Subspace fitting with diversely polarized antenna arrays

Diversely polarized antenna arrays are widely used in RF applications. The diversity of response provided by diversely polarized antenna arrays can greatly improve direction-finding performance over arrays sensitive to only one polarization component. For d emitters, directly implementing a multidimensional estimation algorithm would require a search for 3d parameters: d directions of arrival (DOAs), and 2d polarization parameters. A more efficient solution is presented based on the noise subspace fitting (NSF) algorithm. It is shown how to decouple the NSF search into a two-step procedure, where the DOAs are estimated separately. The polarization parameters are then obtained by solving a linear system of equations. The advantage of this approach is that the search dimension is reduced by a factor of three, and no initial polarization estimate is required. The algorithm can be shown to yield asymptotically minimum variance estimates: provided no perfectly coherent signals are present. Simulation examples are included.>