The Effect of Reverberation on Active Sonar Performance

This report investigates the performance of an active sonar, which is limited by reverberation, although noise and limitations due to both noise and reverberation are also discussed. If the transmitted pulse is narrowband, the difference between the frequencies scattered by the target and the reverberation due to their (hopefully) different motion relative to the sonar is used to reduce the effect of reverberation. If the transmitted pulse is broadband, the ability of the processor to decrease the response to reverberation emanating from scatterers whose radial distance to the sonar is different from the radial distance to the target is used to reduce the effect of the reverberation. In either case, the improvement in performance against reverberation due to the processing is calculated using various assumptions on the nature of the reverberation the processing. The effect on the results of varying many of these assumptions is also investigated. The results may be used to investigate under what circumstances a sonar is limited by noise only, by reverberation only or by both. In any case, the performance of the sonar given the average signal power, average reverberation power and noise spectrum level and other quantities related to the assumptions made may be estimated.