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.