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 Unrealsitic Fmax simulation of IBM 90nm in cadence 

Last post Thu, Jul 12 2012 10:32 AM by Tawna. 4 replies.
Started by niranjan1984 12 Jul 2012 08:49 AM. Topic has 4 replies and 3474 views
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  • Thu, Jul 12 2012 8:49 AM

    Unrealsitic Fmax simulation of IBM 90nm in cadence Reply

    Hello All,
      I am trying to measure Fmax of IBM 90nm technology in cadence. I am measuring S parameters and plotting Gumx. I get Fmax around 500GHz for 90nm while reported Fmax for 90nm are around 300GHz. I am using rfmos transistor & technology uses BSIM4.4 model. I am not sure what I am doing wrong please help.

    Thanks

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    • Post Points: 20
  • Thu, Jul 12 2012 8:56 AM

    Re: Unrealsitic Fmax simulation of IBM 90nm in cadence Reply

    Probably best to contact IBM, since it's their model.

    Andrew

    • Post Points: 20
  • Thu, Jul 12 2012 9:23 AM

    Re: Unrealsitic Fmax simulation of IBM 90nm in cadence Reply

    Thanks Andrew. Just want to make sure that if Gumx in spectre is the Masons Unilateral Gain (U) ? Please clarify, I read few contradicting posts

    1. Fmax simulation in cadence http://www.cadence.com/Community/blogs/rf/archive/2011/08/11/measuring-fmax-for-mos-transistors.aspx tells you have to plot Gumx to get Fmax

    2. Few posts say Gumx is not U http://www.designers-guide.org/Forum/YaBB.pl?num=1272508752/1,http://www.edaboard.com/thread167090.html

    Please clarify

     

    Thanks

    • Post Points: 20
  • Thu, Jul 12 2012 9:33 AM

    Re: Unrealsitic Fmax simulation of IBM 90nm in cadence Reply

    Search in cdnshelp for Gumx - you'll see the equation. I'm not really familiar with "Mason's Unilateral Gain"- maybe Tawna will chime in - but the documentation does describe the equation in terms of the s parameters.

    Andrew.

    • Post Points: 20
  • Thu, Jul 12 2012 10:32 AM

    • Tawna
    • Top 25 Contributor
    • Joined on Fri, Jul 11 2008
    • Snohomish, WA
    • Posts 208
    • Points 5,500
    RE: Unrealsitic Fmax simulation of IBM 90nm in cadence Reply
    Hopefully the screenshot below will show up.   

    Here is equation 8.3 of Mason Unilateral Gain from Vendelin, Pavio, and Rohde’s book

    Microwave Circuit Design Using Linear And Nonlinear Techniques.  

    We don’t calculate U.   You could come up with a calculator expression for this.

    The closest we calculate is Gumx.

    Chapter 10 of the MMSIM11.1 Virtuoso® Spectre® Circuit Simulator and Accelerated Parallel Simulator RF Analysis User Guide

    contains the different gains that we calculate and their equations.

    GA (available gain) is the power gain obtained by optimally matching the output of the network.

    GP (power gain) is the power gain obtained by optimally matching the input of the network.

    GT (transducer gain) shows the insertion effect of a two-port circuit. This quantity is used in amplifier design.

    Gumx (maximum unilateral transducer power gain)

    Gmax (maximum available gain) shows the transducer power gain when there exists a simultaneous conjugate match at both ports.

    Gmsg (maximum stable gain) shows the gain that can be achieved by resistively loading the two-port such that k = 1 and then simultaneously conjugately matching the input and output ports. For conditionally stable two-ports, you can approach the maximum stable gain as you reduce the input and output mismatch. If you attempt a simultaneous conjugate match and k < 1, the two-port oscillates.

    Best regards,

    Tawna
    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 5
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Started by niranjan1984 at 12 Jul 2012 08:49 AM. Topic has 4 replies.