Diversity performance of multimode antennas in directive angle of arrival scenarios

Abstract

The growing demand for wireless communications with increased spectral efficiency seeks for multi-element antenna techniques in personal communications to support high data rates by means of multiple-input multiple-output (MIMO) transmission schemes. Since the integration of multi-element antenna equipment at the mobile device needs to be well-aligned with the required form factors and aesthetical design issues, antenna array concepts with spatially decorrelated radiators are almost difficult to be implemented. Multimode antenna configurations operating with independent polarizations and different radiation patterns may substantially reduce size requirements since they do not necessarily require spatially separated phase centers. This article provides the theoretical framework for the analysis of the diversity efficiency of multimode antennas in directive angle-of-arrival scenarios. The analysis applies an idealized mathematical model of a multimode antenna based on the characterization of orthonormal, spherical harmonics. This mathematical foundation enables a detailed in-depth study of the impact of finite pattern correlation and branch power imbalances on the diversity efficiency of the multimode antenna. Based on the introduction of reliable performance metrics, the model enables a separate analysis of both effects. It serves as a guideline for the determination of the diversity efficiency when applying multimode antenna elements in mobile fading scenarios with defined angle-of-arrival scenarios. © 2008 Springer Science+Business Media, LLC.