For more detailed information, see [[Waveform, Bandwidth, Stability]].
==Defining The Building the Physical Structure==
[[Image:FDTD1.png|thumb|200px|[[FDTD Module]]'s Navigation Tree.]]
In [[EM.Cube]]'s [[FDTD Module]], a physical structure consists of sets of objects that are grouped together and identified by their material types. All the objects belonging to the same material group share the same color and same material properties. Materials are divided into seven categories that are listed under the '''Physical Structure''' node at the top of the Navigation Treenavigation tree:
* [[#Perfect Conductors|Perfect Electric Conductor (PEC) Objects]]
Under each material node, you can create new material groups of the same type/category but with different properties (color, texture, or electric and magnetic constitutive [[parameters]]). These material groups are used to organize the CAD objects you draw in the project workspace or import from external model files. When you create a new geometrical object such as a Box or a Sphere, it is inserted under the currently active material type. There is only one material group that is active at any time. It is recommended that you first create material groups, and then draw new objects as part of the active material group. However, if you start a new EM.Tempo project from scratch, and start drawing a new object without having previously defined any material groups, a new default PEC group is created and added to the navigation tree to hold your new CAD object.
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===Defining Material Types===
To define a new material group, follow these steps:
* Click the '''OK''' button of the dialog to accept the changes and close it.
Once a new material node has been created on the navigation tree, it becomes the "Active" material group of the project workspace, which is always listed in bold letters. You Then you can now draw start drawing new objects under that node. Any material can be made active by right clicking on its name in the Navigation Tree and selecting the '''Activate''' item of the contextual menu. ===Moving Objects among Material Groups=== If two or more material groups are defined in the Navigation Tree, only one of them can be active. By default, the last material defined is active. [[Image:FDTD21(1).png|thumb|325px|Moving objects from one FDTD material group to another.]] You can move one or more selected objects at a time among different material groups. Right click on the highlighted selection and select '''Move To > FDTD >''' from the contextual menu. This opens up another sub-menu with a list of all the available material groups already defined in your EM.Tempo project workspace. Select the desired material node, and they all the selected objects will move to that material group. The objects can be added under selected either in the active nodeproject workspace, or their names can be selected from the Navigation Tree. All In the objects belonging case of a multiple selection from the Navigation Tree using the keyboard's '''Shift Key''' or '''Ctrl Key''', make sure that you continue to hold the same keyboard's '''Shift Key''' or '''Ctrl Key''' down while selecting the "Destination" material group share 's name from the same color and contextual menu. In a similar way, you can move one or more objects from an FDTD material propertiesgroup to one of [[EM.Cube]]'s other modules. In this case, the sub-[[menus]] of the '''Move To >''' item of the contextual menu will indicate all the [[EM.Cube]] modules that have valid groups for transfer of the selected objects. You can also move one or more objects among different from [[EM.Cube]]'s other modules to a material groups using their contextual menugroup in the [[FDTD Module]]. This is especially useful when importing structure from external model files. Keep in mind that in [[EM.Cube]] you can import external objects only to '''[[CubeCAD]]'''. Â
If planned carefully, taking advantage of EM.Tempo's material hierarchy rule would make the construction of complex objects easier. For example, a dielectric coated metallic cylinder can be modeled by two concentric cylinders: an inner PEC of smaller radius and an outer dielectric of larger radius as shown in the illustration below. The portion of the dielectric cylinder that overlaps the inner PEC cylinder is ignored by the FDTD engine because the PEC cylinder takes precedence over the dielectric in the material hierarchy. Alternatively, you can model the same structure by an inner solid PEC cylinder enclosed by an outer hollow pipe-shaped dielectric cylinder.
===Moving Objects Among Material Groups===
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If two or more material groups are defined in the Navigation Tree, only one of them can be active. By default, the last material defined is active. When you draw new objects, they are inserted under the active material node of the Navigation Tree, which is always listed in bold letters. Any material can be made active by right clicking on its name in the Navigation Tree and selecting the '''Activate''' item of the contextual menu.
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[[Image:FDTD21(1).png|thumb|325px|Moving objects from one FDTD material group to another.]]
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You can move one or more selected objects to any other material group. Right click on the highlighted selection and select '''Move To > FDTD >''' from the contextual menu. This opens another sub-menu with a list of all the available material groups already defined in your [[FDTD Module]] project. Select the desired material node, and all the selected objects will move to that material group. The objects can be selected either in the project workspace, or their names can be selected from the Navigation Tree. In the case of a multiple selection from the Navigation Tree using the keyboard's '''Shift Key''' or '''Ctrl Key''', make sure that you continue to hold the keyboard's '''Shift Key''' or '''Ctrl Key''' down while selecting the "Destination" material group's name from the contextual menu.
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In a similar way, you can move one or more objects from an FDTD material group to one of [[EM.Cube]]'s other modules. In this case, the sub-[[menus]] of the '''Move To >''' item of the contextual menu will indicate all the [[EM.Cube]] modules that have valid groups for transfer of the selected objects. You can also move one or more objects from [[EM.Cube]]'s other modules to a material group in the [[FDTD Module]]. This is especially useful when importing structure from external model files. Keep in mind that in [[EM.Cube]] you can import external objects only to '''[[CubeCAD]]'''.
==Computational Domain & FDTD Mesh Generation==