A simple tridiagonal loading method for robust adaptive beamforming

Various uncertainties exist in real sensor arrays, which can significantly deteriorate the performance of adaptive beamformers. In this communication, we propose a simple tridiagonal loading method, called automatic tridiagonal loading (ATL), to enhance the robustness of adaptive beamformers. The ATL uses a symmetric tridiagonal matrix to regularize the sample covariance matrix, which approximately imposes a smooth constraint on the weight vector of beamformer. We also present a parameter-free method to determine the loading level based on the output power of a low sidelobe beam in the presumed direction of the desired signal. Thus, ATL does not require user-defined parameters. Moreover, simulation experiments show that ATL has better robust performance than other widely used robust techniques, although the computational cost of ATL is almost the same as the standard Capon beamformer.