having problem in simulating single stub tuning in CST

Hello everybody, I have a problem in simulating single stub tuning in CST Design studio , the problem is
1 - general transmission line is two port , i don't know how to connect it with a resistor,although connecting resistor to the ground often gives me right answers, but when i try to calculate S parameter while using single stub in TL ,it's answers are very wrong and unreal , even it doesn't answer 0 in center frequency , for exmaple i tried to simulate one of the examples of POZAR book , but it's answer is wrong ,
2 - even with a coax cable or coupled trans line i got wrong answers,
thank u for your HEeeeeeeeeeeeeeelp!

Can you post a pic of your simulation setup? Would be much easier to understand your problem!

well, first of all thank you for your consideration ,
and here you can see it ,../imgqa/eboard/Antenna/rf-qtggg45x2gm.png
thanks

To be sure: is your problem how to use the SW or how to calculate the length of the transmission line and the length of the stub?

thank you WimRFP,but I know the length of the tras line and the length of the stub ,because it is one of the examples of Pozar book, titled microwave engineering , i haven't change the numbers in CST , my problem is the software is turning back wrong answers , i used the Transmission line model in CST Design .

Did you check it with a hand calculation (or easier Smith chart) to make sure you know what to expect? I'm sorry I can't help with the SW.

thank you again WinRFP, yes i checked it with a calculator manually, and the circuit must be matched in 2GHz ,(S11=0) .i think that i have a problem with cst design enviroment

Hello mohammaddmt,

there are many possible problems which can cause a mismatch. Maybe you upload your CST-file and will check it, maybe easier. Which CST version you are using.
Kind regards!
Johnjoe

thank you very much johnjoe , ok , now i upload my files , my CST version is 2011 .this folder has 4 files , that has four diefferent ideas for the image that i put above, thank you very much for your consideration . http://davvas.com/jk64sd0s3igr you have to wait 10 seconds , thanks,note that the 404 Error is a popup , the original link is working,

jeez, these threads ***** me up! Get a two colored smith chart (red and green) and learn how to match at a single frequency there. ONce you understand the whole impedance/admittance concept, then go screw with fancy programs!

you piff44 , i exactly know how to match with Z and Y smith chart , you'd better know that i'm studying at graduate in university, so you better shut your **** up , ok?

As I understood, his problem is not the matching but simulation setup. In this case a smith chart would be not very helpful . But I understand what do you mean.

Thank you johnjoe for beeing reasonable and sensible

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Hi again everybody, right now i simulate this circuit with ADS , and it answered pretty good , so the conclusion is "just for these kinds of simulation" it's better to use ADS rather than CST , thank you all very much.
hope you all to be happy
Kind regards

LOL. I suspect you do not have clue 1 about how to do it, but am not 100% sure. only maybe 98%. good luck sport

@biff44: I didn't expect these reactions from you, as it is very likely that Mohammad has problems with how to use the SW and not how to solve it by hand, his example image goes through 50 Ohms at 2 GHz.

@mohammaddmt: please stay polite, even when a posting may offend you. Biff44 has a high helped/postings ratio, so he is a clever guy.

I really hope you both can clear this issue (maybe via the private mail system).

Wim

Sorry, but your link doesn't work.

- - Updated - - -

Hi again everybody, right now i simulate this circuit with ADS , and it answered pretty good , so the conclusion is "just for these kinds of simulation" it's better to use ADS rather than CST , thank you all very much.
hope you all to be happy
Kind regards
thank you johnjoe for your attention!

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