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 How can I read Smith Chart in Virtuoso? 

Last post Thu, Feb 10 2011 8:25 AM by Tawna. 3 replies.
Started by StillLearning 06 Feb 2011 05:15 PM. Topic has 3 replies and 2451 views
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  • Sun, Feb 6 2011 5:15 PM

    How can I read Smith Chart in Virtuoso? Reply
    Hello everyone,

    I am confused with the Smith Chart that Cadence’s Virtuoso plots. I have never seen such a representation of Smith chart over the past 20 years of my familiarity with and use of paper-based Smith Chart.

    Could someone help me with reading Virtuoso’s Smith Chart? I need to make a correspondence between the paper-based Smith Chart and that displayed by Virtuoso. For example, where is the Center of Virtuoso’s Smith Chart? There is no correspondence at all between the two.

    Thank you in advance for your attention and guidance.
     

    Still Learning.
    • Post Points: 20
  • Mon, Feb 7 2011 8:43 AM

    • Tawna
    • Top 25 Contributor
    • Joined on Thu, Jul 10 2008
    • Snohomish, WA
    • Posts 212
    • Points 5,625
    RE: How can I read Smith Chart in Virtuoso? Reply
    Hi Still Learning,
     
    The paper based and Virtuoso Smith Charts should be the same (e.g. the center of the chart is in the same place,
    the values on the chart should correspond with the paper chart).  Of course paper Smith Charts have much more detail!
    What subversion of software are you using?  Is it possible to submit a Service Request so we can look at this more
    closely...just in case you discovered a bug?   The Smith Chart readability was greatly improved in IC6.1.5 Virtuoso.
     
    best regards,
    Tawna
    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 20
  • Thu, Feb 10 2011 8:10 AM

    Re: RE: How can I read Smith Chart in Virtuoso? Reply
    Hello Tawna,
    Thank you for your attention to my issue. I am afraid I disagree with you, as there is no correspondence, whatsoever, between the paper-based and the Cadence-created Smith Charts.

    For example, the Center of the Paper-based Smith Chart is always the number "1," and there is no "negative" number on the horizontal or vertical axes of the Paper-based Smith Chart; however, the Cadence-generated Smith Chart has variable numbers at its geometrical center as well as a mixture of positive and negative numbers on both axes. What does a negative number on the horizontal or vertical axes of the Smith Chart mean?

    Furthermore, on page 519 of the document titled: "Virtuoso Spectre Circuit Simulator RF Analysis User Guide_7.2," there is a statement that reads as follows: "In the center of the Smith Chart, the values of S11 and S22 are greater than 1, so the center of the Smith chart is part of the unstable region." How does the author claim so? Where did he/she obtain the S11 or S22 magnitude from the Smith Chart? As you see, there is so much ambiguity in the documentation as well as the Software representation of the data.As a user, I am disappointed at how Cadence makes simple things complicated. As mentioned in my first message, I have used paper-based Smith Chart for 20 years, and am very familiar with its concept; however, Cadence makes me waste a lot of time to simply view some mundane information, which I can plot by hand on the paper. I hope an overhaul of the way Cadence develops its software happens so that we spend more time on innovation than dealing with software-related issues. I have been using Cadence for two (2) years, and, unfortunately, I do not see such a sign of improvement.Regarding your question, I am using IC 6.1.4 version of Virtuoso, and have no control over choosing the version, as my superior has that authority.

    Thank you,

    Still Learning
    • Post Points: 20
  • Thu, Feb 10 2011 8:25 AM

    • Tawna
    • Top 25 Contributor
    • Joined on Thu, Jul 10 2008
    • Snohomish, WA
    • Posts 212
    • Points 5,625
    RE: RE: How can I read Smith Chart in Virtuoso? Reply
    Hi Still Learning,
     
    You may have run into a bug.  Please file a Service Request.
    I am in a class right now, so I cannot dive deeply into this, unfortunately.
    There is also a known bug with the Smith Chart that was just fixed in the
    latest ISR of IC6.1.4 and also in IC 6.1.5.  The Smith Chart is
    MUCH better in IC 6.1.5.
     
    We are also improving the documentation - I completely agree that
    it needs work.
     
    I am very interested in hearing more about how you would like the Smith Chart
    improved.  (I am sitting next to the Product Engineer for ViVA in this class.)
    Please email me off-line and we can continue our discussion further.
     
     
    Best regards,
     
    Tawna Wilsey
    tawna@cadence.com
    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 5
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Started by StillLearning at 06 Feb 2011 05:15 PM. Topic has 3 replies.