[SI-LIST] Re: doubt about crosstalk
- From: "Gregory R Edlund" <gedlund@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 25 Jul 2002 08:07:00 -0500
Ibrahim,
I used the word "loop" a little loosely since the return current is
actually spread across a plane. Maybe we should switch to talking about
the density of the magnetic field lines. I am envisioning that the density
of the magnetic field lines between the signal and the guard goes UP
compared to the same region without the guard because some of those field
lines used to extend toward the other signal. However, the presence of
return current in the guard means that the magnetic field lines remain
partially contained between the guard and the signal, i.e. not as much flux
reaches from one signal to the other. I say partially because some of them
still go over the top in a microstrip structure.
I hope my "intuition" is electromagnetically correct here because I
certainly didn't solve Maxwell's equations anytime in the past 24 hours!
To find the truth, we could run a field solver like Ansoft's 2D that plots
the density of various field quantities.
[begin gushing]
Isn't field theory cool? It's got to be one of the most impressive
achievements in human history. We can all make pictures in our heads of
things we can't even see just because we all took the same class! Damned
impressive.
[end gushing]
Greg Edlund
Senior Engineer
Signal Integrity
IBM Engineering Solution Services
3605 Hwy. 52 N, Dept. HDC
Rochester, MN 55901
gedlund@xxxxxxxxxx
Subject: [SI-LIST] Re: doubt about crosstalk.
Date: Wed, 24 Jul 2002 14:13:45 -0500
From: "Ibrahim Khan" <ikhan@xxxxxxxxxxxxxxxxxxx>
Greg,
I have a question here. If the return current is also flowing in the
guard trace then hav'nt we basically increased the loop size on both
traces.
Thanks
Ibrahim Khan
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