Tri-Mode Dual-Patch MIMO Antenna With High Isolation for 5G Terminal Applications

This communication presents a low-profile tri-mode multiple-input-multiple-output (MIMO) antenna module with high isolation for fifth-generation (5G) terminal applications. The shared radiator consists of two rectangular microstrip patches, which are capable of integrating with the back cover of the mobile devices. Three orthogonal modes, i.e., TM20, antiphase TM20, and TM01 modes are excited on a dual-patch radiator to generate polarization diversity for the first time. Meanwhile, the equivalent circuit models for the above three modes are also carefully studied. A pair of shorting pins are introduced to adjust the TM20 and antiphase TM20 modes to operate at the same frequency with good impedance matching. In addition, to further improve the isolation, a pair of differential-fed coupling strips are used to excite the TM01 mode. To validate the concept, a dual-element six-port MIMO antenna based on the proposed tri-mode dual-patch antenna module was designed, fabricated, and measured. Measured results show that the impedance bandwidth, with a reflection coefficient below −6 dB for all ports, spans from 4.8 to 5.0 GHz. The isolation is better than 30 dB. Good diversity characteristics are also proved by the measured radiation patterns, which demonstrate the proposed antenna has the potential to be applied in the 5G terminal systems.