Before you can run an FDTD simulation, you have to define a source to excite your projectâs physical structure. EM.Tempo offers a variety of excitation mechanisms for your physical structure depending on your particular type of modeling problem or application:
# '''[[FDTD_Source_Types#Ideal_Source|Ideal Source]]''': A stand-alone localized voltage source with an internal resistance.# '''[[FDTD_Source_Types#Lumped_Source|Lumped Source]]''': An ideal source that must be place on a wire (a PEC line object).# '''[[FDTD_Source_Types#Distributed_Source|Distributed Source]]''': A source with a prescribed impressed field component that is defined on a rectangular region of space parallel to a principal plane.# '''[[FDTD_Source_Types#Waveguide_Source|Waveguide Source]]''': A distributed source that must be placed across a hollow PEC box object.# '''[[FDTD_Source_Types#Plane_Wave_Source|Plane Wave Source]]''': A distributed source with a plane wave profile defined using a virtual box object enclosing the entire physical structure. # '''[[FDTD_Source_Types#Gaussian_Beam_Source|Gaussian Beam Source]]''': A distributed source with a complex-valued focused Gaussian beam profile defined using a virtual box object enclosing the entire physical structure.
# '''Huygens Source''': A distributed source defined based on know tangential electric and magnetic field components on the surface of a virtual box object.
===Understanding the FDTD Source Types===
Click here to learn more about the various '''[[FDTD Source Types]]'''.
===Defining Ports===
Using simple lumped sources, you can simulate a variety of transmission line structures in [[EM.Tempo]] including filters, couplers or antenna feeds and you can calculate their scattering [[parameters]]. This approach may become less accurate at very high frequencies when the details of the feed structures become important and can no longer be modeled with highly localized lumped ports. In such cases, it is recommended to use âDistributed Sourcesâ, which utilize accurate modal field distributions at the ports for calculation of the incident and reflected waves.
Click here to learn more about '''[[Using Lumped Sources to Model Transmission Line Feeds]]'''.
Click here to learn more about '''[[Using Sources & Loads in Antenna Arrays]]'''.
[[File:FDTD56.png|thumb|300px|EM.Tempo's Lumped Load dialog.]]