Subramanya, the only way to keep reference over splited plane is to use stitching caps to provide a current return path from one plane to the other. This is not an ideal solution, as crosstalk will rise, but at least it helps to control EMC behavior. You can also use an non symmetrical impedance cell that keeps the signal lines closer to the non splitted GND-plane (i.e. thin dielectric between signal and gnd, and thicker dielectric between power and signal). This reduces the amount of return current that has to pass the split. Regarding the copper thickness I recommend to use the SI-List archive //www.freelists.org/archives/si-list there have been many useful information, software tool recommendations and formulas that were discussed. BR Gert ---------------------------------------- Absender ist HARTING Electronics GmbH & Co. KG; Sitz der Gesellschaft: Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596; persönlich haftende Gesellschafterin: HARTING Electronics Management GmbH; Sitz der Komplementär-GmbH: Espelkamp; Registergericht der Komplementär-GmbH: Bad Oeynhausen; Register-Nr. der Komplementär-GmbH: HRB 8808; Geschäftsführer: Edgar-Peter Duening, Torsten Ratzmann, Dr. Alexander Rost -----Ursprüngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von Subramanya C.K Gesendet: Montag, 25. Juni 2012 08:20 An: si-list@xxxxxxxxxxxxx Betreff: [SI-LIST] Split in Reference Planes for XAUI Dear Gurus, This is an old topic on split planes, but just wanted to get an opinion from experts regarding reference plane for XAUI signals in my current assignment. There is a possibility that some of these XAUI lines in my new PCB might cross the split planes in power layer that is beneath this signal layer where these XAUI lines are routed. These islands in the power layer are used for -48V and RTN power rails of the system. I am unable to accommodate these lines elsewhere on the PCB due to space constraints. Is there any way by which I don't end up losing ground reference for these lines? Another question, is there a rule of thumb to determine the copper thickness / area of copper layers based on the power requirement? Thank you all in advance for your help.. Best Regards, Subramanya C K P Save Trees. Don't print this E-Mail unless it's really necessary **************** CAUTION - Disclaimer ***************** This e-mail contains PRIVILEGED AND CONFIDENTIAL INFORMATION intended solely for the use of the addressee(s). If you are not the intended recipient, please notify the sender by e-mail and delete the original message. Further, you are not to copy, disclose, or distribute this e-mail or its contents to any other person and any such actions are unlawful. This e-mail may contain viruses. Infosys has taken every reasonable precaution to minimize this risk, but is not liable for any damage you may sustain as a result of any virus in this e-mail. You should carry out your own virus checks before opening the e-mail or attachment. Infosys reserves the right to monitor and review the content of all messages sent to or from this e-mail address. Messages sent to or from this e-mail address may be stored on the Infosys e-mail system. ***INFOSYS******** End of Disclaimer ********INFOSYS***------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list 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 or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu