Research On Scattering Pattern And Acoustic Field Reconstruction Of Underwater Targets

The acoustic scattering pattern of underwater targets are of great significance for target identification,classification,and acoustic field control applications.However,the multipath effect of acoustic wave transmission in shallow water waveguide is serious,which leads to serious distortion of the received signal,and it is impossible to analyze the scattering pattern of the target.What's more,in the actual environment,in addition to the scattered echo of the target,the array also receives interference waves from other objects and sound sources.Therefore,how to reconstruct the target's scattering pattern and acoustic field from the received sound pressure data in waveguide environment is the focus of this paper.This paper describes the reconstruction of target scattering function with unknown position,from received data on a vertical line array(VLA)in shallow water waveguide.When locating an unknown target,the point spread function(PSF)in conventional matching field processing(CMFP)does not have global strict shift invariance.This paper proves that with the same effective mode number,the PSF retains the shift invariant property and can thus be deconvolved from CMFP by Richardson-Lucy(R-L)algorithm to provide accurate position information for the mode decomposition of the active signal.Then,the anechoic pool experiment data was used to verify the effectiveness and limitations of the two positioning methods.When reconstructing the target scattering pattern,this paper defines the mode amplitude of the active signal.At each frequency,the mode amplitude is estimated by modal decomposition,and combined with the target position information,the broadband target scattering spectrum with respect to vertical angle is accurately reconstructed with moderate number of modes.Secondly,combined with the principle and method of radiated acoustic field reconstruction,this paper uses the pressure data measured in the near field to reconstruct the target scattered field at any position.In the simulation of reconstructing the target's scattering field by using the equivalent source method,this paper analyzes the influence of the equivalent source shape and of the spatial position of the reference hydrophones on the phase reconstruction,and proposes an optimal scheme for reconstructing the scattered far-field.Finally,based on the experimental data of Qiandao Lake,this paper uses the equivalent source to reconstruct the target scattered field at each hydrophone,and analyzes the cause of the reconstruction error.Then,the feasibility of reconstructing the scattered field based on the equivalent source method is proved.