▎ 摘　　要

This letter presents a graphene-based tunable circular reactive impedance substrate (G-CRIS) operating at THz frequency. The proposed RIS is composed of sectoral graphene patch elements, arranged in two concentric rings and printed over silicon dioxide layer which is backed by a thin gold layer. The reactive behavior of the CRIS is made tunable by applying different chemical potential on graphene patches. This tunable CRIS is employed further to improve the operational bandwidth of a THz antenna. The CRIS loaded antenna exhibits miniaturized resonance at the lower band and wideband characteristics at the upper band. Both gain and efficiency of the antenna have been studied throughout the operating band. It is found that at THz frequency this graphene-based RIS is more suitable than metallic RIS for controlling the operational bandwidth. (C) 2017 Published by Elsevier GmbH.