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plotting Smith charts

dzakharian

Hello,

I'm running an .sp analysis with a simple setup--port set to 100ohm, with 100ohm load.  I'm plotting results on a Z-Smith, which i thought should give me Re(Z)=1 (normalized)... but instead I'm getting something like 2e-12 as the prime center.  I don't understand why this is the case.  I'm relatively new to Smith charts, but I'm guessing the plot actually shows reflection coefficient, not the impedance?  If this is the case, how can I request an impedance plot?

I'm on version 6.1.8.

Many thanks in advance for your help,
David

Parents

  • I did some more experimenting and consulting with colleagues, and at this point I'm pretty sure the Smith chart option always shows the scattering parameters, regardless of whether I choose Z-smith or Y-smith.  I'm ultimately interested in getting the normalized complex port impedance... can this be done without resorting to manual transformation from scattering parameters to impedance?

  • in reply to dzakharian

    Dear dzakharian,

    dzakharian said:
    I'm ultimately interested in getting the normalized complex port impedance... can this be done without resorting to manual transformation from scattering parameters to impedance?

    I'm not sure if you tried the technique described in the following URL:

    https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1O0V00000911gRUAQ&pageName=ArticleContent

    Basically, this technique relies on a short ocean script to execute following the completion of your S parameter simulation. It is an extra step, but would prevent you from needing to do a transformation of your output S-parameters to complex impedance. Perhaps you have already tried this - in which case I apologize for my forum post!

    Shawn

  • in reply to ShawnLogan

    Hi Shawn,

    Thanks for the reply.  I'll give that ocean script a shot, but I believe that it still plots the scattering data, not the complex impedances (at least there is nothing in that script that would do the conversion).

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