Attenuation characteristics of near-field electromagnetic noise through microstrip line for magnetic absorbers with different levels of conductivity

Abstract

Attenuation characteristics of near-field electromagnetic noise through microstrip line attached with electromagnetic thick films with different levels of electrical conductivity for frequencies in the range of 0.1–6GHz were investigated with numerical simulation via the three dimensional finite-element high-frequency structure simulator (HFSS) code. The electromagnetic absorption of the semiconducting magnetic or nonmagnetic films highly increased up to 80% at above 1GHz, while the absorption of the nonmagnetic conductor or the insulating films was significantly diminished. The remarkable enhancement in the loss factor of the semiconducting magnetic or nonmagnetic films was attributed to the increase in loss factor of the eddy-current loss. Even though the reflection of the semiconducting magnetic films at above 58S∕m was significantly lowered by the magnetic loss effect compared to that of the semiconducting nonmagnetic films, the reflection below 1GHz was still high enough to incur electromagnetic interferences. It was confirmed from the numerical results of magnetic field that the radiation noise was highly generated with increasing conductivity at above 58S∕m because of the rereflection of the radiated noise from the surface of the magnetic films with high level of conductivity. As a result, the near-field electromagnetic noise was effectively reduced by controlling conductivity to the semiconducting level of below 5.8S∕m for the magnetic films with high permeability in the measured frequency.