Thick Metal Modeling in Sonnet
Modeling true metal thickness
The Thick Metal feature allows you to more easily and accurately analyze physically thick metal in your circuit. In most planar applications, using our thin sheet metal models which incorporate proper loss modeling for both low and high frequency will provide sufficiently low error levels. However, there are situations where the actual metal thickness must be included in the model geometry:
- When the spacing between adjacent conductors is on the order of the metal thickness
- When the spacing to the return current path (usually called "ground") is on the order of the metal thickness
- When the thickness of the transmission line itself approaches that of it's width
Sonnet employs a multi-sheet model to capture the important effects of current penetration into the metal, an effect that is noticeably pronounced at low microwave frequencies where the skin depth of penetration is comparable to the metal thickness itself. At these frequencies, the effective spacing between a pair of coupled transmission lines can be appear to be wider due to the fact that a signficant amount of current is distributed beneath the conductor surface. Using multiple sheets to model a finite-thickness conductor captures this effect much more accurately than relying on a tube sheet model alone.
Setup window for a thick metal type
Sonnet allows you to configure and change the sheet count for a given metal type definition quickly and easily for model convergence testing.
An MMIC balun model using Sonnet thick metal definitions for Metal3