Is it possible to measure a DUT on a VNA smaller than ......

[tisutma]

Hello guys


I have a question about the calibration kits for a VNA. Is it possible to measure a DUT (devise under test) smaller than the thru that I used for calibrating the VNA?.
This because I 'm trying to characterize two SMA connectors. But the mount where I insert the connectors yields a physical lenght smaller than the thru of my calibration kit. Then my measure results has an expected behaviour in the last part of the measured band. And I don't know why. Somebody sugest me that is due the question that I posted here.

Any advice?.

Best regard's

 

[Mazz]

Re: Is it possible to measure a DUT on a VNA smaller than ..

In the definition of your cal kit there should be the also the electrical length of the thru.
It means that at the end of the calibration procedure you'll have the cal planes at the edge of the cable connectors. If this is true, measuring the thru itself you'll measure a certain length(phase of s21 not zero)!
In this way you can characterize anything is inserted between your cal planes, the phisical dimensions being indipendent from it.
I hope i've catched the point.
Mazz

 

[sergio mariotti]

I agree with Mazz, but let me add some concepts.
The standard used to calibrate the VNA sholu'be known for their "inperfections", for example a non-zero-lenght thru shoul'd be known for its delay, Zo, and Loss. This latter parameter is the most NON accurate parameter and impact strongly on the loss measurement of the low loss DUT (like connectors alone).
For example, for the popular 3.5mm , the most known factories that produce standards (Agilent, Anritsu, Maury) give no or very different informations about the loss.