High-resolution 2-D imaging using ultra-wideband MIMO sonar

An ultra-wideband (UWB) imaging system can provide better cross-range resolution by using large-bandwidth waveforms. Nevertheless, the conventional sonar imaging system can hardly emit and process UWB waveforms directly due to limited system bandwidth. To solve the problem, a 2-D imaging approach based on an UWB multiple-input multiple-output (UWB-MIMO) sonar is proposed. The UWB-MIMO sonar is composed of multi transmitting sensors and a receiving rectangular array. At the transmitting end, a group of OFDM-LFM pulses are emitted simultaneously via multi transmitting sensors. At the receiving end, via matched filtering, the echo components corresponding to each LFM pulse are picked out, and all of them are further synthesized into UWB signals. Therefore, the transmission and processing of a single UWB pulse is replaced by the transmission and processing of a group of OFDM-LFM pluses. As a result, with the adoption of the UWB-MIMO sonar, UWB signals are synthesized during a single pulse illumination and better cross-range resolution is obtained.