Ty, You might look at "Networks and Devices Using Planar Transmission Lines", DiPaolo. The equations yield excellent insight into non-coupled and coupled line theory. You can get a good match for the effective relative permittivity by adjusting the value of "h", where "h" is the height of the conductive enclosure boundary above the trace (similar to the solver approach). The equation set should yield solutions as good as or better than the authors you have mentioned for the non-coupled case. You are talking exclusively about the non-coupled case, right? However, be aware that closed-form solutions break down when you use them for coupled lines. Error can be as high as 30%. A simple 2-D solver will yield far more accurate results when you need to know Zodd, Zeven, and crosstalk. Ken -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of steve weir Sent: Thursday, July 16, 2009 8:45 AM To: Ty Beeman Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Buried Microstrips 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 ------------------------------------------------------------------ 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