S-parameters

The S-parameters calculation in the time domain allows you to evaluate S-parameters as a function of time. This calculation type is available for all transmission line types.

Example

• Example - Calculate S-Parameters in the Time Domain

S-parameters Calculation Walkthrough

To perform a time-domain S-parameters calculation, follow these steps:

1. Set the initial calculation settings:

   • Set Target to Transmission line
   • Set Target type to Single-ended, Diff pair, Coplanar single-ended, or Coplanar diff pair
   • Set Mode to Time domain
   • Set Parameters to S-parameters

   

2. Select the required transmission line model and review it in the preview area.

   

3. Define the input parameters for the transmission line, including source and load impedance.

   

   Available parameters are listed below. Some of them may not be available for certain transmission line types.

   • H – Dielectric thickness (mm). For each dielectric layer, you can specify its own thickness using the H1..H4 parameters (the number of H(n) parameters is determined by the number of dielectric layers).
   • Er – Dielectric constant. For each dielectric layer, you can specify its own dielectric constant using the Er1..Er4 parameters (the number of Er(n) parameters is determined by the number of dielectric layers).
   • W1 – Trace width (mm).
   • W2 – Trace width after undercut (mm).
   • T1 – Trace thickness (mm).
   • C1 – Coating thickness (mm).
   • CEr – Coating dielectric constant.
   • D1 – Distance from the trace to the reference plane (mm).
   • S1 – Diff-pair trace spacing (mm).
   • TC – Conductor conductivity (S/m).
   • tgδ – Loss tangent.
   • LTL – Line length (mm).

   • FREQ – Frequency (MHz).

     A frequency range (FREQ) is initially specified for the FREQ parameter.

     

     When needed, you can specify a custom range of values or change the step. Do not disable the parametric sweep, as single calculations make no sense in this calculation type.

   • ZS – Source impedance (Ohm).

   • ZL – Load impedance (Ohm).

   Surface roughness parameters:

   • a – Nodule radius (µm).
   • N – Number of nodules in a unit area.
   • Af – Unit area (mm²).

4. Click Calculate in the lower-right corner of the calculation tab to run the calculation.

   

   Before running the calculation, you can click the dropdown arrow next to the Calculate button to choose between two calculation saving options:

   

   • Overwrite calculation – Saves the modified input parameters to the current calculation, overwriting previous data.
   • Save as new calculation – Saves the modified input parameters to a new calculation. This calculation will appear in the Projects panel.

Calculation Results for Single-Ended and Coplanar Single-Ended Lines

For single-ended and coplanar single-ended transmission lines, the following parameters are calculated:

• S11 – Input reflection coefficient.
• S21 – Forward transmission coefficient.
• S12 – Reverse transmission coefficient.
• S22 – Output reflection coefficient.

Use the settings in the Calculation results panel to customize the presentation of calculated parameters in table and graph formats.

Table Form

• The Mode setting specifies display mode for the calculation results. Available options include:

  • Magnitude
  • Magnitude (dB)
  • Real/Imaginary

  

Graph Form

• Axis Y setting — Specifies the value to display on the Y-axis. Available options include:

  • Magnitude
  • Magnitude (dB)

  

• S-parameter — Specifies the parameter or multiple parameters to display in the graph.

  

  

Calculation Results for Differential and Coplanar Differential Lines

For differential and coplanar differential transmission lines, S-parameters are calculated in single-ended and mixed modes.

Use the settings in the Calculation results panel to customize the presentation of calculated parameters in table and graph formats.

Table Form

• The Mode setting — Specifies display mode for the calculation results. Available options include:

  • Magnitude/phase
  • Magnitude (dB)/phase
  • Real/Imaginary

  

Graph Form

• Axis Y setting — Specifies the value to display on the Y-axis. Available options include:

  • Magnitude
  • Magnitude (dB)

  

• S-parameter — Specifies the parameter or multiple parameters to display in the graph.

  

  

See Also

• Example - Calculate S-Parameters in the Time Domain