Re: [SI-LIST] : 20-H Rule for Power Planes

S. Weir (weirsp@a.crl.com)
Sat, 05 Jun 1999 12:59:02 -0700

The zig-zag edge is an interesting idea I have not heard of before. At
first thought, I would not consider it to be of much use, as I expect it to
actually accentuate the field difference resulting from minute currents in
the ground plane outside the 20H perimeter. My expectation is that it is a
losing game put enough curvature in such an edge to effectively suppress
the natural slot antenna by dispersing the radiating pattern, because those
curves will themselves increase area loop of the ground currents in the
region, greatly increasing the efficiency of the antennae. I think that
the tried and true practice of irregular via spacing in the "outer fence"
and across the planes themselves is one of the better practical defenses
against high peaks in the plane cavity resonances.

Regards,

Steve.
At 09:22 AM 6/1/1999 -0500, you wrote:
>
>
>S. Weir wrote:
>>I don't think so. The geometry of the planes themselves still has the
>>abrupt edge. All we have done is to move the center point of the fringing
>>pattern so that the field gradients across any susceptor antennae, (
>>traces, metalwork ) near the board edge is less. To do what you suggest,
>I
>>believe that we would need a material where we could grade the dielectric
>>constant. Does anyone feel differently?
>
>how about a zig zag edge, with the zigzag period
>much less than a wavelenght?
>
>
>
>**** To unsubscribe from si-list: send e-mail to
>majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
>si-list, for more help, put HELP. si-list archives are accessible at
>http://www.qsl.net/wb6tpu/si-list ****
>

**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****