Abstract A tunable terahertz four-port multiple-input-multiple-output (MIMO) graphene-based microstrip patch antenna with self-multiplexing ability is designed and numerically studied. Insertion of cross-slot in the graphene patch improved the isolation level to the order of 50-documentclass12pt{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$-$$end{document}70 dB in the four-port MIMO mode operation. Four separate biasing pads are used to obtain independent frequency tunability, which gives rise to MIMO and/or self-diplexing, self-triplexing, and self-quadruplexing operation, by using different combinations of dc bias voltages. The MIMO and self-multiplexing actions are attained while using common ground plane and continuous graphene patch. The MIMO performance parameters like envelope correlation coefficient (ECC), diversity gain, mean effective gain, port-to-port isolation, etc. are found to be within the acceptable limits. A four-port equivalent circuit model of the MIMO antenna is presented to provide insight into the radiation mechanism and to validate the simulation results. The designed four port antenna is found to provide ECC in the order of 0.0073 and isolation in the range of 35–43 dB while it is operated in the self-diplexing with two-port MIMO mode operation.
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