EMC measurements in time domain

Abstract

This thesis investigates time domain electromagnetic interference (TDEMI) measurement method as a modern alternative to traditional frequency domain EMI testing. Instead of the conventional frequency domain measurement, TDEMI captures the full EMI signal in the time domain and converts it into the frequency domain using a discrete Fourier transform (DFT). This method provides the potential for significantly faster measurements, which is especially beneficial in pre-compliance testing and high throughput environments. The accuracy and time efficiency of the process are compared to traditional frequency domain measurement techniques by implementing the signal processing algorithms and evaluating system performance with practical measurements. Results were compared to those from a CISPR16-compliant EMI receiver.

A core finding was the critical role of using a suitable window function in the time domain. Windowing improves accuracy, especially at lower frequencies, and the best amplitude accuracy was achieved using a flat top window.