On Tue, 29 Oct 2019 at 18:28, <erik@...> wrote:
The manual optimization took way too much time so I learned how to do
non-linear least squares multiparameter fit in Octave. The created Octave
scripts are attached. Loaddata.m loads the uncalibrated datasets. optim.m
runs the optimization to minimize the residue (residue.m) by repeating
calibration (calib.m) with tuned parameters. Don't complain about my
ineffective use of Octave. This is my second day of usage
What is on the y-axis of your graphs?
There's absolutely no way that C0 should be as high as 500. Someone
recently showed for that Keysight kits, having just a delay and C0 was
sufficient at 1500 MHz or so. So forget C1 for one minute, and just worry
about
1) Get the offset delay right - assuming C0=C1=C2=C3=0
2) Optimise for a value of C0
Look at the values on the Keysight website
to give you some idea of the typical values of C0. There are tons of kits
there, so I will list the first 3 I have, but plus one with a smaller
connector.
*85050B 18 GHz APC7. *
This since is genderless, there is no male or female.
C0=90.4799
*85054B 18 GHz type N*
C0=89.939 (male open)
C0=104.13 (female open)
*85852B 26.5 GHz 3.5 mm, so closest to SMA. *
C0=49.433 for both male and female.
*85056A 50 GHz 2.4 mm (I don't have such a kit, but I will just list it, as
its a smaller than 3.5 mm connector)*
C0=29.722 (male open), 29.72 (female open)
Your coax could have quite a loss at the top end, which means a complex
value (by complex, I do mean real and imaginary) of characteristic
impedance.
You would be better with a length of RG401 (6.3 mm OD), but if not, the
cheaper RG402 (3.5 mm OD). Those would have lower loss than your RG58.
But you seem to be ignoring any offset delay, and without that being
somewhere near correct, it is pointless worrying and C0, C1, C2 or C3.
What is your calibration standard? Is it the standard male open supplied
with the NanoVNA? If so, I could give you some sensible starting values.
Dave
--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
Tel 01621-680100 / +44 1621-680100
