Calculation of 3-D acoustic scattering characteristics of a target in near-field at high-frequency

3-D acoustic scattering characteristics calculation will play an important role in characteristic prediction, reduction and identification of an underwater target. In this paper, 3-D acoustic scattering characteristics of an underwater complex target in near-field at high-frequency is effectively calculated based on principle of multi-beam forming and rotating platform imaging using the back-projection (BP) algorithm. To generate the 3-D acoustic image of an underwater volumetric target, a sonar array with linear equally spaced elements in the vertical direction is fixed, and the target rotates in the horizontal plane around a fixed vertical axis. Each element in the array transmits a high-frequency signal and receives the echo while the target rotates at a certain aspect. Firstly, the height information at a certain angle is obtained by beamforming in frequency domain. Then two dimensional acoustic scattering characteristics in both range and cross range of each beam is reconstructed by the BP algorithm in the rotating platform imaging. By this method, the 3-D acoustic scattering characteristics of the generic BASIS submarine are reconstructed. Experiment shows the validity of the method.