* '''Domain Energy''' for calculating the total electric and magnetic energy in the computational domain
* '''[[Hybrid_Modeling_using_Multiple_Simulation_Engines#Generating_Huygens_Surface_Data | Huygens Surface]]''' for collecting tangential field data on a box
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Of EM.Tempo's frequency domain observables, the near fields, far fields and all of their associated [[parameters]] like directivity, RCS, etc., are calculated at a certain single frequency that is specified as part of the definition of the observable. To compute those frequency domain data at several frequencies, you need to define multiple observables, one for each frequency. On the other hand, port characteristics like S/Y/Z [[parameters]], VSWR and periodic characteristics like reflection and transmission coefficients, are calculated over the entire specified bandwidth of your project.
<!--[[Image:Info_icon.png|40px]] Click here to learn more about the various '''[[FDTD Observable Types]]'''.-->
[[Image:Info_icon.png|40px]] Click here to learn more about for a general discussion of '''[[Data Visualization and Processing]]''' in [[EM.Cube]].
=== Computing Port Characteristics in FDTD ===Â Of EM.Tempo's frequency domain observables, the near fields, far fields and all of their associated [[parameters]] like directivity, RCS, etc., are calculated at a certain single frequency that is specified as part of the definition of the observable. To compute those frequency domain data at several frequencies, you need to define multiple observables, one for each frequency. On the other hand, port characteristics like S/Y/Z [[parameters]], VSWR and periodic characteristics like reflection and transmission coefficients, are calculated over the entire specified bandwidth of your project. Of EM.Tempo's source types, lumped sources, waveguide sources and distributed sources let you define one or more ports for your physical structure and compute its port characteristics. To do so, first you need a "Port Definition" observable in the navigation tree. One of EM.Tempo's real advantages over frequency-domain solvers is its ability of generate wideband S/Z/Y parameter data in a single simulation run.
[[Image:Info_icon.png|40px]] Click here to learn more about '''[[Data_Visualization_and_Processing#Computing_and_Graphing_Port_Characteristics | Computing and Graphing Port Characteristics]]'''.
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[[Image:FDTD77.png|thumb|400px|Time-domain evolution of the electric field at a given point.]]
=== Examining the Near Fields in Time and Frequency Domains ===
[[Image:FDTD77.png|thumb|400px|Time-domain evolution of the electric field at a given point.]]
EM.Tempo's FDTD time marching loop computes all the six electric and magnetic field components at every Yee cell of your structure's mesh at every time step. This amounts to a formidable amount of data that is computationally very inefficient to store. Instead, you can instruct EM.Tempo to save a small potion of these data for visualization and plotting purposes. Using a '''Field Probe''' at a specified point, you can record the a time-domain field component over the entire FDTD loop. The time-domain results are also transformed to the frequency domain within the specified bandwidth using a discrete Fourier transform (DFT).