RF MODULE

32 | CHAPTER 2: TUTORIAL MODELS
This is done by calculating the scattering parameters, or S-parameters, of the structure
as a function of the wall position. The S-parameters are a measure of the transmittance
and reflectance of the bend. For a theoretical background on S-parameters, see the
section “S-Parameters and Ports” on page 57 in the RF Module User’s Guide.
This model only includes the TE 10 mode of the waveguide. Thus the model can be
made in 2D as the fields of the TE 10 mode have no variation in the transverse direction.
Figure 2-2 shows the 2D geometry.
Model Definition
DOMAIN EQUATIONS
The dependent variable in this application mode is the z-component of the electric
field E. It obeys the following relation:
– 1
∇ × ( µ r ∇ × Ez)
⎛ jσ
εr– --------- ⎞ 2
– k0Ez
=
0
⎝ ωε ⎠
0
where µ r denotes the relative permeability, ω the angular frequency, σ the conductivity,
ε 0 the permittivity of vacuum, ε r the relative permittivity, and k 0 the free space wave
number. Losses are neglected so the conductivity is zero everywhere.
BOUNDARY CONDITIONS
The waveguide walls are assumed to be perfect, lossless metallic walls which is the
default boundary condition. The two ends of the waveguide are assigned as ports,
where the inport is the left-most boundary, and the top boundary is the outport.