Identification of EMI noise sources through the use of Fourier and wavelet transforms

This paper presents the analysis of the electromagnetic noise generated by a switch mode power supply, by means of discrete Fourier transform (DFT) and continuous wavelet transform (CWT). The circuit operating point was changed, and the subsequent evolution in the noise voltage, measured on a line impedance stabilization network (LISN), was studied using the two different post-processing techniques mentioned above. The study yielded a deep insight into how the modifications in the noise source over time, as those caused by operating point variations, affect the noise spectra captured on the LISN.