Hello All I just signed on to the SI list and the discussions have been very useful. I have been puzzling over the Maxwellian Capacitance and Inductance matrices produced by ANSOFT TPA and I have some questions based on this a) Pat has confirmed the method I was using to calculate the self capacitance. However for inductance I have just been using L11 as the self inductance. Is this correct? b) However I am still puzzled over which # to use to compare with TDR measurements. The TDR measurements we do use a fixture from ALTAIR microwave which has a Cu sheet on which the package balls sit and grounds all other pins in the package except for the pin of interest. I have not got a good answer yet as to which number in the simulation matrix I should compare the TDR meas. to. Appreciate it if anybody has a suggestion. Thanks Anil Pannikkat MTS Package Development Ph : 408-544-7542 Altera Corporation Fax: 408-544-6419 101, Innovation Drive, M/S 4101 Email: apannikk@xxxxxxxxxx San Jose, CA 95134 WWW: http://www.altera.com -----Original Message----- From: Zabinski, Patrick J. [mailto:zabinski.patrick@xxxxxxxx] Sent: Friday, August 31, 2001 10:40 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: non-negative off diagonal capacitive matrix elements ?? Ray, The electrostatic induction matrix (note: this is NOT the capacitance matrix) represents mutual capacitance as negative numbers in the off-diagonal elements. Accordingly, as Mick pointed out, the off-diagonal elements must be non-negative. For the one positive off-diagonal you do have, it is five orders of magnitude lower than the self capacitance, so I would tend to believe the error was due to numerical round off. You can try increasing the accuracy of the tool, but the value is so low, I recommond manually setting the value to zero. Simply FYI: the on-diagonal elements of the electrostatic induction matrix are not self-capacitance as some folks tend to believe. The on-diagonal values represent the capacitance of that element assuming all other elements were at ground potential. To obtain self capacitance, simply add all the values in the matrix row (i.e., C11 = B11 + B21 + B31 + ..). Pat > > I've just extracted the RLGC matrices for 5 coupled > striplines using Apsimtech RLGC. > > As expected, the diagonal elements of the capacitive matrix are > positive capacitance values. All the off-diagonal elements are > negative EXCEPT one. Is this correct. It has been a while since I've > thought about this, but I was under the impression the capacitive > off diag element were all negative. Anyone know for sure ?? > > The element in column 1 row 5 is the one I question: > > > 3.1600e-15 > -4.9360e-16 3.2540e-15 > -2.0080e-17 -4.8990e-16 3.2540e-15 > -1.3380e-18 -1.9820e-17 -4.8990e-16 3.2540e-15 > 3.1280e-20 -1.3380e-18 -2.0080e-17 -4.9360e-16 3.1600e-15 > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field 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 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