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Error in ADS - RF Cafe Forums

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Post subject: Error in ADS Posted: Tue May 02, 2006 5:05 am


Joined: Tue May 02, 2006 4:59 am
Posts: 15
I use the Budget tool and got that error message :

[b]Error detected by HPEESOFSIM during Budget Analysis `Budget'.
Term3: ERROR: During Budget cascaded noise analysis; possible element with
unrealistic S-parameters; look for |S11| > .8; |S22| > .8; |S12| near, equal
or greater than |S21|. [/b]

Maybe anyone understand it ?
I know its depend on the attenuators location but im not understand why .


Post subject: ADS error messagePosted: Tue May 02, 2006 6:32 pm


Joined: Wed Feb 22, 2006 3:51 pm
Posts: 104
That's actually a more-helpful error message than many, because it tells you what to look for in your design. Unfortunately it's not very specific - it doesn't tell you where to look, and it gives 3 alternatives.

The S11 and S22 checks say that maybe there's a severe impedance mismatch between two stages, the S12/S21 message says that maybe there's a large amount of (unexpected/undesired) feedback around an active stage.

Good Luck!


Post subject: Posted: Tue May 02, 2006 10:03 pm

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany

I took the initiative and replied to this post directly by email as we had already a brief correspondence in the past. I mentioned that the main cause of such a problem is instability (As fred47 mentioned), this is also noticed by the values of S11, S22 which are greater than 1. This is likely to be caused by poor matching. I also suggest you to do the budget analysis simulation step by step from the start: Block after block. And to see in which step the error message displays. By doing that you can find out the problemtaic element and check it separately.

Good luck!

Best regards,

- IR

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