==Running FDTD Simulations==
===Strategy for an Accurate & Efficient FDTD EM.Tempo's SimulationModes ===Â The FDTD method is one of the most versatile numerical techniques for solving electromagnetic modeling problems. Choosing the right settings and optimal values for certain numerical [[parameters]] will have a significant impact on both accuracy and computational efficiency of an FDTD simulation. Below are a number of steps that you should typically follow by order when planning your FDTD simulation:Â * Identify material types and proper domain boundary conditions.* Identify the source type and excitation mechanism.* Define the project observables.* Mesh the physical structure and examine the quality of the generated mesh and it geometric fidelity.* Determine the proper temporal waveform.* Select the simulation mode and run the FDTD engine.
[[Image:FDTD57.png|thumb|390px|EM.Tempo's Run dialog.]]
[[Image:FDTD58.png|thumb|600px|EM.Tempo's Simulation Engine Settings dialog.]]
[[Image:FDTD66.png|thumb|480px|EM.Tempo's output window.]]
For certain problems, more than one combination or choice of settings and [[parameters]] may still give acceptable results. In most cases, EM.Tempo tries to make these choices convenient for you by suggesting default settings or default parameter values. For example, EM.Tempo by default generates an "adaptive" type mesh with a default density of 20 cells per effective wavelength. The default computational domain features CPML walls placed a quarter free-space wavelength away from the large bounding box of the entire physical structure. A modulated Gaussian waveform with preset optimal [[parameters]] is used to drive the project's excitation source by default. You can change most of these settings arbitrarily. For example, you can set up your own computational domain with different types of boundary conditions, customize the FDTD mesh by modifying a large number of mesh settings and use other types of excitation waveforms.
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{{Note|Keep in mind that you are always responsible for the choice of excitation source and the project observables. In other words, EM.Tempo does not automatically provide a default excitation source or does not suggest default observables.}}
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Once you build your physical structure in the project workspace and define an excitation source, you are ready to run an FDTD simulation. The simulation engine will run even if you have not defined any observables. Obviously, no simulation data will be generated in that case. EM.Tempo currently offers several different simulation modes as follows (click on each type to learn more about it):
=== Running a Wideband FDTD Analysis ===
Analysis The FDTD method is EMone of the most versatile numerical techniques for solving electromagnetic modeling problems.Tempo's simplest Choosing the right settings and most straightforward optimal values for certain numerical [[parameters]] will have a significant impact on both accuracy and computational efficiency of an FDTD simulation mode. It runs the Below are a number of steps that you should typically follow by order when planning your FDTD time marching loop oncesimulation:Â * Identify material types and proper domain boundary conditions. At * Identify the end of source type and excitation mechanism.* Define the simulation, project observables.* Mesh the time-domain field data are transformed into physical structure and examine the frequency domain using a discrete Fourier transform (DFT)quality of the generated mesh and it geometric fidelity. As a result, you can generate wideband frequency data from a single time-domain simulation run* Determine the proper temporal waveform. The other * Select the simulation modes will be explained later in this manualmode and run the FDTD engine.
To open Wideband analysis is EM.Tempo's simplest and most straightforward simulation mode. It runs the Simulation Run Dialog, click FDTD time marching loop once. At the '''Run''' [[Image:run_icon.png]] button end of the '''Simulate Toolbar''' or select '''Menu > Simulate > Runsimulation, the time-domain field data are transformed into the frequency domain using a discrete Fourier transform (DFT).As a result, you can generate wideband frequency data from a single time-domain simulation run..''' from the menu bar or use the keyboard shortcut {{key|Ctrl+R}}The other simulation modes will be explained later in this manual.
To start open the FDTD simulationSimulation Run Dialog, click the '''Run''' [[Image:run_icon.png]] button of the '''Simulate Toolbar''' or select '''Menu > Simulate > Run...''' from the menu bar or use the keyboard shortcut {{key|Ctrl+R}}. To start the FDTD simulation, click the {{key|Run}} button at the bottom of this dialog. Once the simulation starts, the "'''Output Window'''" pops up and reports messages during the different stages of the FDTD simulation. During the FDTD time marching loop, after every 10th time step, the output window updates the values of the time step, elapsed time, the engine performance in Mega-cells per seconds, and the value of the convergence ratio U<sub>n</sub>/U<sub>max</sub> in dB. An [[EM.Cube]] FDTD Tempo simulation is terminated when the ratio U<sub>n</sub>/U<sub>max</sub> falls below the specified power threshold or when the maximum number of time steps is reached. You can, however, terminate the FDTD engine earlier by clicking the '''Abort Simulation''' button.
=== The FDTD Simulation Engine Settings ===