| This thesis proposes a method for design tunable metamaterial.A rotatable microstructure is set in the metamaterial unit as well as the azimuth is the unique tunable structured parameter.By tuning the azimuth of the rotatable part,the effective parameters of the whole unit can be changed.The units are combined into an array,and each unit in the array can be adjusted separately,so as to achieve the manipulations of the incident beam.The proposed metamaterial has the advantages of high energy transmission,tunable and can achieve multiple functions.The characteristics of designed unit such as phase,refractive index,can be adjusted within a relatively large range.This thesis firstly uses the equivalent medium method to analyze and calibrate the characteristics of metamaterial,and then design devices with different functions base on generalized Snell's law,and lastly combines theoretical calculations,finite element simulations and some experiments to verify the performance of the designed devices.Further,base on the principle of resonance,two sub-wavelength tunable structured units are designed for transmission and reflection,the phase and amplitude can be effectively modulated by tuning the azimuth of the rotatable part.According the characteristics of the designed metamaterial,and combine with the beam steering principles and methods,a variety of metamaterial devices are designed and be verified by simulations and experiments,include coding focusing lenses,super-resolution imaging lenses,asymmetric transmission channels,etc.The method for design metamaterial proposed in this thesis provides an idea for reconfigurable metamaterials which do not take up extra space.The structure of unit is simple and tunable,the array can be reconfigured and the devices possess multiple functions.The proposed method decrease the dependence of parameters of material and the proposed metamaterials possess significance in the field of function wave,as electromagnetics and acoustics. |
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