HP 8753C amplifier measurements

[rfguy2020]

Hello,

I have HP 8753C (firmware 04.12) with 85044A test set. I have been using it mostly for antenna measurements (S11).

I'm trying to use it for amplifier measurement. I'm measuring Mini-circuits ZX60-V62+ as I can see values from data sheet. I have performed one-path 2-port calibration, since my test set does not allow full 2-port calibration. I have added 20dB attenuator to B port as maximum allowed power level is +20dBm.

S11 is really strange sometimes it is positive (>0dB), sometimes it is something I expected and sometimes it is between those two. S21 looks more or less expected, but it seems to go strange sometimes as well.

If I don't connect my amplifier to port B and just add termination to amplifier output, then my S11 is expected. So for some reason, S11 goes wild if I connect amplifier output to port B through 20dB attenuator. I don't understand how it detects that I have connected active device to port B? Is there something broken in my VNA or do I have to change some settings?

[rfguy2020]

I figured out root cause by myself. I actually need to rotate the device for reverse and forward measurement as VNA instructs. For passive devices it does not make big difference if I don't follow this instruction, but amplifier or non reciprocal devices gives totally wrong results.

[DrNefario]

An HP 85046A test set is the type that can automatically switch the ports around while making the measurements.