Design Of Electromagnetic Metamaterial Absorber For Large Angle Oblique Incident

Metamaterials is an artificial periodic composite material with sub-wavelength scale,which possess supernormal physical properties that cannot be realized by natural materials.Through the design of the basic structure unit,the electromagnetic property can be regulated with more freedom,and the field component can be constructed independently and freely.With the complexity of radar stealth application environment,oblique incidence metamaterial design has become a hot field.The main contents of this paper are as follows:1.Calculate the wave impedance of free space and explore the variation law of wave impedance of different polarization modes with incident angle.By deducing brewster's Angle of different polarized waves,the electromagnetic parameters of different polarized waves to absorb large angle at oblique incidence are investigated.The overall electromagnetic parameters are further optimized through the magnetic resonance classical square ring metamaterial structure design to realize the large Angle absorption.Through experimental tests,in the 2-4 GHz frequency band,the designed structure achieves 90% high-efficiency absorbing in the angle range of 0°-60°.2.Based on the concept of perfect matching layer in electromagnetics,the absorbing structure for specific angle and specific frequency point is designed.Through double square ring of anisotropic metamaterial structure matching layer structure to realize tangential and longitudinal field component control,regulating the matching layer of tangential and normal dielectric constant and magnetic permeability,further perfect match specific angle of electromagnetic parameters.At the same time,the basic theories of matching layer model is established,based on the current distribution on the surface of the metamaterials to discuss the important influence on the different reflectivity parameters.Through the optimization of structural parameters,in the frequency band of 5-8GHz,the optimized structure achieves 90% high-efficiency absorbing in the angle range of 0°-70°.3.The metamaterial structure is used to improve the overall electromagnetic parameters of the material,so as to realize the large-angle absorption performance.The electromagnetic parameters at different angles are inverted and the corresponding impedance and reflectivity are calculated by the method of oblique incidence S parameter inversion.Based on the analysis of the electromagnetic parameters of the two polarization at different angles,the decrease of the absorbing property of the composite material at large angle is caused by the large mismatch of the impedance,and the design requirements of the material which can absorb the corresponding electromagnetic parameters at large angle are put forward.This paper focuses on the theoretical analysis of large angle absorption of oblique incident,and explores the electromagnetic parameters,which is of great significance in radar stealth.