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Calibration with pre-amplifier

Question asked by jem on Nov 7, 2011
Latest reply on Nov 7, 2011 by jem
Hi there,

I am using a PNA N4252A along with a 82017A amplifier to increase the output power at the PNA port. The schematic is basically the same as figure 13 of except that only S11 measurement are taken.

I wish to use my E-Cal module ( N4691A) for calibration, therefore I set the PNA 'Port Power' at -36 dBm in order to have a power of around -7 dBm at the end of my cable (recommended for this E-Cal kit) during calibration. After calibration I increase the 'Port Power' to -10 dBm to have a power level around 20 dBm at the end of my cable.

I noticed that my calibration is quite a bit off after the power is increased. It is offset by about 5 dB and it is quite wavy... I understand that I will see some difference due to the change of state of the step attenuator, however I was really not expecting that much. Especially since the reference receiver is fed by the coupled signal from my pre-amp...

Can anyone explain why I see so much changes?