[[EM.Cube]] provides special waveguide sources that can excite either the TE<sub>mn</sub> or TM<sub>mn</sub> modes of a rectangular waveguide which is oriented along one of the three principal axes. In other words, the plane of the waveguide source must be parallel to one of the principal (XY, YZ or ZX) coordinate planes.
[[Image:FDTD44.png|thumb|200px|[[FDTD Module]]'s Waveguide Source dialog.]]
{{Note|In order to create a waveguide source, you must have at least one "Hollow" Box object with no caps or only one end cap in your project.}}