Design And Preparation Of Flaky Absorber Oriented Electromagnetic Noise Suppression Sheet

With the development of miniaturization,high frequency,and integration of electronic devices,the operating frequency of many products has reached more than GHz.During operation,high-frequency microwave integrated devices will form an extremely complex electromagnetic environment and cause serious electromagnetic interference problems.The use of noise suppression materials can easily and effectively solve such problems.Satisfying noise suppression performance requires high magnetic permeability that is of high magnetic loss.In this paper,the effect of volume content,orientation,spatial distribution and aspect ratio on the effective magnetic permeability of composite materials are studied by establishing a model of alloy powder/binder composite material.And a gigahertz wideband electromagnetic noise suppression sheet is developed by tape casting,and the influences of the magnetic permeability and thickness of the noise suppression sheet on the noise suppression performance are studied.The details are as follows:(1)The impacts of the saturation magnetization M_s,the magnetic anisotropy field H_e,and the damping coefficient?on the intrinsic magnetic permeability of the alloy powder are simulated by using the Landau-Lifshitz-Gilbert equation.For the flaky alloy powder,the influence of the aspect ratio on the effective permeability of the alloy powder/polymer matrix composite is studied by the modified Bruggeman equation.(2)By modeling and simulation via electromagnetic simulation software,the influences of volume fraction,orientation and aspect ratio of the ferromagnetic flake particles embedded in the non-magnetic matrix on the effective permeability are studied.The simulation results show that the effective permeability of the composite increases with the increase of the particle filling ratio,and compared with the agglomeration state of the particles,the uniform parallel distribution of the flaky particles is conducive to obtaining a higher effective permeability;Based on uniform distribution,when?=0°,the composite has the largest imaginary part of the permeability;in the 0.3-9 GHz band,the higher the aspect ratio of the flaky particles,the greater the imaginary part of the effective permeability of the composite,and the resonant peak moves towards low frequencies.(3)By jointly analyzing the simulation and experimental results,the influences of the size and permeability of the noise suppression sheet on the microstrip line on the noise suppression performance are revealed.It is shown that,most of the electromagnetic wave energy on the microstrip line is distributed in a certain range(width 20mm,thickness 0.8mm)both horizontally and vertically.Once the size goes beyond the above range,the suppression performance cannot be significantly improved.By preparing the noise suppression sheet sample via casting process,it is found that,when the permeability increases,the power loss ratio of the sample increases,and the attenuation band is extended to a lower frequency.The power loss ratio of the composite film with the magnetic powder content of 85wt%and the thickness of 0.2mm reached 0.9 in the range of 1.4-6.4GHz and 0.97 at 2.7GHz particularly,which satisfies the application requirements of the GHz broadband electromagnetic noise suppression sheet.