Design Of Transponder For Diver Detection Sonar To Target Simulation Based On OMAP-L138

In recent years,underwater frogmen have constituted an important threat to maritime military targets such as nearshore ports,terminals and military installations.Therefore,the diver detection sonar(DDS),which can detect threatening small targets such as underwater frogmen,robots and small vehicles,has made great progress.However,due to the small scattering intensity and wide range of motion of small underwater targets,how to improve the target detecting accuracy of DDS is the key and difficult point at the current stage.In order to solve this problem,this paper studies the target simulation transponder of the DDS.Such the transponder is designed to simulate the frogman's target and position before DDS is put into use,and to test its performance regularly after the sonar is put into use.When working,it is carried by a small underwater target such as a frogman.After receiving the emission signal of the DDS,the target simulation transponder will transmit a strong delayed signal for target simulation.After receiving the weak scattering wave of frogman and the strong signal from the target simulation transponder,the DDS will use a strong signal as a reference to analyze the weak signal and test its ability to locate weak target echoes.The algorithm and acoustic parameters are adjusted successively to make it close to accurate positioning.In addition,in order to further reduce the test cost of the DDS,the target simulation transponder studied in this paper provides a new working mode.In this mode,after receiving the acoustic signal from the DDS,the transponder can emit two type of signals: one is used to simulate the weak scattering signal of the frogman,and the other is the strong signal used for target simulation.After receiving these two signals,the DDS will still use the strong signal as the reference to test the detection and localization of the weak signal.Such a working mode can preliminarily test the ability of the detection algorithm of the DDS for the weak target,hence achieving the purpose of calibrating the detection accuracy of DDS.The main work of this paper focuses on the overall scheme design,hardware platform design,signal processing technology research and experimental verification of the target simulation transponder.According to the working principle of the DDS,the function and parameter selection of the two working modes of the target simulation transponder for system demonstration and design support are presented.On this basis,the selection and design of the hardware system are given,including the overall structure block diagram,DSP selection,AD/DA selection,hardware interface configuration and CCSsoftware configuration.In this hardware system,the OMAP-L138 is used as the core board,AD8568 is used as the receiving board,and DA5724 is used as the transmitting board.In addition,for the signal processing of the transponder,the process of the DDS signal,calculation of the arrival time of the DDS signal,and the setting of the adaptive threshold are studied.In order to ensure the stability of the transponder,the adaptive frequency domain matching filter is applied to the transponder for the first time,which improves the detection probability of the transponder for the DDS signal.At last,target simulation transponder was verified by both laboratory and fixed-point pool experiments.The experimental results were in line with the design requirements.