Research On Broadband And Reconfigurable Electromagnetic Manipulation Theory And Their Applications Based On Metasurfaces

Bandwidth is one of the core problems that restrict the development of wireless communication,and it also plays an important role in the performance of the communication system.However,the bandwidth of the communication system is limited to different degrees.Therefore,how to broaden the bandwidth of the communication system,achieve broadband communication system,and then solve the problem of the limited bandwidth of communication system,is a hot issue that the world’s experts in the field of wireless communication have been committed to.Generally,the bandwidth of the communication system can be broadened based on algorithms or devices.As an essential part of communication,electromagnetic(EM)devices can be used to control,transmit,and receive EM waves and will directly affect the performance of the whole communication system.As a new kind of EM device,metasurfaces have the advantages of low profile,easy processing,and integration,and amplitude,phase,and polarization of EM waves can be simply controlled based on metasurfaces.Therefore,it is of great significance to broaden the bandwidth of communication systems and then solve the problem of the limited bandwidth by studying the broadband and reconfigurable EM manipulation theory and its application based on the metasurface.In this paper,based on the theory of frequency reconfigurable metasurface multifunctional integration,frequency reconfigurable metasurface vortex wave generation,and broadband and reconfigurable metasurface multi-channel multiplexing,combined with the thermotropic phase transitions material vanadium dioxide(VO2),the broadband and frequency-reconfigurable characteristics of the metasurface are realized which broaden the working bandwidth of the metasurface by using the phase response of the unit cell and Pancharatnam-Berry(PB)phase.The main contributions of this dissertation are summarized as follows:(1)Research on the fundamental theory of broadband and reconfigurable metasurfaces:Aiming at the problem of the lack of a detailed and in-depth introduction of relevant theory.In this dissertation,the generalized Snell’s law and geometric phase principle are studied based on different methods,and the EM equivalent model and simulation method of VO2 are introduced.(2)Research on the theory and application of broadband achromatic metasurface EM waves focusing:Aiming at the problem of the narrow working frequency band of metasurface lens and the complicated design method of achromatic metasurface lens.In this dissertation,firstly,the theory of EM wave focusing based on metasurfaces is studied,including achromatic metasurface lens theory,and on this basis,an improved design method of broadband achromatic metasurface lens is proposed by using the fitting curve.Then,based on theoretical research,a broadband achromatic metasurface lens is designed for EM wave focusing by using the phase response of the unit cell and PB phase.(3)Research on the theory and application of frequency reconfigurable metasurface multifunctional integration:Aiming at the problem that the metasurface can only achieve a single function and the working frequency band of the multifunctional metasurface is narrow.In this dissertation,firstly,the theory of multi-functional integration based on metasurfaces is studied,including the metasurface EM interference model and Fabry-Perot-like scattering theory,and simulation of the scattering process base on MATLAB.Then,based on theoretical research,a frequency reconfigurable multifunctional metasurface is designed for EM wave polarization and transmission-reflection state control by using the phase response of the unit cell and VO2.(4)Research on the theory and application of frequency reconfigurable metasurface vortex wave generation:Aiming at the problem that the working frequency band of the metasurface for generating the orbital angular momentum(OAM)vortex wave is narrow and the performance of the generated OAM vortex wave is fixed.In this dissertation,firstly,the theory of vortex wave generation based on metasurfaces is studied,including generating OAM vortex waves,increasing EM wave transmission distance,realizing beam deflection,and generating non-diffraction OAM vortex waves based on metasurface.Then,based on theoretical research,a frequency reconfigurable metasurface is designed using for generating dynamic deflection non-diffraction OAM vortex wave by using the phase response of the unit cell and VO2.(5)Research on the theory and application of broadband and reconfigurable metasurface multi-channel multiplexing:Aiming at the problem that the working frequency band of the metasurface for realizing OAM multiplexing is narrow,the methods for realizing OAM multiplexing based on the metasurface is complicated,and the number of realized multiplexed channels is limited.In this dissertation,firstly,the theory of multi-channel multiplexing based on metasurfaces is studied,including OAM single-dimensional multiplexing based on the single-frequency angle-multiplexed metasurface,and on this basis,a method for multi-dimensional multiplexing of spatial and frequency domains based on the broadband angle-multiplexed metasurface is proposed.Then,based on theoretical research,a broadband angle-multiplexed metasurface is designed for multi-dimensional and multi-channel multiplexing by using the PB phase.Furthermore,a broadband frequency reconfigurable metasurface is designed for multi-dimensional and multi-channel multiplexing by using VO2.In this paper,the theory and method of EM control for broadband and reconfigurable characteristics based on the metasurface are studied,and the broadband and reconfigurable metasurface is applied to the communication to realize different EM devices.The theory and application of the research are of great significance for how to realize the miniaturization,integration,and multi-function of the communication system,broaden the bandwidth of the communication system,make the communication system more stable,stronger against interference,faster,more reasonable and efficient use of spectrum resources,and constantly improve the system capacity.