陆架斜坡海域信号水平纵向相关特性实验研究

Experimental study on horizontal longitudinal correlation of the signal at the continental slope area

对于复杂的海洋传播环境,如波导环境扰动、各阶模态之间的干涉、环境噪声等,声信号在传播过程中波形会随空间和时间起伏变化.接收信号之间的空间相关性是直接影响阵列处理增益的重要因素之一,因此研究信号的空间相关特性对提高信号处理的性能有重要意义.本文中,利用一次海上试验测量数据对陆架斜坡海域不同位置处接收信号的水平纵向相关特性以及水平纵向相关性随船运动的起伏变化情况进行了研究.海上试验在中国南海海域开展.试验中,接收阵为一个192元水平拖曳阵,以2 m/s的速度移动,声源为一个宽带声源,深度为95 m左右,用钢缆与发射船船尾相连.实验过程中发射船停机漂泊.声源发射信号为260–360 Hz的线性调频信号.为了降低环境噪声对水平纵向相关性测量结果的影响,数据处理过程中先对接收信号进行带通滤波和匹配滤波处理.然后,将接收阵划分若干个部分重叠的短的子阵列并对各子阵接收信号进行宽带波束形成处理.最后,利用各子阵宽带波束形成输出信号计算水平纵向相关系数.结果发现,该海域接收信号水平纵向相关长度的测量结果大体分布在13–60 m的范围内,普遍小于浅海波导环境,信号水平纵向相关特性易受斜坡海域声场干涉结构和海洋波导环境起伏的影响,随空间和时间变化明显.

Due to the complex underwater propagation environment, such as environment disturbance, interference between normal modes, and ambient noise, the waveforms of received signals change over space and time and cause the attenuation of the spatial correlation between the received signals. The spatial correlation between the received signals affects the performance of the array signal processing directly. Thus, it is important to study the spatial correlation characteristics between received signals. In the paper, the horizontal longitudinal correlations between the received signals for 4 different locations at the continental slope area and the changes of the horizontal longitudinal correlations during the movement of the ships are studied by analyzing the experiment data. The experiment is carried out in the South China Sea. In the experiment, the receiving array, a horizontal linear array with 192 sensors, is dragged by a ship moving with 2 m/s, and the source with a depth of 95 m is dragged by another ship drifting at sea. The transmit signal is linear frequency modulation signal, with a frequency of 260 to 360 Hz. To reduce the effects of the ambient noise on the horizontal longitudinal correlations, the band-pass filter and the matched filter are applied first. Then the receiving array is divided into many partly overlapped short subarrays and the broadband beamforming is applied to the signals after filtering on each subarrays. Finally the beamforming outputs are used to calculate the horizontal longitudinal correlation coefficients between received signals. Results show that the horizontal longitudinal correlation length of the received signal is at the range of 13 to 60 m, which is generally less than the correlation length in the shallow water environment, and that the horizontal longitudinal correlations between the received signals change over space and time obviously and are dependent on the interference structure of the sound field and the environment disturbance.