运动目标辐射声场干涉结构映射域特征研究

浅海低频声场呈稳定而显著的干涉特征,并蕴含声源状态和波导特性等信息.本文研究运动目标辐射声场干涉结构的简化映射以及映射域能量分布对目标运动状态的指示特征.理论分析了声压场和矢量声场空(时)频干涉谱图的二维傅里叶变换映射特征,推导了匀速运动目标时频干涉谱图映射域能量脊斜率与波导不变量以及距变率、航向角的关系式,证明了映射域脊斜率符号、脊斜率绝对值变化等对目标来袭或远离以及目标威胁程度的指示,并进行了数值仿真和海上试验研究.实测结果与理论、仿真分析有较好的一致性.研究结果表明:二维傅里叶变换可将声压场和矢量场时(空)频谱图干涉结构简化,匀速运动目标辐射声场干涉结构映射域的能谱脊斜率、距变率、航向角与波导不变量有解析关系式,声强谱、动能密度谱、声强流谱等声场干涉结构经映射后更为一致,映射域脊能简明的指示目标运动状态和威胁程度.

Characteristics of mapping domain of the acoustic field interference structures radiated by a moving target

In shallow water exist the stable and significant interference characteristics of low frequency sound propagation, which contain the information of the sound source state and waveguide peculiarity. A simplified mapping method for describing the scalar and vector sound field interference structure radiated by a moving target, and an indicatory mechanism of the target state implicated in the energy distribution of the mapping domain are investigated in this paper. The mapping characteristics of two-dimensional Fourier transform of the vector sound field time (space) frequency interference spectrum are analyzed theoretically. Relations among waveguide invariant, range-rate, heading angle, and energy ridge slope of the mapping domain for time-frequency interference spectrum produced by a uniformly moving target are derived. Indication of target attacking or moving away, and the degree of threatening through symbols or the absolute value change of mapping domain’s ridge slope are demonstrated. Then numerical simulation and sea trial research are carried out. Experimental results with theoretical analysis and simulation results are in good agreement with each other. Research results show that the scalar and vector field time (space) frequency interference structure can be simplified by the two-dimensional Fourier transform. The mapping domain ridges, range-rate, heading angle and waveguide invariant show an analytic relationship among them. Variation embodied in the form of scalar and vector field interference structure obtained after mapping are more consistent with each other. The ridge of mapping domain can indicate the moving state of target concisely.