3D field solvers like Simberian, Ansoft, CST, when properly set-up yield very accurate results. If the object is to develop CF equations that are more accurate than existing over some data range, I think you need to do the leg work of obtaining / generating the data set, and then performing the fit. To put it another way: If there was a straight forward way to yield accurate results from CF equations over a wide data range, there wouldn't be much demand for 3D solvers in this space. Ty Beeman wrote: > Hello, > As part of a class project, we have been given the assignment of using > closed loop equations to "accurately" predict the characteristic impedance, > etc. of microstrips. > > To solve for surface microstrips, we have used the equations from: E. > Hammerstad and O. Jensen, "Accurate models for microstrip computer-aided > design." These equations give us results that are very close to field > solvers. > > However we're kind of stuck in getting accurate results for a buried > microstrip. We are using the equations found in: Brian C. Wadell, > "Transmission Line Design Handbook." When we use the surface microstrip > equations above to solve for Z-buried we can get close, end up with some > errors as much as 4% and off by as much as 3 ohms or more.. If we use the > Wadell equation for surface microstrip to solve for Z-buried, our error is > around 5% when comparing to field solvers. > > Looking at it a little closer, we find that our calculated effective er is > different than that given by the field solvers. > > All we can seem to find in the reference materials is the same (or similar) > calculation that is in Wadell's book or old IPC equations. > > So our questions are: > > 1. Are there any other equations for buried microstrips that others have > found to be more accurate, especially for effective er and impedance? > > 2. Can anyone recommend any other reference material on buried microstrips? > Are there any good IEEE papers on the subject? > > We know we may have to settle for what we have now, given the reference > material, but we're hoping there's something a little more accurate > available. > > Thank you, > Ty Beeman > Logan Talada > Students > Tompkins-Cortland Community College > > > ------------------------------------------------------------------ > 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 technical documents are available at: > http://www.si-list.net > > 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 > > > > -- Steve Weir Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 California office (866) 675-4630 Business (707) 780-1951 Fax Main office (401) 284-1827 Business (401) 284-1840 Fax Oregon office (503) 430-1065 Business (503) 430-1285 Fax http://www.teraspeed.com This e-mail contains proprietary and confidential intellectual property of Teraspeed Consulting Group LLC ------------------------------------------------------------------------------------------------------ Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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