Readings from my VNA Card Have Unexpected Spikes After Changing IFBW

Updated May 16, 2018

Reported In

Hardware

  • PXIe-5632
  • PXIe-5630

Issue Details

I have a VNA card for PXI that is giving expected readings after calibration. When I calibrate for 1 kHz IFBW and measure 1 kHz IFBW, my measurements might look like this:

But if I change IFBW to 100 kHz, the readings start showing strange spikes and dips:
For both these cases, I can see that correction is active since the symbol for this remains green at the bottom of the window. Is there something wrong with my calibration?

Solution

This is not unexpected behavior. After performing a VNA calibration, it is not recommended to change any parameters of your setup. The correction boolean will show True as long as calibration parameters are applied to the measurement data - however, this does not guarantee that the calibration parameters are valid. Read more about this property in the related article: Calibration Settings:Correction Enabled Property

Additional Information

If you have a 2 port VNA, make sure to calibrate for both directions. Otherwise, your S12 and S22 measurements could give unexpected data like in the screenshots above. 

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