Three-Dimensional Mixed Far-Field and Near-Field Sources Localization Utilizing Cross Tripole Array

In this paper, we propose a parameters estimation method for three-dimensional (3-D) mixed far-field and near-field sources based on nonuniform cross tripole array where location and polarization estimates are considered. By designing several special fourth-order cumulants and making use of the shift-invariant properties in cumulant domain, the 2D-DOA and polarization information at five known tripoles are captured. With the 2D-DOA estimates, a matrix equation is derived to classify the source type and determine the coarse locate estimates. Then, the coarse parameters estimates can be used as references for disambiguating the cyclically ambiguous estimates to obtain the high accuracy estimation of 2D-DOA and range. Compared with the existing methods, The proposed one can separate and locate the mixed sources in 3-D space with the priori knowledge of only five sensors' positions. Moreover, it does not restrict the array sensors to be uniformly placed with inter-element spacing no more than a quarter or one-eighth wavelength, and thus, the array aperture can be extended by extending the inter-sensor spacing. Additionally, requirements for the placement of five known tripoles are analyzed. Numerical results show that the proposed algorithm achieves high parameter estimation accuracy.