hi the return current tries to flow in both reference planes, not just in one of them. check this document: http://www.buenos.extra.hu/iromanyok/Accurate_Impedance_Control-2columns.pdf page 7-8, especially the last image on page 7. also check a previous discussion few days ago on the si-list: "[SI-LIST] Return current and stack up" regards, Istvan Nagy, CCT, UK ----- Original Message ----- From: "abin.cv" <abin.cv@xxxxxxxxxxxxxxxxxx> To: <si-list@xxxxxxxxxxxxx>; "rskiruban" <rskiruban@xxxxxxxxxxxxxxxxxx> Sent: Saturday, June 20, 2009 4:46 AM Subject: [SI-LIST] Assymetric stip line > hi, > Assymetric stip line > > Layer 1 GND > Dielectic 8mils > Layer 2 Signal (100MHz to 200MHz) > Dielectric 12mils > Layer 3 Power (Split plane 3.3V and GND) > > The high speed signals (Around 50 signals) in the Layer 2 encounters split > in the > layer 3. The split width is 10mils. Please let me know whether this split > will > have serious impact on the signal quality. > > More over the split plane is 12 mils away from the signal layer. But the > Full GND > plane (Layer1) is near to the signal. Won't the signal will take this GND > plane as reference > for their return current. > > > Thanks in advance > > ------------------------------------------------------------------ > 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 technical documents are available at: > http://www.si-list.net > > 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 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 technical documents are available at: http://www.si-list.net 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