Advanced Evaluation of Minimum Insertion Loss of Power-Line EMI/RFI Filters in RF and Microwave Frequency Bands

This paper concerns a new approach for the characterization of power-line electromagnetic interference/radio-frequency interference (EMI/RFI) filters in a general impedance environment and continues to broaden the scope of one of previously published works. Specifically, the paper focuses on analyzing the lowest possible insertion loss of three-wire, single-phase EMI/RFI power-line filters in their stop-band at high megahertz or gigahertz frequencies. In contrast to the published work, the presented approach takes into account the reflections of converted modes at the filter input and output ports. A commercial single-phase EMI/RFI filter is analyzed in the frequency range of 1 to 10 GHz, in terms of common mode, differential mode and their conversions, by using the measured S-parameters of the filter and subsequently processing the obtained data. The results show that due to the reflections of conversion modes back into the structure of the filter, insertion loss values can be more than 20 dB lower than the results achieved by the previous known methods.