[SOLVED] ADS : Warnings of co-simulation Momentum-LSSP

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Nathan1

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Hello everyone,
I'm working on the RF rectifier circuits and currently using Momentum and LSSP of ADS for my simulations. However, I have the following warnings :

1- "Simulator uses frequency lower than frequency range of model. The S-parameters are extrapolated" and
2- "S-parameters passivity is enforced"

as can be seen in the attached screenshot.

The frequency plan for emmodel is the same as the sweep frequency for LSSP. Why do I have these warnings?
Your help will be greatly appreciated.

Thanks a lot.
 

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Nathan1 said:
The frequency plan for emmodel is the same as the sweep frequency for LSSP. Why do I have these warnings?
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For non-linear simulation it is not enough to specify the frequency range of interest, you also need the emModel response at DC and at least a few harmonics!

This means your emModel needs to start at 0 Hz and go up to the harmonics that you specify in LSSP simulation controller!
 
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If I give you an example you'll understand quickly.
Let say your Operating frequency is 1GHz and you do a HB simulation with 10 harmonics. So max. available frequency is 10GHz. You should simulate your EM structure up to 10GHz to avoid this warning AND extrapolation.\
Because an extrapolation might give you a bit error.
If a DC current flows trough this EM structure, add manually a DC in your EM simulation set-up to prevent low side extrapolations.
 
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Thanks a lot, @volker@muehlhaus. It solved the problem.
--- Updated ---

@BigBoss, thanks for the detailed explanation.
 

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