A shallow sea target depth estimation method based on array DOA of continuous acoustic signals

Continuous acoustic signals suffer from modal aliasing due to the persistent generation of multiple-order modes, which degrades depth estimation accuracy. To address this issue, this paper proposes a target depth estimation method for continuous acoustic signals based on hydrophone array direction-of-arrival (DOA) estimation. The approach involves receiving continuous acoustic signals via a horizontal line array, estimating the target's azimuth using the array, and performing time-domain correction on the received signals. The corrected time-range 2D signal matrix is then projected into the frequency-wavenumber (F – K) domain to separate the normal modes of the continuous signal. Based on the estimated azimuth, a theoretical dispersion curve is derived, and a binary mask filter is designed to extract the energy of each modal order. A depth estimation function is constructed by matching the energy of the received signals with the acoustic field model predictions at various search depths. Simulation results demonstrate that the proposed method achieves depth estimation errors below 5% for 100 ~ 200Hz acoustic targets with azimuth angles of 0° and 30° over a 10-second duration in Pekeris waveguides under signal-to-noise ratios (SNR) exceeding 0dB, indicating its practical engineering value.