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IMDx source power calibration question

Question asked by d_finz on Jul 21, 2013
Latest reply on Jul 22, 2013 by d_finz
I am performing a IMDx measurement using a N5241A PNA-X with two internal sources and combiner; port 1 is the input and port 2 is the output.  I'm measuring IM3 relative to carrier at the output of the DUT with the output tone powers set to -5dBm in the tone power dialog box; I've also set power leveling to "Set Output Power, Receiver Leveling" and checked "Coupled Tone Powers" and "ALC On".

When I'm performing the source calibration on channel 1, I've been setting the power level to approximately -35dBm since the DUT has approximately 40dB of gain.  The internal sources sweep across the frequency range of interest at -35dBm with no errors.  Then, a second sweep begins that according to the measurement window is at -5dBm.  The calibration fails significantly at this point (by 35-40dB) and several "Src1 Unlevel" and "Src2 Unlevel" error messages pop up on the screen.

I configured the two sources' output power to be controlled by the resulting -5dBm signal present on port 2 in the tone power dialog box as I described above; why does the analyzer try to measure this power on Port 1?

I'm assuming the significant calibration failure is due to there not being any signal on Port 2 and so there is no power getting to the B receiver; why didn't the calibration wizard prompt me to connect a cable from Port 1 to Port 2?  Plus, if there is a way to calibrate the B receiver with a -5dBm signal using the calibration wizard, can I use the two internal sources?  It's apparent that the two sources are not capable of producing two tones at -5dBm.