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[Solved] NanoVNA says impedance of my 3200R resistor is 542R-1250X at 50 MHz
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ogden:

--- Quote from: hendorog on October 18, 2019, 08:32:53 pm ---The SOLT calibration on the nano, and in the software I've seen for it, is just a response cal on the through. It doesn't correct for load match or source match.

--- End quote ---

Nano does full phase/magnitude SOLT calibration for both reflected S11 and thru S21 and not as you say "just a response cal on the through". Please explain what you mean by saying so and why you think it is so.
hendorog:

--- Quote from: ogden on October 18, 2019, 08:46:43 pm ---
--- Quote from: hendorog on October 18, 2019, 08:32:53 pm ---The SOLT calibration on the nano, and in the software I've seen for it, is just a response cal on the through. It doesn't correct for load match or source match.

--- End quote ---

Nano does full phase/magnitude SOLT calibration for both reflected S11 and thru S21 and not as you say "just a response cal on the through". Please explain what you mean by saying so and why you think it is so.

--- End quote ---

Ok you have prompted me to have a closer look at the code and the nano is a bit better than I thought. It isn't what I would call 'Full calibration' though:

Where I'm coming from is, in order of accuracy:
1. Response calibration is the lowest form of through calibration. This is just a normalisation and corrects for Transmission tracking.
2. * Enhanced Response calibration. Uses the OSL information to correct for source match as well. It doesn't correct for load match. You can use an attenuator to improve load match.
3. 1 path 2 port calibration. I _think this should_ correct for everything and be almost as good as a Full 2 port cal, but requires a manual DUT reversal.
4. Full 2 port calibration, the ultimate, but it is not possible on the nano.

* I now think the Nano implements Enhanced Response cal. Whereas previously I thought it was just a Response cal. So one step better than I thought. Which is good.

I'm not sure if this is widely known. I haven't seen this laid out anywhere.

Here is a page on ER and Response cal:
Response:
http://ena.support.keysight.com/e5071c/manuals/webhelp/eng/measurement/calibration/basic_calibrations/thru_response_calibration_transmission_test.htm
Enhanced Response:
http://ena.support.keysight.com/e5071c/manuals/webhelp/eng/measurement/calibration/basic_calibrations/enhanced_response_calibration.htm

Edit: all of the above is related only to the _through_ measurement - i.e. S21. Perhaps that wasn't clear either.
S11 measurements are based on the OSL cal. That is fine as long as you disconnect two port devices and terminate them with a good load. Otherwise the measurement will be influenced by the nano not correcting for Load match.

ogden:

--- Quote from: hendorog on October 18, 2019, 09:36:03 pm ---3. 1 path 2 port calibration. I _think this should_ correct for everything and be almost as good as a Full 2 port cal, but requires a manual DUT reversal.

--- End quote ---
No. You are drifting away from topic. Accurate impedance measurements mentioned in the paper you linked uses only S11 and S21. As you already find out, Nano does both.


--- Quote ---Edit: all of the above is related only to the _through_ measurement - i.e. S21. Perhaps that wasn't clear either.
S11 measurements are based on the OSL cal.

--- End quote ---
Obviously. "T" letter in the SOLT abbreviation means "through". And S11 do not  have "through" because it is single port :D


--- Quote ---That is fine as long as you disconnect two port devices and terminate them with a good load. Otherwise the measurement will be influenced by the nano not correcting for Load match.

--- End quote ---
Terminating open ports of DUT is impedance measurement basics, but thank you for reminding - perhaps someone will benefit from this info.
hendorog:

--- Quote from: ogden on October 19, 2019, 07:04:44 am ---
--- Quote from: hendorog on October 18, 2019, 09:36:03 pm ---3. 1 path 2 port calibration. I _think this should_ correct for everything and be almost as good as a Full 2 port cal, but requires a manual DUT reversal.

--- End quote ---
No. You are drifting away from topic. Accurate impedance measurements mentioned in the paper you linked uses only S11 and S21. As you already find out, Nano does both.

--- End quote ---

Nope. The point is valid. The link I referenced doesn't mention that cal type, which is why I pointed that out as a separate item.
It is a cal type implemented on the 8753. The 8753 supported an 85044 T/R test set.

Actually being able to measure S11 and S21 isn't the point. The point is how accurately you can measure them. That accuracy is dependant on the type of cal you do. This entire discussion is about how to measure various impedances accurately is it not?
ogden:

--- Quote from: hendorog on October 19, 2019, 11:29:50 am ---
--- Quote from: ogden on October 19, 2019, 07:04:44 am ---
--- Quote from: hendorog on October 18, 2019, 09:36:03 pm ---3. 1 path 2 port calibration. I _think this should_ correct for everything and be almost as good as a Full 2 port cal, but requires a manual DUT reversal.

--- End quote ---
No. You are drifting away from topic. Accurate impedance measurements mentioned in the paper you linked uses only S11 and S21. As you already find out, Nano does both.

--- End quote ---

Nope. The point is valid. The link I referenced doesn't mention that cal type, which is why I pointed that out as a separate item.
It is a cal type implemented on the 8753. The 8753 supported an 85044 T/R test set.

Actually being able to measure S11 and S21 isn't the point. The point is how accurately you can measure them. That accuracy is dependant on the type of cal you do. This entire discussion is about how to measure various impedances accurately is it not?

--- End quote ---

I did mean that NanoVNA S21 and S11 measurement and calibration capabilities are enough to perform measurements described in the article. I suspect that you think that S21 thru calibration do not measure/calibrate Port2 impedance. Well, it does. BTW components such as resistor & inductor (some other components as well) are "single port devices" that do not need to be rotated during impedance measurements.
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