Techniques for sonar target identification

We describe bistatic and mostly monostatic techniques that are useful for target classification by means of active sonar. The echoes returned by any submerged elastic body, exemplified here by a wolfram carbide (WC) sphere, contain features caused by the poles of the scattering amplitude of the problem. We have found these poles and shown that they naturally split into two large sets from which one can separately extract shape or material composition information. The composition information seems easier to determine than details about the shape. Together these sets of poles unambiguously characterize any scatterer.