geometries can be effective. This paper reviews the principles underlying the MSBA sonar in shallow water and presents results from several experiments that demonstrated the utility of MSBA. The results are discussed in terms of a classical sonar model with basic statistical considerations to define limits on the detection, classification, and localization with multiple receivers.