SubsetAndChangePortAssignment

[Ulrich Kiefner]

Hi,

I want to use the script.SubsetAndChangePortAssignment method in Python. The programming reference tells to exclude ports by assigning the number -1 in the "ports" argument. 

When I use '-1' for the port that I want to remove, the function throws the error 
"Exception: VNA port description '-1' is not valid"

In a simple example I want to extract S11 from a two-port network:
script.SubsetAndChangePortAssignment('test.s2p', '1,-1', 'test_S11.s1p')

Am I doing something wrong?

Kind regards,
Uli

[Michael Wollensack METAS]

Hi,

this is a bug which was introduced in V2.2.0 when I added support for mixed-mode S-parameters in 2018.

This will be fixed in the upcoming V2.9.x.

In the mean time you can use the following workaround:

# script.SubsetAndChangePortAssignment('test.s2p', '1,-1', 'test_S11.s1p')

script.Subset('test.s2p', '1', 'test_S11.sdatb')

# script.SubsetAndChangePortAssignment('test.s2p', '-1,1', 'test_S22_at_S11.sdatb')

script.Subset('test.s2p', '2', 'test_S22.sdatb')

script.ChangePortAssignment('test_S22.sdatb', '1', 'test_S22_at_S11.sdatb')

see

https://wollmich.github.io/metas-vna-tools-programming-reference/html/M_Metas_Vna_Tools_Script_1_Subset.htm

https://wollmich.github.io/metas-vna-tools-programming-reference/html/M_Metas_Vna_Tools_Script_1_ChangePortAssignment.htm

The results are stored as sdatb-files and not Touchstone files. If you want to convert them see https://groups.google.com/g/vnatools/c/aNVqApM_nuI/m/9ou_bYMyAgAJ.

Regards

Michael