Uni-planar MIMO Antenna for Sub-6 GHz 5G Mobile Phone Applications

For sub-6 GHz 5G-enabled smartphones, a design for a uni-planar MIMO antenna system is proposed. Following the pattern diversity concept, the MIMO antenna consists of four loop-shaped radiators placed at each corner of the mobile phone board. The single antenna element is meant to resonate at 3.5 GHz. The impedance bandwidth of a single antenna element is noted to be 1.28 GHz (3-4.28 GHz) for
$\mathrm{S}_{11}\leq-6\ \text{dB}$
, and it is equal to 720 MHz (3.18-3.9 GHz) for
$\mathrm{S}_{11}\leq-10\ \text{dB}$
. For a single antenna element, a peak realized gain of 3.64 dBi is observed with an antenna efficiency of >90%. Isolation of >10 dB between antenna elements is achieved for the MIMO configuration. Furthermore, the designed MIMO antenna provides enough radiation coverage to support different sides of the mobile phone board, which is an important feature for future 5G-enabled handsets.