Theoretical And Experimental Research On The Widely-Spaced Phased-MIMO Sonar Detection

With the development of marine transportation industry and the increasing of number of ships, active sonar in shallow sea and offshore faces new challenges:the first problem is that the number of interference is much larger than the number of targets, the second is that the energy of noise is much bigger than that of the signal. The rapid development of multiple input multiple output (MIMO) technology in the field of radar results in a new active research area of the MIMO sonar key technology.The time delay spread and Doppler spread of underwater acoustic channels are first analyzed. Then the plane wave model and the normal mode model are utilized to describe the channels. Active sonar faces reverberation suppression, so time reversal processing is used for reverberation suppression. For enhancement of spatial-temporal identification of a target, a broadband co-located MIMO processing model is proposed, and some orthogonal waveforms are designed for underwater acoustic channels. Furthermore, a widely-spaced phased-MIMO sonar framework based on the idea of coherent processing of phased-array sonar is investigated to enhance detection of a weak target. Considering the waveguide environment, the transmit-receive interactive mechanism is used to obtain the high echo-to-reverberation ratio (EER) required by MIMO processing.The mian achievements include:1) A widely-spaced broadband phased-MIMO spatial-temporal model based on the transmit-receive interaction mechanism is proposed and its detection performance is quantitatively analyzed.2) A widely-spaced TR-MIMO sonar experiment system is designed to enhance EER.3) The Moganshan lake experimental results have shown that the widely-spced phased-MIMO sonar system performs better than the conventional phased-array sonar, and the potential of the widely-spaced MIMO sonar system based on time reversal focusing.