Physical evidence of mode conversion along mode-selective transmission line

This work investigates mode conversion along a longitudinally uniform mode-selective transmission line (MSTL) and demonstrates physical evidence of the mode conversion. Mode conversion of the fundamental mode is observed through examining the field distributions of the MSTL. Characteristic mode conversion frequency is defined based on the distribution properties of the longitudinal magnetic field component and the intrinsic physical implications. The accuracy and effectiveness of this definition are verified numerically and experimentally. The result indicates that a quasi-TEM fundamental mode and a quasi-TE10 fundamental mode dominate in the MSTL below and above this frequency, respectively. This mode conversion could have specific applications in the design of microwave, millimeter-wave, and THz wideband and multi-band components and systems.