Boundary Type

E-Field Behavior

Used to model...

Default Boundary Conditions (Natural and Neumann)

Field behaves as follows:

• Natural boundaries — The normal component of D changes by the amount of surface charge density, tangent component of E is continuous. No special conditions are imposed.
• Neumann boundaries — E is tangential to the boundary. Flux cannot cross a Neumann boundary.

Ordinary E-field behavior on boundaries. Object interfaces are initially set to natural boundaries; outer boundaries are initially set to Neumann boundaries.

Symmetry

Field behaves as follows:

• Even Symmetry (Flux Tangential) — E is tangential to the boundary; its normal components are zero.
• Odd Symmetry (Flux Normal) — E is normal to the boundary; its tangential components are zero.

Planes of geometric and electrical symmetry.

Balloon

Two options are available:

Charge — The charge at “infinity” balances the charge in the drawing region. The net charge is zero. Use for capacitance calculations.

Voltage — The voltage at “infinity” is zero.

Electrically insulated structures (Charge option) or electrically grounded structures (Voltage option). For the voltage case, the balloon boundary will not be equipotential in general.

Matching

(Independent and Dependent)

The E-field vector on the dependent boundary is forced to match the magnitude and direction (or the negative of the direction) of the E-field vector on the independent boundary.

Planes of symmetry in periodic structures where E is oblique to the boundary.