Design Of Low Frequency Band Absorbing Materials Based On Periodic Structure

Low-frequency absorbing material can effectively absorb and attenuate the low-frequency electromagnetic wave energy,which is required to be of thin light weight and high-efficiency absorption property with a broadband absorption frequency.To expand the absorbing bandwidth and improve low-frequency absorption property,the bottleneck of the core of current problems of electromagnetic wave absorbing technologies needed to solve.Compared with the traditional absorbing structure,the absorbing metamaterial structure has the advantage of small geometrical size,which is more conducive to the application in practical situations.In this paper,the periodic low frequency absorbing structure and the corresponding physical mechanism is analyzed.What's more,the absorbing mechanism of low-frequency broadband absorbing structure based on Non-Foster circuit is studied,and the design of broadband and high-efficiency absorbing periodic structure is proposed.In this paper,the active and passive periodic absorbing structures are taken as the research object,and the equivalent circuit model is established.By analyzing the surface current and field distribution,the broadband absorbing mechanism of the low-frequency periodic absorbing structure is revealed.The main research contents are as follows.:1.The design of several periodic resistive film absorbing structures(square,non-uniform square)in the absorption performance change principle is established.According to different graphic structures,a reasonable equivalent circuit model is established based on the surface current and field distribution of the structure.Secondly,According to the proposed equivalent circuit model,the reason for the change in absorption performance is analyzed.Analysis When the structural size parameters of the structure change,the equivalent circuit parameters change correspondingly,resulting in a change in the resonant frequency.Through the structure design of non-uniform resistance film,good absorption is achieved at 0.68 GHz and0.70 GHz.2.The absorption characteristics of several metal-type periodic absorbing structures(single layer and multi-layer)are designed.For different graphic structures,a reasonable equivalent circuit model is established based on the surface current andfield distribution of the structure.Secondly,According to the proposed equivalent circuit model,the reason for the change in absorption performance is analyzed.Analyze the corresponding changes in the equivalent circuit parameters when the chip resistor is added to the structure,and analyze the cause of the change in the resonant frequency.Among them,70% of the absorption bandwidth is 0.85 GHz-1.4 GHz through multi-layer structure design,which greatly broadens the bandwidth.3.Aiming at the metal pattern absorbing structure,this paper proposes a periodic absorbing structure based on the Non-Foster circuit model.According to the transmission line theory and the concept of impedance matching,a negative capacitance with a certain value or It is a negative inductance,achieving-10 dB reflection coefficient in the range of 0.18G-5GHz,which is based on the field distribution of the overall structure combined with the equivalent circuit theory to analyze the reason for its wide band.