[SI-LIST] Re: Dielectric loss modeling
- From: "burke_ipc" <burke@xxxxxxxxxxxxxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 01 Dec 2004 09:12:29 -0000
The conductance matrix, Gij, can be calculated from the capacitance
matrix, Cij, by:
(1) Gij = Cij{ 1-(Eo/Em)(1-tanh((Em/Eo)-1)))}w*tandelta
where
Em/Eo is the effective dielectric constant for line i
If the dielectric is uniformly distributed the approximation:
(2) Gij=Cij*w*tandelta
can be used.
In verifying some applications (such as xtk-xfx) some time ago (it
may not be the case now) we found something very similar to what you
are describing. In a homogeneous stripline situation equation (2)
above was confirmed. However, in a non-homogeneous microstrip
configuration we either found the dielectric material above base
ground was used, or some average dielectric material (as I say, it
has been a while, and would have to go through some notes to
determine exactly the case).
In any regard, we concluded that some apps do take short cuts (or at
least have in the past).
I have mentioned before in this forum, and I will again here. You
may download the FREE version of IFSPro EZStack and validate the
models you are creating (specifically G in this instance) against
our application, as we DO NOT base our solution on the above
assumption.
http://www.interactive-products.com
Regards,
Brian Burke
--- In si-list@xxxxxxxxxxxxxxx, "Sogo Hsu" <sogo.hsu@xxxx> wrote:
>
> Hi, Gurus,
>
> One topic confused me for a long time, I look forward somebody
here
> can help me to clarify. To model the dielectric loss for trace, it
> is used to express the conductance as
>
> G(f) = G0 + freq * Gd
>
> where G0 is in terms of leakage current loss at DC and Gd is
> dielectric loss. As I know, Gd is expressed as
>
> Gd = 2* pi * (tan delta) * C
>
> where (tan delta) is loss tangent. and (tan delta) is defined as
> conductivity / (2* pi * freq * epsilon). As a result,
>
> G(f) = G0 + freq * (2*pi*(conductivity)/(2 * pi*freq*epsilon))*C
> G(f) = G0 + (conductivity/epsilon) * C
>
> My questions are
>
> (1) Ideally, G0 is equal to (conductivity/epsilon) * C, as well as
G
> (f) is frequency independent variable! Is it right?
>
> (2) Base on the definition, loss tangent is proportial to 1/freq.
> However, we typically treated loss tangent as a constant versus
> frequency. If loss tangent is a constant, it means conductivity is
> proportion to frequency if we assumed epsilon is stable versus
> frequency. Is it true regarding a constant loss tangent or a
linear
> frequency dependent conductivity? Or, both of them is wrong.
>
> (3) We verify the extracted RLGC file against Hspice in v.
2004.09.
> We found the Gd is exactly the half of above equation for
Microstrip
> line in inhomogeneous medium. The rsults for Stripline agree with
> the above equation. It seems Gd for Microstrip line is the average
> value of dielectric and free space area. It is reasonable? Does
> anyone verify the same issue before?
>
> Best regards,
>
> Sogo Hsu, Ph. D.
>
> Simulation center/Foxconn
>
>
>
>
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