On 2D-Imaging Algorithm for Underwater Target in Near-Field

In the imaging algorithms of Inverse Synthetic Aperture Sonar (ISAS), Range-Doppler Algorithm (RDA) and Polar Formation Algorithm (PFA) can be only suitable for far-field imaging. For obtaining near-field imaging, Computed Tomography Algorithm (CTA) is introduced. Five point-targets in near-field at different locations are imaged with RDA, PFA and CTA, respectively. Imaging results show that five point-targets imaged by CTA can be distinguished evidently, and imaging resolutions are much higher than those of RDA and PFA. Based on echo calculated with the technique of CAD and the principle of physical acoustics (Kirchhoff approximation), the submarine model in near-field is imaged by using three different kinds of algorithms above-mentioned. Simulation results demonstrate that 2D-imaging generated by CTA can differentiate four spotlights of the submarine model's bow, bridge, broadside and stern, which can be used in 2D-imaging of underwater target in near-field effectively.