=== Excitation Waveform & Frequency Domain Computations ===
[[Image:FDTD48A.png|thumb|700px|EM.Tempo's Excitation Waveform dialog showing a custom modulated Bessel temporal waveform.]]
When an FDTD simulation starts, your project's source starts pumping energy into the computational domain at t > 0. [[Maxwell's Equations|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: