[SI-LIST] Buried Microstrips
- From: Ty Beeman <ty.beeman@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 16 Jul 2009 10:25:54 -0400
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
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