Far Field

Far Field plots are used to plot the value of a global variable for the far field of an electromagnetic field or acoustic pressure field.

•	For the RF Module and the Wave Optics Module, the variables are the far-field norm, normEfar and normdBEfar; the components of the far-field variable Efar; and the axial ratio, axialRatio and axialRatiodB.

•	For the Acoustics Module, the variables are the far-field pressure ffc1.pfar and sound pressure level ffc1.Lp_pfar.

The variables are plotted for a selected number of angles on a circle (in 2D) or a sphere (in 3D). The angle interval and the number of angles can be manually specified. Also the circle origin and radius of the circle (2D) or sphere (3D) can be specified. For 3D Far Field plots, you also specify an expression for the surface color.

The far-field plot plots a surface shape by deforming the specified circle or sphere in 2D and 3D, or a circular slice in 1D. For each evaluation point on the specified circle or sphere, the plot deforms the specified circle or sphere from the evaluation point in the radial direction so that the deformed surface shape distance from the origin becomes equal to the value of the specified expression on the evaluation point on the specified circle or sphere.

The main advantage with the Far Field 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.

Default Far Field plots are automatically added to any model that uses far-field calculations. You can add a Far Field plot node to any plot group (Polar, 1D, 2D, and 3D):

•	1D or Polar plots () for 2D, 2D axisymmetric, or 3D geometry

•	2D plot () for 2D axisymmetric or 3D geometry

•	3D plot () for 2D axisymmetric or 3D geometry

For a 3D Plot Group and 2D Plot Group, select the Far Field plot from the More Plots submenu

Go to Common Results Node Settings for links to information about these sections: Data, Title, Range, Inherit Style, and Coloring and Style. For 3D plot groups, see the list for Color. For Far Field plots, only Solution data sets are available as inputs.

Expression

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 edit 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.

Evaluation

1D Plot Group and Polar Plot Group

Under Angles, enter the resolution. 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).

For 1D Far-Field plot nodes referring to a solution in a 2D axisymmetric or 3D component, under Reference direction and Normal, specify a reference direction from which the angle is measured and a normal to the circular slice of the far-field bulb. The defaults are {1, 0, 0} for the reference direction and {0, 0, 1} for the normal using 3D components and {0, 0, 1} for the reference direction and {0, 1, 0} for the normal using 2D axisymmetric components.

If a pressure acoustics interface is used in the component from which the data set is taken, you can also add a Radius (SI unit: m) under Evaluation distance for a radius-dependent far-field expression.

2D and 3D Plot Groups

Under Angles, enter the θ resolution. The default is 10. Enter the resolution. 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 the Compute directivity check box. If the Compute directivity check box is selected, 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 far-field calculation), then plot and evaluate the whole field to get the directivity.

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

•	start (the default is 0 degrees)

•	θ range (the default is 180 degrees)

•	start (the default is 0 degrees)

•	range (the default is 360 degrees)

If a pressure acoustics interface is used in the component from which the data set is taken, you can also specify the following settings for a radius-dependent far-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.

Legends

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.