Design Of Broadband Metamaterial Absorbers And Characteristics Analysis

With the ability to absorb electromagnetic wave,electromagnetic absorbing materials,which can effectively reduce the electromagnetic scattering signal of the target and further reduce the probability of target’s being detected by radar,have a wide range of application prospects.Metamaterials are composed of sub-wavelength structural units,which can achieve extraordinary electromagnetic properties,such as negative refraction,stealth,and perfect absorption.The traditional metamaterial absorber working in radar band is composed of a metal resonant unit,a dielectric layer and a metal base plate.It is mainly processed by mature printed circuit board technology.Although the absorption rate is close to 100%,it cannot be bent and the conformal ability is poor consequently.At the same time,it only can be coated on the surface of invisible target in the form of independent structures,limiting its integration with the target,which hinders its practical application to a certain extent.The purpose of this dissertation is to provide a metamaterial design scheme for structural-functional integrated materials,and to lay a simulation foundation for exploring structural-functional integrated metamaterials.Taking advantage of the good electrical conductivity,load-bearing mechanical properties of carbon fiber and its potential of integration with target’s structure,this dissertation mainly designs a new type of carbon fiber metamaterial absorber.Its broadband absorption characteristic is studied and the dependence of absorption characteristics on geometrical parameters is analyzed in simulation.A simple hollow cross structure metamaterial absorber composed of a carbon fiber layer,a glass fiber layer and a patterned carbon fiber layer is designed.The simulation results show that the polarization-independent electromagnetic absorptivity of the metamaterial is higher than 90% in the frequency range of 14.6 to 23.3 GHz.In order to reduce the design complexity,a split cross rectangular bar structure metamaterial absorber is further presented and the simulated polarization-independent absorptivity of greater than 90% is achieved in the frequency range of 14.7 to 24.8 GHz.Through the design of structure parameters,the absorptivity of greater than 90% is achieved in the whole Ku band,which proves that this type of absorber can complete the on-demand design of the working frequency band.To ensure both the design simplicity of metamaterial and its polarization-independent absorption when expanding the bandwidth,a circle ring structure carbon fiber metamaterial is adopted and its absorption performance is studied.The broadband electromagnetic absorbing metamaterials working in Ku-band and X-band are designed respectively,and the simulation results show that the ring structure metamaterials have excellent broadband absorption capability.The dual-ring structure metamaterial is designed and optimized in simulation,the absorption bandwidth of 27.4 GHz which can cover the Ku-,K-and Ka-band is achieved.The electromagnetic absorption characteristic of the dual-ring structure metamaterial with honeycomb lattice is further studied.The simulated absorptivity is over 90% in the range of13.9 to 40.8 GHz,and the absorbability is insensitive to polarization.