This article demonstrates the reduction of electro-magnetic interference (EMI) in an enclosed high-power-density wide-bandgap (WBG) four-pole DC to DC boost converter. The authors introduce a new methodology for characterizing the EMI in WBG power electronics. The converter's physically compact design and its enclosure induce a problematic level of common-mode EMI that leads to failure of electromagnetic compatibility (EMC) compliance tests. Utilizing common-mode equivalent modeling (CEM) and rapid frequency-domain circuit analysis, this methodology allows the designer to assess the common-mode EMI problem independently from the mixedmode measurements and design an optimized filter accordingly.