Co-located radio direction finding in polarization fading conditions with increased Euclidean space dimension of signal vectors

In this paper the problems of co-located radio direction finding based on the polarization-selective reception in the polarization fading conditions are considered. A direction finder and the direction finding algorithm based on a four-element antenna system are explored. The four-element antenna has a tri-orthogonal loop antenna combined with a vertical dipole, and allows four orthogonal directional patterns to be formed with a single phase center. It has determined that using of proposed antenna system makes it possible to perform all signals processing which is necessary for direction finding in the four-dimensional Euclidean space of signal vectors (extended signal space) in comparison with the known co-located direction finders based on three-orthogonal antennas. The theoretical analysis with proof of main theses, which are theoretical foundation of the direction finding algorithm in conditions of uncertainty and temporary instability of received signal polarization ellipses is considered. A description of the proposed direction finding algorithm with obtaining of the main relations, a description of the basic computational procedures and an evaluation of the additional advantages and possibilities due to extended dimension is given. A description of the physical experiment which has made for an experimental approbation of the proposed direction finding algorithm and an embodiment of the direction finder is presented. The results of a physical experiment showing that an increase of the signal space dimension produces a noticeable positive effect are given. Based on results, a conclusion about the possibility and feasibility of direction finders and direction finding algorithms realizing, primarily in the HF range, for which the presence of polarization fading is a typical situation is made.