EMI analysis methods for synchronous buck converter EMI root cause analysis

DC/DC synchronous buck converters cause broadband emissions. A variety of methods are applied to analyze the root cause of the EMI. Time-domain voltage measurement and joint-time-frequency analysis allows to determine the location of the noise source. The near field scan reveals the current paths, and impedance measurement and 3D modeling can be used for further analysis of the noise source. A dual port TEM cell allows to distinguish E from H field coupling, This paper shows the application of those methods to a synchronous buck converter and reveals the sources of EMI leading to advice on the optimal PCB design. Finally, an innovative method of using a TEM cell measurement to predict the maximum possible radiated emissions is introduced.