Adding an S-Parameter Configuration

Define an S-parameter configuration and add it to the model.

  1. Add an S-parameter configuration using one of the following workflows:
    • On the Request tab, in the Configurations group, click the  Multiport S-parameter icon.
    • In the configuration list, click the . From the right-click context menu, select Multiport S-parameter.


    Figure 1. The Request S-parameters dialog.
  2. In the Port column, from the drop-down list, select the port.
  3. In the Properties column, specify the following:
    • For waveguide ports, specify the type (TE1 / TM2/ TEM3), indices and rotation of the mode.
    • For ports other than waveguide and FEM modal ports, specify the reference impedance. If no impedance is specified, a default reference impedance of 50 Ohm is used.
  4. In the Active column, select the check box to use the port as a “source” (else the port is only a “receiving” port).
    Note: For example, if a Port1 and Port2 is defined, but only Port1 is active, only S11 and S21 are calculated.
  5. [Optional] Select the Export S-parameters to Touchstone file check box to export the S-parameters to a .snp file.
    For each S-parameter configuration, a separate Touchstone file is created. The file name is in the form <FEKO_base_filename>_<requestname>(k).snp where:
    FEKO_base_filename
    file name of the model
    requestname
    request name
    n
    number of ports
    k
    a counter (integer) to distinguish between the results of multiple requests with the same name and the same number of ports.
    Note:

    Feko does not normalise the S-parameter values to a global reference impedance when exporting S-parameters to Touchstone file. The values are referenced to the impedance specified on each port.

    CAUTION:
    Some industry tools that use the Touchstone format, often assume that all values are referenced to a common impedance. When exporting S-parameters for use in an industry tool that supports only a single reference impedance, specify the reference impedance for each port to ensure the correct interpretation.

During the calculation of S-parameters, the specified reference impedances are added as loads to the ports. These loads remain in place after the S-parameter calculation. If the loads are removed once the S-parameter calculation is complete, the full matrix computation and LU decomposition step are repeated for the MoM solution method. This is typically the most time-consuming step in the analysis.

  1. [Optional] Select the Restore loads after calculation check box to remove the loads once the S-parameter calculation is complete.
  2. In the Label field, add a unique label for the request.
  3. Click Create to request the S-parameter results and to close the dialog.
The port numbers in an S-parameter solution are indexed based on the order of appearance in the port list on the Request S-parameters dialog, and not on the label of the selected port.
1 transverse electric (TE)
2 transverse magnetic (TM)
3 transverse electric and magnetic (TEM)