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

[mfarhan1]

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

 

[Yahia Muhammad]

Re: Z0 with ADS

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

 

[mfarhan1]

Re: Z0 with ADS

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

 

[Yahia Muhammad]

Re: Z0 with ADS

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

 

[mfarhan1]

Re: Z0 with ADS

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

 

[khouly]

Re: Z0 with ADS

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

 

[barmak]

Re: Z0 with ADS

Why don't you try LineCalc tool in ADS ?

 

[pewang]

Re: Z0 with 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.

 

[bkd]

Z0 with ADS

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

 

[mfarhan1]

Re: Z0 with ADS

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

 

[khouly]

Re: Z0 with ADS

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