RE: [SI-LIST] : Total Conductive and dielectric Losses for a microstrip trace

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From: Jian X. Zheng (jian@zeland.com)
Date: Fri Mar 02 2001 - 11:24:46 PST


Hi, Paul:

I use our IE3D full-wave simulator to check your results. It seems to me
your calculated loss is too low.

I assume the conductor is gold with conductivity of 4.9e+7 s/m. For a 75-ohm
line of width 33 mils, the subtrate thickness should be about 33 mils. The
thickness is 0.7 mils. The DK = 3.9.

If I assume there is no dielectric loss, the Alpha = 0.50 dB/m.
If I assume there is no metallic loss, the Alpha = 1.34 dB/m.
If I assume both metallic loss and dielectric loss are there, the Alpha =
1.84 dB/mm.

The calcualted effective DK = 2.86.

I trust the results of our IE3D simulator. Thanks!

Best regards,
-----------------------------------------------------------------------
Jian-X. Zheng, Ph.D
Zeland Software, Inc., 48890 Milmont Drive, 105D, Fremont, CA 94538, U.S.A.
Tel: 510-623-7162, Fax: 510-623-7135, Web: http://www.zeland.com
---------------------------------------------------------------------

> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Matt Bibee
> Sent: Friday, March 02, 2001 10:36 AM
> To: Denomme, Paul S.
> Cc: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Total Conductive and dielectric Losses for a
> microstrip trace
>
>
> Your tool should give you the per meter RLGC matrices at your desired
> frequency. The classic equation is:
> alpha=Re{sqrt[(R + jwL)(G +jwC)]} where alpha is in Nepers/m. I
> forget the
> conversion factor. That's the total loss. Is there an advantage
> to seperating
> loss into conductor and dielectric? If you have it available the hspice W
> element can accept RLGC params in matrix format and will model skin and
> dielectric loss.
>
> "Denomme, Paul S." wrote:
>
> > I am currently working on a job and have a microstrip trace on
> > GETEK. The trace width is 33 mils 1/2 oz., running at 1GHz, 75
> ohms, Dk of
> > 3.9, and Loss tangent of .01. I am trying to calculate the
> total conductive
> > loss and the total dielectric losses for this microstrip case. For
> > conductive losses I obtained 0.189dB/M which seems correct to me. I
> > obtained this result from Ansoft 2D analyzer. I am also trying
> to determine
> > the dielectric losses for this trace but I am not sure if I can use a
> > formula for this calculation or not. The formula for
> dielectric loss I have
> > is
> >
> > Ad=(27.3*SQR(Er)*LossTangent)/Wavelength
> >
> > The Ansoft software gave me an effective Dk of 2.88 which is .74 of the
> > Dk=3.9. I am thinking that I could use the .74*Losstangent as
> the effective
> > loss tangent and
> > plug in the effective dielectric constant and the effective loss tangent
> > into the above equation to get the dielectric losses. Can
> anyone tell me if
> > I am way off base on this one? or am I right on the money?
> >
> > I would appreciate any feedback.
> >
> > Regards,
> >
> > Paul S. Denomme
> > paul.denomme@viasystems.com
> >
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