How to find the characteristic impedance of microstrip after simulating S parameters?

Dear all
I have a simple question, if i make a microstrip or strip line (with out properly calculating its width) in ADS momentum and its characteristic impedance is unknown then how can i find its characteristic impedance after simulating S parameters, It has some thing to do with the reflection S11 but how please tell me?
PLs: i dont want to use the equations and formulas because they change with the substrate configration
waiting for quick responce

put a 50 ohm termination and calculate S11 and from the reflection coefficient ( magnitude and phase of S11 ) you can calculate the impudence of the line
or if u know the width and substrate parameters u can use line calc in the ADS to get the line impedence

thanks yahia
i cant use line calc because i am tuning the design, (say i dont know substrate just the result of simulation) second thing i know that using S11 i can find but how? can you tell me the relation? there are many but believe me no one is working

the substrate must be in the main design

and the relation
Γ=(Z-Z0)/(Z+Z0) ;

take care if the line is loded you must get the effect of the load
Γ is S11 magnitude and phase

brother lets start with simple example i have connected an ideal line of Z 25ohm with 50ohm termination both sides now according to formula S11=(Z-Z0)/(Z+Z0) ; which comes out to be 0.333<180 or -0.333 BUT THE MOST CONFUSING THING IS THAT ADS GIVES 0.6<-180, now stupid me i am totally confused why ADS is giving 0.6 instead of 0.33, please help me or try it by your self
waiting
faran

i have tried what u talking about about and ADS gave me the mag(S(1,1)) is 0.35
and this is very close

khouly

Why don't you try LineCalc tool in ADS ?

This file talke about the differency between how the circuit simulation and EM simulation handle the "match". I hope it's helpful for your question.

You should use the smirt chart to drawing the S11 and then you can see in the marker the impedance ( go with S11 value)

Added after 1 minutes:

You do not need to use any equation. But If you want to drawing the resistance and reactive impedance you can use the equation like above

dear all thanks for your support, i am uploading little image of a microstrip line which is according to line calc has 25ohm impedance, the termination are of 50ohm, now as i said earlier i am getting 0.6 as magnitude of S11 instead of 0.33, its visible in image, i dont know where is the problem,
@ khouly please check where is the difference,
@ bkd, smith chart result shows 0.251*Z0 which is 12.55
waiting for more help

i think the differnce also in the length of the line ur using ,
try to change it and u will change the S11 , why ?
coz the line will be termiated with the other port in S11 measurments so the length so the Zin of the laoded line will change with its lenght

Khouly