Design Of Broadband Ultra-thin Composite Absorber Based On Electromagnetic Metamaterials

Electromagnetic metamaterials as a new field of scientific research has been widely concerned in physics,chemistry,electromagnetics,materials science,engineering and other fields.The periodic absorbing structures are studied based on the electromagnetic metamaterials,the purpose of this paper is to design an ultra-thin and wide band absorbing structure in the low frequency band(1-8GHz).Different from the traditional three-layer absorbing structure(metal electrical resonance,dielectric materials,metal backplane)which has a large thickness,narrow absorption bandwidth and frequency is hard to adjust.In this paper,the composite structure is combined with the magnetic absorbing coating,which not only overcome the shortcomings of the traditional absorbing structure,but also has the characteristics of wide angle and polarization insensitivity.The main contents of this paper are as follows:(1)In this paper,a kind of four-layer structure of ultra-thin low-frequency composite absorbing structure is designed by adding a layer of magnetic absorbing coating on the traditional three layer structure.This structure can achieve the absorption rate of more than 90% on the 2.98GHz—3.90 GHz,The total thickness of the absorbing structure is about 1/24 of the center wavelength and the unit cell size is about 1/8.5 of the center wavelength.(2)Based on the change of dielectric material and the optimization of structural parameters,a kind of composite absorbing structure with low-frequency and ultra-wide bandwidth is designed.This structure achieves an absorption rate of greater than 90% on the 2.17 GHz-6.86 GHz and the relative bandwidth of up to 104%.The total thickness of the absorbing structure is about 1/15 of the center wavelength.At the same time,it has the advantages of polarization insensitivity and wide angle incidence and so on.(3)Innovatively use magnetic absorbing coating for the design of the multi-layer multi-ring absorber and put forword an ultra-thin ultra-wideband absorber.The absorber is designed to balance the thin thickness and the wide bandwidth of the previous two absorbing structures,and its multi-ring is embedded in the dielectric substrate.This structure can achieve the absorption rate of more than 90% on the 2.96GHz—5.33 GHz and the relative bandwidth is 57.17%.The total thickness of the absorbing structure is about 1/18 of the center wavelength.