| With the rapid development of communication technology,holographic antenna has become a hot spot in theoretical and engineering research.It is a kind of leaky wave antenna which has many advantages such as low-profile,simple feed,no complicated feed network,and flexible construction.Compared with traditional phased array antenna,holographic antenna is more compact in structure and has better electromagnetic compatibility characteristics.Holographic antenna can effectively avoid excessive loss and achieve high gain and high directivity.It puts forward a new idea in the field of antenna design.But the big problem that the holographic structure needs to solve is that since the holographic structure is obtained by the interference of the target field and the source field,if the source field is unchanged and the target wave with different radiation directions is needed,the overall holographic structure must be changed.In actual applications,multiple antennas need to be configured to meet engineering needs.Therefore,research on beam-steering holographic antenna has been put on the agenda.Starting from the research significance and background of holographic antenna,this thesis introduces the development status and development history of holographic antenna and leaky wave antenna at home and abroad,and explains their research value and importance.After that,the related principles of the holographic antenna and the leaky wave antenna are analyzed,and the similar overlapping points of the leaky wave principle and the holographic principle are discussed.This thesis discusses the feasibility of combining the two to design a highly directional antenna with adjustable beams.Then,starting from the mechanism of holographic impedance-modulated surface,this thesis clarifies the principle and method of surface impedance extraction.First,the surface impedance value and the side length of the radiating patch unit are function-fitted to obtain a two-dimensional holographic impedance-modulated surface antenna fed by a monopole antenna.Due to the original design intention of achieving beam control with the holographic structure unchanged,the electric control element varactor diode is introduced into the unit,and the function relationship between the capacitance value of the varactor diode and the surface impedance value is fitted.The capacitance value of the patch at each position of the impedance-modulated surface is determined.The radiation pattern of the beam-steering holographic impedance-modulated surface antenna under the radiation directions of 30 and 45 is given.It is confirmed that changing the capacitance value of each unit can achieve different angles of radiation,so as to achieve the purpose of beam control.Then,starting from the principle of the Fabry-Perot cavity,this thesis designs a onedimensional Fabry-Perot holographic leaky wave antenna under a fixed radiation angle.The working mechanism of the antenna leads to the idea of adding an electronic control element to control the antenna radiation direction angle.Antennas with different radiation directions have different leakage coefficients and phase shift constants.The phase shift constant and leakage coefficient of the antenna can be controlled by loading varactor diodes on the HIS unit and the FSS unit,so as to change the antenna radiation direction.The capacitance value of the varactor diode loaded by the HIS unit can affect the phase shift constant of the antenna,and the capacitance value of the varactor diode loaded by the FSS unit is related to the leakage coefficient of the antenna.According to the above two principles,two types of beamsteering Fabry-Perot holographic leaky wave antennas based on the reconfigurable HIS unit and the reconfigurable FSS unit are realized,and the radiation direction of the antenna is effectively controlled. |
PDF Full Text Request