On 26 August 2012 10:33, Volker Braun <[email protected]> wrote: > Sounds very much like a non-linear fit will be able to figure out the 8 > unknown parameters. You need a formula ("model") for impedance(frequency) > depending on the parameters.
Maybe this is not as hard as I thought, and wrote half an hour ago. There is a very simple model for the impedance of a transmission line of length l, terminated in some known impedance. So I have a model of an upen circuit with 4 unknowns. Having calibrated the VNA, I will know what the measured impedance is at 500 or so frequencies. That's a fairly simple non-linear fit. Then I repeat the process for the short circuit to find out the other 4 parameters. None of this requires access to the correction factors that the VNA computes during its calibration routine. Since you Sage does not have such a complex fitting routine, it might be possible to expose that from GSL as you say, or if Mathematica has it, I'd be tempted to use that. I would have only 4 unknown scalar quantities, which are fixed with frequency, and 500 measurements of the complex impedance taken with the VNA Perhaps I was making harder work of this than I needed to - nothing unusual for me! Dave -- You received this message because you are subscribed to the Google Groups "sage-support" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support?hl=en.
