Distributed broadband phased-MIMO sonar for detection of small targets in shallow water environments

A joint processing framework is proposed for a distributed-phased multiple-input–multiple-output (phased-MIMO) sonar for detection of a small target. A transmit–receive-interactive strategy is combined with the array processing for a high signal-to-noise ratio (SNR) required by the distributed MIMO detection. The former provides the approximate location of a likely target by transmitting a probe signal to sense the environment. Then, the transmitting beams are steered to illuminate the target from different angles by which target echoes are enhanced and reverberation is suppressed. It is seen from the receiver operating characteristic curves that the distributed-phased-MIMO sonar is intermediate to the distributed MIMO sonar and the phased-array sonar in the low-SNR scenario. In the at-lake experiments of localisation of a small target, the distributed-phased-MIMO sonar system performs better than other two sonar systems due to exploiting the diversity gain and the transmitting array gain.