Modeling of bistatic scattering from an underwater non-penetrable target using a Kirchhoff approximation method

Abstract

A numerical triangulation and transformation into the time domain of a Kirchhoff approximation (KA) method is proposed for the modeling of bistatic scattering from an underwater non-penetrable target. The time domain solution in this approximation can be split up into two parts: the solution of reflected field, contributing around the specular direction, and the solution of shadow radiation, contributing around the forward direction. An average solution in the time domain satisfying the reciprocity principle is presented. The solution is expressed in terms of non-singular functions. The proposed method is validated against a normal mode method for bistatic scattering from a rigid sphere. Moreover, the reflected and shadow highlights on the surface of the sphere are shown to verify the integration surface of the reflected field and shadow radiation. It is also tested against a finite element method and an experiment involving a scaled Benchmark Target Strength Simulation Submarine model. The time-angle bistatic spectra for the model are evaluated by the direct and transformed average solutions of KA, and the former accelerates its speed of calculation. The results are good, and show that this method can be used to predict the bistatic scattered field of a non-penetrable target.

Keywords

• Kirchhoff approximation
• Bistatic scattering
• Time domain
• Reciprocity
• Experiment