In this letter, an 8×8 multiple-input-multipleoutput(MIMO) antenna that operates in the sub-6 GHz(4.7-5.1 GHz) spectrum for 5G MIMO smartphone applicationsis presented. The design consists of a fullygrounded plane with closely orthogonal antenna pairsplaced symmetrically on the corners of the smartphoneand each antenna element consists of an F-typemonopole with dimensions of 18×7.5 mm~2. Firstly, thediversity characteristics of orthogonally placed antennasare used to reduce the coupling between antennas. On theother hand, diagonal antennas are connected by a neutralline (NL) to further improve isolation and etched slotson the ground to reduce the coupling between antennapairs. A good frequency bandwidth (S11 < ?10 dB) of4.7-5.1 GHz has been obtained for the MIMO antenna,and the isolation is lower than 16 dB. In addition, totalefficiency (TE) is greater than 77.5, and the envelopecorrelation coefficient (ECC) is lower than 0.025. Thefabricated antenna prototype is tested and offers goodperformance.
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