Non-resonating noise filter

It is noted that a commercially available noise filter does not always represent the attenuation characteristics shown in the catalog, but sometimes magnifies the noise voltage when the filter is applied between the AC power cable and the equipment. This degradation mechanism is clarified here by considering the resonance phenomena involved in the input/output impedances and their phase angles, taking the circuits connected to the filter input/output into consideration. The filter has been realized on the basis of a non-resonating filter comprising a high-loss inductor and capacitor. The no-degradation attenuation characteristics of the filter can be improved by realizing a dull series resonance point and a small phase angle in use of high loss inductor and capacitor