John, Some of this idea detailed in Howard Johnson's Black Magic, he has a picture of a differential pair changing layers, with anticopper surrounded by stitch vias, tying top and bottom copper pours together. This is the basic idea I've used is to ensure that the return currents follow the signal. Place anticoper around the via and a copper ring around that incorporating stitch vias. I'm imagining a 'planar coax' with ground shields on either side of the route. I look forward to comments from experts in this area. Randy Subject: [PCB_FORUM] Coaxial vias Date: Thu, 8 May 2008 08:44:42 -0700 From: john.r.smith@xxxxxxxxx To: icu-pcb-forum@xxxxxxxxxxxxx Has anybody used a coaxial via in Allegro? Can anybody share with me how I might create these in Allegro? Thanks John _________________________________________________________________ Windows Live SkyDrive lets you share files with faraway friends. http://www.windowslive.com/skydrive/overview.html?ocid=TXT_TAGLM_WL_Refresh_skydrive_052008