I've been taking measurements with a VNA then running them through a passivity
checker. The basis for the code was originally posted by Ray. I've modified it
to meet my needs. Added plotting capabilities, log mag format handling, and
nudging of the non-passive values when only a few points are out of spec etc.
I don't think I broke anything in the process but what I've noticed is that
the eigen values of some of my measurements are very noisy. The better
measurements oscillate too but they trend upward with increasing frequency.
The suspect measurements oscillate between near 0 and approximately 0.4 from
point to point across the higher frequency bands. The magnitude of the
s-parameters seem to be noisy as well. I've gone through my setup to make sure
that my cables don't have loose/bad connections. Replaced some connectors
that seemed inadequate and while things got marginally better the measurements
still contained noise. The noise source seems to be my
fixturing. Unfortunately I don't think I can improve this given my time
constraints.
The only thing that I've noticed is that the time domain simulations take
longer than those created with a data set that isn't as noisy.
Is there a way to decide if these models are accurate enough to be reliable?
Regards,
Travis
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