Design of Flexible and Transparent Metamaterial Absorber with Broadband
Electromagnetic metamaterials absorbers provide indispensable technical support and important application value for communication,radio,radar,stealth technology and medical imaging due to their excellent electromagnetic wave regulation performance.Current research targets wideband absorbers,essential for handling multiple bands and adapting to complex electromagnetic environments.Traditional absorbers face challenges like complex structures and low transmittance and inflexibility,limiting technological progress.Recently,the transparent flexible metamaterial absorbers based on conductive films have played a great role in improving the absorption bandwidth.Nevertheless,most of the transparent flexible metamaterial absorbers that have been proposed still do not meet the size and thickness limitations of absorbers in special application scenarios such as mobile communication devices and satellite communication antennas.Therefore,the study of transparent flexible absorber with high absorption efficiency,thin thickness,light weight and wide absorption frequency band is of great significance for practical application.In this study,a transparent,flexible,small size and low profile metamaterial absorber is designed based on indium tin oxide conductive film and polyvinyl chloride.The absorber is mainly composed of three parts:a patterned conductive film layer at the top,a medium layer in the middle and a base layer completely covered by a low square resistance conductive film.Firstly,by combining the impedance matching principle,CST Studio Suite 2021 simulation software is used to calculate the absorptivity and S-parameters.Constantly adjust the pattern of the top conductive film,and finally determine the top periodic unit pattern.Secondly,other structural parameters are optimized by parameter scanning to achieve the best absorption,and the influence of the change of key parameters on the absorptivity is analyzed.In addition,the absorption performance of the 10X10 array structure at different bending angles is verified and compared with that of the planar surface.At the same time,the absorptivity of the unit structure is simulated under different polarization angles and incident angles.Moreover,in order to evaluate the effect of systematic geometric parameter errors that may exist in the actual machining of the designed structure,the robustness analysis of the structural geometric parameters is carried out.The results show that the absorber has excellent structural stability and can be manufactured for practical engineering applications.Finally,the physical mechanism of the wideband absorption of the absorber is systematically analyzed through the power loss density,the surface current distribution and the electromagnetic field energy distribution.Electromagnetic simulation software is used to conduct full-wave simulation,and the simulation results demonstrate that within the frequency range of 8.22 GHz to 22.76 GHz,the absorptivity of the metamaterial exceeds 90％,achieving an impressive absorption bandwidth of 14.54 GHz with a relative absorption bandwidth of 93.9％.In addition,the proposed absorber normalized impedance is calculated through the S-parameter in the simulation results,and the real part of the normalized impedance is close to 1 and the imaginary part is close to 0 in the operating frequency band.It shows that the design realizes the impedance matching with the free space and achieves the perfect absorption effect.In order to obtain the best absorption effect,the structural parameters of the absorber(slit width w,arrow cross width b,dielectric layer thickness tPVC and surface conductive film square resistance R)are scanned to determine the specific value of the structural parameters of the absorber.At the same time,the absorptivity of the 10X10 array is simulated under curved and planar conditions,the results show that the absorber can maintain excellent absorption performance even when bending.While the polarization angle is adjusted in the range of 0°～45°,the absorptivity does not change,showing excellent polarization insensitive characteristics.Notably,by adjusting the incidence angle of the incident electromagnetic wave from 0° to 60°,the results show that in TE mode,the oblique incidence angle of 45° can still maintain over 75％absorptivity,while in TM mode,even if the incidence angle of 60° can also maintain the absorptivity of more than 75％.Through analyzing surface current distribution,it is shown that the surface conductive film is an important cause of electromagnetic resonance.The current loop forms at the top and bottom layer causes magnetic resonance and thus magnetic loss,and the current loop form at the top layer causes electric resonance and thus electric loss.At the same time,the magnetic field energy is larger than the electric field energy at the same scale,which indicates that the absorber is mainly dominated by magnetic resonance.Based on the impedance matching principle,a completely original reflective metamaterial absorber with broadband microwave absorption,high flexibility and awesome transparency is proposed in this study.Notably,this absorber exhibits insensitivity to electromagnetic wave polarization and maintains excellent absorption performance at angles of incidence below 60° for most application scenarios.Moreover,excellent absorption properties are maintained under conformal conditions.The proposed electromagnetic metamaterial absorber holds significant potential applications in medical devices,aerospace technology,and radar stealth technology.
MetamaterialBroadband absorberImpedance matchingFlexible structurePolarization insensitiveOptical transparentConductive films
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