I am using PNA-X with FW A.09.90.1 (the upgrade to the newer firmware should be next year). I would like to perform high power pulsed measurements (S11,S21, Output power) of the power amplifiers. Since I am using pulsed pre-amplifiers, I perform calibration in pulsed mode using average power sensor. I have done everything according to the Application Note "Active-Device Characterization in Pulsed Operation Using the PNA-X".
I calculated the attenuator values between couplers and receivers not to exceed -20 dBm. For the calibration purposes I enabled averaging to reduce the random errors.
I tried Enhanced Response Calibration using 85054B calkit with load standard replaced by the high power load. The second calibration I performed using TRL method with 68.042 mm air line.
After both calibrations I enabled receiver leveling and everything worked. I performed measurements of attenuators and the results looks reasonable. When I started measurements of the PA, I obtained errors on the PNA-X (receiver leveling failed, power set to the limit). I am observing a peak of the R1 power. What's more, the results of the S11 are unreal - S11 went above 0 dB. S21/B power also looked strange - the variation of the gain was above 5 dB. I have measured this PA using different method and the results are "normal".
Please help me in finding the problem in my setup. I am attaching the csa file of the PNA-X.