One of the major causes of emissions can be excessive loop areas caused by a long return path for signal currents due to the division of the ground plane. Review the ground return path for signal lines that bridge the gaps. Ideally, the signal return path on the ground plane should be directly under the signal line for the entire route. Any path variation will create a loop antenna that will radiate. If you have total ground isolation, there can be a very large loop because there is no metalic return path. You will have to create a short path using high frequency bypass capacitors to bridge the gap as close as possible to the signal line. Just keep thinking about how you can reduce the loop areas.
Richard Woods Sensormatic Electronics Tyco International -----Original Message----- From: Paolo Peruzzi [mailto:paolo.peru...@esaote.com] Sent: Monday, February 25, 2002 10:34 AM To: emc-p...@majordomo.ieee.org Subject: PCB floating area layout Hi all, I'm dealing with a PCB that has a floating section isolated from the rest of the board for safety purposes (patient applied part). I found out some problems with emissions, due to the coupling between the floating part and of the PCB and the earthed one. My questions are concerning the layout design of the floating area: 1) Is it best to minimize the HF capacitive coupling between the earthed ground and the floating ground or to maximize it? 2) Is it best to reduce the amount of the floating ground or to increase it? Does it depend on the goodness of the "main ground", i.e. how much it is "cold" ? (I see the board as a dipole with one end connected to earth, and the other floating). Thanks, p.p. ------------------------------------------------------------- ESAOTE S.p.A. Paolo Peruzzi Research & Product Development Design Quality Control Via di Caciolle,15 tel:+39.055.4229306 I- 50127 Florence fax:+39.055.4223305 e-mail: paolo.peru...@esaote.com ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
