Resonance phenomena in the section of a loaded below-cutoff waveguide

The paper considers a below-cutoff waveguide serving as a coupling element between two other waveguides and calculates the cross-sectional size of the below-cutoff waveguide for which resonance phenomena are possible. Expressions are presented for calculating the length of a loaded below-cutoff waveguide section with consideration of the geometry of the coupling of this section to the two other waveguides. In particular, the transmission coefficient of a symmetrical H-junction of two rectangular waveguides is studied as a function of the relative length of the below-cutoff waveguide and of reduced frequency.