No, Perry, I have not had problems, even with ungrounded thieving, as long as the copper islands were very small compared to a wavelength at the frequency of concern. Under that condition, no significant current flows in them and they do not contribute to further radiated emissions.
What frequency to be concerned about, now, that can trip you up; my 350 MHz signal was the seventh harmonic of a 50 MHz clock. If you have (say) a 1.5 GHz clock, then you can see thieving will have to be very small indeed. Incidentally, you have to put thieving on a ground plane too, but in THAT case it takes the form of holes of some kind If you are not careful, the board manufacturer will make them SLOTS, and that can be a very bad thing, even for small traces, when a slot is located over a high-frequency clock. Not only will it radiate, it will do bad things to the wave form. Cortland ====================== Original Message Follows ==================== >> Date: 17-Jan-01 08:27:15 MsgID: 1077-21697 ToID: 72146,373 From: "Perry Qu" >INTERNET:[email protected] Subj: Re: [Fwd: [SI-LIST] : Copper balance] Chrg: $0.00 Imp: Norm Sens: Std Receipt: No Parts: 1 List-Post: [email protected] Date: Wed, 17 Jan 2001 11:22:09 -0500 From: "Perry Qu" <[email protected]> Organization: Alcatel CID Subject: Re: [Fwd: [SI-LIST] : Copper balance] Hi! Cortland: Thanks for your comments. In your experience, does the size/spacing of the copper dots or islands matter as long as their dimension is much smaller than the wavelength for the highest possible frequency on the card ? Any special considerations other than that ? Regards Perry ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
