Microstrip-Fed Monopole Antenna Planar Array for Multiple-Input–Multiple-Output Applications

Abstract

This article provides a novel antenna structure for the case of multiple-input–multiple-output applications. This structure is composed of four antenna elements that operate at 5.8 GHz. Each element is a small microstrip-fed monopole antenna, consisting of a rectangular patch and a truncated ground plane. In addition to the use of spatial diversity, as is employed in the naive multiple-input–multiple-output antennas, the underlying scheme makes use of a combination of pattern and polarization diversity to increase the signal reliability. In order to measure the array performance of the proposed multiple-input–multiple-output antenna, the so called total active reflection coefficient metric, which incorporates multi-port characterizations into a single formulation, is employed as the performance metric. This enables the giving of an indication regarding the actual coupling between multiple-input–multiple-output antenna elements, rather than the use of the scattering matrix, which aims to measure the pair-to-pair coupling for a multi-port device. The proposed antenna is designed to achieve a good reflection coefficient as well as an acceptable isolation between antenna elements. It is shown that there is close agreement between the simulation and the measurement results of the proposed structure. Accordingly, the corresponding reflection coefficients, mutual couplings, and radiation patterns are presented and discussed.