Radiation Pattern plots are used to plot the value of a global variable for the radiation pattern of an electromagnetic field or acoustic pressure field.

The main advantage with the Radiation Pattern plot, as compared to making a Line Graph, is that the circle or sphere used for defining the plot directions is not part of the geometry for the solution. Thus, the number of plotting directions is decoupled from the discretization of the solution domain.

To add this plot type, right-click a plot group node and choose Radiation Pattern from the More Plots menu. For 2D and 3D Radiation Pattern nodes, you can right-click to add a Deformation subnode if desired.

For the standard settings, see Expressions and Predefined Quantities. In 3D, you can also select the Threshold check box and then enter a threshold value as a scalar number in the associated text field. The threshold value corresponds to the evaluated radius that maps to the plotted radius 0. The default, if the Threshold check box is cleared, is the minimum radius among those evaluated for. Additionally, in 3D, select the Use as color expression check box to use the radiation pattern plot expression defined in this section also as the color expression. The Color section is then not available.

Under Angles, enter the Number of angles. The default is 50.

Select a Restriction: None (the default) or Manual. If Manual is selected, enter values (SI unit: deg) for start (the default is 0 degrees) and range (the default is 360 degrees). If you want to compute the beam width, select On from the Compute beam width list. Then, a Level down field appears, where you can specify a nonnegative number to compute the beam width at a certain level down from the reference direction. The unit for that level is the same as the unit for the expression used in the radiation pattern plot (dB, for example, for an exterior-field sound pressure level). The beam width is the width of the lobe around the reference direction (in degrees). When you compute the beam width, the computed values appear in a Beam width table with columns for the parameter (typically a frequency), the beam width, and the null-to-null beam width (the angular separation from which the magnitude of the radiation pattern decreases to zero away from the main beam; see the figure below).

For 1D Radiation Pattern plot nodes referring to a solution in a 2D axisymmetric or 3D component, under Center enter the coordinate at the center of the evaluation circle. Under Normal specify the normal to the circular slice of the far-field bulb. The default normal is {0, 0, 1} for the normal using 3D components and {0, 1, 0} for the normal using 2D axisymmetric components.

If a Pressure Acoustics interface is used in the component from which the dataset is taken, you can also add a Radius (SI unit: m) under Evaluation distance for a radius-dependent exterior-field expression.

Under Reference direction specify a reference direction from which the angle is measured. The entered vector is projected onto the evaluation plane. The default direction is {1, 0, 0} for the reference direction using 3D components, {0, 0, 1} for 2D axisymmetric components, and {1, 0} for 2D components.

A schematic of the evaluation circle is depicted in Figure 21-5. In 3D, you can preview the evaluation circle in the geometry by clicking the Preview Evaluation Plane button at the bottom of the Evaluation section. An example of the resulting plot is depicted in Figure 21-6.

Under Angles, enter the Number of elevation angles. The default is 10. Enter the Number of azimuth angles. The default is 20.

Select a Restriction: None (the default) or Manual. If None is selected in a 3D plot group, you can also select On or Off from the Compute directivity list. If the Compute directivity list is set to On, you can enter or select an expression for the directivity in the Directivity expression field. The direction for the strongest radiation and the directivity value (also in dB) display in a Directivity table window (see The Table Window and Tables Node). So if, for example, you model a speaker that is located in an infinite baffle (and symmetry is used in the radiation pattern calculation), then plot and evaluate the whole field to get the directivity.

If Manual is selected, enter values (SI unit: deg) for:

If a pressure acoustics interface is used in the component from which the dataset is taken, you can also specify the following settings for a radius-dependent exterior-field expression. Under Sphere from the list, select Unit sphere (the default) or Manual. If Manual is selected, enter values for the x, y, and z coordinates at the center of the sphere (SI unit: m). The default is 0. Enter a Radius (SI unit: m). The default is 1 m.

For 2D axisymmetric radiation pattern plots, you can evaluate the azimuthal () angle once for each angle when you specify a name of the variable for the () angle in the Azimuthal angle variable field and use it in the expression for the radiation pattern. Doing so slows down the evaluation, so if the Azimuthal angle variable field is empty, an evaluate-once-and-revolve approach is used instead.

This section is available in 1D plot groups only. Select the Show legends check box to display the plotted expressions to the right of the plot. In plots where each line represents a certain time value, eigenvalue, or parameter value, these values are also displayed.

When Automatic is selected from the Legends list (the default), the legend texts appear automatically. You can add a prefix or a suffix to the automatic legend text in the Prefix and Suffix fields. If Manual is selected from the Legends list, enter your own legend text into the table.