hi, Zheng Thanks for you advice on full wave simulations. However, even in the static cases (which is mostly used), it depends on your definition. Patrick already pointed out the deference. The book I mentioned has a conversion eqation. It is not difficult to derive them based on different voltage references for linear systems. I didn't use your software. I use Ansoft Q2D & Q3D. If you have their manual, you can easily find examples. For example, on p.6-13 for Q2D and p.6-10 for Q3D. If your software adopts different definition, it is another story. In any case, they must be consistent. In Maxwell's (or induction) definition, all off-diagonal must be non-positive, on the other hand, in the other definition, all off-diagonal must be non-negative. Of course, as Patrick described, in numerical computations, even we control the solution conditions verty well, we can not expect ideal results, especially, when the orders of all entries are quite different. So a practical method is to ignore those items relatively approaching zeros. Regards. Mick -----Original Message----- From: Jian-X. Zheng [mailto:jian@xxxxxxxxxx] Sent: Friday, August 31, 2001 1:51 PM To: xlzhou@xxxxxxxxx; Raymond.Anderson@xxxxxxx; si-list@xxxxxxxxxxxxx Subject: RE: [SI-LIST] Re: non-negative off diagonal capacitive matrix elements ?? Hi, Nick: If you use static solver to solve for the capacitance matrix, you should get non-negative capacitance. If they are not, it should be caused by error (numerical or analytical). However, you can not guarantee it if you are using full wave solvers. It is not the problem of the accuracy in full wave solvers. On full-wave solvers, extraction of the capacitance matrix is basically matching. The solvers can predict negative off diagonal capacitances because they may represent the trend of the system responses better in a specific frequency range. Thanks! Best regards, --------------------------------------------------------------------------- Jian-X. Zheng, Ph.D. Zeland Software, Inc., 48890 Milmont Dr. 105D, Fremont, CA 94538, U.S.A. Tel: 510-623-7162, Fax: 510-623-7135, Web: http://www.zeland.com --------------------------------------------------------------------------- -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Zhou, Xingling (Xingling) Sent: Friday, August 31, 2001 10:39 AM To: 'jian@xxxxxxxxxx'; Raymond.Anderson@xxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: non-negative off diagonal capacitive matrix elements ?? Hi, Zheng I think you are talking about another definition which is good for SPICE simulations. But for fied solvers, it is better to use Maxwell's definition. We can find the details in any multi-conductor books. There is a clear description in Brian Young's book, pp.233-235. Regards. Mick -----Original Message----- From: Jian-X. Zheng [mailto:jian@xxxxxxxxxx] Sent: Friday, August 31, 2001 1:17 PM To: Raymond.Anderson@xxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: non-negative off diagonal capacitive matrix elements ?? Hi, Ray: I think it is possible some off diagonal capacitances can be negative. However, if most of them are negative, I believe it must be from numerical error or incorrect extraction setup. In my experience, the capacitance between adjacent lines should never be negative. Regards, --------------------------------------------------------------------------- Jian-X. Zheng, Ph.D. Zeland Software, Inc., 48890 Milmont Dr. 105D, Fremont, CA 94538, U.S.A. Tel: 510-623-7162, Fax: 510-623-7135, Web: http://www.zeland.com --------------------------------------------------------------------------- -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ray Anderson Sent: Friday, August 31, 2001 10:08 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] non-negative off diagonal capacitive matrix elements ?? 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 -Ray ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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