A sinusoidal waveform is single-tone and periodic. Its spectrum is concentrated around a single frequency, which is equal to your project's center frequency. A Gaussian pulse decays exponentially as t → ∞, but it has a lowpass frequency spectrum which is concentrated around f = 0. A modulated Gaussian pulse decays exponentially as t → ∞, and it has a bandpass frequency spectrum concentrated around your project's center frequency. For most practical problems, a modulated Gaussian pulse waveform with EM.Tempo's default [[parameters]] provides an adequate performance.
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{{Note|All of EM.Tempo's excitation sources have a default modulated Gaussian pulse waveform unless you change them.}}
If you use a Gaussian pulse or a modulated Gaussian pulse waveform to drive your FDTD source, after a certain number of time steps, the total energy of the computational domain drops to very negligible levels. At that point, you can consider your solution to have converged. If you drive your FDTD source by a sinusoidal waveform, the total energy of the computational domain will oscillate indefinitely, and you have to force the time loop to terminate after a certain number of time steps assuming a steady state have been reached.
The accuracy of the FDTD simulation results depends on the right choice of temporal waveform. [[EM.Cube]]Tempo's default waveform choice is a modulated Gaussian pulse. At the end of an FDTD simulation, the time domain field data are transformed into the frequency domain at your specified frequency or bandwidth to produce the desired observables.
In addition to the default waveforms, [[EMImage:MORE.Cubepng|40px]] allows the ability Click here to define custom waveforms by either time or frequency specifications on a per source basislearn more about EM.Tempo's '''[[Standard Waveforms and Discrete Fourier Transforms]]'''.
[[Image:MORE.png{{Note|40px]] Click here to learn more about All of EM.Tempo's '''excitation sources have a default modulated Gaussian pulse waveform unless you change them.}}Â In addition to the default waveforms, [[Waveforms and Discrete Fourier TransformsEM.Cube]]'''allows the ability to define custom waveforms by either time or frequency specifications on a per source basis.
===Defining Ports===