Extraction of parasitic parameters of EMI filters using scattering parameters

Parasitics of EMI filter, including electromagnetic couplings among filter components and circuit layout usually render the filter ineffective above several MHz. These parasitic parameters must be accurately extracted and systematically studied before effective methods can be found to improve EMI filter performance. This work employs scattering parameters to extract these parasitic parameters through measurements. The extraction is verified by experiments. Both one-stage and two-stage EMI filters are investigated in the paper.