Theoretical And Experimental Research On TR-MIMO Sonar Detection

It is a challenge of underwater acoustic signal processing to detect a target in shallow ocean environments. On one hand, the replica vector design of matched filter is restricted by time-delay spread and Doppler spread of underwater acoustic channels, and the non-Gaussian sea bottom reverberation will greatly reduce the detector performance. On the other hand, target spatial diversity scintillations generally result in the unreliable detection performance of active sonar.Time reversal processing (TRP) demonstrates the spatial-temporal focusing properties of a waveguide. TRP is matched field processing with known channel knowledge. Time reversal beamforming can focus acoustic energy on a target of interest by which the enhanced target echoes can be obtained. Transmit-receive interaction technique regards the target echo as a guiding source for time reversal transmission after first transmitting a probe signal, and can focus the time-reversed echo signal on the target. Multiple input multiple output (MIMO) technology utilizes the waveform diversity and target diversity for enhancement of detection performance through incoherent processing. This paper combines TRP and MIMO processing to build a distributed TR-MIMO sonar system. The TR-MIMO sonar system takes advantages of the potentiality of TRP and the superiority of MIMO processing, via coherent and incoherent processing for enhancing detection of an extended target in shallow ocean environments.Numerical simulations have shown that the TR detector has the better adaptability than the conventional detector in a waveguide environment. In detection of an extended target, the distributed TR-MIMO detecting system has shown its stability in comparing with the conventional TR detector. MoGanshan Lake experimental results have verified the feasibility of the distributed TR-MIMO sonar detection framework.