Wideband MIMO Antenna Systems Based on Coupled-Loop Antenna for 5G N77/N78/N79 Applications in Mobile Terminals

A wideband 8-antenna multiple-input and multiple-output (MIMO) system that can cover 3.3-5.0 GHz is proposed for the 5G new radio N77/N78/N79 application in mobile phones. The wide bandwidth of the MIMO antenna system is obtained by the proposed coupled-loop antenna, which has three coupling sections located separately at its top central and two sides. Due to this special arrangement, the coupled-loop antenna can support three resonance modes of loop antenna: 0.5λ, 0.75λ, and 1.0λ modes. The distinctive feature of the proposed coupled-loop antenna design is that it can excite the 0.75λ modes, which has not been reported before. The wide bandwidth is obtained by the combination of the three resonance modes. To evaluate the performance of the proposed 8 × 8 MIMO antenna system, the antenna isolation, envelope correlation coefficient (ECC), and channel capacity (CC) are all investigated. Antenna prototypes for an 8-antenna MIMO system located along the edge of mobile phones are fabricated and measured, and; quite good agreements between simulation and measurement are obtained.