Ray-tracing-based time-domain wideband fractional delay beamforming for underwater acoustic positioning

Underwater acoustic positioning systems are essential for underwater vehicles positioning and navigation. In this paper, a time-domain wideband fractional delay beamforming (WFDB) technique is proposed to improve underwater localization capability of planar arrays. In our method, digital delay lines are combined with adaptive-finite-impulse-response filters to achieve high accuracy beamforming results and reduce the design burden of the WFDB systems. Further, the beamforming results are used in the ray tracing method to eliminate curvature effect of sound rays caused by the inhomogeneity of water, and therefore improving the computation accuracy of target position. We further develop a hexagonal planar array of 30 elements to verify the WFDB method in an indoor experimental pool. The experimental results demonstrate that the proposed method could successfully mitigate the ray bending problem and accurately estimate the position of targets in low SNR condition.