Products > Test Equipment
Kirkby calibration kit alternatives?
<< < (18/44) > >>
hendorog:

--- Quote from: suj on February 25, 2018, 06:56:22 pm ---
--- Quote from: G0HZU on February 25, 2018, 05:51:58 pm ---...It's a shame this Lx correction can't be added to the 8753 firmware in some way.

--- End quote ---

By the way. It should be possible to do it off-line with Metas. It has a built-in driver for the 8753 and 8720 series (as well as 8510C, ENA, PNA). You can make measurements and off-line error correction using this software. Definitions of the "short" element that you can prepare have the option of defining L.
The procedure is shown in the tutorial on the program's website.
It looks like a Swiss army knife  ::)

--- End quote ---

Bingo. I was thinking of using scikit-rf, but Metas would no doubt be more straight forward.

Really looking forward to getting hold of it.
G0HZU:

--- Quote ---By the way. It should be possible to do it off-line with Metas.
--- End quote ---
Wow, that sounds great. I hope to get a copy of METAS soon :)

See below for a quick and dirty OPEN and SHORT made from a pair of SMA F-F bullets. One has a commercial SC end cap for the short. Sadly, the two bullets are from different manufacturers so they are not going to be the same but the end cap for the short is a known part and it isn't expensive. Maybe $9?

So maybe if I buy some Amphenol SMA F-F bullets from Farnell ($8 ea?) we could have a go at making a cheap cal kit for the masses?

But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below?


hendorog:
I was having a heck of time with this one. The fit wasn't lining up with the Metas one by suj

Then I found a bug in the model calculation for the Lx params. Fixed that and tada, now it lines up :)
Although it does tend to find another result at 53 ohms Z0. This one took a bit of nudging.


--- Code: ---Optimization results:
offs_delay = 32.331122 ps
offs_loss = 6.333923 Gohm/s
offs_Z0 = 60.858025 ohm
L0 = 872.429450 * 1e-12 H
L1 = 5981.654164 * 1e-24 H/Hz
L2 = 37028.127991 * 1e-33 H/Hz^2
L3 = 3160.750516 * 1e-42 H/Hz^3

Residual RMS error : -53.679006 dB

--- End code ---


hendorog:

--- Quote from: G0HZU on February 25, 2018, 07:22:10 pm ---
--- Quote ---By the way. It should be possible to do it off-line with Metas.
--- End quote ---
Wow, that sounds great. I hope to get a copy of METAS soon :)

See below for a quick and dirty OPEN and SHORT made from a pair of SMA F-F bullets. One has a commercial SC end cap for the short. Sadly, the two bullets are from different manufacturers so they are not going to be the same but the end cap for the short is a known part and it isn't expensive. Maybe $9?

So maybe if I buy some Amphenol SMA F-F bullets from Farnell ($8 ea?) we could have a go at making a cheap cal kit for the masses?

But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below?

--- End quote ---


I did a bit of blue sky thinking:

There is nothing preventing us from having different coefficients for different frequency ranges.
The fit will be better by limiting the frequency range it is over.

Also, if the cal is done offline in software, then changing coefficients (i.e. recalibrating using a different set of coefficents) is purely software and doesn't require another sweep. So it would be technically possible to do a full sweep and change cal definitions on the fly. The definitions would match the real cal standards very closely.

In fact I expect this could be as good or better than a high quality cal kit - assuming it only has one set of coefficents for the entire range of the kit. Perhaps this is how the eCal units work?
suj:

--- Quote from: G0HZU on February 25, 2018, 07:22:10 pm ---But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below?

--- End quote ---

Two cases for the "open" element and two for the "short" element. For each element once Z0 opened and once set to 50 \$\Omega\$


--- Code: ---Agilent Definition
Standard Type: Open
Offset Z0 (Ohm): 60.711892
Offset Delay (ps): 27.289762
Offset Loss (GOhm/s): 3.507799
C0 (E-15 F): 414.232256
C1 (E-27 F/Hz): -6871.633507
C2 (E-36 F/Hz^2): -4959.099088
C3 (E-45 F/Hz^3): 470.623016

Agilent Fit Error
RMS Error
0.001900
Max Error
0.003349
_______________________________________________
Agilent Definition
Standard Type: Open
Offset Z0 (Ohm): 50.000000
Offset Delay (ps): 58.437897
Offset Loss (GOhm/s): 2.711473
C0 (E-15 F): -304.566047
C1 (E-27 F/Hz): -8873.121112
C2 (E-36 F/Hz^2): 2622.781977
C3 (E-45 F/Hz^3): -343.691735
Agilent Fit Error
RMS Error
0.002197
Max Error
0.003648
_______________________________________________
Agilent Definition
Standard Type: Short
Offset Z0 (Ohm): 56.059063
Offset Delay (ps): 41.557996
Offset Loss (GOhm/s): 3.717653
L0 (E-12 H): -222.842514
L1 (E-24 H/Hz): -19759.249841
L2 (E-33 H/Hz^2): 11091.105982
L3 (E-42 H/Hz^3): -651.849387
Agilent Fit Error
RMS Error
0.001378
Max Error
0.003844
_______________________________________________
Agilent Definition
Standard Type: Short
Offset Z0 (Ohm): 50.000000
Offset Delay (ps): 32.074189
Offset Loss (GOhm/s): 4.973737
L0 (E-12 H): 492.787861
L1 (E-24 H/Hz): -6736.857074
L2 (E-33 H/Hz^2): -3868.927304
L3 (E-42 H/Hz^3): 506.666193
Agilent Fit Error
RMS Error
0.001556
Max Error
0.004609

--- End code ---

Open element, Z0 open:





Open element, Z0=50 \$\Omega\$:





Short element, Z0 open:





Short element, Z0=50 \$\Omega\$:



Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod