I am using ADS2014 for designing high frequency PCB. My PCB will contain a chip that has internal differential 100 Ohm termination (attaching the structure). How to measure differential s parameters for the same?

1) You can use a termination (Term) in a differential configuration

2) You can compute single ended S-parameters and convert to mixed mode S-parameters using:

DesignGuide > Signal Integrity Applications > Mixed Mode Simulation

1) You can use a termination (Term) in a differential configuration

2) You can compute single ended S-parameters and convert to mixed mode S-parameters using:

DesignGuide > Signal Integrity Applications > Mixed Mode Simulation