Feasibility Study of Adding a Common-Mode Choke in PLC Modem for EMI Suppression

The feasibility of adding a common-mode (CM) choke in the analog front end (AFE) circuit of a power line communication (PLC) modem to reduce the CM noise coupling onto the power line is investigated. Based on a two-current-probe measurement approach, the CM and the differential-mode (DM) equivalent electrical models of a PLC modem are first developed. Both the CM and the DM attenuations due to the addition of a CM choke when the PLC modem is connected onto the power line network are then determined. Besides the CM noise attenuation, the impact of the CM choke on the PLC signal, which is DM in nature, is also studied.