Direction-of-arrival and range estimation using active sonar with horizontal array in sound shadow zone of deep water

When detecting targets in sound shadow zones of deep water using bottom bounce mode, the bending of sound rays due to changes in the sound speed profile often leads to significant errors in estimating the azimuth, depth, and distance of targets using conventional horizontal arrays. The positioning technique utilizing multipath time delays and elevation angles of sound rays is an effective method to reduce errors, but horizontal arrays are unable to directly measure the elevation angles of sound rays. To address this issue, this paper proposed a method based on the ray acoustics model in deep-sea shadow zones. By utilizing the multipath time delays and measured azimuths of sound rays from different observation points of a moving horizontal array, the decoupling of sound ray elevation angles and the true azimuth of the target is achieved. A method is then presented for estimating the distance and azimuth of the target using the multipath time delays and elevation angles of sound rays, which improves positioning accuracy. Simulation experiments and analysis of influencing factors verify the correctness of this method. The results of sea trials indicate that the estimated distance and azimuth values are highly consistent with the actual distance and azimuth of the target, thus validating the effectiveness of the proposed algorithm.