Reading/plotting s4p – Touchstone files of 4 port devices – does not work properly. Measurement file of 2 pairs of cables is plotted with positive S11, >20dB. I checked the s4p file in notepad, it is correct.
Would be great if you can share the project (snp-files plus schematics) that shows the problem. Using QucsStudio package file would be best, of course.