S-parameter definition in ADS?

S-definition in the testbook is under the condition that the port is matched,for example ,S11 is the reflection coefficeint of port 1 when the port 2 is matched.
But when I studied some example of ADS, I found they do not consider the match between the term and the circiut to be simulated. This is in contradiction with the defintion.

Could anyone give me some guide? Thanks!

yes,it is right
the term dose not match to the circuit' port impedance
but to the characteristic impedance of the transmission line between the port and the circuit
and always the charachteristic impedance of the line 50ohm

Just like Network Analyzer, it never knows the output impedance of DUT and the microstrip line impedance before N.A. port but it always wirtes "S11" on display
screen.

The user should judge the data you measured is "S11" or "Gamma"

S-parameter measurement and usefulness does not depend on a match. If you calibrated your network analyzer in 50 ohms and then measure the S-parameters of a device that has some input/output impedance other than 50 ohms (mismatched), you are measuring the S-parameters referenced to 50 ohms.

You might want to read page six of the classic HP app note S-Paramater Design AN 154.