Analysis of side-lobe generation in graphene reflectarrays, considering the impact of losses

The surface wave generation in microstrip antennas and reflectarray antennas composed of microstrip patches is an unavoidable phenomenon. The wave incidence on discontinuities and edges causes side-lobe generation and main beam declination. In this paper, the side-lobe production in reflectarrays is analyzed using the Fourier transform technique in relation to its structural parameters. In reflectarray antennas composed of graphene unit-cells, the side-lobe production is quite different from the metal ones due to the graphene intrinsic characteristics, such as Ohmic losses and kinetic inductance. In this paper, 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, in 1 THz. Also a reflectarray structure composed of aluminum unit-cells with structural parameters similar to the graphene reflectarray is simulated and the results are compared. The losses in graphene reflectarray absorbs part of the Surface waves and increases the directivity, In comparison with the metal ones. It is found necessary to design the structure in such a way that the losses be appropriate for optimum gain pattern.