=== Advanced CMPL Setup ===
[[Image:fdtd_manual-11.png|thumb|400px|The boundary ABC cells placed outside the visible domain box.]]
[[Image:FDTD15.png|thumb|400px|CPML Settings dialog.]]
In many electromagnetic modeling problems you need a boundary condition that simply absorbs all the incoming radiation. For problems of this nature, an absorbing boundary condition (ABC) is often chosen that effectively minimizes wave reflections at the boundary. EM.Tempo uses Convolutional Perfectly Matched Layers (CPML) for absorbing boundary conditions. Usually two or more ABC layers must be placed at the boundaries of the physical structure to maximize wave absorption. The boundary CPML cells in the project workspace are transparent to the user. But, in effect, multiple rows of CPML cells are placed on the exterior side of each face of the visible domain box.
{{Note|[[EM.Tempo]]'s default quarter wavelength offset for the domain box is a very conservative choice and can be reduced further in many cases. A offset equal to eight free-space grid cells beyond the largest bounding box usually give a more compact, but still valid, domain box.}}
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<table>
<tr>
<td> [[Image:fdtd_manual-11.png|thumb|400px|The boundary ABC cells placed outside the visible domain box.]] </td>
<td> [[Image:FDTD15.png|thumb|400px|CPML Settings dialog.]] </td>
</tr>
</table>
===Modeling Planar Structures of Infinite Extents===