An EMI Filter Selection Method Based on Spectrum of Digital Periodic Signal

This paper describes a new method for the selection of an appropriate signal line Electromagnetic Interference (EMI) filter. To date, EMI filter selection has been based on the measurement of the radiation of the entire device. The new selection method based on the signal's Fast Fourier Transform (FFT) measurement has proved to be efficient. The EMI filter is optimized separately for each line. The method described in this paper involving a Central Processor Unit (CPU) module demonstrates that the proposed FFT-based selection method is better than the radiation-based one. The radiation level in the frequency range 30 MHz to 1 GHz is lower for approximate 2 – 6 dBμV/m.