Transparent Absorption Research Baesd On Graphene/Frequency Selective Surface Composite Structure

The rapid development of electronic and wireless communication technologies has made the space electromagnetic environment increasingly complex,and has imposed increasingly higher requirements on electromagnetic shielding.Some display screens and observation windows in optoelectronic equipments require high light transmittance and strong electromagnetic shielding efficiency.The comprehensive performance of the electromagnetic shielding materials put forward higher requirements.The existing transparent electromagnetic shielding materials are usually based on the reflection mechanism,which may cause secondary reflections to make the space electromagnetic environment more complicated.Therefore,there is an urgent need for transparent electromagnetic wave absorbing materials mainly based on absorption mechanisms.Graphene provides a possible way for the realization of highly transparent electromagnetic wave absorbing materials.In this paper,firstly,the basic electrical parameters such as the electrical conductivity of graphene are analyzed in detail,and then the method of establishing the electromagnetic model of graphene in the electromagnetic simulation software CST(Computer Simulation Technology)is studied based on this,and the speed and modeling accuracy are taken into consideration comprehensively.It was later determined that graphene was modeled using a two-dimensional impedance plane.This model has a good agreement with the actual measurement results for the conventional square resistance single-layer graphene shielding efficiency analysis,and then studied the corresponding relationship between the square resistance and the square resistance graphene transmission characteristics.The transmission characteristics of monolayer and bilayer graphene stacks were analyzed using Maxwell’s equations and verified by CST simulation.Simulations show that the absorption rate of the double-layer graphene stack structure is modulated by the dielectric thickness between the two layers of graphene due to interference,and the maximum absorption rate is 62.7%,which does not satisfy the shielding requirements.Based on the above work,a highly transparent graphene/frequency selective surface(FSS)composite structure was proposed.The equivalent reactance model is obtained for the band-resistance FSS.The equivalent circuit method is used to analyze the transmission characteristics.Compared with the CST simulation results,the deviation of the resonant frequency is less than 1 GHz,which verifies the accuracy of the analysis method.Then,the relationship between light transmittance and structural parameters of FSS is analyzed,and the ring and square ring units FSS with a light transmittance of about 98% and different resonant frequencies are designed.The graphene and FSS are stacked to form a composite structure.The simulation results show that the composite structure can achieve high microwave absorption near the designed frequency and high light transmittance in the optical band.Finally,graphene samples and FSS samples were prepared by chemical vapor deposition and ultraviolet lithography,respectively,to form a composite structure.The experimental results show that the composite structure can achieve good microwave absorption characteristics,and its average light transmittance is high.At 91%.At 25 GHz,the composite structure has an absorption rate of 98.56% and a 3d B bandwidth of 8 GHz.The developed graphene/FSS composite structure can basically meet the requirements of high light transmittance and high electromagnetic absorption,and has wide application value in the field of optical windows such as display screens and observation screens of precision photoelectric instruments.