Modulation Frequency Analysis for EMC

The determination of the electromagnetic noise sources is particularly difficult for complex equipment having several broadband noise sources, such as switching power supplies. In this work the use of modulation frequency analysis is proposed to identify broadband noise sources. The modulation frequency graph reveals special patterns related to the switching frequencies that can be used to determine the relevant sources at each electromagnetic frequency. Two case studies are presented using prototypes of industrial and infrastructure equipment where modulation frequency analysis helped determining the noise sources. Suggestions for the selection of the analysis parameters are also given.