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

Scott McMorrow (scott@vasthorizons.com)
Mon, 02 Aug 1999 22:54:59 -0700

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Rich,

In HSPICE 99.2 frequency dependent resistance modeling
was changed.

Previous versions of HSPICE model frequency dependent
resistance as:

R(f) = Ro + Rs*sqrt(f)

The changes occured after Dmitri left.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

"Mellitz, Richard" wrote:

> I need a little clarification here. I must be thinking too slow. > > Do HSPICE versions prior to 99.2 not use the Sqrt(f)*(1+j)*Rs? > > Do Quad Design's W models use the Sqrt(f)*(1+j)*Rs? > > If the Sqrt(f)*(1+j)*Rs are only valid for cylindrical conductors, then > should we not use W elements for microstrip and strip line or are they just > less accurate. If so, how much less and at for what frequencies? > > Dmitri you said you used Rs*Sqrt(f) in the W element. Is this Rs the curve > fit coefficient for Re(rs) or the |rs|? > > ...Richard Mellitz > Intel > > -----Original Message----- > From: Dmitri Kuznetsov [mailto:vdm@iname.com] > Sent: Monday, August 02, 1999 3:02 PM > To: si-list@silab.eng.sun.com > Subject: Re: [SI-LIST] : Proposal: Rs > correlation/collaboration for W-Elements > > I agree with Richard, the really important factor is > accuracy of Rs and > Gd values. As they are multiplied by frequency, a small > error makes a > huge difference. But for a given Rs and Gd, my algorithm in > W element > will give you mathematically accurate answer. > > I would like to comment on the Sqrt(f)*(1+j)*Rs skin-effect > equation > introduced in Hspice 99.2. It has mathematically correct > imaginary > part, and does not require frequency-response correction. > But this > equation is only valid for cylindrical conductors and only > at higher > frequencies. > > This skin-effect equation produces the corresponding > inductive component > Ls(f)=Rs/(2*Pi*Sqrt(f)). Thus, the inductance becomes > infinite at dc. > This substantially alters the waveforms especially when Rs > is large. > > This was the reason I used Rs*Sqrt(f) in W element. This > equation gives > asymptotically correct loss, and I was restoring the correct > imaginary > part for any, not just cylindrical, configuration by > applying > frequency-response correction. > > Regards, > Dmitri Kuznetsov > > ======================================================= > Dmitri Kuznetsov, Ph.D. > Principal Engineer > > ViewLogic Systems, Inc. e-mail: vdm@viewlogic.com > 1369 Del Norte Rd. Tel: (805)278-6824 > Camarillo, CA 93010 Fax: (805)988-8259 > ======================================================= > > "Mellitz, Richard" 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>> > > > > > ------------------------------------------------------------------------ > > Name: Mathcad - > ms_loss_eq.pdf > > Mathcad - ms_loss_eq.pdf Type: Acrobat > (application/pdf) > > Encoding: base64 > > **** To unsubscribe from si-list: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list, for more help, put HELP. si-list archives are accessible at > http://www.qsl.net/wb6tpu/si-list **** > > **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****

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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> Rich,

In HSPICE 99.2 frequency dependent resistance modeling
was changed.

Previous versions of HSPICE model frequency dependent
resistance as:

R(f) = Ro + Rs*sqrt(f)

The changes occured after Dmitri left.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com
 
 
 

"Mellitz, Richard" wrote:

I need a little clarification here. I must be thinking too slow.

Do HSPICE versions prior to 99.2 not use the Sqrt(f)*(1+j)*Rs?

Do Quad Design's W models use the Sqrt(f)*(1+j)*Rs?

If the Sqrt(f)*(1+j)*Rs are only valid for cylindrical conductors, then
should we not use W elements for microstrip and strip line or are they just
less accurate. If so, how much less and at for what frequencies?

Dmitri you said you used Rs*Sqrt(f) in the W element. Is this Rs the curve
fit coefficient for Re(rs) or the |rs|?

...Richard Mellitz
Intel

                -----Original Message-----
                From:   Dmitri Kuznetsov [mailto:vdm@iname.com]
                Sent:   Monday, August 02, 1999 3:02 PM
                To:     si-list@silab.eng.sun.com
                Subject:        Re: [SI-LIST] : Proposal: Rs
correlation/collaboration for W-Elements

                I agree with Richard, the really important factor is
accuracy of Rs and
                Gd values.  As they are multiplied by frequency, a small
error makes a
                huge difference.  But for a given Rs and Gd, my algorithm in
W element
                will give you mathematically accurate answer.

                I would like to comment on the Sqrt(f)*(1+j)*Rs skin-effect
equation
                introduced in Hspice 99.2.  It has mathematically correct
imaginary
                part, and does not require frequency-response correction.
But this
                equation is only valid for cylindrical conductors and only
at higher
                frequencies.

                This skin-effect equation produces the corresponding
inductive component
                Ls(f)=Rs/(2*Pi*Sqrt(f)).  Thus, the inductance becomes
infinite at dc.
                This substantially alters the waveforms especially when Rs
is large.

                This was the reason I used Rs*Sqrt(f) in W element.  This
equation gives
                asymptotically correct loss, and I was restoring the correct
imaginary
                part for any, not just cylindrical, configuration by
applying
                frequency-response correction.

                Regards,
                Dmitri Kuznetsov

                =======================================================
                 Dmitri Kuznetsov, Ph.D.
                 Principal Engineer

                 ViewLogic Systems, Inc.     e-mail: vdm@viewlogic.com
                 1369 Del Norte Rd.             Tel: (805)278-6824
                 Camarillo, CA 93010            Fax: (805)988-8259
                =======================================================

                "Mellitz, Richard" 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>>
                >
                >
------------------------------------------------------------------------
                >                                Name: Mathcad -
ms_loss_eq.pdf
                >    Mathcad - ms_loss_eq.pdf    Type: Acrobat
(application/pdf)
                >                            Encoding: base64

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