Graphene-based Fabry-Perot cavity leaky-wave antennas: towards an experimental validation

It has recently been shown that the relaxation time of a graphene sheet is the crucial parameter that governs the radiation performance in graphene THz antennas based on either plasmonic or nonplasmonic leaky waves. Moreover, the radiating properties of these devices have always been derived assuming an ideal dipole-like source, and no full-wave and experimental results on realistic feeders have been reported, yet. To this purpose, in this work we aim at bringing the designs of graphene-based Fabry-Perot cavity leaky-wave antennas (FPC-LWAs) towards an experimental stage. First, the antenna design is validated with full-wave simulations, by modeling not only the antenna structure, but also a realistic THz source, namely an open-ended waveguide. Another considerable difference with the previous designs is the use of a cylindrical geometry. As a result, the radiation patterns now exhibit a remarkable omnidirectionality over the azimuthal plane, as the beam is scannable from broadside up to 45°. Second, THz measurements are carried out to characterize graphene samples deposited over silicon substrates. The relaxation time is estimated by combining the transmittance measurements of a sample with well-established theoretical models for the graphene surface conductivity. These results shed several issues for the future developments of graphene-based FPC-LWAs.