Sub-6 GHz quad-band frequency tunable MIMO antenna for 5G applications

This paper describes a slot-based, reconfigurable multiple-input multiple-output (MIMO) quad-band antenna for sub-6 GHz 5G applications. The structure contains a simple arrangement of closely spaced stub-loaded monopole radiating elements and a partial ground plane, realized on FR-4 epoxy substrate with a board dimension of 50 mm x 25 mm x 1 mm. The design has a C-shaped slot and PIN diodes for frequency reconfigurability. The ground plane includes two stubs embedded in it to improve port isolation. The antenna works in four frequency bands: 3.22-5.82, 3.3-4.4, 3.7-5.1, and 4.68-5.64 GHz with port isolation below -20 dB. Scattering parameters, envelope correlation coefficient (ECC), diversity gain (DG), total radiation efficiency, mean effective gain (MEG), and multiplexing efficiency are all determined to validate the fabricated MIMO antenna. The calculated values confirm that the developed antenna is quite promising for sub-6 GHz 5G MIMO systems.