Experimental study on horizontal MIMO SONAR

Angular resolution is one of the most important performance measures in a long-range SONAR. It is necessary to increase array aperture size (AAS) for better angular resolution. Usually, the AAS of SONAR is increased by using more receiving sensor elements or synthetic aperture techniques. Unlike these traditional methods, multi-input multi-output (MIMO) technology can improve the angular resolution on the transmitter side. In this paper, we present experimental result on horizontal MIMO SONAR. We implement an active SONAR with horizontal array sensor system that consists of uniform linear receiver array of 16-elements and transmitter array of two elements. In order to maximize the AAS induced by the virtual steering vector, we put two transmitters at each end of the array platform, and probe signals are designed such that the peak aperiodic cross correlation of two transmitted signals is small enough to neglect the interference due to the other transmitted signal. Then, the equivalent AAS of the MIMO SONAR is twice of the phased array SONAR. We demonstrate the improved angular resolution of the implemented horizontal MIMO SONAR through experiment near the pier.