Compact wideband MIMO mobile-antenna system design using mode-based decoupling techniques

Abstract

This work focuses on designing small mobile antennas and their multiple-input multiple-output (MIMO) applications. In this study, it was investigated that small mobile antennas can obtain high radiation performance only when a tight coupling with the ground plane is generated through ground-mode tuning (GMT) of the ground plane. Furthermore, a novel mode-based decoupling concept is presented for their MIMO applications, based on a four-port network and by considering the ground-mode effect. Consequently, the proposed mode-based decouplers can effectively sustain high radiation performance and improve the isolation while providing low correlation by generating diagonally directed radiation patterns. In the proposed MIMO system, both GMT structures and mode-based decouplers are implemented utilizing the metal rims around the ground plane, thereby occupying very compact clearance, and the measured MIMO antennas fully covered 0.69 to 1 GHz band with high isolation up to 20 dB and low envelope correlation coefficient (ECC) value below 0.5, sufficiently applicable in mobile devices.