A compact four-element multiple-input multiple-output (MIMO) antenna is proposed for 5G applications. The offset fed antenna structure is designed from a rectangular and semicircular monopole antenna. In this novel MIMO structure, the surface current and near fields of left element are mainly concentrated toward left and that of right element towards right, and thus high isolation is achieved between left and right elements even without using any isolation technique, whereas the little surface current at the nearby edges of top and bottom elements helps in achieving high isolation. The fabricated prototype has board dimensions of 0.374λ0×0.275λ0, where λ0 is the free-space wavelength at 3.3 GHz. The structure offers isolation > 20 dB between the elements over 3.3-6.3 GHz. The envelope correlation coefficient (ECC), diversity gain (DG), and mean effective gain (MEG) confirm to MIMO antenna specifications. The antenna offers stable nearly omnidirectional radiation patterns.
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