Figure 4
From: Highly-efficient three-dimensional waveguide couplers using impedance-tunable transformation optics

Coupling efficiency of the coaxial waveguide coupler for the TEM mode as a function of frequency.
From: Highly-efficient three-dimensional waveguide couplers using impedance-tunable transformation optics
Coupling efficiency of the coaxial waveguide coupler for the TEM mode as a function of frequency.