Types of Excitations and Loads

Discrete Sources, Incident Field, and Loads

A structure in AN-SOF can be excited either by discrete sources or by an incident electromagnetic field. For the latter, refer to Excitation by an Incident Field. Discrete sources can be placed on any wire segment, and multiple sources may be added—up to one per segment if needed.

A source represents the feed point of a transmitting antenna or an electrical generator. There are two types of sources:

• Voltage sources
• Current sources (used to model impressed currents)

For each source, you must define its amplitude and phase. Additionally, you can assign an internal impedance to simulate non-ideal sources. The impedance can take one of the following forms:

• Series RL (inductive)
• Series RC (capacitive)
• Fixed complex impedance (R + jX)

In addition to sources, lumped loads can be inserted into any wire segment to model passive components or matching circuits. Six types of loads are available:

• Series RL impedance (inductive)
• Series RC impedance (capacitive)
• Fixed R + jX impedance (reactance does not scale with frequency)
• Series RLC circuit
• Parallel RLC circuit
• Trap RLC circuit

To model a pure resistor, set an inductive load with L = 0.

Note:

You can set the units for inductance and capacitance in Main Menu > Tools > Preferences. Supported units include:
• Inductance: pH, nH, µH, mH, H
• Capacitance: pF, nF, µF, mF, F

In the 3D workspace:

• Sources are represented by a yellow circle
• Loads are indicated by a green-highlighted wire segment (see Fig. 1)

Tips

• To customize the default colors of sources and loads, go to: Main Menu > Tools > Preferences > Workspace tab.

• To change the size of the source displayed in the workspace, go to Main Menu > Tools > Preferences > Workspace tab, and adjust the Source Size % setting.

• Voltage sources have their internal impedance in series.
  To model an ideal (perfect) voltage source, set the impedance to zero.

• Current sources have their internal impedance in parallel.
  To approximate an ideal current source, use a very high impedance (e.g., 1 MΩ).

Excitation by Sources

To excite the wire structure using discrete sources, go to the Setup tab, open the Excitation panel, and select the Discrete Sources option (see Fig. 2).

If the Set Input Power option is enabled, you can specify the total input power delivered to the structure. In this case, the amplitudes of the voltage and current sources will be automatically adjusted to match the desired input power.

To add a source to a wire segment, first right-click on the desired wire and select “Source / Load / TL (Ctrl + Ins)” from the pop-up menu. A toolbar will appear at the bottom of the screen. Use the slider on this toolbar to select the specific wire segment where you want to place the source.

For more details, see The Source/Load/TL Toolbar.