Bistatic sonar cross sections and time-frequency signatures of simple targets insonified by an acoustic pulse

Abstract

The area of acoustics is concurrently trying to develop the concept of impulse sonar. Using a time-frequency approach the very broadband echoes generated by a target when such devices are used can show the time evolution of the resonance features that identify the target. This will enhance the target recognition capability of the traditional sonar cross section (SCS). To this end, the bistatic scattering interaction of acoustic pulses of short duration with targets of simple shapes are studied. The targets are solid spheres and spherical shells. To model the output of an impulse sonar, the waveform incident on the target is a short, ultra-wideband pulse that consists of a few sinusoidal cycles within a Blackman window. For each target the bistatic SCS is displayed as a function of frequency and bistatic angle. Analyzing the scattered waveform when the designed short pulse is incident on each target for a few selected bistatic angles gives information of how and how much scattered pulses are affected by the scattering direction, or the relative location of the transmitter and receiver. The methodology developed by us could be used to assess the performance, including the possibility of target recognition, of any impulse sonar system.