Research On Reconfigurable Holographic Impedance Modulation Antenna

In the increasingly developed communication system,with the continuous advancement of technology,antennas that can meet the needs of large capacity,multi-function,and ultrawideband are becoming more and more urgent.Reconfigurable antennas have become important research topics for antennas.Holographic antennas have attracted much attention because of its low-profile characteristic,which means it can be integrated,and basically not require additional feeding structures.However,according to the holographic theory,it can be found that once the holographic structure is determined,the radiation direction angle of the holographic structure is often fixed,so the reconstruction of the holographic antenna has high research value.This thesis first introduced the research situation of holographic antennas and reconfigurable antennas at home and abroad.Then,it discussed the relationship between the optical holography and the holographic antenna,elaborated the principle and concept of the holographic structure based on the impedance modulation surface,analyzed the realization of holographic antenna structure’s element form and the extraction method of surface impedance,and studied the factors that affect surface impedance such as size of radiation patch and dielectric constant.Then,the change rule of surface impedance was studied after changing the dielectric constant.Taking liquid crystal material as an example,the feasibility of realizing the reconfigurability of a holographic antenna based on the change of the dielectric constant is verified by utilizing the characteristic that its dielectric constant changes with the magnitude of the applied electric field.Next,a varactor diode was loaded on the radiating unit,and the influence of the capacitance value of the diode on the surface impedance was discussed.Applying it to the design of holographic antennas,it is found that controlling the size of the capacitance of the varactor diode can also realize the reconfigurability of the holographic antenna.Finally,by combining the holographic theory with the amplitude weighting principle,the correspondence between the arrangement of the unit excitation amplitudes and the holographic pattern in the holographic structure was calculated.A PIN tube was added to the unit structure of the antenna,and switch was controlled to achieve different beam pointing,then the reconfigurable holographic antenna was eventually completed.A holographic antenna forms a holographic pattern by constructing a certain radiating unit to realize the expected antenna electromagnetic wave beam.The above implementation of holographic reconfigurability uses electronic control elements to control unit performance from different angles,which achieves the purpose of beam control,and has certain reference and research value.