浅海非均匀水平阵宽带声场信号无源孔径扩展

Broadband passive aperture extension based on non-uniform horizontal array in shallow water

大孔径水平阵对于浅海低频水声物理实验研究和应用至关重要,然而受实际情况制约,通常使用的水平基阵孔径十分有限,通过孔径扩展处理来扩展基阵孔径是一条重要途径.传统的无源孔径扩展方法是建立在均匀线阵、匀速相对运动和相干窄带连续信号的基础上的,难以适用于非均匀阵以及非连续宽带声源的情况.针对这些问题,提出了非均匀阵宽带声场信号的无源孔径扩展方法.使用静止布设在海底的非均匀水平短阵接收运动声源重复发射的宽带声信号,先开展均匀空间插值,然后在阵元域和波束域进行宽带扩展孔径处理。仿真和实验结果表明,在水深约70 m的浅海波导环境中,纵向间隔27.5 m的2个阵元接收20〜200 Hz宽带声场,其空间插值结果与真值的相关系数大于0.99,说明宽带声场插值方法的合理性。在水平非均匀、纵向孔径250 m的短阵接收声场无法分析简正波频散特征的情况下,仿真和实验数据经过宽带无源孔径扩展处理得到孔径大于1 km的均匀线阵的声场,能高分辨区分各阶简正波,证明所提方法是有效的.

In order to research and apply the low frequency acoustic physics in shallow water,broadband signal of a large aperture horizontal array is required.Unfortunately,a large aperture array is expensive and difficult to place,and so it is expected to use aperture extension technique with a short array to get a large aperture array signal.Most existing passive aperture extension methods are based on towed uniform linear array at a constant speed and coherent narrowband continuous signal.They are not applicable to the cases of non-uniform array and discontinuous broadband source signal.To solve these issues,passive aperture extension method based on non-uniform horizontal array and broadband signal is proposed.Instead of a towed linear array,a static seafloor-deployed non-uniform horizontal array is used to receive broadband source signal,which is moving horizontally and launched repeatedly.After uniform interpolation in space,broadband signal passive aperture extension technique in element domain or beam domain is used to produce signal of a large virtual aperture array.In shallow-water waveguide with depth of about 70 m,the 20~200 Hz signal received by 2 elements,whose longitudinal space is 27.5 m,are processed by linear interpolation method.Simulation and experiment results show that the correlation coefficients between the signals produced by interpolation and the real ones are greater than 0.99,which verifies the rationality of the proposed interpolation method.Dispersion characteristics of the normal modes can be identified by the broadband passive aperture extension in beam domain or element domain with the extended aperture greater than 1 km,but cannot be identified by conventional beamforming with a short array aperture of 250 m,which verified the effectiveness of the proposed method.