Toggling Terminal Type

By default, Q3D Extractor's AC RL and DC RL solvers use Constant Voltage (equipotential) terminals. For AC-RL calculations, a constant voltage is held over the perimeter of the terminal face. For DC-RL calculations, a constant voltage is held over the area of the terminal face.

However, in some applications, the properties of these terminals can lead to unwanted or non-physical inductance values.

An alternate form of excitation, the Uniform Current, enforces the condition that the current along the perimeter of a terminal is uniformly distributed for AC-RL calculations, and that the current over the area of a terminal is uniformly distributed for DC-RL calculations.

For AC-RL calculations, both Constant Voltage and Uniform Current terminals use the following procedure for extraction:

1. For excitation of the structure, one terminal is excited with 1V while all other terminals are kept at 0V.
2. Q3D Extractor solves the system equation:

        

   and calculates inductance using the terminal equation:

        

   with Y being the inverse of jωL.

For DC-RL calculations, see: Extracting DC Inductance from the Field Solution.

The differences between Constant Voltage and Uniform Current are described below.

Constant Voltage

• The potential on the terminal perimeter is constant for AC calculations, and constant on the terminal area for DC calculations.
• The current distribution is non-uniform on the perimeter of the terminal, or on the terminal area.
• Introducing additional terminals will change the path of the current, and self-inductance entries may also change.

Uniform Current

• Forces a uniform current distribution on the perimeter of the terminals for AC calculations, or on the area of the terminals for DC calculations to approximate those terminals as point ports.
• For terminals comprising multiple disjoint facets, each facet has its own constant current density different from all other facets. This is for the scenario of a terminal defined over a pingroup.
• The voltage on the terminal is not constant, and voltage (1V or 0V) will be observed at one point only.
• Due to the uniform current distribution, the self-inductance is usually higher.

Changing a Terminal's Type

You can change a terminal's type to either Constant Voltage or Uniform Current, as appropriate. Q3D Extractor can support having both types in a single design.

To change the type of a single terminal:

1. From the Project Manager, double-click a sink or source terminal.

   The [Source / Sink] window appears.

   

2. Select either Constant Voltage or Uniform Current.
3. Click OK.

Changing All Terminals

To change all terminals in the design to one type, perform one of the following:

• Select Q3D Extractor > Nets > Toggle Terminal Type > All to [Constant Voltage / Uniform Current].
• Right-click in the modeling workspace and select  Toggle Terminal Type > All to [Constant Voltage / Uniform Current].
• In the Project Manager, right-click a terminal and select Toggle > All Terminals to [Constant Voltage / Uniform Current].