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Is it possible to save the rational model of the S-parameter block?

Hello,

I'm doing a parametric AC simulation (mmsim 11.1). I need a lot of steps, but the single simulations are fast.

When I add an S-parameter block the parametric simulations slows down because a rational fitting process is required at each simulation step ("Starting rational fitting process." message appears in the output log form).

Is it possible to save the rational model of the S-parameter block? I would like spectre could calculate the rational model only at the beginning of the sweep and then use it on the following sweep steps.

Thank you

Best regards

Aldo

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Tawna over 13 years ago

Hi Aldo,

What Andrew has said is correct.   And you really do want to read the nport appNote.  (/blogs/rf/archive/2012/01/03/nport-application-note-has-been-updated-and-re-released.aspx?postID=1306677 )   Specifically the section on "Using the nport in SpectreRF simulations" if you are using SpectreRF. There are some situations where you must use rational interpolation in SpectreRF.

Also, check out the blog "My Favorite Nport Settings". (/blogs/rf/archive/2011/03/23/my-favorite-nport-settings.aspx?postID=1260942 ).

Rational interpolation can be a reasonable choice if you have lumped elements.  However, the rational model is not as robust and accurate as the convolution based model (linear or spline), particularly when the s-parameter data models distributed systems with long propagation delay, or the DUT is a multi-port system with the number of ports > 4.

It is important to use the latest MMSIM ISR when simulating a circuit containing nports. R&D has made significant improvements to the nport, and more are in the works.

If you have a specific SR/CCR open with Customer Support/R&D, I can take a look at it briefly. But I would need to know the SR number.

Best regards,

Tawna
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Tawna over 13 years ago

Hi Aldo,

What Andrew has said is correct.   And you really do want to read the nport appNote.  (/blogs/rf/archive/2012/01/03/nport-application-note-has-been-updated-and-re-released.aspx?postID=1306677 )   Specifically the section on "Using the nport in SpectreRF simulations" if you are using SpectreRF. There are some situations where you must use rational interpolation in SpectreRF.

Also, check out the blog "My Favorite Nport Settings". (/blogs/rf/archive/2011/03/23/my-favorite-nport-settings.aspx?postID=1260942 ).

Rational interpolation can be a reasonable choice if you have lumped elements.  However, the rational model is not as robust and accurate as the convolution based model (linear or spline), particularly when the s-parameter data models distributed systems with long propagation delay, or the DUT is a multi-port system with the number of ports > 4.

It is important to use the latest MMSIM ISR when simulating a circuit containing nports. R&D has made significant improvements to the nport, and more are in the works.

If you have a specific SR/CCR open with Customer Support/R&D, I can take a look at it briefly. But I would need to know the SR number.

Best regards,

Tawna
Cancel
Vote Up 0 Vote Down

Cancel

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