| In recent years,electromagnetic waves have been widely used in the fields of communication,scientific research and military due to their fast propagation speed.With the development of electromagnetic equipment,the electromagnetic interference caused by electromagnetic interference has caused pollution to the environment.Therefore,it is necessary to study how to suppress the impact of electromagnetic radiation.As the object of attention of scientists,electromagnetic wave absorption and electromagnetic interference shielding are very useful solutions,among which metamaterial wave absorption technology is the key research object.Metamaterials are artificially engineered materials that can achieve electromagnetic properties that cannot be achieved by a variety of natural materials,thus becoming an innovative point in many research fields.Metamaterial absorbers have natural advantages in the field of subwavelength device design,and are one of the excellent candidates for electromagnetic wave absorbing materials.However,due to the resonant properties of subwavelength devices,the narrow operating wavelength range of absorbers limits their practical applications in energy harvesting and energy shielding with broadband absorption requirements,and early metamaterial absorbers are expensive to fabricate.Therefore,metamaterial absorbers are mainly studied for ultra-thin,ultra-broadband,and simple fabrication.Compared with traditional absorbers,metamaterials have many unique features in microwave and terahertz applications.In this dissertation,taking broadband absorber as the research object,an ultra-broadband ultra-thin water microchannel metamaterial absorber in microwave band and an all-dielectric water-based metamaterial absorber in terahertz band are designed respectively.In addition,the two metamaterial absorbers can be fabricated by 3D printing,the fabrication process is simple,and the fabrication cost is reduced.For the microwave section,this thesis designs an ultra-broadband and ultra-thin water microchannel metamaterial absorber device.The water channel metamaterial structure can be prepared by printing polylactic acid(PLA)environmentally friendly materials through a 3D printing process.The CST simulation results show that it can obtain more than 90% absorption rate in the broadband range of 9.6-98.9 GHz,the relative bandwidth can reach 165%,and the thickness of the device is only 3 mm;the experimental results are basically consistent with the CST simulation results,which proves the design scheme feasibility.At the same time,this type of absorber has a wide incident angle,good thermal stability,and is insensitive to changes in brine concentration.If the demand scenario does not require high device thickness,the absorption band is also extended to more than 200 GHz by means of a double-layer barrier unit structure,and the total device thickness is maintained within 5.9 mm.For the terahertz band,this thesis designs an all-dielectric water-based metamaterial absorber device,whose water channel metamaterial structure is wrapped by polytetrafluoroethylene(PTFE)material.The CST simulation results obtained more than90% absorption in the 0.35-3 THz broadband range,the relative bandwidth can reach158%,and the thickness is only 540 μm,and when the frequency exceeds 3 THz,there will still be more than 90% absorption.And the device is an all-dielectric metamaterial absorber,which greatly broadens the application range.To sum up,this paper designs an ultra-broadband and ultra-thin water microchannel metamaterial absorber in the microwave band and an all-dielectric water-based metamaterial absorber in the terahertz band.The research in this thesis covers the microwave and terahertz bands.To a large extent,the defects of narrow absorption bandwidth,thick device and small application range of metamaterial absorbers are solved. |
