Study On Metamaterials-based Absorber

Electromagnetic metamaterials are artificial electromagnetic structures.Compared with the incident electromagnetic wave,the size of the metamaterials is subwavelength,and the arrangement is periodic.Because their surface patterns and design structures can be varied,metamaterials exhibit a lot of unusual physical properties.We can freely control the amplitude,phase and direction of polarization of the electromagnetic wave by adjusting the size and periodic arrangement of the structure.Electromagnetic metamaterial absorbers have thinner thickness,wider absorption band and higher absorption efficiency,which are incomparable to traditional absorbers.This paper focuses on the research of new type of metamaterial absorbers,and the contents of the study are as follows:(1)As the detection band of modern radar becomes wider and wider,the thickness required by conventional ultra-wideband metamaterial absorbers is often very large.An optical transparent ultra-wideband absorber based on water is designed.The basic unit consists of twolayer water cylinders with different diameters stacked vertically.The full-wave simulation results show that the absorber is not only effective for both polarization waves,but also has two absorption bands in the range of 4.6-33.7GHz and 51-83 GHz,and the absorption efficiency is more than 90%.In addition,the proposed water-based MA has wide-angle absorption properties for both TE and TM waves.It is interesting that the absorption performance is better and better with the increase of incident angle when a TM polarized plane wave is incident.Since the total thickness of the proposed MA is only 6.4 mm,it may have potential applications in the window of stealth equipment and electromagnetic compatible construction.(2)With the development of weapons and equipment,the application circumstances is becoming more complicated than ever before and the stealth technology in high temperature flight environment is in urgent need of research.Most of the MAs generally work only below200 °C,they cannot work for high temperature microwave absorption.As the temperature increases further,the magnetic response gradually deteriorates and is completely eliminated above the Curie point temperature,usually unable to exceed 700?.A resistance-type refractory microwave absorber with high absorptivity is designed and experimentally realized.The unit cell consists of a continuous metal plate,a refractory spacer layer and a square resistance film on the surface.The full-wave simulation results show that the absorption efficiency of the designed single-layer resistance-type refractory absorber is higher than-6d B in the range of7.94GHz-19.47 GHz,and the thickness is only 1.6mm.The absorption efficiency of doublelayer resistance type refractory absorber is higher than-4.5d B in the range of 4-18 GHz and the thickness is only 3.2mm.The optical transparent ultra-wideband absorber may have potential applications in stealth equipment window and electromagnetic compatibility structure,and the resistance type refractory absorber opens a gate to control microwaves at high temperatures by metamaterials.