High-accuracy Single-beam Sounding Using Small Bandwidth and Rough Sound Speed

For the single-beam sounding system, the accuracy of the depth estimation result is basically based on the instant system bandwidth and the measurement of the sound speed. Traditionally, to improve the accuracy, a large instant system bandwidth and the high-accuracy sound speed measurement are required. However, the large instant system bandwidth and the high-accuracy sound speed measurement will dramatically increase the cost of the single-beam sounding system. In this paper, a new single-beam sounding method using a comb-spectrum signal with a relatively small bandwidth and a roughly measured sound speed is proposed. In the method, the comb-spectrum signal is composed by a set of frequency diverse continuous wave (CW) pulses. Because of the frequency gap between the CW components, their echoes have different phase shifts. These phase shifts caused by the frequency offset are similar to the array manifold vector of uniform linear array (ULA). Hence, similar to the spatial spectrum estimation of the ULA, we use the MUSIC algorithm to process the echoes of these CW components. By scanning along the depth and the sound velocity dimensions, we show that the MUSIC algorithm can output a peak close to the true depth and the true averaged sound velocity. Due to the high accuracy of the MUSIC algorithm, the proposed method can use a small instant system bandwidth and a rough sound speed measurement to obtain a high accuracy depth estimation result. Finally, give the numerical simulations to show the superiority of the proposed method.