A Compact MIMO Antenna Design Using the Wideband Ground-Radiation Technique for 5G Terminals

This paper introduces a 4 x 4 multiple -input and multiple -output (MIMO) antenna application based on the conception of the characteristic mode of 5G terminals. The proposed antenna used a series capacitor and a parallel capacitor to control input impedance matching, while the resonance frequency was controlled by employing a resonance loop capacitor. In this way, we achieved a compact miniaturization antenna that uses ground radiation for the target 5G New Radio (NR) operating bands with n48, n77, and n78 bands. The simulation and measurement data revealed that the -6 dB bandwidth of the proposed antenna was approximately 1,240 MHz (ranging from 3.14 GHz to 4.38 GHz), while the efficiency also improved from 38.7% (reference) to 49.1% (proposed) within the 3 GHz to 4.6 GHz range. Furthermore, the radiation pattern exhibited satisfactory radiation performance. Therefore, it was concluded that the proposed 4 x 4 MIMO antenna set technology has promising prospects for application in 5G communication terminals in the future.