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Optimization of StabFact issues.

Question asked by jimmydean on Apr 29, 2014
Latest reply on May 1, 2014 by jimmydean

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I'm having issues getting the optimization function to work with StabFact. It worked once before but I can't recall exactly how I got the function to perform properly. Optimization however works for the nf(2) alone.
This is the error message: http://i.imgur.com/krSF5Xx.png
Any ideas?

Thank you.

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Toby Oct 14, 2015 11:22 PM
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Your screenshot doesn't show the equation defining the variable +StabFact1+.
Otherwise it has to be a function call on your S-parameter, and as far as I can remember the
function calculating the stability factor is spelled differently. Check the doku.
Toby
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- jimmydean @ Toby on Apr 30, 2014 1:19 AM
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  I've done some searching/troubleshooting and referred to help docs but still no luck. Here's the defined StabFact in schematic. You can see if this picture and the last that I attempted two different expressions for StabFact (stab_fact(S)): http://imgur.com/bZR3ZcE
  
  Edited by: jimmydean on Apr 30, 2014 2:19 AM
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  - Toby @ jimmydean on Oct 14, 2015 11:22 PM
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    Now it's getting fun, because everything looks fine.
    I'd suggest to disbale the optimizer, store +dump=stab_fact(S)+ with a MeasEqu, run the simulation, and inspect the result you get carefully. Look for dimensions, sizes, and numerical content of +dump+.
    Maybe the result is complex (-> mag(stab_fact(S)) would do the trick).
    The conent of dump has to be "real", and the innermost sweep dimension has to be "freq". Otherwise the specified goal function cannot be evaluated. (-> your error message !)
    
    Toby
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    - aehoward @ Toby on Apr 30, 2014 11:09 AM
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      There is an example in the Amplifier DesignGuide that has an optimization of feedback network parameter values to improve the stability factors mu and mu_prime. From any schematic, select DesignGuide > Amplifier > Feedback Network Optimization to Attain Stability.
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    - jimmydean @ Toby on May 1, 2014 11:01 PM
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      Good call, Toby. The S-params were evauating at 0 Hz giving an undefined value in the dump. Changing the S-params to a sweep 100 MHz (not 0) - 3 GHz fixed it. Thanks!
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Optimization of StabFact issues.

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