Researches On Novel Electromagnetic Metamaterials Absorber And Polarization Converter

Several new electromagnetic metamaterial absorbers(MMA)and electromagnetic metamaterial polarization Converters(MPC)are designed,based on the theory of electromagnetic metamaterials in this paper.In the first part,a broadband electromagnetic metamaterial absorber and a frequency selective surface absorber(FSSA)with a transmission window are designed and fabricated on the X-band and Ku-band based on flexible materials.The first unit cell structure is a combination of a hollow octagon and a hollow similar square with the same center,and using the method of loading lumped resistance.The proposed structure exhibits a broad band with ranging from 7.58 to 17.25 GHz with more than 90% absorptivity with vertical electromagnetic wave incidence and there are three resonant frequencies which are nearly perfect absorptivity in this band.The absorber is also featured with good wide angle incidence.The second unit cell structure is a combination of two concentric octagon with a transmission window in the background.The absorptivity is more than 90% from 9.21 to 18.11 GHz,which is broadband absorption,with vertical electromagnetic wave incidence.Innovation point for this absorber includes Teflon material,the relative bandwidth is 77.88% and 65.15% respectively,and the polarization insensitive property.In the second part,a broadband electromagnetic metamaterial polarization Converter is proposed in the X-band and Ku-band.The unit cell structure is combination with two rectangular metal patch inclined 45 ° and center symmetry.The range of the polarization conversion rate more than 90% is: 7.56-14.80GHz(bandwidth is 7.24 GHz,the relative bandwidth is 64.76%);the range of the polarization conversion rate more than 80% is: 7.37-15.06 GHz 7.79 GHz,the relative bandwidth is 69.46%).There are three resonant frequencies which emerges perfect polarization conversion ratio in this range.Through the experiment,the measurement which is basically consistent with the simulation is obtained.The innovation of this work is as follows: simple structure,high polarization conversion rate and wide operating frequency band.In the third part,an electromagnetic metamaterial low-frequency miniaturization multifunctional device is researched.It achieves absorption and polarization conversion in the very high frequency(VHF)and ultra high frequency(UHF)bands respectively.Based on the three-dimensional "corrugated" structure,five column dielectric substrates are laid on the bottom dielectric substrate,the "snake" wire structure,which extends the current path and reduces the absorption frequency,is laid on two xoy planes of the columnar dielectric substrate and mirroring is the same.And then connected with a metal wire structure from left to right or from right to left into a current path.Finally involving of defect effect in the photonic crystal,a comb dielectric substrate of FR-4 is inserted between the two adjacent cylindrical dielectric substrate tightly,so that the energy of the induced current is localized one or more times.The simulation show that the absorptivity and polarization conversion rate featured stable with wide angle incidence.Through the experiment,the measurement which is basically consistent with the simulation is obtained.The innovation of this work is as follows: the perfect absorption of 99.97% is achieved at the low frequency(0.258GHz);the structure is small and the compression ratio reaches 50.56,which achieves miniaturization;it also achieves a six-frequency absorption and dual-frequency polarization conversion function in the 0.1-2GHz frequency band,which is multi-functional.