Tunable THz leaky-wave radiation from periodic chains of graphene-coated circular rods

The beam-scanning properties at a fixed frequency in the low terahertz range of one-dimensional periodic leaky-wave antennas composed by a periodic chain of circular dielectric cylinders coated with graphene are studied. A rigorous full-wave modal solver, based on the lattice-sums technique combined with the transition-matrix approach, is applied to the analysis of transverse electric (TE) and magnetic (TM) leaky modes, where the transition matrix suitably takes into account the conductivity of the external graphene sheet. The reconfigurable features of the leaky-wave structure have been investigated in terms of the dispersion behaviors of the phase and attenuation constants of the radiating proper $n=-1$ space harmonic of the Bloch leaky modes. The beam-scanning performance, variation of the beamwidth, and the appearance of grating lobes as functions of the graphene chemical potential are investigated. Three-dimensional structures composed by a finite number of graphene-coated dielectric rods sandwiched by metal or perfect magnetic conductor plates are finally validated through full-wave simulations, showing a good beam-scanning capability for both TE and TM polarizations, respectively, and a remarkable agreement with the theoretical leaky-wave model.