Enhancement of radiated noise suppression on flexible magnetic thick film electromagnetic interference filters with high-frequency permeability on data signal cable

摘要

Frequency-dependent impedance characteristics of flexible thick film EMI niters were investigated for enhanced suppression of high-frequency noise currents in the frequency range from several tens of megahertz to 1.5 GHz. The inductance of the rolled magnetic film filters was much lower than that of the conventional ferrite bead at lower frequencies but the inductance exceeded the level of the ferrite bead above 33-125 MHz because of the higher frequency dependence of real permeability. The enhanced impedance was mainly due to the increased inductance for the rolled thick film filters at lower frequencies of 210-550 MHz, depending on the complex permeability. The enhanced permeability at the higher frequency was attributed to the increased inductance and resistance of the rolled magnetic thick film filters. The higher frequency dependence of impedance was, the better the effect was reached to filter out the common-mode noise. It is found that the noise emission from a data signal cable is effectively suppressed by employing the flexible magnetic thick films as a common-mode noise filter in the 50 MHz-1.5 GHz frequency band.