Hi Doug,
The current density is not lower in the middle of the plane - it is just visual
impression. Smaller number of arrows is used in the middle of the metal layer
and it may create impression that the density values are lower in the middle
(same for power flow densities). Each arrow and color presents the Current
Density value in A/m^2 at a particular location within the metal. Density of
the arrows does not correlate with the current density (see more at webinar #7
at https://www.simberian.com/Webinars.php).
The value of the current density is actually lower on the opposite side of
planes and gradually decreases from one side to another - it is obvious on the
color or blanket plots shown at
https://www.simberian.com/AppNotes/PlaneCurrentDensity.gif ;
It would be different if trace is at the edge of the plane or near a cut-out in
the plane. You will see current higher at the edges and on the opposite side of
the plane - I think I visualized it at some demos.
Best regards,
Yuriy
-----Original Message-----
From: Doug Brooks [mailto:dbrooks9@xxxxxxxxxxxxxxx] ;
Sent: Sunday, December 8, 2019 12:59 PM
To: shlepnev@xxxxxxxxxxxxx; 'SI'
Subject: Re: [SI-LIST] Skin effect on ground plane?
Hi Yuriy
Your simulation is exactly what I was looking for. But I have one question.
You show that at moderate frequencies there is current density on both
the top and bottom surfaces of the plane, with a lower current density
down the centerline of the plane. But at very high frequencies the
current density only exists on the top surface of the plane (closest to
the trace) with effectively no current density on the bottom surface.
What causes the difference in the two conditions, and why?
Thanks
Doug
Yuriy Shlepnev wrote:
Hi Doug,
Yes, there is proximity as well as skin effects on the planes - the area
where signal power flow is shrinking with the frequency and current flowing
in thinner and thinner surface layer (result of absorption by the metal). And
all signal power is in dielectric and air! :)
See illustrations for microstrips at
https://www.simberian.com/ScreenCasts.php?id=38 and in some other demo-videos ;
at https://www.simberian.com/ScreenCasts.php?view=table or at Simbeor channel ;
at https://www.youtube.com/user/simbeor/videos
Best regards,
Yuriy
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Doug Brooks
Sent: Friday, December 6, 2019 10:32 AM
To: SI
Subject: [SI-LIST] Skin effect on ground plane?
We all know what the skin effect is on a trace. And we all know the
return signal path is on the plane directly under the trace.
The question is, is there a corresponding skin effect on the ground plane?
Doug Brooks
