Hi Enrico,
please find the answer below:-
1. Can we have the output I / Q (on J12 / J13) of a single channel (only J1 for example) instead of all mixed together?
No you can't. Using more channels at the same time you cannot see the I/Q output of each channel - they are all mixed together. What you can do is just applying the input signal to each channel grounding all the others for best signal performance so that you can see the relative I/Q output signal.
Hope it helps
Regards,
Fabio
Applications Engineer
TI Healthtech/Imaging