Re: [SI-LIST] : Re: Antenna Problem on the Board

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From: Sainath Nimmagadda (sainath@lsil.com)
Date: Mon Jun 04 2001 - 09:01:03 PDT


1. Can we apply the physics/math of circular motion to motion of an electron
along a right angle, even curved, bend of a trace ?

2. If the "radiation due solely to change in direction of the electron in a
right angle bend of a trace would be similarly small", how much would it be?

Thanks,
Sainath

"Daniel, Erik S." wrote:

> Mary, Prasad -
>
> > Be careful how you mix quantum and classical EM theory.
> > Using this line of reasoning, we would expect a loop
> > of wire carrying DC current to radiate.
>
> Classically, a loop of wire carrying DC current does radiate, but only a
> very very tiny amount. For a single electron traveling in a small circle of
> a 1 mil radius (say) at 10^5 m/s (a generously high drift velocity for a
> metal), the Larmor formula yields a radiated power of ~10^-24 watts.
> Radiation due solely to change in direction of the electron in a right angle
> bend of a trace would be similarly small -- much smaller than radiation due
> to an RF current in the trace (which may still be small in many cases --
> several others have commented on this).
>
> None of these considerations are quantum mechanical unless the dimensions
> are tiny (e.g., electron orbits around an atomic nucleus). Relativity can
> play a significant role if the velocities are large, in which case the
> radiation increases dramatically.
>
> - Erik
>
> ==================================================================
> Erik Daniel, Ph.D. Voice: (507) 538-5461
> Mayo Foundation Fax: (507) 284-9171
> 200 First Street SW E-mail: daniel.erik@mayo.edu
> Rochester, MN 55905 Web: www.mayo.edu/sppdg/
> ==================================================================
>
> > -----Original Message-----
> > From: owner-si-list@silab.eng.sun.com
> > [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Doug McKean
> > Sent: Friday, June 01, 2001 10:57 AM
> > To: Signal Integrity
> > Subject: Re: [SI-LIST] : Re: Antenna Problem on the Board
> >
> >
> > Prasad,
> >
> > Yes, and thanks. Again, this is only my opinion.
> >
> > When you apply the vector definition of acceleration to
> > include directional change of a vector field such as an
> > electric or magnetic field, then you should get emission.
> >
> > Aside from all this theoretical talk, how this results in
> > actual practice, I haven't seen an increase in emissions
> > to be significant.
> >
> > Now, concerning bends in traces with regard to crosstalk,
> > I think I can say there is concern.
> >
> > - Doug McKean
> >
> >
> >
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