On a PNA-X, I want to perform a vector mixer calibration where the LO for my DUT’s mixer is being set by a PLL (internal to the DUT). The signal generator for the “LO” is really setting the PLL reference frequency, so it is not equal to f[Port 1] – f[Port 2]. What is the best way to set up this type of vector mixer calibration?
As a simple example shown below, say I have an 8 GHz reference signal with a PLL generating a 9 GHz LO, with the DUT input = 10 GHz and DUT output = 1 GHz. If I set up the VMC with an LO of 9 GHz, it won't work since the source needs to be 8 GHz for the DUT.
Do I need to add an identical PLL to the Reference Mixer path, and tell the PNA that the LO is 9 GHz instead of the 8 GHz reference frequency? Or would a calibration work with two sources generating 8 GHz & 9 GHz if their 10 MHz ref are tied together? Any other way to do this?
What is the measurement you are trying to make on this DUT? If you just need group delay, then you will have a much easier time setting up an SMC+Phase channel than a VMC. Also, in your example you specifying everything at a fixed frequency, but I am assuming you are sweeping something? If the LO is not swept, then you can set this up by saying the LO frequency is 9 GHz and use the PNA-X 2nd source to supply the 9 GHz signal to the reference and calibration mixers. you can then use an external source that has 10 MHz lock to the PNA-X and it is NOT being controlled by the PNA-X to supply the 8 GHz signal to the PLL. I am not sure if the problem can be solved if you have to sweep the LO.