| Terahertz is between microwave and optical frequency,from 0.1THz to 10 THz.Terahertz communication combines the advantages of microwave communication and optical communication,it has high transmission rate,large capacity,strong directionality,high safety,high penetrability and so on.Terahertz communication will be the trend of the future communication system.First,metamaterials and graphene are introduced.Metamaterials are composite materials with artificial structures.The properties of the metamaterial depend not only on the material itself,but also on the artificial structure and the geometry of the artificial structure.Utilizing metamaterial properties can improve electromagnetic device performance.Graphene has high electrical conductivity,high thermal conductivity,and high carrier mobility.Controlling the doping level or adjusting the bias voltage can change the chemical potential of graphene,thereby changing the surface conductivity of graphene.The combination of graphene and metamaterials is of great significance and value for improving the performance of terahertz antennas.Second,three kinds of terahertz metamaterials are designed and simulated,which are metal-ring metamaterial,grapheme-monocyclic metamaterial and grapheme-metal composite metamaterial.The left-hand bands are 0.622-1.160 THz,2.74-5.29 THz and 4.06-6.42 THz,respectively.The transmission coefficients in left-hand band are higher than 75%,95% and 60%,respectively.The pass band characteristics of metamaterials are good,they are suitable for designing antennas.Finally,the three metamaterials are used in the design of corresponding terahertz antennas,and we found that the terahertz antenna bands are extended after adding the metamaterials.Graphene is loaded in the designed terahertz antennas,the bands of grapheme-based terahertz antennas have been further extended.The surface conductivity of graphene is adjusted by the bias voltage,to realize the frequency tunable of terahertz antennas.The wide-band and frequency-tunable terahertz antennas designed in this thesis provide guarantee for high-quality terahertz communication.They can achieve directional,anti-jamming,and high-secure terahertz communication under harsh natural conditions such as sandstorms and heavy smog. |
