How to simulate phase noise in ADS

Hello everbody,
I am trying to simuate my design by ADS, it is VCO differntial. I can plot phase noise for one port single ended but how can i simulate phase noise for a differential struture? it means vo2-vo1
Thank you in advance

please to help.I am waiting your support I need to plot phase noise for vo2-vo1 but ADS tell that can not know this port

why not attach your file for more support?