Eight-port Diagonal Antenna with High Isolation and High Efficiency for 5G Smartphone

Abstract

In this letter, an 8x8 multiple-input-multiple-output (MIMO) antenna that operates in the sub-6 GHz (4.7-5.1 GHz) spectrum for 5G MIMO smartphone applications is presented. The design consists of a fully grounded plane with closely orthogonal antenna pairs placed symmetrically on the corners of the smartphone and each antenna element consists of an F-type monopole with dimensions of 18x7.5mm2. Firstly, the diversity characteristics of orthogonally placed antennas are used to reduce the coupling between antennas. On the other hand, diagonal antennas are connected by a neutral line (NL) to further improve isolation and etched slots on the ground to reduce the coupling between antenna pairs. A good frequency bandwidth (S11 < -10 dB) of 4.7-5.1 GHz has been obtained for the MIMO antenna, and the isolation is lower than 16 dB. In addition, total efficiency (TE) is greater than 77.5%, and the envelope correlation coefficient (ECC) is lower than 0.025. The fabricated antenna prototype is tested and offers good performance.