generate the X-parameter on a nonlinear system

Hi dears,

I have nonlinear system and I would like to generate the X-parameter. Can I do that through the ADS or it should be by using NVNA?
Also, how to have my circuits as XNP file.

Thank you for your cooperation and helping.

ADS can create X-parameters if you have a accurate model but the best way is to characterize it using with VNA ( they are extremely expensive )