A Multiple-Input Multiple-Output Antenna with Metamaterial Enhancement for 5G Channel Sounding in the Upper 6 GHz Band

This paper presents a compact 2 × 2 multiple-input multiple-output antenna system designed for 5G smartphones operating in the upper 6 GHz band, and which is to be initially considered as a prototype resembling a user terminal in a channel sounding system. The antenna incorporates a split-ring resonator metamaterial layer, enhancing its gain by at least 1.5 dB across the entire bandwidth without increasing the size of the antenna. The results show a good agreement between the simulations and measurements, achieving a strong isolation, below −18 dB; a low envelope correlation coefficient, lower than 0.025; as well as an efficiency exceeding 75%, making it highly suitable for 5G wireless applications, including both indoor as well as outdoor wireless channel characterization.