Diversely polarized antenna array systems

Abstract

This thesis is concerned with the use of diversely polarized antennas in an array system as the advantage of this array architecture over a uniformly polarized array is its capability to separate multiple signals based on their polarization characteristics. Overall system performance is substantially improved due to an extra degree of signal discrimination. In this thesis, the aim is to address and explore several issues regarding the employment of the diversely polarized antennas in order to assess the array performance and its characteristics. First of all, the geometrical properties of the array manifold associated with polarization-sensitive array are explored from the differential geometry perspective. The fact that the array manifold incorporates all information about the array and signal environments allows it to completely characterize the whole system. In this work, a new mathematical framework is proposed to analyze three- parameter diversely polarized manifold, where important notations to describe the local characteristics of the manifold are provided. Second, issues regarding the presence of uncertainties in polarization-sensitive arrays are investigated. The array system considered so far is assumed to be free from errors and uncertainties. However, in practice, the system performance is affected considerably by various types of uncertainties that deviate from the assumed conditions. A framework based on the sensitivity analysis of manifold shape property is presented to evaluate the array robustness to uncertainties. In addition, a novel calibration method is proposed utilizing the concept of diversely polarized manifold. Third, problems regarding the presence of manifold ambiguities are addressed. Manifold ambiguity is an undesirable situation often encountered when there exists linear dependence amongst array response vectors. This study aims to investigate issues regarding the identification, classification, as well as the eradication of some types of ambiguities. A general framework to identify diversely polarized manifold ambiguity is presented, followed by two novel techniques to resolve ambiguities. Finally, issues regarding the use of polarization-sensitive antennas in CDMA- based systems are addressed. The framework is essentially based on an integration of polarization-sensitive antennas, space-time array processing, and the spread-spectrum multiple access technology. First, the properties of Polarization- Spatio-Temporal ARray (Polar-STAR) manifold is investigated based on a direct relationship with the diversely polarized manifold. Then, the array's ultimate detection capabilities are presented. Finally, a self calibration method for a polarization-sensitive asynchronous DS-CDMA system is proposed.