In the process of measuring mixer, using VMC method has been a problem for me, we obtained by measuring the phase of mixer in the end is the relative phase or absolute phase measurement? We add reference mixer, and eliminates the influence of reference mixer in the calibration, then we get the measured parameters of MUT is relative to the calibration mixer? That is to say, if we use the different calibration mixer, the MUT’s parameters will change? I really want to resolve this problem, I hope someone can help me, thank you very much!
When you use the VMC calibration and measurement method, the absolute transmission phase of the MUT (VC21 phase) is relative to the calibration mixer, but the group delay is absolute. In other words if you calibrate with different calibration mixers and measure the same MUT you are likely to get different phase values at the same frequency, but the group delay at the same frequency will be the same within the uncertainty and repeatability range of the measurement.