Re: [SI-LIST] : Analytical formula of characteristci impedance for microstrip andstripline

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From: Perry Qu (perry.qu@alcatel.com)
Date: Tue May 22 2001 - 07:49:35 PDT


Hi! Brian:

I think what you have in region * really depends on the PCB manufacturing
process. If it is a core-prepeg structure, suppose that Dielectric II is
core, you should use the same prepeg material in Region * and Die I .

Also, assuming the reference conductor is on top or below the trace, the
material at region * won't affect your transmission line characteristics
much. Those material right above or beneath the trace is crutial. For
example, in FR4, during lamination process, you may end up with uneven
distribution of glass and resin, which affect dielectric constant
significantly.

Regards

Perry Qu

"Wang, Brian" wrote:

> Scott and Steve,
>
> Thank you.
>
> My next question is related to the model:
>
> --------------------------------
> Dielectric I
> --------------------------------
> * Region | Trace | * Region
> --------------------------------
>
> Dielectric II
> ---------------------------------
>
> What material is used in the * regions?
> Or upper half part in the * regions is as same as Dielectric I,
> and lower half as same as Dielectric II?
>
> Any comments?
>
> Brian
>
> -----Original Message-----
> From: Scott McMorrow [mailto:scott@vasthorizons.com]
> Sent: Monday, May 21, 2001 3:46 PM
> To: Wang, Brian
> Cc: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Analytical formula of characteristci impedance
> for microstrip andstripline
>
> Brian,
>
> SpectraQuest does not use analytical formulas. It uses
> a numerical field solver to calculate RLGC matrices, from
> which characteristic impedance and propagation delay
> are calculated from. It uses the Boundary Element Method
> which is quite fast and reasonably accurate for most
> 2D structures.
>
> If you go to the SpectraQuest help dialog and search
> for "field solver" you will find a bit more information.
>
> regards,
>
> scott
>
> "Wang, Brian" wrote:
>
> > Hi,
> >
> > I'd like to know what analytical formulas used in SpecctraQuest
> > to have characteristci impedance and propagation delay.
> > Welcome to advice on this issue. Thanks.
> >
> > Brian
> >
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>
> --
> Scott McMorrow
> Principal Engineer
> SiQual, Signal Quality Engineering
> 18735 SW Boones Ferry Road
> Tualatin, OR 97062-3090
> (503) 885-1231
> http://www.siqual.com
>
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