**From:** Jian Zheng (*jian@zeland.com*)

**Date:** Fri Mar 17 2000 - 08:39:02 PST

**Next message:**MikonCons@aol.com: "Re: [SI-LIST] : A basic question"**Previous message:**mjs: "[SI-LIST] : Fast edges with limited plane capacitance"**In reply to:**Peterson, James F (FL51): "[SI-LIST] : A basic question"**Next in thread:**MikonCons@aol.com: "Re: [SI-LIST] : A basic question"

Hi,

If the transmission line has only one single dielectrics, the product of L

and C is a constant. There is no way you can change the product. Otherwise,

you will get your TEM wave running faster or slower than the light speed in

the dielectrics. However, if you have multiple dielectrics, you can still

adjust the geometry shape to get the best value of L and C. No matter how

much you do, you can not make the 1/SQRT(LC) > Cmax and 1/SQRT(LC) < Cmin,

where Cmax is the light speed at the dielectrics with the minimum EPSr*MUr

(permittivity & permeability) and Cmin is the light speed at the dielectrics

with maximum EPSr*MUr. Thanks!

Best regards,

----------------------------------------------------------------------------

------------

Jian-X. Zheng, Ph.D

Zeland Software, Inc., Web: http://www.zeland.com

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*> -----Original Message-----
*

*> From: owner-si-list@silab.eng.sun.com
*

*> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Peterson, James F
*

*> (FL51)
*

*> Sent: Friday, March 17, 2000 5:01 AM
*

*> To: 'si-list@silab.eng.sun.com'
*

*> Subject: [SI-LIST] : A basic question
*

*>
*

*>
*

*> 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?
*

*>
*

*> regards,
*

*> Jim
*

*>
*

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**Next message:**MikonCons@aol.com: "Re: [SI-LIST] : A basic question"**Previous message:**mjs: "[SI-LIST] : Fast edges with limited plane capacitance"**In reply to:**Peterson, James F (FL51): "[SI-LIST] : A basic question"**Next in thread:**MikonCons@aol.com: "Re: [SI-LIST] : A basic question"

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