Enhancing Gain and Isolation of a Quad-Element MIMO Antenna Array Design for 5G Sub-6 GHz Applications Assisted with Characteristic Mode Analysis

This paper presents a novel quad-element array with multiple inputs and multiple outputs (MIMO) designed for 5th generation sub-6 GHz applications. The MIMO system achieves a wide impedance bandwidth, high gain, and high isolation among its components, representing significant advancements in sub-6 GHz antenna applications. The radiating element, an elliptical resonator with a circular slot, is fed by a 50 Ω, achieves a broad characteristic bandwidth from 3.7 to 5.7 GHz with a gain of 1.81 dBi. Characteristic Mode Analysis (CMA) was employed to elucidate the evolution phases of this design. The quad-element MIMO antenna array maintains a compact size and broadband characteristics by arranging mirrored elements on the same ground plane. Implemented on a cost-effective FR-4 substrate measuring 44 × 44 x 1.6 mm 3 , the recommended MIMO antenna array, enhanced with a partial ground plane having a vertical strip, yields a realized gain of 3.01 dBi and a radiation efficiency of 71% in the 5G sub-6 GHz band. Noteworthy properties include high isolation, diversity gain (DG), and envelope correlation coefficient (ECC), verifying the appropriateness of the suggested MIMO scheme for 5G transmission and reception in sub-6 GHz applications.