CST2013: Asymptotic Solver Specials (SBR)

Simulation: Solver Start Simulation Settings

This dialog box provides you with some more advanced control of the SBR solver's parameters. In many cases, however, one of the configuration accuracy defaults (low / medium / high) will be sufficient. Within this dialog box you will most likely need to change the Ray density / wavelength parameter only. Please note that this dialog box will only be shown when the solver type is set to SBR.

The dialog box consists of three frames, the Mesh frame, the Solver frame and the Ray storage frame. The Mesh frame mainly deals with settings concerning the mesh generation whereas the Solver frame provides access to some of the solvers more specific options controlling accuracy and simulation speed. The Ray storage frame finally controls the way how the rays are stored for visualization purposes.

Use curved triangles

This setting specifies whether the mesh triangles will be curved for a better representation of non-planar geometries. If this option is not checked, the mesh will be created such that it consists of planar triangles only. Using curved triangles will usually improve accuracy, at the expense of a little bit higher memory consumption and longer simulation times.

Normal tolerance (degrees)

This parameter specifies the maximum allowable tolerance of the (planar) triangle normals as compared to the true normals of the structure's geometry. Lower settings will lead to a more accurate geometrical representation at the expense of generating more triangles. For curved triangles, this parameter is quite insensitive and therefore the default setting can be accepted in most cases. If this parameter is set to zero, no constraint concerning the normal tolerance will be applied during the mesh generation.

Surface tolerance

This parameter specifies the maximum allowable deviation of the (planar) triangle for the actual geometry in model dimensions. Lower settings will lead to a more accurate geometrical representation at the expense of generating more triangles. For curved triangles, this parameter is quite insensitive and therefore the default setting can be accepted in most cases. If this parameter is set to zero, no constraint concerning the surface tolerance will be applied during the mesh generation.

Max edge length / wavelength

This setting specifies the maximum allowable length of the triangle edges as compared to the wave length of the upper frequency limit as it is specified globally. This parameter has a strong influence on the number of triangles generated for a particular mesh. The solver run time will suffer from drastically varying triangle sizes, so extreme settings should be avoided.

Max edge length / structure diag.

This setting specifies the maximum allowable length of the triangle edges as compared to the size of the structure (bounding box diagonal). This parameter has a strong influence on the number of triangles generated for a particular mesh. The solver run time will suffer from drastically varying triangle sizes, so extreme settings should be avoided.

Ray density / wavelength

This parameter specifies the number of rays which are launched per wavelength of the actual simulation frequency. For electrically smaller structures, this parameter may need to be increased in order to achieve a better accuracy. Typical values are in between 10 for electrically very large structures and 40 or more for electrically not very large structures. This parameter is the main parameter to vary for controlling solver accuracy and performance.

Minimum number of rays

For electrically smaller structures, there may be too few rays launched due to the Ray density / wavelength setting. In order to ensure that a reasonable number of rays are launched to properly illuminate all regions of the structure, this parameter defines a lower bound for the number of rays. For more accurate simulations of electrically not very large structures you may need to increase this parameter.

Max. area of ray tube / wavelength^2

This parameter controls the maximum ray tube cross section for consideration of a particular beam for the scattered field computation. The scattering results become inaccurate for beams with very large cross sections, therefore it makes sense not to consider these beams since their contribution will be very small anyway. There is normally no need to change this setting.

Exit blockage check

This option specifies whether the visibility of a reflection point for a particular ray from the current observation point will be checked or not. For better accuracy it is recommended to turn this option on. In some cases it may be useful to turn this option off in order to quickly obtain potentially less accurate results.

Include metallic edge diffraction

This option specifies whether diffraction at edges should be included in the simulation which will improve the accuracy at the expense of longer simulation times. It is generally recommended to turn this option on for more accurate results.

Allow storage of incident rays

This option controls whether the incident rays will be stored if the corresponding rays option is set for the excitation. If this option is turned off, ray storage will be suppressed for all incident rays.

Allow storage of initial hit points

This option controls whether the points where the incident rays hit the structure will be stored if the corresponding rays option is set for the excitation. If this option is turned off, the initial hit point storage will be suppressed for all incident rays.

Allow storage of observed rays

This option controls whether the scattered rays will be stored if the corresponding rays option is set for the excitation as well as the observation direction. If this option is turned off, scattered ray storage will be suppressed.

Max. number of incident rays stored per direction

This option allows you to set an upper limit for the number of incident rays being stored per direction and per reflection level. This option is important in order to avoid storing huge files which may slow down the computation tremendously. Please note that this limit is set for each reflection level independently. Therefore, a limit of e.g. 1000 means that up to 1000 rays will be stored which do not intersect with the structure, another up to 1000 rays will be stored which are reflected once and so on.

Max. number of initial hit points stored per direction

This option allows you to set an upper limit for the number of points where the incident rays hit the structure being stored per excitation.

Max. number of observed rays stored per direction

This option allows you to set an upper limit for the number of scattered rays being stored per incident direction and per reflection level. This option is important in order to avoid storing huge files which may slow down the computation tremendously. Please note that this limit is set for each incident direction and reflection level independently.

Angular tolerance for observed rays (degrees)

This option allows you to set an angular tolerance for the scattered rays which will be used for assigning these rays to a particular observation angle.

Defaults...

This button will open another dialog box which allows to restore the settings for a particular accuracy default (low / medium / high).

OK

Accepts the changes and closes the dialog.

Cancel

Closes this dialog box without performing any further action.

Help

Shows this help text.