Performance analysis of structured gradient algorithm

The structured gradient algorithm uses a structured estimate of the array correlation matrix to estimate the gradient required for the constrained LMS (least-mean-square) algorithm. This structure reflects the structure of the exact array correlation matrix for an equispaced linear array and is obtained by spatial averaging of the elements of the noisy correlation matrix. In its standard form the LMS algorithm does not exploit the structure of the array correlation matrix. The gradient is estimated by multiplying the array output by the receiver outputs. An analysis is presented of the two algorithms to show that the covariance of the gradient estimated by the structured method is less sensitive to the look-direction signal than that estimated by the standard method