Absorption Characteristics of Cylindrical Electromagnetic Wave Absorbers with Controlled Graded Compositions

摘要

We have been proposed functionally graded material type electromagnetic wave absorbers (FGM type EM wave Absorbers) which have an absorption layer with graded composition distribution for the improvement in absorption performance and material strength. In this paper, we investigate an electromagnetic noise problem of the FGM type EM wave absorbers for a hollow cylinder. The FGM layer which have nonhomogeneity only though the radius is considered to be multilayered absorption layers in which the material properties are homogeneous inside each layer. Incident electromagnetic wave is also assumed an electromagnetic plane wave. Therefore, the approximate analytical solutions of electromagnetic fields in the FGM layer and scatted electromagnetic fields in outer medium of the absorber are derived based on the method of separation of variables and the eigen mode expansion of cylindrical coordinate system. Numerical calculations are carried out for the FGM type EM wave absorbers composed of epoxy resin matrix and conductive titanium oxide particles. The absorption performances are quantitatively evaluated. The effects of material composition and absorption layer thickness on the absorption characteristics are then discussed. In addition, a possibility of the material design on the FGM type cylindrical absorber suitable for the absorption of EM wave and heat dissipation is suggested.