A Direction-Finding Model With Spatial Polarization Characteristics

The representation of electromagnetic wave polarizations and co-polarizations of antenna elements has extensively been studied and documented. Various approaches to the description of polarization have been derived across different applications, and these different definitions may lead to confusion and ambiguity. In addition, in a joint direction of arrival (DoA) and polarization estimation, the receiving antenna polarization in the maximum gain direction is usually equated to the one from any incoming wave direction, leading to unacceptable estimation errors. To this end, a direction-finding model is proposed in this article, which makes use of arbitrarily polarized antennas to explore spatial polarization characteristics. Specifically, the relationship between the co-polarization of a transmitting and receiving antenna and the polarization of radiated electromagnetic waves is derived from a unified Cartesian coordinate system. Subsequently, a definition of quantification for antenna polarization is proposed, which can represent the polarization in direction-finding solutions more naturally and intuitively. In consideration of rotation and spatial polarization characteristics of the receiving antenna, the proposed direction-finding model is thus developed with a unified polarization representation. Moreover, an application algorithm based on this model is formulated. The attractive features of the proposed model are verified by simulations and experiments.