| Sonar array is one of the most widely used devices in underwater acoustics because of its strong signal gain,strong interference suppression and high spatial resolution.However,the directivity and spatial gain of the array are affected by many factors,such as gain error,array position migration,amplitude-phase error and inter array coupling.In the array formation process of sonar array,the array elements of complex array are mainly arranged in close rows.Due to the influence of array size and array formation technology,there is a certain position deviation between the array elements and the sound field coupling between the array elements.After array formation,it is difficult to guarantee the amplitude and phase consistency between the array elements,and there is an inevitable initial amplitude and phase difference between the array elements.This deviation will have a certain impact on the signal processing of the array,so it is necessary to carry out the array online calibration after array formation to determine the parameters of the array system.In the field of hydroacoustic,due to the limitation of acoustic propagation speed in water medium,the wave wavelength at low frequency is longer,lake water with sufficient depth is wider,operating platform is stable,sound field model is relatively simple,and various complex testing and calibration work of array can be carried out.However,in most cases,the development and testing of arrays generally need to be carried out in indoor pools.Indoor anechoic pools can only simulate the free field within a certain frequency band,and the free field required for low-frequency underwater acoustic measurement is difficult to meet in indoor laboratory environment.Therefore,in order to meet the requirements of underwater acoustic metrology,this thesis studies the amplitude-phase consistency calibration of complex arrays in finite space.A new amplitude-phase consistency calibration method for complex arrays in finite space combining holographic acoustic field reconstruction with matching search compensation is proposed.Firstly,an amplitude-phase consistency search function has been established combining the sound field separation technology of near-field acoustic holography in finite space and the optimization idea of matching search algorithm,and seek the objective function value which meets the amplitude-phase consistency calibration method between arrays.Then,the complex array element amplitude-phase consistency calibration is realized by compensation correction.Secondly,In order to improve the DOA estimation performance of the actual measurement array,the amplitude-phase consistency of the complex array is compensated by online search again in the free field.This thesis takes small cylindrical array and linear array as the analysis objects,carries out theoretical modeling and simulation analysis of cylindrical finite space sound field,completes sound field reconstruction in finite space based on sound field separation technology,studies the construction conditions of stable sound field,analyzes the influence of various test parameters on the accuracy of sound field reconstruction,and combines intelligent optimization algorithm to achieve amplitude and phase consistency calibration between array elements.At the same time,the mathematical model of the measurement array and signal directivity error estimation is established,and combined with the matching search method of optimization problem,the amplitude and phase consistency search compensation of array is realized.Through computer simulation and experimental verification,the high precision calibration of array elements is completed,which proves that this method can accurately obtain the amplitude and phase consistency between array elements and effectively improve the performance of array DOA estimation after calibration. |
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