Research On Tunable Electromagnetic Absorber Based On Gravity Field

With the great improvement of wireless communication technology,the traditional absorbing materials could not meet the demand of various applications.Electromagnetic absorber with smaller thickness and high absorption becomes a new research hotspot.There are a wide variety of regulation techniques for the metamaterials,but most of them are cumbersome to achieve.And researches of novel regulative ways have been almost neglected.Therefore,it is of great significance to propose a convenient non-contact regulation.In this paper,based on the gravity field regulation(non-contact regulation),three adjustable electromagnetic absorbers and one functional reconfigurable device are designed.The contents are as follows:(1)A single absorption frequency electromagnetic absorber based on gravity field is designed.Based on the traditional structure,two grooves are added in the dielectric substrate.The grooves are filled with the same volume of oil and seawater.Due to the different densities,a 180° rotation can change the position of seawater and oil under the gravity field in the x-y plane.This changes the equivalent permittivity of the designed absorber,which achieves the purpose of gravity field regulation.The simulation results show that this design can switch absorption frequency between9.12 GHz and 10.66 GHz.The shift of the operating frequency achieves 1.54 GHz,which realizes the active regulation.(2)The polarization separation multi-frequency electromagnetic absorber based on gravity field is designed.By combining the fluidity of liquid metal with special structure,the surface resonance in the structure is eliminated and the integration of the device gets improved.Due to the effect of gravity field,the liquid metal flows through rotation.Thus two different shapes of resonant structure are formed,which makes the designed electromagnetic absorber work in two states.The simulation results show that the TE wave and TM wave can be absorbed at different frequencies from 5GHz to 25 GHz.In addition,a 5×5 proportional arrangement is applied to expand the absorption band.In this arrangement,the unit structures with different scale coefficients are arranged in a specific topology to realize the active regulation of narrow-band absorption.(3)A broadband electromagnetic absorber based on gravity field is designed.Seawater is selected as the main lossy dielectric.Based on the U-shaped pipe structure,component 1 is proposed as the basic structure.Then the absorption bandwidth is expanded by stacking component2 and component 1.In the incidence of TM wave,the tunable broadband absorption band is obtained.The absorption frequency of the two operating states are 5.6GHz to 7.91 GHz and4.32 GHz to 5.83 GHz respectively,whose absorption is more than 90%.The metamaterial properties of the device are verified by parameter retrieval.(4)A functional reconfigurable device based on gravity field is designed,which can switch between electromagnetic absorber and frequency selective surface.When liquid metal flows to different positions,it will play different roles.It acts as a metal back plate in the absorber state and resonant structures in the frequency selective surface state.Therefore,the device can switch between a single frequency electromagnetic absorber and a stopband frequency selective surface by gravity field.Single absorption frequency point is obtained at 6.86 GHz in the absorber state,while the stopband frequency varies from 7.96 GHz to 9.50 GHz in the FSS state.At the same time,the validity of the design is verified by the equivalent circuit.