Normal and Antenna Mode Coupling Due to Mode Impedance Mismatch in Two-Conductor Transmission Line

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 derive the telegraph equations for NM and AM using electromagnetic potentials and quantity the coupling effect at the connection of TLs with different mode impedances based on experimental and numerical observations. This study demonstrates that impedance matching of TLs requires the consideration of not only NM impedance but also coupling impedance.