The Key Technology Of Active Sonar Detection Based On Time Reversal And MIMO

Underwater acoustic technology is an effective tool to exploit ocean resources, and plays an important role in military. In shallow water, conventional sonar performance deteriorates due to time delay spread and Doppler shift of acoustic wave propagation in waveguide environment. Hence, it is necessary to investigate the development of the advanced underwater acoustic signal processing methods.Time reversal processing (TRP) is robust to environmental uncertainties due to the ocean considered as a filter integrated into the signal processing scheme. On the base of exploiting the advantage of target diversities, multiple-input multiple-output (MIMO) processing has shown the ability of the enhancement of target detection with mitigating the channel fading and target fading. Therefore, the combination of TRP and MIMO processing is investigated based on theory analysis and waveguide tank experiments.From the viewpoint of coherent and non-coherent jointly processing, the target diversity has been obtained by designing three orthogonal transmitting signals. With transmitting time reversal beamforming, target echo is enhanced while reverberation is suppressed. Focusing beamforming is performed on the received signal, and then the target is detected following by a matched filter and the target range is estimated by referring to the transmitting time. The simulation and experimental results have demonstrated the improvement of detection of targets using TR-MIMO processing approach. Besides, the bear and range of the target are both estimated based on a horizontal linear array.