ACTIVE SONAR WAVEFORM DESIGN MATCHED TO A SPHERICAL TARGET AND AN UNDERSEA CHANNEL

Abstract

Traditionally, active sonar systems employ an enveloped-continuous wave (CW) or linear-frequency modulated (LFM) acoustic pulse that is transmitted into a lossy channel to interact with the target and environment where the received energy is used to determine if target detection occurs. Many frequency components of a wideband pulse are strongly attenuated due to the effects of the channel and target. In this work, a full-wave solution is used to model a complex channel frequency response. A realistic resonant sphere is used to develop the target response. To exploit the channel-target frequency response, two waveform design techniques are used: signal-to-noise ratio (SNR)-based and information-based methods. Both techniques concentrate the transmit energy in the frequency bands where the target echo is large. The advantage of the eigenwaveform (SNR-based) and the mutual-information (information-based) waveform over the wideband acoustic waveform is the increase in detection probability.