Comparison of Radio Frequency Interference (RFI) Issue between Differential and Common Modes in USB Channel

This study addresses the rising concern of radio frequency interference (RFI) issue in high-speed connectors, particularly focus on comparing the radiation noise generated from differential-mode (DM) signals and common-mode (CM) noise. While prior research has concentrated on CM noises and their suppression methods due to their strong radiation efficiency, DM noises, despite possessing weaker radiation efficiency, have received less attention in past research. However, it is worth noting that DM signals possess at least 20 dB higher energy than CM signals in digital systems. To compare the radiation caused by CM noise and DM signals, a 3D model with USB 3.0 high-speed connector system is constructed and validated through full-wave simulations and near-field measurements. The simulated results reveal that radiation caused by DM signals exhibit comparable significance to that caused by CM noises in digital systems. This finding underscores the importance of considering DM signals and CM noises in digital systems and provides new insights into mitigating interference in electronic devices.