Use the Release from Far-Field Radiation Pattern node to release rays with an intensity and power distribution based on a far-field radiation pattern. The far-field radiation pattern must first be solved for in a previous study.
The Release from Far-Field Radiation Pattern node can be used for multiscale electromagnetics modeling. First, the Electromagnetic Waves, Frequency Domain interface should be used to compute the electric field in the immediate vicinity of a radiation source, such as an antenna or waveguide. The
Far-Field Domain node and its default subnode,
Far-Field Calculation, should be added to this instance of the Electromagnetic Waves, Frequency Domain interface. In this wavelength-scale model, the mesh must be fine enough to resolve individual oscillations of the electric field, fulfilling the
Nyquist criterion. Typically this requires 10 linear elements or 5 second-order elements per wavelength.
The Release from Far-Field Radiation Pattern node is only available in 3D. However, the far-field function used to initialize the ray intensity and polarization can be defined either in a 3D model component or a 2D axisymmetric model component. If the previous model component was a 2D axisymmetric component, the intensity distribution of released rays will also be assumed to be axisymmetric.
Enter Initial coordinates based on space dimension (
qx,0,
qy,0, and
qz,0) for the ray positions or click the
Range button (
) to select and define a range of specific coordinates.
If Specified combinations is selected, the number of initial coordinates entered for each space dimension must be equal, and the total number of rays released is equal to the length of one of the lists of initial coordinates. If
All combinations is selected, the total number of rays released is equal to the product of the lengths of each list of initial coordinates.
In the Initial Coordinates section, you can click the
Preview Initial Coordinates and
Preview Initial Extents buttons to visualize the ray release positions. Clicking
Preview Initial Coordinates will cause a point to appear in the Graphics window for every release position. Clicking
Preview Initial Extents will cause a bounding box to appear, indicating the spatial extents of the released rays.
Note that unlike the Release from Grid feature, the options
Expression and
Lambertian are not available here. In addition, if
Conical is selected, the cone must be isotropic. This is because each ray is assumed to subtend approximately the same solid angle, so direction distributions that give unequal weight to some directions (like
Lambertian) or options with no direction distribution at all (like
Expression) cannot initialize the ray intensity and power in a consistent and physically meaningful way.
Enter an expression for the Far-field variable name. The default expression is
Efar. This expression must match the variable name in a corresponding
Far-Field Calculation feature.
Enter the Euler angles (Z-X-Z). The labels Z-X-Z indicate the order in which rotation about the different axes is performed. First, the local coordinate system of the radiation pattern is rotated about its
Z-axis by the angle
α. Then it is rotated about its
X-axis (which is now at an angle
α to the global
x-axis) by the angle
β. Finally, this local coordinate system is rotated about its new
Z-axis by the angle
γ. All three inputs are plane angles (SI unit: rad) with default values of 0.
This section is only shown if Monochromatic is selected from the
Wavelength distribution of released rays list in the physics interface
Ray Release and Propagation section.
The Use frequency from the far-field calculation as the ray frequency check box is selected by default. While this check box is selected and the
Release from Far-Field Radiation Pattern feature is active, the frequency or vacuum wavelength of released rays will be determined by the
Frequency Domain or
Wavelength Domain study in the
Values of Variables not Solved For section of the
Time Dependent solver settings. Usually, this previous study was used to solve for the far-field radiation pattern using the Electromagnetic Waves, Frequency Domain interface.
While this check box is selected and the Release from Far-Field Radiation Pattern node is active, the frequency or wavelength specified in the
Ray Properties node is ignored.