A unified framework for multiple-input multiple-output and bistatic synthetic aperture sonar processing

Conventional monostatic synthetic aperture sonar (SAS) imaging is based on the point target assumption, and may suffer from the target scattering fluctuation within the scope of the synthesized aperture. Bistatic sonar can sample target scattering pattern (TSP) at any angle rather than from only the back scattering direction. It offers potential advantages when faced with an anisotropic target, but is still subject to limited mainlobe width of the TSP. In this paper we construct a unified framework of coherent and non-coherent processing, where the concept of multiple-input multiple-output (MIMO) and SAS are closely integrated to overcome the above-mentioned problem. Both bistatic sonar and MIMO sonar embody the concept of "Multi-", admitting the existence of spatial fading of acoustic targets and trying to make use of it. It is straightforward to migrate a conventional SAS to MIMO-SAS by putting multiple transmitters to insonify the target from different angles. An example realization of the framework using two transmitters is demonstrated.