Hi Stacy, You may check out a paper titled "Effects of 20-H Rule and Shielding Vias on Electromagnetic Radiation From Printed Circuit Boards" presented at EPEP2000. The paper concluded, from both theoretical analysis and numerical computation, that for the two-plane structure, 20-H rule yields more radiation than the normal structure. Also the numerical result shows that the usage of shielding vias would cut down the radiation effectively. The link to the paper and the presentation (with additional cases study) is at http://www.sigrity.com under the heading Support and Technical Documentation paper # 2. Best Regards Winson Yu -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Stacy L Gore Sent: Wednesday, July 25, 2001 10:52 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] EMI and Power plane card edge clearance distance I remember reading something (article, e-mail) about the EMI benefits of etching back power/ground sandwich planes at different levels. (i.e. power plane back 50 mils from the card edge and the ground plane back 100 mils). Anybody know anything about this or have a comment one way or another? Stacy L. Gore Hardware Engineering Staff Raytheon - Garland Site Phone - (972) 205-4208 Fax - (972) 205-8083 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu