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Improving calibration for High Power Amplifier Setup

Question asked by GT_test001 on Mar 16, 2015
Latest reply on Mar 1, 2018 by maxplus
*PNA Model* E8363C; A.09.42.22; Options 010, 014, P02

*Goal:* characterize Gain, Abs Output Power, VSWR, Gain Compression of a 100W amplifier.
*Test setup:* similar to Fig 4 of App Note 1408-10 except I do not need the preamp and my output test coupler is 30 dB.  I also am not using the 10 dB between the rcvr B in and Cplr Arm.
Desired Port 1 power (DUT input) will be from -25dBm to 0 dBm.

*PNA config:* 101 pts, IFBW = 1kHz, Avg = 7

*Issue1:* S21 with thru in place of DUT is not flat (>1.5 dB) after calibration
I first conduct a power calibration with my power meter/sensor on Port 1 (-25dBm to 0 dBm in 1 dB steps).
Then I replace my DUT with the eCal module (N4691-60004) and do a full 2 port S-param calibration (at port power of -10 dBm).
Next I put a _thru in for my DUT_ and look at S21 (dB) and do not get the flatness I would expect.  I try to minimize test cable movement and am careful with all connections.
If I do a Response Thru cal then I can get flatness < 0.05dB, but thought full 2 port would be the best cal and also want to meas other S-params.
I have varied IFBW, Averaging, Initial port power level, test cables, test coupler, with similar results.

*Issue2:* Can I display the absolute power at the DUT (offset the output losses of the test coupler and cables)?
In order to see the absolute output power of the DUT, I'm measuring Receiver B/1.0 (source = P1).  Can I offset this data (over freq) to display the power out at my DUT instead?

*Issue 3:* Can you confirm that my PNA configuration does not allow for internal adjustment of the Receiver B attenuation?   Also, will I need to add attenuation externally (cplr arm to RCVR B in) in order to reduce the Receiver B compression?
Any help is appreciated.  

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