Wideband Diversity MIMO Antenna Design with Hexagonal Slots for 5G Smart Mobile Terminals

In this paper, we propose a wideband polarization diversity multiple-input multiple-output (MIMO) antenna array for 5G smart mobile devices. The proposed MIMO antenna array consists of 8-ports dual-polarized L-shaped lines that highly excite radiating slots, where the elements are placed at four-corners of a compact mobile unit of size 75 × 150 mm2. The uniqueness of the proposed MIMO antenna structure comes from the deployment of octagon-shaped resonant slots within the metallic ground plane, i.e., the octagonal-slots are etched from the bottom (ground) layer of the main mobile board. Due to the unique slots in the ground plane, wideband impedance has been achieved (3.38– 3.8 GHz at −6-dB threshold). The proposed smart phone 8 × 8 diversity MIMO antenna is designed to support the spectrum of commercial sub-6 GHz 5G communications and cover the frequency range of around 3.5 GHz band with high decoupling between antenna ports. The proposed array is designed, numerically simulated, fabricated, and tested. Good agreement between simulated and measured results was achieved. The MIMO antenna has a satisfactory far-field performance along with very low envelope correlation coefficient (ECC) < 0.055, high diversity of more than 9.95, and very low specific absorption rate (< 1 W/kg for a 10-g human tissue).