The Research Of Lightweight And Wideband Absorber Based On Three-dimensional Lossy Metamaterial

Electromagnetic(EM)metamaterials(MM)are a kind of artificial EM materials with extraordinary EM characteristics,which are arranged by subwavelength unit structures periodically.Due to the size of the MM unit is usually far smaller than the wavelength,the EM characteristics of MM depends on the structure of the unit and can be characterized by effective media theory.The researchers can design the structure of the unit to realize the fantastic physical characteristics which cannot be obtained by the natural material.Therefore,the MM can control the EM wave efficiently.MM absorbers,as an important research orientation of MMs,have developed continuously in recent years with related novel researches emerging.Because of the artificial design of MM unit,MM absorbers can break the limit for the EM characteristics of natural materials,and can be wideband and lightweight compared with traditional absorbers.Even we can scale the MM absorbers overall to apply them at other frequency band of EM wave.According to the concept of MM and the relevant researches of MM absorber,we designed a lightweight and wideband absorber based on lossy three-dimensional(3D)MM in the paper.We have test different structures and methods of fabrication to realize better performance of absorbing,and the related researches are as follows:1.We designed a 3D paper-based wideband MM absorber according to the concept of paper-based electronic component.The structure of the MM absorber is the grid structure arranged periodically,which is fabricated by crossing the standing paper sheets with resistance array drawn on them.To fabricating the sample of the MM absorber,we researched the influence factors for the square resistance of pencil-drawn resistance strips,and utilized automatic drawing machine to draw the resistance strips.The sample of the MM absorber have been tested and can realize wideband absorption with the thickness of 19mm.The bandwidth of over 90%absorptivity is ranging from 2.5GHz to 40GHz.2.We tried to replace the resistance strip array by resistance films that can be mass produced,such as ITO films and carbon films,and designed a new structure of the 3D wideband absorber.First,we used ITO films to form latticed unit to make up the optical transparent MM absorber.However,the technology of producing ITO films cannot obtain stable high square resistance.Thus,we replaced them by carbon films to fabricate MM absorber.We tested the MM absorber and verified that the absorber can realize the refectivity of less than-10dB in the range of 1.5-40GHz with the limit of 25mm.The areal density of the MM absorber is 1.48kg/m2,so the MM absorber is wideband and lightweight.3.We tried to broaden the bandwidth of the MM absorber.First,we analyzed limitation of the bandwidth for the MM absorber by optimizing the parameters of the MM absorber with genetic algorithm in MATLAB.Then,we analyzed the mechanism of absorption,tuned the structure of the MM absorber and the lower bandwidth limit of the MM absorber was expanded to 1.1GHz with the thickness of 30mm.In the next part,we analyzed the method of combined absorber and combine the 3D wideband absorber with low-frequency tunable absorber.Finally,the combined absorber was tested,and can realize tunable absorption in the band of 0.78-1.39GHz and wideband absorption in the band of 1.4-18GHz with the absorptivity of over 90%.The test demonstrated that we can achieve the ultra-wideband absorption generally in the range of 0.7818GHz by combining the two MM absorbers.