Quantitative Analysis of Normal Mode and Antenna Mode Coupling in Two-Conductor Transmission Line Using Electromagnetic Potentials

This paper examines the generation of electromagnetic noise caused by coupling between normal mode (NM) and antenna mode (AM) in a two-conductor transmission line (TL). We employ telegraph equations based on electromagnetic potentials to analyze NM and AM. Through experimental observations and numerical simulations, we quantify the coupling effects that occur when transmission lines with differing mode impedances are connected. For detailed analysis of coupling noise mechanisms, three-dimensional electromagnetic potential simulations are conducted to observe the voltage and current distributions of NM and AM within the TLs. This study demonstrates that impedance matching of TLs requires the consideration of not only NM impedance but also coupling impedance.