# S-Parameter Coupling in a Stepped Waveguide Section

Calculate the transmission and reflection for a stepped waveguide transition from the Ku- to X-band. Use two solver methods, the method of moments (utilising waveguide ports) and the finite element method (utilising FEM modal ports).

The waveguide consists of a Ku-band section and an X-band section. Only the H10 mode with cutoff frequency, ${f}_{c}=\frac{{c}_{0}}{2a}=9.4871$ GHz is considered.

The Ku-band section dimensions are as follows:
• a = 15.8 mm
• b = 7.9 mm
The X-band section dimensions are as follows:
• a = 22.9 mm
• b = 10.2 mm

Calculate S-parameters from the cutoff frequency to 15 GHz.