Acoustical imaging of underwater objects using the bistatic ramp response signals

Abstract

Underwater acoustical imaging techniques and the inverse analysis of acoustic scattering problems have now found many important engineering applications. Most of the inverse techniques use the backscattering signals in the acoustical far field to retrieve the shape and size information of an underwater object, such as the ramp response technique. This paper addresses a modified ramp response technique, which could be used to reconstruct the 3D image of an object for the bistatic case. This technique shows that the bistatic ramp response is proportional to the profile function of an underwater object based on the small bistatic angle assumption. The numerical examples demonstrate that the bistatic ramp response technique is still valid to obtain an excellent profile function even for the bistatic case with a fairly large bistatic angle. The numerical results also suggest that, if the object is of a more slender shape, then its bistatic ramp response will be closer to the exact profile function for a larger bistatic angle. Finally, a 3D image of a spheroid with a/b = 5 has been reconstructed using the bistatic ramp response signals in three incident directions. This bistatic ramp response technique allows us to reconstruct the 3D image of an underwater object with only one receiver.