Robust Adaptive Beamforming Under Baffle Condition

In shipboard sonar array beamforming applications,the array is installed on the underwater vehicle,affected by the acoustic scattering vector mask,then the array receiving signals both in the far field target signals but also the scattering of the near-field scattering body,especially the scattering signal to wave direction near the direct wave to wave direction,traditional robust adaptive beamforming algorithm performance will be greatly reduced.In order to determine the influence of baffle plates on the results of beamforming and to find a robust beamforming method that can still maintain some robustness under baffle conditions,robust adaptive beamforming under baffle conditions is studied in this paper.The main contents of the paper are as follows:(1)The sound field with scattered signals from rigid spheres is simulated.The influence of scattered sound field on the result of array beamforming is analyzed from the Angle of distortion factors and scale.Meanwhile,the influence of scattered sound field on the direction of arrival estimation is analyzed.(2)The derivation process and robustness principle of classical algorithms such as diagonal loading,norm constraint,robust Capon beamforming and covariance matrix reconstruction are discussed.The performance of each robust adaptive beamforming algorithm in the presence of interference signals generated by baffle scattering,such as main lobe migration,output signal-to-noise ratio and robustness,is compared through simulation.(3)An improved norm constraint method is proposed for the presence of interference signals generated by baffle scattering.The algorithm introduces the interference signal generated by baffle scattering in the derivation of norm constraint method,and then deduces the solution of the weight vector.The proposed method is compared with the previous robust adaptive beamforming method,and the simulation results show that the improved norm constraint algorithm proposed in this paper has a great advantage in the presence of interference signals generated by rigid ball baffle scattering.