TRL Calibration on difference impedance

[Edoardo]

Hi everyone,

I want to test a theory that we had. One of my collegues built an EVB for a chip with a 70 ohm impedance, and built a TRL cal kit with the same impedance.

For our measurement we must include port extension in the VNA. 

I'd like to test if we can obtain a good measurement if we tune our VNA impedance to 70 ohm, then we do the calibration and the port extension, and we perform measurements on such impedance.

I've obtained raw measurements for all those things (raw meaning with a VNA calibrated up until the cables on 50 ohm) and I'd like to create a TRL calibration on a specific nominal impedance. Is there a way to do so?

Thanks!

[Henrik Forstén]

TRL calibration reference impedance is the TRL line impedance even if
the calibration result z0 is by default 50 ohms. Using scikit-rf
NISTMultilineTRL for 70 ohm line you should specify z0_line = 70. z0_ref
should be either 50 or 70 depending on if you want the resulting
S-parameters to be referenced to 50 or 70 ohms. NISTMultilineTRL also
has ref_plane argument that can do port extensions accurately with the
solved transmission line propagation constant.