Research On Low Frequency Broadband Wave Absorbers Based On Electromagnetic Metamaterials

With the continuous development of modern technology and electronic equipment,the problems of multi-antenna system interference,electromagnetic radiation and electromagnetic pollution are becoming increasingly serious.Electromagnetic absorbers use high loss materials or strong resonant structures to dissipate and absorb the energy of incident electromagnetic waves,which can not only improve stealth performance and electromagnetic compatibility,but also be used to suppress electromagnetic radiation pollution.Therefore,electromagnetic absorption technology has attracted a lot of attention from researchers in both military and civilian fields.Practical applications require absorbers that are thin,light,wide,and strong,but the inherent deficiencies of traditional absorbers such as high density,large thickness,and narrow absorption bands make it difficult to meet the growing demand.In this paper,based on magnetic materials,dielectric layers and resistive films,three types of broadband metamaterial absorbers are designed to achieve low frequency,broadband and efficient absorption.The main achievements are as follows:Firstly,a low-frequency high-efficiency broadband absorber was designed using discrete magnetic materials.The absorber consists of a multilayer magnetic material,a resistive film and an air layer,and can achieve an absorption efficiency of more than90%in the frequency range of 0.92-18GHz with a relative thickness of 0.03λ_L.The influence of the structure of each layer on the absorption effect is analyzed and the structural impedance of the absorber is calculated by transmission line theory.This multilayer magnetic metamaterial can be used to design low-frequency broadband absorbers.Secondly,a two-period low-frequency broadband metamaterial absorber is designed based on the surface magnetic material and free-space impedance matching.The simulation results show that the absorption efficiency of the absorber is higher than 90%in the frequency range of 0.94-20GHz,and the relative bandwidth reaches182%.The absorbing mechanism of the structure is analyzed by impedance matching theory and equivalent circuit model.Finally,a multi-scale broadband strongly absorbing metamaterial absorber is designed based on the stacking of a high-impedance surface with an air layer.The results show that the absorber can achieve perfect absorption(absorption efficiency more than 99%and reflection less than 1%)in the frequency range of 8.9-13GHz and19-24GHz under the vertical incidence of electromagnetic waves.The absorption mechanism is analyzed by equivalent circuit and impedance matching theory,and the effect of each resistive film layer on the wave absorption effect is discussed.