The effect of the ref node of the s2p data item in ADS

[superdida]

Hi everyone, I encountered a problem in my simulation using ADS. Usually I always connect the ref node of the 2 port s-parameter item to ground, and it seems working well.
Yesterday, I used design guide in ADS to generate a interdigital capacitor,and simulate it in Momentum as a two port network.The s parameter got from the simulation was imported to a 2 port s-parameter data item.Problem arised that different results were obtained when I let the ref node of the s-parameter item unconnected.
What's the effect of the ref node,help me!! Thanks!!

 

[GGAPBE96]

The ref node represents the ground reference of your circuit.
If it is not connected to the ground,it means the ground of your circuit is floating.