Add TUG multiline TRL and a method to compute switch terms indirectly

[ZiadHatab]

Hi!

I have included my multiline TRL method. In the attached file, you will find test code using both measurements and synthetic data I copied from this example. The plots below show the Monte Carlo test I performed with additive noise.

I did not adopt the structure of the NISTMultilineTRL with regard to inputs. In my case, you pass the line measurements and reflect measurements in different variables. Also, in my case, you can run the code without reflect measurements if only the propagation constant and S21 and S12 of the calibrated DUT are relevant. The mathematical details of the calibration procedure can be found here.

Also, I have included a method to compute the switch terms using reciprocal devices without prior calibration of the VNA. Tests are included in attached file. You can read more about the math behind this here.

PR_tests.zip

[Ttl]

Code looks good but it needs tests (for both TRL and switch term solving). See here for NISTMultilineTRL tests. A notebook similar to NISTMultilineTRL that would show how it's used and its advantages would be also welcome though not absolutely necessary.

[ZiadHatab]

I didn't know about the test. I will adapt the ones made for NISTMultilineTRL.

Regarding the notebook, do you think I should rewrite the current notebook to include both multiline TRLs with comparison, or add a new notebook?

[jhillairet]

Regarding the notebook, do you think I should rewrite the current notebook to include both multiline TRLs with comparison, or add a new notebook?

If your can use the same data from the multiline TRLs, I would suggest to add a new section in the same notebook explaining your method and showing the results. If you can't use the same data for any reason, I would suggest to create a dedicated notebook.

[ZiadHatab]

yes, I can use the same data. I already was using the same data in the test files I attached when I opened this PR.

[jhillairet]

Great addition, thanks. I've just added some details in the docs.

[jhillairet]

Thank you @ZiadHatab .

I found your blog posts also very good, nice work. If you want, you could eventually consider adding some advanced tutorials on the scikit-rf doc ;) Open-access litterature on calibration maths and switch terms are rare.