Compact Reconfigurable MIMO Antenna for 5G and Wi-Fi Applications

Four miniaturized four-element multiple-input multiple-output (MIMO) antenna designs are proposed, designed, and fabricated with dimensions of 26 mm x 26 mm x 0.8 mm each. The first MIMO design operates at 3.5 GHz, while the second operates at 5.2 GHz. The first and second designs are combined into a third design that can be reconfigured to operate at either 3.5 GHz or 5.2 GHz. A new concept of balance is introduced to address the issue of small ground faced by the previous designs. This concept is applied to the third antenna design, resulting in a fourth design of reconfigurable MIMO operating at 5.2 GHz or 3.5 GHz. The antenna demonstrates good impedance matching at both operating frequencies, with isolation levels of approximately 25 dB and 21 dB, envelope correlation coefficients (ECC) less than 0.0001, diversity gain (DG) of around 10 dB at both frequencies, and peak realized gains of 3.5 dBi at 3.5 GHz and 4 dBi at 5.2 GHz. The radiation efficiency of the fourth compact antenna design is approximately 88% at 3.5 GHz and 91% at 5.2 GHz. The measured results show excellent agreement with the simulated results for all four antenna designs.