Investigation of losses on directivity improvement in the graphene reflectarray design

The surface-wave generation in microstrip antennas and reflectarray antennas composed of microstrip patches is an unavoidable phenomenon. The incidence of surface-waves on discontinuities and edges results in side-lobe generation and main beam declination. In this paper, the side-lobe production in reflectarrays is analyzed using the Fourier transform technique and aperture field estimation. In reflectarray antennas composed of graphene unit-cells, the side-lobe production is somewhat different from the metal ones due to the graphene intrinsic characteristics, such as Ohmic losses and kinetic inductance. In this paper, the impact of graphene Ohmic losses on the side-lobe reduction and directivity improvement is analyzed. A reflectarray composed of graphene cell-clusters is designed and simulated for the investigation of the generation of surface-waves and side-lobes in the far-field pattern, at 1 THz. And the impact of losses, on directivity improvement, have been examined for different reflection angles.