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:
# '''Ideal Source''': A stand-alone localized voltage source with an internal resistance.# '''Lumped Source''': An ideal source that must be place on a wire (a PEC line object).# '''Distributed Source''': A source with a prescribed impressed field component that is defined on a rectangular region of space parallel to a principal plane.# '''Waveguide Source''': A distributed source that must be placed across a hollow PEC box object.# '''Plane Wave Source''': A distributed source with a plane wave profile defined using a virtual box object enclosing the entire physical structure. # '''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.
When an FDTD simulation starts, your project's source starts pumping energy into the computational domain at t > 0. Maxwell's equations are solved in all cells at every time step until the solution converges, or the maximum number of time steps is reached. A physical source has a zero value at t = 0, but it rises from zero at t > 0 according to a specified waveform. [[EM.Tempo]] currently offers four types of temporal waveform: