[SI-LIST] : RE: Split Plane

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From: Barry Ma (barry_ma@altavista.com)
Date: Thu May 25 2000 - 12:07:09 PDT


Brad,

Here is my two cents worth.
In high speed digital design, one of design purposes is to make all pwr/gnd planes RF equipotential, although they have different DC potentials: 0V, 3.3V, and 5V. Those planes are supposed to have the same RF potential when linking them by using interplane capacitance and decoupling capacitors. - We may try some other way to reduce the impedance of power bus, and expand the bandwidth of power distribution system....

Anyway there must be some RF potential difference existing between those planes, although we tried our best to make them equipotential. Given this, it's still hard to generally assert that ground planes certainly make fewer contributions than power planes to the total radiation level.

Regards,
Barry MA
bma@ANRITSU.com

------------
On Thu, 25 May 2000, "Brad Crowell" wrote:

Barry,
 
I agree with your assertion that the power planes are OK to use as a
reference plane. In my case, the additional ground planes were added to
provide a ground reference for every signal. This is supposed to improve the
EMC issues. I'm a little out of my realm here but the ground referenced
signal is said to radiate less than a power plane referenced signal. So not
having the personal experience to refute this claim, the ground planes were
added to satisfy the concerns of our client. I would certainly be interested
in hearing the comments of those on this list on this issue.
 
Thanks,
Brad
 
Brad Crowell
AMIRIX Systems

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