On Joint Active-Passive Recognition of Underwater Low-Speed Small Targets Using Target Strength and Source Level

For improving the recognition performance of underwater low-speed small targets, we propose the joint active-passive recognition method of underwater low-speed small targets using the target strength (TS) and the source level (SL). In the considered method, TS and SL are together regarded as a joint active-passive feature. Specifically, the extraction methods of TS and SL are given according to the processing procedures of the active and the passive sonar. Two forms of application of the considered method are given. For the first form, the joint active-passive feature is directly used to recognize underwater low-speed small targets. For the second form, the joint active-passive feature is fused with other traditional features to achieve a better recognition performance. The results indicate that the joint active-passive feature itself has a good distinguishability even at a relatively low signal-to-noise ratio (SNR). Due to the good distinguishability, the recognition performance has been significantly improved by fusing the joint active-passive feature with other traditional features. The considered method can reliably recognize underwater low-speed small targets despite the adverse impacts of their weak echoes and radiated noise, which provides a potential way to recognize underwater low-speed small targets located at long ranges.