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PNA-X noise figure for converters channel strange behavior

Question asked by rok on May 31, 2011
Latest reply on Jun 7, 2011 by rok

I am noticing some strange mismatch between the settings for the noise figure for converters channel. I am currently using the A.09.33.05 firmware and am using the standard receiver to measure noise figure for converters.

In the first screenshot, you see the desired settings set properly. Note that the 'Port Powers Coupled' is unchecked.

But, if I check the settings using a different mechanism through the 'Stimulus' settings dialog window, on the 'Power' tab, I get a different result, namely:
-'Port Powers' checked (not correct!)
-Output Port 2 Power Level is set to '-15dBm' (but greyed out)

Now here's where the problem occurs. If I click 'OK', it will corrupt all my settings! So if you check the settings again through the 'Power and Attenuators' mechanism, you get the third screenshot.
Now you see that all the port powers are set to the setting used for the LO power! I tried the same experiment using the latest release of A.09.33.07, but with the same results.

I only found this out because I was getting some crazy-looking noise figure waveforms and upon further investigation was able to find and duplicate the problem. I believe this is pretty serious, since it may have damage my PNA-X standard receiver since my downconverter gain is >25, and I have my port 2 receiver set to "Reverse the main arm and coupled arm of the test-port coupler" configuration as stated in the help file.  Currently, I am testing across ports 1&2, but the problem may also happen for ports 3&4 as well. I will attach the .csa state file in the next post (due to attachment limit of 3) so you can see if you can duplicate this problem on your side.