Dual-polarized plasmonic leaky-wave antenna based on anisotropic graphene-modulated metasurface

Abstract

Conventional isotropic graphene metasurfaces (MTSs) are limited to supporting surface plasmon polariton (SPP) waves exclusively in either transverse magnetic (TM) or transverse electric (TE) modes. To overcome this limitation, an anisotropic MTS composed of an anisotropic graphene patch (AGP) unit cell was proposed, enabling the simultaneous propagation of both TM-SPP and TE-SPP mode waves. Devices such as waveguides and splitters based on this design have also been developed. This paper presents, for the first time, a dual-polarized plasmonic modulated leaky wave antenna (LWA) based on an anisotropic graphene metasurface (MTS) operating in the terahertz (THz) band. To achieve dual polarization, the graphene MTS must support the simultaneous propagation of both transverse magnetic (TM) and transverse electric (TE) surface plasmon polariton (SPP) mode waves. The detailed design procedure for the proposed antenna is then presented. First, the optimal propagation characteristics for achieving phase matching of both modes and high efficiency in the MTS antenna are determined using an equivalent circuit model. Next, the required modulated surface impedance for both orthogonal modes, enabling broadside radiation, is calculated and realized using the proposed AGP unit cell. Finally, a dual circularly polarized antenna based on the proposed MTS is implemented. The results indicate that the proposed antenna achieves directivities of approximately 21.5 dBi, radiation efficiency of about 26%, and sidelobe levels (SLLs) exceeding − 15 dB for both polarizations.