Research On Wideband Metamaterial Absorber

Electromagnetic metamaterial has been a new research field,since the implementation of left-handed materials in 1996,which have received increasingly attention. As a member of metamaterial family, metamaterial absorbers have received more and more attention because of their wide application.This thesis first introduces the concept of electromagnetic metamaterials and metamaterial absorbers, and discussesthe evolution and research achievements of metamaterial absorbers briefly,which is a research field of electromagnetic metamaterials.Then the absorbing mechanism and the concept of effective medium have been studied. According to the disadvantages in the current effective electromagnetic parameter extraction algorithms,an new method to extract the electromagnetic parameters of the metamaterials has been developed. The accuracy of the proposed method is greatly improved, and the branch problem can be correctly chosen by proposed. Two numerical examples are given to verify the correctness of the proposed algorithm.For the problem of narrow absorbing band, three new metamaterial structures are designed according to two methods.According to magnetic loss of materials, we designed two new metamaterial absorbers. The first one is a multilayer structure consisting of the iron ring. The whole thickness of this structure is only 1.78 mm. The simulation results of the proposed structure demonstrate that a wide bandwidth from 10 GHz to 21 GHz is obtained with the absorption higher than 90%. Furthermore, insensitive polarization and wide incident angle of the proposed structure can be obtained. The wave-absorbing mechanism of this structure are analyzed accroding to surface current, impedance, dielectric loss and effective media parameters, respectively. The second one is a single layer structure composed of the permalloy patch. The thickness of this structure is only 0.64 mm, but a very wide absorbing bandwidth can be obtained. The two examples fully illustrate good performance.Finally,a new metamaterial absorber is designed based onthe resistance loss. The whole thickness of this structure is 3mm. The simulation results demonstrate that a wide bandwidth is obtained inthe range from 6GHz to 16.1GHz with the absorption higher than 80%. The wave-absorbing mechanism of this structure is stuided based on surface current, impedance, dielectric loss, and optimized gemoetry sizes of the new proposed structure.