**From:** ytang (*ytang@axonphotonics.com*)

**Date:** Fri Sep 01 2000 - 16:57:18 PDT

**Next message:**Ozgur Misman: "RE: [SI-LIST] : "skin effect/depth calculation results""**Previous message:**George_Tang@Dell.com: "RE: [SI-LIST] : "skin effect/depth calculation results""**In reply to:**C Deibele: "Re: [SI-LIST] : "skin effect/depth calculation results""**Next in thread:**George_Tang@Dell.com: "RE: [SI-LIST] : "skin effect/depth calculation results""

The discussion is rather hot.

I would say,

the impedance of a transmission line is affected only by the structure

confining electric field, it doesn't matter with what it is connected to.

The circuit nearby may change the impedance a little by interfering with its

electric field.

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

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

*> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of C Deibele
*

*> Sent: Friday, September 01, 2000 4:32 PM
*

*> To: George_Tang@Dell.com; si-list@silab.eng.sun.com
*

*> Subject: Re: [SI-LIST] : "skin effect/depth calculation results"
*

*>
*

*>
*

*> George_Tang@Dell.com wrote:
*

*> >
*

*> > This is great from a theoretical stand point. But in reality,
*

*> > the trace impedance, Zo, is fixed at a certain range by either
*

*> > the driver or receiver. You will need to make the widest
*

*> > possible trace while keeping the same impedance. This brings
*

*> > us back to the original discussion.
*

*> >
*

*> > George Tang
*

*> >
*

*>
*

*> I disagree completely, George. What in the world are you
*

*> talking
*

*> about?? I do not know how one can make a constant impedance
*

*> by
*

*> varying line widths. You certainly know that impedance is a
*

*> distributed quantity. Varying line widths varies the
*

*> impedance.
*

*> How then, can one make the widest possible trace while
*

*> keeping
*

*> the same impedance constant?
*

*>
*

*> It is clear from the most basic funamentals of
*

*> transmissionline
*

*> theory, see Pozar for example, that one only one geometry
*

*> will
*

*> enjoy the least transmission attenuation. The driver and
*

*> receiver
*

*> are irrelevant to that standpoint.
*

*>
*

*> The driver and receiver may dictate a range of impedances
*

*> that can
*

*> be used. but other than that, one can easily transverse
*

*> from the saddle
*

*> point of the least attenuation.
*

*>
*

*> For example, George, in coax, the best impedance is 77
*

*> ohms. That is
*

*> to say, 77 ohms has the least copper attenuation. so, are
*

*> you
*

*> saying that the driver and the receiver change this
*

*> intrinsic property
*

*> of physics?
*

*>
*

*> Your point George, is equivalent to saying that the source
*

*> and
*

*> driver dynamically change Maxwell's Equations, which I am
*

*> certain you will
*

*> agree must satisfy Maxwell's Equations.
*

*>
*

*> In fact, probably the only time one may disregard
*

*> the simulations I presented are for wavelengths much longer
*

*> than the geometry in question. And in these circumstances,
*

*> then skin depth is of importance.
*

*>
*

*> I think Pozar goes through the coax example in Chapter 2....
*

*>
*

*> I hope everyone was on their toes...I made a mistake in my
*

*> text. The text is only valid for the coax case of a >>
*

*> delta.
*

*>
*

*> For the point of Bill Owsley, you are correct, but I think
*

*> we are concerned for the case of "ALL THINGS BEING EQUAL".
*

*> So, if for the original problem, given a certain trace
*

*> width,
*

*> does it help to reduce copper loss if one widens the trace
*

*> or thickens the trace? I can imagine that the effect of
*

*> surface
*

*> roughness might be reduced if the trace would be thickened.
*

*>
*

*>
*

*> Craig Deibele
*

*>
*

*>
*

*> --
*

*> Craig Deibele, PhD, PE
*

*> Fermilab--Beams Division
*

*> PO Box 500 MS 341
*

*> Batavia IL 60510
*

*>
*

*> my opinions only....not of the gov't...nor of the lab...
*

*>
*

*> **** To unsubscribe from si-list or si-list-digest: send e-mail to
*

*> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
*

*> si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
*

*> si-list archives are accessible at http://www.qsl.net/wb6tpu
*

*> ****
*

**** To unsubscribe from si-list or si-list-digest: send e-mail to

majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE

si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.

si-list archives are accessible at http://www.qsl.net/wb6tpu

****

**Next message:**Ozgur Misman: "RE: [SI-LIST] : "skin effect/depth calculation results""**Previous message:**George_Tang@Dell.com: "RE: [SI-LIST] : "skin effect/depth calculation results""**In reply to:**C Deibele: "Re: [SI-LIST] : "skin effect/depth calculation results""**Next in thread:**George_Tang@Dell.com: "RE: [SI-LIST] : "skin effect/depth calculation results""

*
This archive was generated by hypermail 2b29
: Tue May 08 2001 - 14:29:26 PDT
*