Research And Design Of Reconfigurable Artificial Electromagnetic Absorbing Materials

Artificial electromagnetic material is a kind of material that contains artificial structure and exhibits special electromagnetic characteristics.In this paper,reconfigurable electromagnetic absorber with tunable absorbing frequency are studied.The reconfigurable absorber are improved in absorptivity,frequency tuning range,absorption bandwidth and polarization insensitivity.This paper mainly completes the following works:1.According to the structure of reconfigurable absorber based on ring FSS designed in this paper,the effect of separate metal wires in Frequency Selective Surface(FSS)is analyzed,and the equivalent circuit model is obtained.Based on the equivalent circuit model,the calculation formula of material's reflection coefficient is deduced,and the calculation of reflection coefficient is completed in matlab.This model paves the way for the research and design in this paper.2.The research and design of reconfigurable absorber based on varactor diodes are completed,and the processing and testing are completed.Firstly,the method of material selection is studied,including the selection of dielectric layer and varactor diodes.Secondly,the design method of FSS is studied,and the FSS cell which looks like a character“?” is preliminarily determined.Then,according to the simulation results and the actual size of the diode,the horn-like metallic wire is introduced to improve and optimize the material structure.Finally,the material processing and testing are completed,and the measurement results are in consistent with the simulation results.3.The single-polarized graphene-based reconfigurable microwave absorber have been studied and designed.Firstly,the equivalent circuit of the ring FSS surface is given to explain its working principle.Then,the selection method of the ring FSS is determined.After that,two structural improvement strategies are proposed,which greatly enlarge the square resistance of graphene and effectively increase the tunable range of absorbing frequency.In addition,a reconfigurable absorber based on graphene and rectangular ring FSS is designed,and some uncontrollable factors affecting the properties of the material are analyzed.Finally,the optimized reconfigurable absorbing materials based on ring and elliptical ring FSS are presented and compared.4.The research and design of polarization insensitive graphene-based reconfigurable absorber are completed.Firstly,the influence of feeder direction on polarization characteristics of materials is studied.It is proved that the absorbing materials in this paper can only use vertical feeders.Secondly,field effect structure is applyed to realize vertical feeding.After that,in order to improve the polarization insensitivity of the material,the FSS cell-intensive arrangement with better polarization symmetry is adopted.Finally,the design and optimization of the material are completed,and the reconfigurable absorber with wide frequency tunable range,wide absorption bandwidth and excellent polarization insensitivity is obtained.