switch-term measurements - NIST StatistiCAL

I am trying to use NIST StatistiCAL software for a one-tier calibration. It asks for a "switch-term calibration" standard. I have no idea what this is and cannot find information on it in their documentation or in my textbooks.

Does anyone have any information or know what a switch-term measurement is?

Here is what the NIST manual states about it:

You can read about TRL switch terms in
D. C. DeGroot, J. A. Jargon, and R. B. Marks, "Multiline TRL Revealed," 60th ARFTG Conference Digest, pp. 131-155, Dec. 5-6, 2002.

If you are using the "PNA netgrabber" that comes with Statistical to do the measurements, the PNA Netgrabber will automatically measure the switch terms when you measure the thru standard in the "thru" mode instead of measuring it in the "normal" mode.

If you named your thru measurement file as "thru.s2p", then the PNA Netgrabber will store the Switch Terms Measurement in a "Gthru.s2p" file automatically after measuring the thru standard in the "thru" mode.

The suffix G in "Gthru.s2p" indicates that the measurement file is a switch terms file and it should appear in the folder where the rest of your measurement files are.