When you start a new project in EM.Tempo, a default-type domain is automatically created with a default offset value set equal to a quarter free-space wavelength (0.25λ<sub>0</sub>). As soon as you draw your first object, a blue domain box shows up in the project workspace and encloses your object. As you add more objects and increase the overall size of your structure, the domain box grows accordingly to encompass your entire physical structure. When you delete objects from the project workspace, the domain box also shrinks accordingly.
[[Image:FDTD14.png|thumb|350px|[[FDTD Module]]'s Domain Settings dialog.]]
===Changing the Domain Settings===
By default, the domain box is shown as a wireframe box with blue lines. You can change the color of the domain box or hide it.
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[[Image:FDTD14.png|thumb|left|480px|EM.Tempo's domain settings dialog.]]
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===Settings the Domain Boundary Conditions===
[[Image:FDTD13.png|thumb|300px|[[FDTD Module]]'s Boundary Conditions dialog]]
EM.Tempo supports four types of domain boundary conditions: PEC, PMC, Convolutional Perfectly Matched Layers (CPML) and Periodic Boundary Conditions (PBC). By default, all the six sides of the computational domain box are set to CPML, representing a completely open-boundary structure. Different boundary conditions can be assigned to each of the six walls of the domain box. The periodic boundary conditions are special ones that are assigned through EM.Tempo's Periodicity Dialog and will be discussed later under modeling of periodic structures. The current release of [[EM.Cube]] allows periodic boundary conditions only on the side walls of the computational domain, and not on the top or bottom walls.
The PEC and PMC boundary conditions are the most straightforward to set up and use. Assigning the PEC boundary to one of the bounding walls of the solution domain simply forces the tangential component of the electric field to vanish at all points along that wall. Similarly, assigning the PMC boundary to one of the bounding walls of the solution domain forces the tangential component of the magnetic field to vanish at all points along that wall. For planar structures with a conductor-backed substrate, you can use the PEC boundary condition to designate the bottom of the substrate (the -Z Domain Wall) as a PEC ground. For shielded waveguide structures, you can designate all the lateral walls as PEC. Similarly to model shielded cavity resonators, you designate all the six walls as PEC.
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[[Image:FDTD13.png|thumb|left|480px|EM.Tempo's boundary conditions dialog.]]
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=== Advanced CMPL Setup ===
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<td> [[Image:fdtd_manual-11.png|thumb|400pxleft|480px|The boundary ABC cells placed outside the visible domain box.]] </td></tr><tr><td> [[Image:FDTD15.png|thumb|400pxleft|480px|CPML Settings dialog.]] </td>
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<td> [[Image:FDTD24A.png|thumb|360pxleft|480px|The domain box of a patch antenna with a finite-sized substrate.]] </td></tr><tr><td> [[Image:FDTD24.png|thumb|360pxleft|480px|The domain box of a laterally infinite patch antenna with a PEC ground and zero ±X and ±Y and -Z domain offsets.]] </td>
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