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Marker: Compression issue (urgent)

Question asked by htnicolas on Sep 7, 2011
Latest reply on Sep 7, 2011 by yuchenhu

I am performing a fixed frequency power sweep, over a range of frequencies.
I have S21, B, S11 traces displayed, and I am tracking the compression level with a marker.

As you can see on the attached screenshot (where f=10GHz, power sweep from -20 dBm to 0 dBm),
the Compression Pout indicates a level of 13.75 dBm.
However, projecting the position of marker 1 onto the y-axis shows that Pout at 1dB compression should be around 27~28 dBm.

What's happening?
I am using the following commands:
scpi.Execute "calc:par:sel 'MyMeas'"         ' where  MyMeas refers to S21
scpi.Execute "CALC:MARK1:STAT ON"
scpi.Execute "CALCulate:MARKer:FUNCtion COMPression"

This is quite urgent, I really need some help, I have to present this program tomorrow to my supervisor...
Thanks in advance,