===Waveforms & Discrete Fourier Transforms===
{{mainpage| [[Waveforms and Discrete Fourier Transforms| [[Waveforms and Discrete Fourier Transforms|Waveforms And Discrete Fourier Transforms]]]] }}
The accuracy of the FDTD simulation results depends on the right choice of temporal waveform. [[EM.Cube]]'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.
===Defining Custom Output Parameters===
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{{mainpage|Custom Output}}
At the end of an FDTD simulation, a number of computed quantities are designated as "Standard Output" [[parameters]] and can be used for various post-processing data operations. For example, you can define design objectives based on them, which you need for [[optimization]]. The table below gives a list of all the currently available standard output [[parameters]] in [[EM.Cube]]'s [[FDTD Module]]:
| Imaginary Part of Transmission Coefficient
|}
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In the table above, SijM, etc. means the scattering parameter observed at port i due to a source excited at port j. Similar definitions apply to all the S, Z and Y [[parameters]]. If your planar structure has N ports, there will be a total of N<sup>2</sup> scattering [[parameters]], a total of N<sup>2</sup> impedance [[parameters]], and a total of N<sup>2</sup> admittance [[parameters]]. Additionally, there are four standard output [[parameters]] associated with each of the individual S/Z/Y [[parameters]]: magnitude, phase (in radians), real part and imaginary part. The same is true for the reflection and transmission coefficients of a periodic planar structure excited by a plane wave source. Each coefficient has four associated standard output [[parameters]]. These [[parameters]], of course, are available only if your planar structure has a periodic domain and is also excited by a plane wave source incident at the specified θ and φ angles.
All the radiation- and scattering-related standard outputs are available only if you have defined a radiation pattern far field observable or an RCS far field observable, respectively. The standard output [[parameters]] DGU and ARU are the directive gain and axial ratio calculated at the certain user defined direction with spherical observation angles (θ, φ). These angles are specified in degrees as '''User Defined Azimuth & Elevation''' in the "Output Settings" section of the '''Radiation Pattern Dialog'''. The standard output [[parameters]] HPBWU, SLLU, FNBU and FNLU are determined at a user defined f-plane cut. This azimuth angle is specified in degrees as '''Non-Principal Phi Plane''' in the "Output Settings" section of the '''Radiation Pattern Dialog''', and its default value is 45°. The standard output [[parameters]] BRCS and MRCS are the total back-scatter RCS and the maximum total RCS of your planar structure when it is excited by an incident plane wave source at the specified θ<sub>s</sub> and φ<sub>s</sub> source angles. FRCS, on the other hand, is the total forward-scatter RCS measured at the predetermined θ<sub>o</sub> and φ<sub>o</sub> observation angles. These angles are specified in degrees as '''User Defined Azimuth & Elevation''' in the "Output Settings" section of the '''Radar Cross Section Dialog'''. The default values of the user defined azimuth and elevation are both zero corresponding to the zenith.
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If you are interested in calculating certain quantities at the end of a simulation, which you do not find among [[EM.Cube]]'s standard output data, you can define your own custom output. [[EM.Cube]] allows you to define new custom output as any mathematical expression that involves the available standard output [[parameters]], numbers, [[variables]] and all of [[EM.Cube]]'s mathematical functions. For a list of legitimate mathematical functions, click the '''Functions [[Image:functions_icon.png]] '''button of the '''Simulate ''''''Toolbar''' or select '''Simulate > Functions... '''from the menu bar, or use the keyboard shortcut '''Ctrl+I''' to open the Function Dialog. Here you can see a list of all the available [[EM.Cube]] functions with their syntax and a brief description. To define a custom output, click the '''Custom Output [[Image:custom_icon.png]] '''button of the '''Simulate ''''''Toolbar''' or select '''Simulate > Custom Output... '''from the menu bar, or use the keyboard shortcut '''Ctrl+K''' to open the Custom Output Dialog. This dialog has a list of all of your custom output [[parameters]]. Initially, the list empty. You can define a new custom output by clicking the '''Add '''button of the dialog to open up the '''Add Custom Output Dialog'''. In this dialog, first you have to choose a new label for your new parameter and then define a mathematical expression for it. At the bottom of the dialog you can see a list of all the available standard output [[parameters]], whose number and variety depends on your project's source type as well as the defined project observables. When you close the Add Custom Output dialog, it returns you to the Custom Output dialog, where the parameter list now reflects your newly defined custom output. You can edit an existing parameter by selecting its row in the table and clicking the '''Edit '''button, or you can delete any parameter from the list using the '''Delete '''button.
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[[Image:PMOM141.png]]
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Figure 1: [[EM.Cube]]'s Custom Output dialog.
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[[Image:PMOM140.png]]
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Figure 2: Defining a new custom output using the available standard output [[parameters]].
===3D Near & Far Field Animation===