Echo Waveform Prediction Algorithm for a Target in the Shallow Water Wave-Guide

The prediction of the echo waveform from a target submerged in the shallow water wave-guide is considered. Target echo is seriously affected by the interfaces of the wave-guide especially in shallow water. This is unfavorable to the active detecting. It is of great significance both for theory and military affairs to build an accurate model for predicting the target echo in shallow water. Based on Ingenio´s normal mode method, an algorithm for calculating target echo waveform is presented. By decomposing each mode into up-going wave and down-going wave, the target scattering field is expressed in terms of normal modes and plane-wave scattering functions. Then the received echo waveform can be written as a convolution of the derived target scattering field expression and the transmitting signal. Sample numerical calculation is given for a rigid sphere object in a typical case of shallow water environment. Simulation result shows that the multi-way phenomena and coupling of normal modes caused by wave-guide interface can lead to the superposition of normal modes, which lead to the obvious difference between echo waveform in the free space and that in a shallow water wave-guide.