# S-parameter settings

S-parameter settings control excitation assumptions, S-parameter definitions, and optional low-frequency smoothing.

# Assume Ideal Excitation

assume_ideal_excitation: Toggle how incident wave amplitudes are computed for S-parameter calculation.

  • Type: Boolean
  • Options:
    • True: Assume only the excited port has nonzero incident wave amplitude.
    • False: Calculate incident wave amplitudes explicitly at every port.
  • Default: False

Use True when only a selected subset of port simulations is run.

# S-Parameter Definition

s_param_def: Wave definition used to compute scattering parameters.

  • Options:
    • Pseudo: Use the pseudo-wave definition.
    • Power: Use the power-wave definition.
    • Symmetric pseudo: Use the symmetric pseudo-wave definition.
  • Default: Pseudo

When the reference impedance is purely real, all three definitions produce the same S-matrix. The differences matter when Z_ref is complex.

Definition S12=S21S_{12} = S_{21} for reciprocal networks Condition for S11=0S_{11} = 0 Passive ∣S11∣≤1\lvert S_{11} \rvert \le 1
Pseudo waves No Zin=ZrefZ_\mathrm{in} = Z_\mathrm{ref}, impedance match No
Power waves Yes Zin=Zref∗Z_\mathrm{in} = Z_\mathrm{ref}^{*}, conjugate match Yes
Symmetric pseudo waves Yes Zin=ZrefZ_\mathrm{in} = Z_\mathrm{ref}, impedance match No

See S-Parameter Definitions (opens new window).

# Low Frequency Smoothing

low_freq_smoothing: Optional low-frequency smoothing parameters used by the terminal component simulation.

  • Default: None

See Low Frequency Smoothing for the smoothing model and parameters.