Direction of arrival estimation for colocated multiple-input multiple-output sonar array

By studying the influence of symmetrical noise component on multiple-input multiple-output sonar's DOA (Direction Of Arrival) estimation under the condition of low signal noise ratio, a DOA estimation algorithm based on covariance matrix reconstruction method is proposed. Firstly, the noise field is decomposed into symmetrical noise field and asymmetrical noise field, we utilize symmetry property of colored noise matrix and the feature that the imaginary part of covariance matrix has no relation with the symmetry noise, remove the real part of covariance matrix to avoid the influence of colored noise on DOA estimation accuracy. By subtracting the imaginary part of covariance matrix and reducing the dimension, the real part of covariance matrix is reconstructed, which helps to avoid the bilateral spectrum interference. Thereafter, Toeplitz method is applied for the covariance matrix decorrelation amendment, a noise subspace is formed by Singular Value Decomposition (SVD), Finally, we can estimate the DOA of target signal. Both theoretical analysis results and numerical simulation results verify that this algorithm suppress symmetrical noise obviously, the estimation performance of targets azimuth is improved. This method has the characteristics of fast calculation, higher degrees of freedom and stronger target resolution.