Eight-Element Dual-Polarized MIMO Slot Antenna System for 5G Smartphone Applications

In this manuscript, we propose an eight-port/four-resonator slot antenna array with dualpolarized function for multiple-input multiple output (MIMO) 5G mobile terminals. The design is composed of four dual-polarized square-ring slot radiators fed by pairs of microstrip-line structures. The radiation elements are designed to operate at 3.6 GHz and are located on the corners of the smartphone PCB. The square-ring slot radiators provide good dual-polarization characteristic with similar performances in terms of fundamental radiation characteristics. In order to improve the isolation and also reduce the mutual coupling characteristic between the adjunct microstrip-line feeding ports of the dual-polarized radiators, a pair of circular-ring/open-ended parasitic structures is embedded across each square-ring slot radiator. The -10 dB impedance bandwidth of each antenna-element is 3.4-3.8 GHz. However, for -6 dB impedance bandwidth, this value is 600 MHz (3.3-3.9 GHz). The proposed MIMO antenna offers good S-parameters, high-gain radiation patterns and sufficient total efficiencies even though it is arranged on a high-loss FR-4 dielectric. The SAR function and radiation characteristics of the proposed design in the vicinity of user-hand/user-head are studied. A prototype of the proposed smartphone antenna is fabricated and good measurements are provided. The antenna provides good features with a potential application for use in the 5G mobile terminals.