| Metamaterials are new materials that do not exist in nature and are synthesized artificially with special electromagnetic properties.In the field of metamaterial research,metamaterial absorber is an important branch.In this paper,we firstly investigate the electromagnetic metamaterials in depth,and systematically study the theoretical basis and development status of broadband absorbers in microwave and terahertz fields.In order to pursue the good absorption performance of the absorbers under different operating environments,two absorbers with broadband absorption performance are designed in the microwave and terahertz bands each.The first of the two broadband absorbers working in the microwave band is an optically transparent broadband absorber,which consists of ITO conductive film as a super surface to absorb electromagnetic waves,with an absorption rate greater than 90%in the frequency range of 6.2～24.6 GHz and an absorption bandwidth of 18.4 GHz with an average absorption rate of 95.63%.The material composed of this absorber has transparent and flexible characteristics and can be arranged on a surface with curvature and good wide angle incidence.After preparing the absorber sample,the reflectance and transmittance data were obtained by experimental measurements,which have a good match with the simulation results.The second broadband absorber based on conductive plastic,which has an absorption rate greater than 90% in the interval of7.54～70.97 GHz and an absorption bandwidth of 63.43 GHz with an average absorption rate of 95.31%.Additive manufacturing technology was applied in the preparation of the absorber sample,and the absorber shell was fabricated by 3D printing,and the reflectivity data were measured experimentally and matched well with the simulation results.Two broadband absorbers working in the terahertz band,one is a pure dielectric absorber,using materials for doped silicon.Based on the high lossiness of doped silicon in the terahertz band,the absorption in the interval of 1.01～6 THz is greater than 90%,and the absorption bandwidth is 4.99 THz with an average absorption of 96.9% and polarization insensitivity.The second one is a broadband absorber based on the phase change material vanadium dioxide,which can adjust the temperature to change the conductivity of vanadium dioxide and make the absorption performance of the absorber change.At T=300K,vanadium dioxide does not undergo phase change,and the absorber exhibits tri-band absorption.At T=350K,vanadium dioxide undergoes phase change,and the absorption rate is greater than 90% in the 14.5～25.1THz region,with an absorption bandwidth of 10.6THz and an average absorption rate of 95.79%.And it has polarization insensitivity and good wide angle incidence,and can maintain good absorption when the incidence angle varies within 40°. |
