vna calibration error: imperfect short & open

[analog_chip]

Hi,
I am using a cal kit for my vna. After 1 port calibration,
1. marker is at center when loaded
2. marker is at right end with little rotation when open
3. marker is at left end with little rotation when short

I can get rid of the rotation if i enter offset using delay 12 ps. What is the cause of this rotation?
Is my calibration ok? I have seen a youtube video where marker is at perfect left, center and right when terminated with short, load, open.


Thanks!

 

[FvM]

A matter of calibration settings. Maybe you are using a correction table for a specific cal kit?

 

[analog_chip]

Hi Fvm,
Thanks for the reply! I am not using any correction table.
I have a basic doubt: the calkit was already installed by somebody. Sometimes vna will have calkit installed by default or you have to install it. If I want to install a new kit, what are the data about the kit that has to be entered?

 

[FvM]

"Installed cal kit" is another word for a built-in correction table, I think. The calibration is performed related to a nominal reference plane of the connectors which is not necessarily the location of the actual short and open realized in the cal kit. In so far, the observed 12 ps shift (= about 2.4 mm) can be plausible.

For details, you should refer to the VNA and cal kit user manual.