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# Defining the Excitation

## Excitation Panel

Go to the Setup tab in the main window and select the Excitation panel. There are two types of excitations: Discrete Sources and Incident Field, Fig. 1.

### Discrete Sources

The discrete generators placed at the wire structure will be used to calculate the current distribution. The total input power in Watts can be specified, so the voltage/current sources will be adjusted accordingly to achieve the specified input power. If the input power is not specified, then the voltage/current sources will be constant, and the input power will be an output result from calculations.

### Incident Field

An incident plane wave will be used as the excitation of the structure. The direction of incidence and polarization of the incoming field can be set in this panel.

The following parameters must be set for the incident wave excitation:

E-Field Major Axis

In the case of linear polarization, it is the amplitude, in Volts per meter (rms value), of the incoming electric field. For an elliptically polarized plane wave, it is the major axis of the polarization ellipse.

Axial Ratio

It is the ratio of the minor axis to the major axis of the polarization ellipse. If the axial ratio is positive (negative) a right-handed (left-handed) ellipse is obtained. If the axial ratio is set to zero, a linearly polarized wave will be obtained.

Phase Reference

It is the phase, in degrees, of the incident plane wave at the origin of coordinates. Its value only shifts all phases in the structure by the same amount.

Gamma

For a linearly polarized wave, it is the polarization angle, in degrees, of the incident electric field measured from the plane of incidence to the direction of the electric field vector, as it is shown in Fig. 2. For an elliptically polarized wave, Gamma is the angle between the plane of incidence and the major ellipse axis.

Theta

It is the zenith angle, in degrees, of the incident direction.

Phi

It is the azimuth angle, in degrees, of the incident direction.

The definition of these parameters is illustrated in Fig. 2.

When the 3D View button is pressed a user interface is enabled in the workspace, where the direction of arrival of the plane wave and its polarization can be specified easily, Fig. 3.

#### Note

When an incident plane wave is used as excitation, all discrete sources, if any, will not be considered in the simulation.