Research On Tunable Electromagnetic Metamaterial Absorber Based On Ferroelectric Materials

With the rapid development of electromagnetic metamaterials,its absorbing characteristic has attracted widespread attention,since it has thin thickness,light weight,high absorbing rate and frequency adjustable,easy to conformal,etc,make the research of electromagnetic metamaterials in antenna,radar,electromagnetic stealth,solar cells and other areas of military and civilian use to become an important research subject.Based on the theoretical basis and mechanism of electromagnetic metamaterial wave absorbers,several new types of metamaterial wave absorbers in Microwave and Terahertz frequencies are studied in this paper.At the same time,based on the model design and simulation,a kind of dual-frequency metamaterial absorber with adjustable frequency is made and its performance is tested and analyzed.The main content includes the following three parts:（1）A type of metamaterials absorber based on"H"in microwave frequency was studied,relevant structure parameters were optimized by analyzing the continuous optimization of the suction port,when the"H"type in the middle of the beam position changes,the center frequency of metamaterials absorber from 13.34 GHz left to 13.18 GHz,the absorbing the bandwidth of the frequency band extension gradually,implements the metamaterial absorbers,wave absorbing passive tuning bandwidth.（2）Two kinds of terahertz band bandwidth and frequency tunable metamaterial absorbers are studied.A ferroelectric material SrTiO₃,whose dielectric constant can vary with temperature,is selected to change the dielectric constant of the dielectric material by changing the ambient temperature,so as to realize the adjustable resonant frequency of the metamaterial absorber.One of them is SrTiO₃ material with elliptic metal resonant structure and dielectric constant that can change with temperature as the intermediate layer.The simulation results show that when the ambient temperature increases from 200K to 400K,the resonant frequency moves from1.65THz to 2.45Thz,and the frequency shift of the absorbing frequency band reaches 800GHz.The other is to fill the"十"SrTiO₃ material inside the rhombic metal resonant structure.The simulation results show that the absorption rate of the metamaterial absorber is basically unchanged when the ambient temperature changes from 280K to 360K,the incident electromagnetic wave can be basically absorbed completely,and the total frequency shift is90GHz.In addition,by analyzing the distribution of electric field and surface current at the corresponding resonant absorption peaks at different temperatures,the intrinsic absorbing mechanism is revealed.On this basis,the influences of structural parameters,material properties and incident electromagnetic wave characteristics on the performance of the metamaterial absorber are further analyzed.（3）A dual-frequency tunable metamaterial absorber is studied.A frequency tunable metamaterial absorber based on CaTiO₃ dielectric layer is designed.The metamaterial absorber was simulated,designed,fabricated and tested,test results show that the metamaterial absorber samples with the temperature gradually increased from 21.7℃to 76.3℃,the first resonant frequency is increased from 5.10 GHz to 5.39 GHz,the second resonant frequency increased from 6.29GHz to 6.61GHz,realized the double frequency adjustable,verify the validity of the design and simulation.