Bistatic detection and imaging of proud targets in shallow water using coherent space‐time‐frequency processing.

Abstract

An ongoing challenge for underwater sonar systems is to discriminate a man made target (typically having an elastic shell) from surrounding clutter returns especially in the presence of multipath. Network of autonomous systems of unmanned vehicles provides a practical means for bistatic measurements and thus potentially bistatic enhancement for target detection. One popular technique for automatic target detection is synthetic aperture imaging. An aspect that complicates this technique is the evolutional, time dependent aspect of the bistatic echo spectrum from elastic shells especially for the acoustic guided waves echo components at low to midfrequency. To this end, time‐frequency analysis, and, in particular, Wigner‐Ville analysis have been shown to provide a robust processing tool for interpreting the evolutional time dependent aspect of the scattered acoustic wave field especially around the midfrequency enhancement. Time‐frequency methods will be used to enhance the sonar images created from monostatic or bistatic low‐frequency measurements. The proposed approach will be tested using numerical simulations and experimental at‐sea data. [Work supported by the ONR.]