A simple explanation that I've always liked is a diff line with unequal "lengths" (physical and/or mode induced)causes the currents to have different phases or arrival times, and therefore the currents do not cancel completely, i.e., are not exactly 180 phase from each other. Due to the high impedance of the receiver a very small amount of current can develop a large common mode voltage across the receiver input, producing common mode radiation. Microstrips have more issues than striplines due to inhomogeneous permittivties and surface effects. I haven't found right angle "corner" capacitance to have any measureable effect ....yet. If meander sections are tightly coupled, you could have issues even at slow speeds. If you lay them out correctly they pose no problem. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Doug McKean Sent: Tuesday, February 19, 2002 4:20 PM To: Signal Integrity Group Subject: [SI-LIST] Re: Mode conversion In terms of EMI, the full name for "mode conversion" is "differential-to-common mode noise conversion". It's when differential mode noise gets converted to common mode noise. The exact mechanics of this escapes me, but does happen to varying degrees with just about any differential buss layout. The worse the layout, the more common mode noise produced. For instance, put lots of equal to or greater than 90 degree bends in a differential buss layout between points A and B and you will get lots more common mode noise as opposed to a straight buss configuration between the same two points. Not sure if it's some odd/even mode phenonmenon or some additive crosstalk thing. I'm sure someone here would know. - Doug McKean ------------------------------------------------------------------ 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 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 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