| Electromagnetic metamaterials are man-made composites composed of sub-wavelength structural periodic arrangements,which can achieve many interesting physical phenomena and applications that natural materials do not possess,and are widely used in scenarios requiring electromagnetic modulation and absorption,radio frequency identification,radar stealth,etc.Because metamaterials can effectively regulate the loss,transmission and polarisation of electromagnetic waves,they have a wide range of applications in microwave and radio frequency energy harvesting,holographic imaging and electromagnetic stealth.Traditional stealth technology has problems of complex preparation and high cost,and the new application environment has put forward higher requirements for stealth technology.Based on electromagnetic metamaterials,metamaterial absorbers have the advantages of light weight,flexible design,simple preparation and wide range of adaptable frequency bands.For the existing metamaterial absorber absorption efficiency is low,absorption band is narrow,and it is not easy to conformal with the surface and other problems.This study starts from the design theory of traditional absorbers and uses the multilayer composite structure to achieve broadband,conformal and high transmittance characteristics,and designs a broadband flexible transparent metamaterial absorber based on the multilayer structure and a radar-infrared compatible stealth flexible transparent metamaterial absorber based on the multilayer structure respectively.The main research elements of this paper are summarised as follows:(1)A design method for flexible transparent ultra-wideband metamaterial wipers using a multilayer composite structure is explored.By adjusting the size and array position arrangement of the transparent indium tin oxide(ITO)resistive film pattern attached to the flexible substrate polyethylene terephthalate(PET),an ultra-broadband absorption of more than 90% is achieved in the frequency range of 8.6 to 75.8 GHz,with a relative absorption bandwidth of 159%.Based on this,a transparent flexible dielectric polydimethylsiloxane(PDMS)and PET substrate are used to achieve good optical transparency.The broadband absorption mechanism and characteristics of the multilayer structure are also revealed by the surface current distribution of the resonant structure and the absorption effect at different incidence and polarization angles.(2)A flexible transparent composite metamaterial absorber with radar-band microwave absorption and low infrared emissivity is designed using a multilayer structure.The radar wave absorption layer and infrared shielding layer,which can control microwave absorption and infrared emission respectively,were designed and fabricated on a transparent substrate using indium tin oxide material,and the relationship between the two functional layers was investigated.90% absorption was achieved in the wide frequency range from 2.12 to 15.87 GHz,and the emissivity in the infrared band was about 0.25,and the analysis of the equivalent circuit,surface current and absorption rate revealed that it has The absorption characteristics are found to be broadband,polarization insensitive and stable over a wide incidence angle.(3)The absorption mechanisms of the two designed multilayer flexible transparent metamaterial absorbers were analysed by CST and MATLAB simulation software,and the resonant structure arrangement and dimensions were optimised.Samples of the two absorbers were fabricated by magnetron sputtering and laser etching techniques,and their absorption performance was tested in a microwave darkroom.The infrared stealth effect of the dual-use stealth metamaterial absorbers was tested by an infrared thermal imager,and the design of a flexible,transparent,broadband and compatible stealth metamaterial absorber based on the multilayer structure was achieved. |
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