In regards to comment 1. In a high frequency signalling environment, The return current will flow on the nearest plane whether it is power or ground. If you have two planes coupled closely togther you create a capacitor which the high frequency return current uses to traverse the planes and takes the path of least impedance. If there were not two planes coupled together, it would be an EMI catastrophe and you would not know where the return current is flowing.
Regarding comment 2, he was stating that grounding in multiple locations is a bad idea. This can create some ground loops within the chassis. There will be some type of potential difference from one chassis connection point to another and this will create some current in the chassis. This is very bad from an EMI perspective. He believes one Solid connection to the ground plane is sufficient. I would like to hear a take from an EMI person. Regards, Paul S. Denomme Viasystems Inc. Richmond, VA [email protected] > -----Original Message----- > From: Grasso, Charles (Chaz) [SMTP:[email protected]] > Sent: Wednesday, October 27, 1999 2:26 PM > To: '[email protected]' > Cc: 'EMC Group'; 'Signal Integrity' > Subject: [SI-LIST] : Comments from your SI seminar (SendII)` > > Sir, > > A collegue of mine has recently taken your SI seminar. > In discussing the class with him I came across two > statements from the semiar that I would like to discuss > with you and others in the EMC profession. > > Comment 1. On page 109 there is a slide that states: > > Traces crossing cuts in planes can function properly. > > Please explain your rationale. > > Comment 2: On page 110 there is a slide title: > > A bad grounding idea. > > The picture is of a board with multiple ground connections > and distances maked off as lambda/20 > > Clearly this is a shot at the multiple stitching concept that > is prevalent in the EMC world. > > One of the problems in the EMC/SI world is that there is > contradictory information provided to the poor consumer. > > I look forward to a lively debate on these issues. > > > **** To unsubscribe from si-list: send e-mail to > [email protected]. 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 [email protected]. 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 ****
