Correction Method for Magnitude and Phase Variations in Acoustic Arrays Based on Focused Beamforming

The inconsistency in the magnitude and phase variations among the receiving array elements in multibeam soundings can seriously affect the beam pattern characteristics, which reduces the array gain, increases the sidelobe level, and deteriorates the direction-of-arrival (DOA) estimation. The accuracy of the beamforming result may be improved by correcting for magnitude and phase variations among the array elements. Therefore, a novel estimation and correction method based on near-field focused beamforming is proposed to overcome deficiencies of the conventional methods. The magnitude and phase variation model and the corresponding influence on the direction-finding accuracy are analyzed. The near-field focused beamforming model is established for multielement systems, and the root-mean-square error (RMSE) method is used to determine the ideal-source incident angle for correction. We construct the receiving signal covariance matrix in the frequency domain and further estimate the magnitude and phase variations in each array element. The performance and effectiveness of the proposed method are verified by simulations and small anechoic tank experiments. The proposed method requires the employment of a rotation platform that provides necessary rotation information and, thus, can accurately and effectively estimate and correct for variations in the magnitude and phase response of elements in the receiving array. The experimental results show that the sidelobe level can be reduced by approximately 3 dB after the array is corrected, and the angle deviation is reduced by approximately 1.0°.