On Joint Active-Passive Sonar Detection Performance of Underwater Long-Range Low-Speed Small Target

We discuss the feasibility of the joint active-passive sonar detection method of underwater low-speed small targets located at long ranges. Specifically, the transmission loss, the reverberation level, and the noise level related to the joint active-passive detection method are modeled and calculated. The relationship between the figure of merit and the transmission loss is used to analyze the performance of the joint active-passive detection method of underwater low-speed small targets. For obtaining a long detection range, we mainly consider the working frequency of both the active and passive sonars to be much lower than traditional small target detection sonars. The active sonar is set to be worked at a frequency band not higher than 40kHz. Meanwhile, the passive sonar is supposed to work at a frequency band not higher than 1 kHz. The factors that affect the performance of the joint active-passive detection method are analyzed in detail. The results indicate that the considered joint active-passive detection method may have a detection range of more than 2000m in a relatively good underwater acoustic environment, which provides a potential way to significantly increase the working range of the underwater detection sonar system.