Graphene Fabry–Perot cavity leaky-wave antennas. Plasmonic versus nonplasmonic solutions

Tunable THz antennas based on a single unpatterned graphene sheet placed inside a grounded dielectric multilayer are studied with the aim of characterizing their performance in terms of pattern reconfigurability, directivity, and radiation efficiency. The considered structures belong to the class of Fabry-Perot cavity (FPC) antennas, whose radiation mechanism relies on the excitation of cylindrical leaky waves with an ordinary (i.e., non-plasmonic) sinusoidal transverse modal profile. This allows for achieving radiation efficiencies considerably higher than those of alternative graphene-based radiators based on the excitation of surface-plasmon polaritons (SPPs) either in bound or leaky propagation regimes. A customized efficient circuit model has been employed in order to obtain all the radiation characteristics of such graphene FPC antennas, which have been also fully validated by means of a CAD tool. The role of the graphene quality is explicitly taken into account in this comprehensive investigation, proving that it plays a remarkable role in establishing the antenna performance. In particular, it is expected that the standard quality of graphene allows for designing low-efficiency reconfigurable THz antennas based on SPPs and, conversely, high-efficiency FPC antennas with slightly reduced reconfigurability.