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Kirkby calibration kit alternatives?
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hendorog:

--- Quote from: G0HZU on February 25, 2018, 12:15:38 am ---Here's what appears to be the custom coefficients for that Kirkby female OPEN and C0 looks to be about 44fF.


--- Quote ---Female open. (Use OPEN(M) or OPEN -F- depending on model of VNA - see notes above) **
Minimum frequency:  0 GHz
Maximum frequency:  7.0 GHz
Offset Zo: 50.0 ohms
Offset loss: 3.0  G ohm/s
Offset delay: 39.8  ps
C0: 44.36
C1: 156.42
C2: 1159.1
C3: -131.92


--- End quote ---


I just spotted your attached results files.

The optimiser tool you are using looks very powerful. I tried downloading it and the other sparam tool etc and I already have GNU Octave but I wasn't sure what to type in the command line. I tried an edited version of the default example but it didn't like it. I'm a newbie with GNU Octave so I probably haven't installed something correctly. I assume all the plots come from this optimiser tool?

--- End quote ---

Yes it does look very impressive. The docs are here:
https://nlopt.readthedocs.io/en/latest/NLopt_Matlab_Reference/

If you are on Windows, there is a page which summarises the steps. However I would not recommend trying the install just yet. I will document what I had to do as that will make it much much easier for you and anyone else to get it going.
hendorog:

--- Quote from: G0HZU on February 25, 2018, 12:20:37 am ---Try running it up to 6GHz or maybe 7GHz as Fmax. It might give a flatter result?

--- End quote ---

Aha, I did not notice this earlier. The graphs were being output with a hardcoded and therefore incorrect frequency range which did not match the input file.

I am changing the script now to use the fmin and fmax values from the S1P file.

The optimiser itself uses the correct frequency range, and so this won't change the results.

Here are the results from a run with the Cx values limited to the range 30-100 units. Doesn't look very good at the higher freq's.


--- Code: ---Optimization results:
offs_delay = 35.951981 ps
offs_loss = 10.000000 Gohm/s
offs_Z0 = 49.000000 ohm
C0 = 100.000000 * 1e-15 F
C1 = 99.011405 * 1e-27 F/Hz
C2 = 30.000000 * 1e-36 F/Hz^2
C3 = 30.000000 * 1e-45 F/Hz^3

Residual RMS error : -22.299742 dB

--- End code ---
G0HZU:
Yes, that looks bad at the top end. The 30.0000 values look suspicious. Has this hit a limit?

I don't think you need to alter Zo away from 50R on this OPEN because DrKirkby managed to get a really flat line with Z0 = 50 in my earlier post.
Can you try locking in some of his values and see if it works better with fewer variables? I'm off to bed soon so can't do much more tonight...
hendorog:

--- Quote from: G0HZU on February 25, 2018, 01:06:08 am ---Yes, that looks bad at the top end. The 30.0000 values look suspicious. Has this hit a limit?

I don't think you need to alter Zo away from 50R on this OPEN because DrKirkby managed to get a really flat line with Z0 = 50 in my earlier post.
Can you try locking in some of his values and see if it works better with fewer variables? I'm off to bed soon so can't do much more tonight...

--- End quote ---

Yes that one hit all of the limits - I constrained it to 30-100 on all of the C values.

I've opened them back up again and I will lock the Z0 back at 50.
hendorog:
Also, thanks for your help :)
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