RE: [SI-LIST] : A basic question

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From: Daniel, Erik S. (Daniel.Erik@mayo.edu)
Date: Fri Mar 17 2000 - 06:07:48 PST


Jim-

> Can we change C without changing the dielectric constant? Let's say we
> change the thickness between conductor and ground plane. We
> haven't changed
> L (I don't think)

Check again. L changes because now the effective volume available for the
magnetic field changes. Increase C by moving the conductor closer to the
plane, and L is necessarily reduced.

                                        - Erik

==================================================================
Erik Daniel, Ph.D. Mayo Foundation
Voice: (507) 284-1634 Guggenheim 1011B
Fax: (507) 284-9171 200 First Street SW
E-mail: daniel.erik@mayo.edu Rochester, MN 55905
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> -----Original Message-----
> From: Zabinski, Patrick J. [mailto:zabinski.patrick@mayo.edu]
> Sent: Friday, March 17, 2000 8:32 AM
> To: si-list@silab.eng.sun.com
> Subject: RE: [SI-LIST] : A basic question
>
>
> Jim,
>
> Z & Pd are related as you state.
>
> Can C be changed without effecting L? Sure. Simply
> change the dielectric. As long as you keep the same
> physical geometries and only change the dielectric constant,
> C will change with no change in L.
>
> In fact, many of the older EM tools (still some today) relied
> on the Z and Pd relationship. Essentially, it's easier
> to determine C (F/m) for a line than it is L. So,
> after the tool would compute C, it would use the Z and
> Pd relationship to determine L
>
> L = Er/(Co^2 * C)
>
> where
> L = H/m
> Co = speed of light = 3e8 m/s
> C = F/m
>
> Pat
>
>
>
> Pat
>
>
> > SI List:
> >
> > I have a question about the relationship between Z and Pd
> > (prop. delay). The
> > equations used for these two are :
> > Z=(L/C)^(1/2)
> > and
> > Pd=(LC)^(1/2)
> > I guess my question has to do with Pd. How can we equate Pd
> > to both the
> > above equation and the fact that the speed of light is
> > C/((er)1/2)? Which
> > says that prop. delay is just a function of the dielectric
> > constant (or the
> > material that light is propagating through).
> > Can I really reduce C, without increasing L, and thus reduce
> > the Pd of an
> > interconnect? If I can't then the Pd=(LC)^(1/2) has problems.
> > If I can then
> > how does it align with light's speed being just a function of
> > the medium
> > it's traveling through?
> >
> >
>
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