In this letter a four-port multi-input-multi-output (MIMO) antenna for 5G applications is proposed. This antenna is compact with a size of 11.3 mm×31 mm excluding feed lines. The radiation patterns of the antenna show pattern diversity in the azimuthal plane, and each antenna element has an end-fire gain about 10 dBi by employing an array of metamaterial unit cells. The isolation between the antenna elements with edge to edge separation <λ0/5.5 at 28 GHz is enhanced by trimming the corners of the rectangular high refractive index metamaterial region along with a ground stub between antennas. The proposed antenna is fabricated, and each antenna element has return loss, Snn<-10 dB with isolation, Snm>21 dB in the frequency range 26 GHz to 31 GHz, which makes this antenna potential candidate for MIMO application at 28 GHz band enabling 5G cellular communications.
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