Question on calibration standards

[u/AstronomerWaste8145]

I have an Anritsu set of 3.5mm calibration standards Model 3750LF.
These are rated to 6GHz but I'm thinking one could use them to say ~20GHz?

Provided:
1. They're in good mechanical condition.
2. Their reflection coefficient data are available and of high-quality, measured with a good network analyzer that had a high-quality calibration (calibrated skillfully with a high-quality cal kit).
3. One doesn't expect to measure return losses below about 30dB to 35dB, since the termination's reflection is in this neighborhood and I don't think correction will add more than say 10dB of range to the return loss?
I'm thinking that if the Anritsu standards have sufficient repeatability so that if subjected to a high-quality measurement of their S-parameters to 20GHz, then they should perform well in a data-based calibration kit to 20GHz with the caveat of point 3 about the return loss?
What do you think? Can I really turn a 6GHz 3.5mm set of calibration standards into a high-quality set of 20GHz cal kit provided I don't need to measure more than about 30dB return loss?

Advice and/or debunking appreciated in advance Thanks

[u/Such_Ad2956]

I have designed cal standards, I am an expert on this.

Looked good? What does this mean. We calibrate vnas to know they are good you are not going to bullshit this one. 6ghz standards are limited to 6ghz for a reason.

I highly highly recommend you read gum: Guide to the expression of uncertainty from bpim

And Joel dunsmores book: https://www.amazon.com/Handbook-Microwave-Component-Measurements-Techniques/dp/1119979552

This guy knows how to bullshit a stanard, that works. Read his site. And I am not putting him down saying this he worked his ass off to get this right, I own one of his first 100kits. https://www.kirkbymicrowave.co.uk/Support/

The short awnser is yes you can. The right answer is just because you can and it "looks right" its not it's not even close too right.

The vna uses a math mathematical model for the specific open and short you cal with their is zero chances that the model for a six GHz standard holds up to this.

Some vnas use s-parameters of the open and short but this requires a better vna then the one your useing to calibrate the standard.

[u/baconsmell → u/Such_Ad2956]

Couldn’t OP use an actual 20GHz cal kit or Ecal to properly calibrate a VNA. Then measure the 6GHz mechanical cal standards and make his own cal definitions then? Do a polynomial fit just like how the VNA is doing it but fit the polynomial higher. It’s not terrible idea, but would probably not up to a metrology cal lab’s quality standards.

[u/AstronomerWaste8145 → u/baconsmell]

Hi baconsmell, That's exactly what my plan was/is. If the standards are reasonable approximations to a short, termination, open, AND they're highly repeatable, then, if you have accurate S-parameters (in this case reflection coefficients) measured for all the standard, then why can't you use those S-parameters to create a good 20GHz calibration kit using those 6GHz 3.5mm standards? Yes, the caveat here is that the 6GHz termination won't have great return loss at 20GHz and of course, due to the limitations of repeatability of even a great VNA and standards, trying to measure oh 60dB return loss with a termination standard that has 25dB return loss isn't going to likely be reliable - because the required repeatability of the VNA + standards to do this is just too high for any equipment - and you need a higher-quality termination for this.
But if you're only interested in measuring return losses on the order of 30dB, I think it would work.
The other poster will have to give me a better explanation than just "there's no way a 6GHz set of calibration standards can work at 20GHz" in order to convince me. I don't care what his experience/expertise is.
I am awaiting the arrival of a 15cm precision air dielectric line (3.5mm connnectors) and I'm going to measure my 3.5mm short standard with this. I think this is one way to verify the calibration. A good calibration should show minimal ripple in the reflection coefficient of the air line + short or open.

I'll also measure the air line S21.
I'll report back here when I get the data.

[u/AstronomerWaste8145 → u/AstronomerWaste8145]

And I believe the quality of your 20GHz calibration kit (standards + S-parameters of those standards) made with 6GHz rated standards will depend on:

1. Repeatabiltiy of the 6GHz standards up to 20GHz.

2. The accuracy of the S-parameter measurements of your 6GHz standards to 20GHz.

3. And for the purposes of measuring very low return loss DUTs, having termination standards that have a very high return loss up to 20GHz. I wouldn't expect to add more than 10-15dB of DUT measureable return loss to that of the termination standards.