[[Image:Info_icon.png|40px]] Click here to learn more about EM.Tempo's '''[[Waveforms and Discrete Fourier Transforms | Standard & Custom Waveforms and Discrete Fourier Transforms]]'''.
===Defining Ports& Modeling Feeds in Practical Applications===
[[Image:FDTD48.png|thumb|450px|EM.Tempo's Port Definition dialog.]]
{{Note|In order to obtain correct results, the port impedance must equal the characteristic impedance of the transmission line on which the port is established. This is not done automatically in [[EM.Cube]].}}
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You can change the characteristic impedance of a port by selecting it from the Port List and clicking the '''Edit '''button of the dialog. This opens up the Edit Port dialog, where you can enter a new value in the box labeled '''Impedance'''.
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===Modeling Feeds in Practical Applications===
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.