AnsweredAssumed Answered

NF Calibration on PNA-X

Question asked by BryanFast on Mar 10, 2009
Latest reply on Mar 13, 2009 by BryanFast
I'm trying to do a vectored noise figure calibration and I'm coming up with wrong answers when I finish.

Using the prompts, these are my connections:
1) Measure the Noise source (346A) connected to port 2 through a 3.5mm female-female adaptor
2) Perform the 1-Port calibration using a 85052D with the above adaptor in place
3) Remove the adaptor (wrong gender) and connect my cables and probes.  Perform a full 2-Port SOLT probe tip calibration.
4) Answer the thru delay question with an approximated number.  This doesn't seem to change much, because I accidentally put it in the wrong units once with the same result.

The result shows what you'd excpect when measuring a thru standard (NF = 0 +/- 0.2dB).  However when I connect my part I'm getting a NF of about 1.8dB too low across my band of interest. 

Other things I've tried:
1) I've tried moving the reference plane of the noise source portion of the calibration (steps 1 & 2 above) to the DUT end of my cable.  This reduced the error by approx. half, but it's still not right.
2) Increasing my port 1 power level to +5dBm made no apparent difference.

Thoughts?

Bryan  

Outcomes