My understanding with L11 and C11 was that L11 does not include the effect of neighboring nets while C11 does i.e. L11 is self parasitics while C11 = C1g + C12 Any explanations ? Anshuli "Dunbar, Tony" wrote: > For the purposes of clarification:- > > Patrick initially stated "The on-diagonal parameters (e.g., L11) are > typically stated to be the self parasitics, ..." > > My understanding is that, rather than being purely "self parasitics", they > actually include the effects of coupled neighbors. As a consequence, for > example, L11 will actually be different (lower) than it will be if the same > primary structure existed without any coupled neighbors. > > Is that correct? > > Thanks, > Tony Dunbar > > -----Original Message----- > From: Zabinski, Patrick J. [mailto:zabinski.patrick@xxxxxxxx] > Sent: Tuesday, February 18, 2003 2:42 PM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] off-diagonal resistance and conductance elements > > In a coupled-pair of distributed transmission lines (whether intentionally > for differential or unintentionally with crosstalk), most (good) > EM simulators produce a 2x2 matrix of capacitance, inductance, > resistance, and conductance (C, L, R, & G). The on-diagonal > parameters (e.g., L11) are typically stated to be the self > parasitics, which is quite easy to understand. > > For the inductance and capacitance matrices, even the off-diagonal > parastics (e.g., L12, C21, ...) are easy to understand and > well published. > > However, I have not been able to find a good description nor > treatment on the off-diagonal resistance and conductance > elements. Can anyone enlighten me a bit? > > For example, what does R12 respresent? With the lossless/ideal > case setting R12=0, it cannot represent a resistive element > directly between the two traces. So what is it? > > A second yet possibly related question deals with how these > matrices deal with odd- and even-mode using the same matrices. > When looking at any of the common twin-axial cables used > today with Infiniband and other differential protocols, the > two signal conductors are made with "good" (meaning low > loss) materials. In contrast, the outer shield is often > a much lousier (higher loss) material (either through the metallurgy > or thickness). > > For odd-mode signals propagating down one of these twin-ax > cables, we believe the return current for one wire is > effectively captured (at least in part) in the other complement > wire, which would result in reasonably low loss. In contrast, > in even-mode propagation, the return current is within the > outer shield, which in turn results in a higher loss than > the odd-mode propagation. The end result (we have plenty > of measurement data confirming this) is that odd-mode > signals propagate reasonably well, but even-mode signals > attenuate and disperse much more significantly. (note: > for many applications, this is a very good thing.) > > The question is: how can the LRCG matrices be set up such that you > use one set of matrices (in the form of a W-element if you wish) that > can accurately represent both cases? Does the off-diagonal > R & G matrices play a role? > > Thanks, > Pat > > ------------------------------------------------------------------ > 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 > ------------------------------------------------------------------ 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