A quantified method for characterizing harmonic components from EMI spectrum

This paper proposed a new method to characterize the harmonic components from Electromagnetic Interference (EMT) spectrum, which is based on the Grey System Theory and the Fourier Envelope Theory. The proposed method first characterizes the harmonic components from the EMI test data. Then proper time-domain component model (e.g. square, sinusoidal, or convergent oscillation, etc) is identified based on the frequency and amplitude of the harmonic components in the spectrum. Finally, the identified time-domain components are quantified. As an application of this method, the EMI spectrum data of equipment under test (EUT) is used to identify and quantify its major time-domain components. Comparisons between the time-domain components obtained by the proposed method and measured by oscilloscope are presented, which show the accuracy of the proposed method. Furthermore, from the waveform types of identified time-domain components, the major EMI sources can be located.