收发分置目标强度的计算及前向散射信号的分离

Computation of bi-static target strength and separation of forward-scattering sound from objects

研究时域有限差分(FDTD)法计算收发分置弹性目标散射声场的有效性,和实验测量中从直达与散射干涉信号中分离目标前向散射信号的方法。将FDTD法应用于三维声场计算,分别计算了平顶圆柱、球顶圆柱、球锥顶圆柱和扁长回转椭球等几种不同形状的弹性体散射近场空间分布,再用近远场变换方法获取远场目标强度空间分布。模拟结果表明:目标强度的空间指向性是受声波入射方向、无量纲波数kL(k-波数,L-目标特征尺度)、目标形状、材料等影响;在本文所计算的几种不同形状目标的尺度和kL取值范围内,计算得到的收发分置目标强度空间分布均有显著的前向散射与镜反射特征。计算结果得到解析解和实验结果的印证,从而表明了FDTD法计算收发分置目标散射场的有效性。对接收信号采用相关处理方法,能有效地分离出目标前向散射信号,表明对于收发分置目标散射声强的测量,这是一种简单有效的分离目标前向散射信号的方法。

Computation of bi-static target strength （TS） of elastic objects using the Finite Difference Time Domain （FDTD） Method and separation of forward-scattering sounds from interferential signals between the direct and target scattering sounds were researched. 3D scatter sound field of elastic cylinder with flat cap, spherical cap, spherical-core cap, and prolate spheroid was calculated using FDTD, then near-far field translation used to get the TS of far field. The result of simulation shows distributing in space of TS influenced by incidence direct, kL （k-wave number, L-character size of target）, shape, and material of target. Within the range of kL and the size of the objects with different shape in this paper, bi-static TS performs a prominent forward-scattering and enantiomorph-reflecting character. The numerical value simulation results are validated by comparing with analytic and experimental results. The signal correlation processing technology is used to separate the forward-scattering sounds from interferential signals between the direct and the target scattering sounds. The method is a simple and valid one to separation of forward-scattering sounds, which successful in this paper for separating the forward-scattering sounds of the target.