Real-time Simulation Of Underwater Target Echo Signal In Time-space Varying Environment

The fact that the active sonar works in time-space varying environment causes the temporal and spatial changes of signals received by sonar array.To provide the realistic simulated signals under laboratory conditions,the echo signal simulation methods in time-space varying environment are studied in this thesis according to the principle of the active sonar.A real time active sonar array signal simulation system is implemented by using high-speed digital signal processors.The main work of the thesis is organized as follows:The requirements and realization process of active sonar echo signal simulation are analyzed.The entire simulation system can be divided into three basic modules including simulation of the sound source signals,simulation of the target echo signals and simulation of the array elements signals.A simulation method for soft vertical line emitter array signals based on array correction is proposed.The influence of array distortion on array focusing characteristics and target echo simulation is studied by using the matrix estimation equation based on the differential element method and the Gaussian disturbance model of array element position error.The equivalent model of multi-source emission array is proposed and its performance is analyzed.Under the sonar platform and target motion conditions,a multi-highlight model target echo simulation method base on planar elements calculation is proposed.For the change of target highlight characteristics caused by the change of the spatial position,the planar element method is used to calculate the target scattering characteristics,and the intensity and distribution characteristics of the highlight are extracted based on the calculation results of the scattering characteristics under different illumination angle conditions,and then the echo simulation is performed based on the extracted highlight information.The simulation of Doppler shift echo signals of moving target base on cubic spline interpolation is presented.The real-time simulation of active sonar receiving signal under relative motion between sonar platform and target is realized.According to the spatial azimuth characteristic of the received array signals,the receiver array domain signal is implemented based on the precise time delay filter.Based on the high-speed digital signal processor platform,the active sonar target echo array signal simulation system is implemented.The overall architecture of the system and the implementation method of each module are given.The programming and debugging of each module are carried out,and the simulation output of the real-time target echo signals under the environment time-space change and target relative motion conditions is realized.Finally,the simulation performance of the system is verified through the analysis of the output data.