A Technique to Accurately Predict EMI Noise Spectrum in Wide Frequency Ranges Based on the Principles of Spectrum Analyzers

Spectrum analyzers are usually used in measuring the electromagnetic interference (EMI) noise in power electronics systems. However, based on the EMI standards, the measuring of the EMI emissions of the equipment under test (EUT) could be very time-consuming. Conventionally, the fast Fourier transform (FFT) results of the noise signals are used to evaluate the EUT's EMI performance. However, these results are not compatible with EMI standards, and have large difference compared with the standard-compliant measurement. In this paper, a technique to predict the EMI noise spectrum of any input time-domain waveform is proposed. The simulator emulates the spectrum analyzer's performance based on EMI standards. The prediction results from the proposed technique match the EMI standard-compliant measurement results very well in a wide frequency range, with different power converter applications and modulation strategies. Meanwhile, the prediction results can be obtained in a very short time which is much faster than measurement process.