The gain enhancement of a graphene loaded reconfigurable antenna with non-uniform metasurface in terahertz band

In this article, two uniform and non-uniform metasurfaces with near zero permeability are designed and simulated. Retrieval method is used to extract the effective parameters of the designed metasurfaces. Both of designed metasurfaces are placed as the superstrate on the top of a planar terahertz antenna. Therefore, the significant 8 dB gain improvement and 12% efficiency enhancement are achieved for the total structure in the desired frequency of 1 THz. Moreover, using the non-uniform metasurface improves the front to back ratio of the antenna from 13.8 dB to 17.4 dB. The effect of number of unit cells and the distance between antenna and metasurface on the radiation parameters of the antenna are investigated. Finally, three parasitic graphene based strips with optimized lengths are placed near the patch antenna, which can be used to adjust or tune the response of the designed high gain antenna.