Re: [SI-LIST] : Proposal: Rs correlation/collaboration for W-Elements

Dan Bostan (dan@uniant.com)
Tue, 3 Aug 1999 08:49:52 -0500

Dr. Sayre,

Please let me know the URL of the NESA's web site.
Thank you.

Dan Bostan
Engineer
Corvia Networks e-mail: dan@corvia.com
212 Gibraltar Dr. ph: 408.752.0550/x111
Sunnyvale, CA 94089 fax: 408.752.0551

----- Original Message -----
From: Dr. Edward P. Sayre <esayre@nesa.com>
To: <si-list@silab.eng.sun.com>
Sent: Tuesday, August 03, 1999 9:15 AM
Subject: Re: [SI-LIST] : Proposal: Rs correlation/collaboration for
W-Elements

> Dear colleagues:
>
> If we are going to check the accuracy of the .W model, I wish to make the
> suggestion that we use measurements as well for verification. Most field
> solvers do not account for losses in copper or dielectric to as correct an
> extent that I would deem acceptable. Does anybody have a set of test board
> that they would volunteer?
>
> Dr. Dmitri Kuznetsov's comments in a recent si-list communication see
> (7/29/99) are very relevant. The behavior of the skin effect and
> dielectric formulas in the frequency domain, when transformed back into
the
> time domain involve functions that have very special properties.
>
> The losses which are proportional to frequency, namely the dielectric
> losses can be shown to be related to the unit capacitance and the loss
> tangent of the material, Equation (8) for small losses.
> See "OC-48/2.5 Gbps Interconnect Design Rules", Sayre, Chen and Baxter;
> DesignCon99 Proceedings. (Available on NESA's web site). Use of equation
> (8) together with the .W model has been found to be very satisfactory when
> the simulation results are compared to measurements.
>
> Lastly, just as recently mentioned by Scott McMorrow, we too have also
seen
> small differences with respect to the same problem solved by two recent
> versions of HSPICE. I do not think the way to resolve this is through the
> use of field solver predictions.
>
> Sincerely,
>
> ed sayre
>
> However,
>
> At 07:51 AM 8/2/99 -0700, you wrote:
> >Apparently the W element model uses a pseudo-propagation function with
the
> >following form.
> >
> >P(f)=
exp{-sqrt[ (G0+f*Gd+j*2*pi*f*C)*(R0+sqrt(f)(1+j)Rs+j*2*pi*f*L) ]*len }
> >
> >(From HSPICE application note "Boosting Accuracy of W Element
> >for Transmission Lines with Nonzero Rs or Gd Values")
> >
> >Let's assume that this is valid for some conditions. It would be nice to
> >know what the assumptions are.(geometry, frequency, etc.) We can talk
about
> >the validity of the above in another thread.
> >
> >I would like to make a proposal. I would like to know what various field
> >solvers report in regards to the above propagation function. Let's start
> >with a microstrip first (and only look at skin effect). The geometry
> >follows.
> >
> > Height over ground: 0.004"
> > Width of conductor: 0.006"
> > Thickness of conductor: 0.001"
> >
> > Conductivity: 0.58E8 mho/meter
> >
> >Let's all use the same units for Rs. Say:
> > Ohms/(sqrt(Hz)*meter)
> >
> >Now, A colleague of mine has supplied a formula that is used in microwave
> >design. I have attached a PDF file with details. (Too tough for text,
TTFT
> >:-)), I remember foobar)
> >
> >The answer, using the closed form formula for Rs is:
> > 1.806E-03 ohms/(sqrt(Hz)*meter)
> >
> >If this is the magnitude of complex Rs, then Re(Rs) would be
> > 1.277E-03 ohms/(sqrt(Hz)*meter)
> >
> >I have received sidebar results from some of you folks, but I don't want
to
> >post other people answers. However I will compile a table of posted
> >results. There are issues of complex number involved. Remember I'm
looking
> >for the Rs for the above propagation formula.
> >
> >Step 2 will be to do same for a strip line geometry where:
> >
> > Height over ground: 0.005"
> > Width of conductor: 0.0025"
> > Thickness of conductor: 0.0005"
> > Distance between ground planes: 0.0105
> >
> >
> >It would be appreciated if we could find out what "tricks" people are
using
> >to get Rs from their field solvers.
> >
> >Regards,
> >Richard Mellitz
> >Intel
> >
> > <<Mathcad - ms_loss_eq.pdf>>
> >
> >Attachment Converted: "C:\TEMP\attachments\Mathcad - ms_loss_eq.pdf"
> >
>
>
>
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> | NORTH EAST SYSTEMS ASSOCIATES, INC. |
> | ------------------------------------- |
> | "High Performance Engineering & Design" |
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> | Dr. Ed Sayre e-mail: esayre@nesa.com |
> | NESA, Inc. http://www.nesa.com/ |
> | 636 Great Road Tel +1.978.897-8787 |
> | Stow, MA 01775 USA Fax +1.978.897-5359 |
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
>
>
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