Methodology for Optimizing Radiated EMI Characteristics of Power Electronic Circuits This paper proposes a new approach to optimize radiated electromagnetic interference (EMI) of apower electronic application based on measurements in time domain. Using detailed measurements in time domain the Fast Fourier Transformation (FFT) of these data enables to investigate the critical switching-on and switching-off process of semiconductors separately. It was found, that a correlation between time and radiation measurement for the investigated circuit is given. The presented method allows the characterization and optimization of possible sources for radiated EMI during the development stage of a power electronic circuit and contributes to a better general understanding of the influence of parasitic elements in power electronic circuits on radiated EMI.