Research On Pattern Reconfigurable Antenna Based On Metasurface

As a key component in morden communication and radar systems,antenna has gradually got more attation from people,and more demands for better antenna performance have been proposed.In order to simplify the antenna system and reduce the cost,reconfigurable antenna becomes a good choice.This thesis focuses on the design of beam reconfigurable antenna based on the artificial metasurface.The main contents in this thesis can be summarized as follows.Firstly,the current research status and developing direction of metasurface and graphene have been introduced.The reflection coefficient of measurface has been calculated with two-port microwave network method based on equivalent impedance of the periodic cell.Then the result of analytical method has been verified by full-wave electromagnetic simulation with HFSS and CST.Secondly,based on the reconfigurable theory of Fabry-Perot(FP)resonant antenna,a graphene sheet is used as a tuning part of high-impedance surface(HIS)and partly reflecting surface(PRS)that acts as the top and bottom surface of the FP antenna.It is shown that,by adjusting the graphene conductivity,the beam of the directivity pattern can be reconfigurable within about ±75° scanning angle,and the maximum directivity of all states is more than 5dBi.It is obvious that the antenna has good radiation characteristics.Thirdly,a novel beam reconfigurable terahertz(THz)antenna consisted of hybrid copper-graphene high impedance surface(HIS)and a simple excitation above it is proposed in this paper.The beam of this antenna is reconfigurable due to the tunable conductivity of graphene.With different bias voltages between the graphene and electrodes,the conductivity of graphene can be tuned and the reflection characteristics of the HIS are controllable,which finally changes the radiation beam of the whole antenna.This THz antenna works at 1.03 THz.The radiation characteristics of the antenna are studied by virtue of full-wave simulation with the help of CST Microwave Studio.Modulation of radiation beam in a wide deflection range of ±75° is observed.Fourthly,a pattern reconfigurable microstrip quasi-Yagi antenna based on metal-graphene hybrid materials is introduced.The quasi-Yagi patch antenna is printed on the surface of a silicon dioxide substrate.The directing elements are made from metal and extended to the length of the reflecting element by graphene.The metal and graphene strips are printed on the bottom of the dielectric substrate.The H-plane pattern of the antenna can be scanned from-70 to 70 degrees by controlling the bias voltage of graphene on the upper and lower substrate surfaces.Finally,work in the thesis is summarized and possible improvements are discussed.