That's exactly what I was implying. The effect would be local to where the trace and the plane edge coincide, and the radiation would be a function of field strength (i.e. dc/analog/slow control signals would have very little, 5GHz clock would be very high). -----Original Message----- From: Brad Velander [mailto:[EMAIL PROTECTED]] Sent: Thursday, July 12, 2001 5:55 PM To: 'Protel EDA Forum' Subject: Re: [PEDA] 20H rule, Planes etc (Ex: perimeter stitched ground vi as question) Bruce, this is the manner in which I understand this issue. If I am wrong please correct me, I don't design antennas for a living and know very little about such. I do know that I have read certain descriptions of these problems and the proposed solutions but we all know there are bad solutions backed up by specific experimentations that prove the solution. This is the theory that I would apply to the situation. The manner that planes do not have noise fields between them is achieved 'theoretically' because you have coupled your planes together to near perfection through all of your properly selected, distributed and positioned power supply bypass capacitors. Effectively reducing the differential AC potentials between your planes to "0". Now that is the perfect world which doesn't exist but the real world differences should be relatively small if you have done your power distribution design correctly. Would the application of this to a trace (running parallel to your plane edge) not be exactly the opposite circumstance? There you have definite potential difference between the trace and the plane, much larger differentials then between your two planes. And thus if differentials between two planes with a little noise causes a dipole antenna effect, why would a trace with significantly larger differential not cause the same effect only stronger for the same relative length of the trace against the plane edge? This seems very clear to me but then I don't design antennas so what do I know. I only know that the article I read about traces and the 20H rule to plane edges most definitely showed the desired effect in the results arrived at with the field solvers. Brad Velander, Lead PCB Designer, Norsat International Inc., #300 - 4401 Still Creek Dr., Burnaby, B.C., V5C 6G9. Tel. (604) 292-9089 direct Fax (604) 292-9010 website www.norsat.com > -----Original Message----- > From: Bruce Walter [mailto:[EMAIL PROTECTED]] > Sent: Thursday, July 12, 2001 4:54 PM > To: 'Protel EDA Forum' > Subject: Re: [PEDA] 20H rule, Planes etc (Ex: perimeter > stitched ground > vi as question) > > (clip) > How well this applies to traces over a plane near the edge of > the board, I'm > not sure, but I would imagine the effect would be local, and > would only be > significant if there were a strong field between the two > conductors (poles). > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * - or email - * mailto:[EMAIL PROTECTED]?body=leave%20proteledaforum * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Browse or Search previous postings: * http://www.mail-archive.com/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
