High Resolution Sonar Simulation Techniques

Abstract

A number of factors influence the performance of coherent sonar systems designed to achieve a high degree of spatial resolution for location of small objects on the ocean bottom. First order factors include sonar beamwidth, sidelobe levels, temporal bandwidth, and display dynamic range. Factors over which the sonar designer has no control are target roughness, level of backscatter from the bottom, and refractive effects of the medium. For the computer simulations described in this paper, first order sonar parameters are varied in order to establish their relative importance in the detection of targets. The simulation is accomplished by assigning complex reflectivity values to a two-dimensional array of points representing the bottom and target. The points are weighted according to the directional response of a specified projector, and the complex distribution at the receiving aperture is computed by discrete summations. Receiver array characteristics such as number of elements, length, and shading coefficients and bandwidth are imposed upon the computed aperture distribution and a Fourier Transform operation is performed on the resultant. The magnitude of the transformed distribution represents the sonar image of the bottom and target degraded from the originally assigned values of reflectivity by the characteristics of the sonar. In this paper, a description of the simulation model will be given.