Echo pattern formation in a high-resolution multistatic sonar

More emphasis is falling on sonar systems to display the data received from the underwater environment in a form which enables the observer to classify the echo patterns as being due to a particular target shape. In high resolution monostatic sonar systems, where the resolution cell is smaller than the target dimensions, difficulties arise because the echo patterns formed tend to be specular in nature and show only the acoustic highlights of the target. In this thesis, echo formation is examined in terms of the angular distribution of reflected energy in the medium. The way in which echoes are formed results in a less than optimum display in terms of the number of samples of the target outline. An increase in the number of resolution cells displaying the target outline and an improvement in target shape portrayal can be obtained by using a multi static sonar system, but it is shown that this improvement is dependent on a number of factors. An experimental, high-resolution multistatic sonar system is described which was used to verify and measure the improvement in target shape portrayal. Selected echo patterns obtained with this equipment are shown and the measured performance compared with the predicted performance. An empirical equation, which was derived from the measurements, relates the improvement in the displayed echo patterns to the number of bistatic receivers employed.