Two-dimensional angle-of-arrival estimation in the presence of finite distance sources

When sources are a finite distance away from an array system, most high-resolution bearing estimation techniques exhibit unsatisfactory performance due to the invalidity of the planar wavefront assumption. This problem has been addressed by a far-field approximation (FFA) method based on a preprocessing scheme. By exploiting favorable characteristics of a uniform linear array, the method constructs a FFA covariance matrix, which is Toeplitz and approximates to the far-field data covariance matrix, from the observed data covariance matrix. Then eigenstructure methods can be applied to perform bearing estimation without revising the planar wavefront assumption. This method is extended to the problem of two-dimensional angle-of-arrival (AOA) estimation using a uniform planar array in the presence of finite distance sources. A procedure is derived for reconstructing the 2-D FFA covariance matrix with block-Toeplitz structure. Using the 2-D FFA covariance matrix, eigenstructure methods can be applied in conjunction with a 2-D AOA search to solve the problem. Simulation results confirm the theoretical work