Research On Characteristics Of Low Profile Holographic Impedance Modulated Metasurface Antennas

With the development of modern society,higher requirements are put forward for the antenna performance in the wireless communication system.Therefore,how to make the antenna have the advantages of multi beam,multi polarization and low profile has become the core problem of antenna design.The design theory of holographic impedance modulation surface draws lessons from the optical holographic theory and uses the holographic structure to change the radiation characteristics of the feed antenna.The holographic impedance modulation surface antenna is mainly composed of the source antenna and the holographic impedance modulation surface.The holographic impedance modulation surface is composed of the quasi periodic arrangement of corresponding units,and the impedance can change continuously.This kind of metasurface has further enhanced the regulation ability of electromagnetic wave,especially the regulation ability of beam number and polarization characteristics,and can realize multi beam,multi polarization and high gain radiation.At the same time,the holographic surface can also regulate the generation of vortex electromagnetic waves carrying orbital angular momentum(OAM),which can provide new multiplexing resources for 5g and 6G wireless communication systems.Starting from the study of the characteristics of holographic impedance modulated surface antenna,this thesis gives the design methods of multi beam with multi polarizations holographic antenna,single beam fractional OAM and multi beam fractional OAM holographic metasurface,and processes and tests the multi beam with multi polarizations antenna.The test results are in good agreement with the simulation results.The main research contents of this thesis are as follows: As a two-dimensional surface with special electromagnetic properties,the metasurface is composed of sub-wavelength units arranged in a periodic or quasi-periodic structure.Metasurfaces can control the propagation characteristics of electromagnetic waves by artificially designing the size and structure of units.This ability to manipulate electromagnetic waves makes metasurfaces of high research value in the fields of communication,radar,and holographic imaging.In recent years,it has been a hot topic in the field of electromagnetic research:1.Based on the holographic impedance modulation mechanism,the design theory of the integrated model structure of holographic impedance modulation surface and feed antenna is given.Based on the principle of holographic metasurface,the surface impedance of tensor holographic unit is extracted,and the design method and formula of tensor holographic surface are introduced.2.Based on the holographic impedance modulation surface,the multi beam with multi polarizations antenna is studied,and the impedance distribution required by the multi beam pattern is studied.Combined with the extracted surface impedance,the polarization regulation of the radiation beam is realized by using the subregional design of the array surface impedance.A holographic impedance modulation surface antenna with dual polarization dual beam and three beams with multi polarizations is designed,the dual beam antenna has the characteristics of linear polarization(LP)and right handed circular polarization(RHCP).The two three beams have the characteristics of LP and two RHCP,LP,RHCP and right handed circular polarization(LHCP)respectively,and both have high gain.3.Based on the holographic impedance modulation surface,the generation process of fractional vortex wave is studied,and the generation method of vortex beam is studied.Combined with the holographic impedance modulation mechanism,a holographic impedance modulation surface antenna capable of generating single beam first-order OAM vortex wave is designed,and then the impedance distribution of the array surface is changed to design a holographic antenna capable of generating single beam fractional OAM vortex wave.On this basis,the holographic antenna generating double beam and different fractional OAM is further designed,which lays a foundation for the multiplexing of OAM vortex electromagnetic wave in communication.