Changes

* '''Perfect Electric Conductor (PEC)''': &epsilon;<sub>r</sub> = &mu;<sub>r</sub> = 1, &sigma; = &infin;, &sigma;<sub>m</sub> = 0
* '''Perfect Magnetic Conductor (PMC)''': &epsilon;<sub>r</sub> = &mu;<sub>r</sub> = 1, &sigma; = 0, &sigma;<sub>m</sub> = &infin;
 
== Variety of Source Types in EM.Cube ==
 
In order to perform an electromagnetic simulation in any of [[EM.Cube]]'s computational modules, you need to excite your physical structure using some kind of source. In most cases, you can define more than one source if necessary. In [[EM.Tempo]], a source pumps energy into your FDTD computational domain in the form of a temporal waveform varying as a function time. In the MoM-based modules, [[EM.Picasso|EM.picasso]] and [[EM.Libera]], a source provides the "right-hand-side (RHS)" vector of the MoM linear system resulting from the integral equation formulation of your boundary value problem. In EM.Illuumina, a source is used to illuminate your surfaces. In [[EM.Terrano]], a source acts as a transmitter that launches the broadcast signal into the free space. In [[EM.Ferma]], you need either an electric or magnetic source to set the boundary conditions for the Laplace equation or provide the source term for the Poisson equation.
 
In each module, you should choose the right source type depending on the purpose of your simulation and based on the observables you define for your project. For example, for computing the radar cross section (RCS) of a target, you need a plane wave source. If you are interested in computing the S/Z/Y [[parameters]] of your structure, then you have to choose a source type like a gap or lumped source that supports a "Port Definition" observable.
 
<table>
<tr>
<td> [[Image:Source12.png|thumb|360px|Current distribution on a metallic plate excited by a plane wave source.]] </td>
<td> [[Image:Source13.png|thumb|360px|Current distribution on a metallic plate excited by a short horizontal dipole source above it.]] </td>
</tr>
</table>
 
[[EM.Cube]] provides a large variety of source types listed in the table below:
 
{| class="wikitable"
|-
! scope="col"| Source Type
! scope="col"| Supporting Module(s)
|-
| Lumped Source
| [[EM.Tempo]]
|-
| Waveguide Source
| [[EM.Tempo]]
|-
| Distributed Source
| [[EM.Tempo]]
|-
| Gap Source
| [[EM.Picasso]], [[EM.Libera]]
|-
| Probe Source
| [[EM.Picasso]]
|-
| De-embedded Source
| [[EM.Picasso]]
|-
| Hertzian Dipole Source
| [[EM.Tempo]], [[EM.Illumina]], [[EM.Picasso]], [[EM.Libera]], [[EM.Terrano]]
|-
| Plane Wave Source
| [[EM.Tempo]], [[EM.Illumina]], [[EM.Picasso]], [[EM.Libera]]
|-
| Gaussian Beam Source
| [[EM.Tempo]]
|-
| Huygens Source
| [[EM.Illumina]], [[EM.Picasso]], [[EM.Libera]]
|-
| Transmitter Set
| [[EM.Terrano]]
|-
| Fixed-Potential PEC with Nonzero Voltage
| [[EM.Ferma]]
|-
| Volume Charge Source
| [[EM.Ferma]]
|-
| Wire Current Source
| [[EM.Ferma]]
|-
| Volume Current Source
| [[EM.Ferma]]
|-
| Permanent Magnet with Nonzero Magnetization
| [[EM.Ferma]]
|}
 
== Variety of Simulation Data in EM.Cube ==
 
In most of [[EM.Cube]]'s computational modules, you have to define one or more observables to generate any output data at the end of a simulation. In other words, no simulation data is generated by itself. [[EM.Cube]] provides a large variety of simulation data and observable types as listed in the table below:
 
{| class="wikitable"
|-
! scope="col"| Simulation Data Type
! scope="col"| Required Observable
! scope="col"| Supporting Module(s)
|-
| Electric and Magnetic Field Distributions
| Field Sensor
| [[EM.Tempo]], [[EM.Terrano|Em.Terrano]], [[EM.Illumina]], [[EM.Ferma]], [[EM.Picasso]], [[EM.Libera]]
|-
| Electric and Magnetic Current Distributions
| Current Distribution
| [[EM.Illumina]], [[EM.Picasso]], [[EM.Libera]]
|-
| Temporal Fields
| Field Probe
| [[EM.Tempo]]
|-
| Far-Field Radiation Patterns
| Far Fields - Radiation Pattern
| [[EM.Tempo]], [[EM.Terrano|Em.Terrano]], [[EM.Illumina]], [[EM.Picasso]], [[EM.Libera]]
|-
| Radar Cross Section (RCS)
| Far Fields - RCS
| [[EM.Tempo]], [[EM.Illumina]], [[EM.Picasso]], [[EM.Libera]]
|-
| Huygens Surface Data
| Huygens Surface
| [[EM.Tempo]], [[EM.Terrano|Em.Terrano]], [[EM.Illumina]], [[EM.Picasso]], [[EM.Libera]]
|-
| Port Characteristics (S/Z/Y Parameters)
| Port Definition
| [[EM.Tempo]], [[EM.Picasso]], [[EM.Libera]]
|-
| Periodic Reflection and Transmission Coefficients
| No Observables Required
| [[EM.Tempo]], [[EM.Picasso]]
|-
| Temporal Electric and Magnetic Energy
| Domain Energy
| [[EM.Ferma]]
|-
| Static Electric and Magnetic Energy & Ohmic Losses
| Field Integral
| [[EM.Ferma]]
|-
| Voltage and Current
| Field Integrals
| [[EM.Ferma]]
|-
| Electric and Magnetic Flux
| Field Integrals
| [[EM.Ferma]]
|-
| Resistance, Capacitance, Inductance
| Field Integrals
| [[EM.Ferma]]
|-
| Received Power
| Receiver Set
| [[EM.Terrano]]
|-
| Singal-to-Noise Ratio (SNR)
| Receiver Set
| [[EM.Terrano]]
|-
| Channel Path Loss
| Receiver Set
| [[EM.Terrano]]
|}
 
== EM.Cube Mesh Types ==
 
[[EM.Cube]]'s computational modules use a number of different mesh generation schemes to discretize your physical structure. Even [[CubeCAD]] provides several tools for object discretization. In general, all of [[EM.Cube]]'s mesh generation schemes can be grouped into three categories representing their dimensionality:
 
# Linear Mesh
# Surface Mesh
# Volume Mesh
 
The linear mesh is also known as wireframe mesh and is used by [[EM.Libera]] to discretize the physical structure for Wire MoM simulation. [[EM.Cube]] offer two surface mesh types: triangular surface mesh and hybrid surface mesh. As its name implies, a triangular surface mesh is made up of interconnected triangular cells. [[EM.Terrano]], [[EM.Illumina]], [[EM.Libera]] and [[EM.Picasso]] all use triangular surface mesh generators to discretized surface CAD objects and the surface of solid CAD objects. The hybrid surface mesh is [[EM.Picasso]]'s default mesh. It combines rectangular and triangular cells to discretize planar structures. The hybrid surface mesh generator tries to produce as many identical rectangular cells as possible in rectangular regions of your planar structure.
 
[[EM.Cube]] provides two types of brick meshes to discretize the volume of your computational domain. Brick meshes are entire-domain volume meshes and are made up of cubic cells. Brick meshes are indeed generated by a three-dimensional arrangement of grid lines along the X, Y and Z dimensions. [[EM.Tempo]] offers an Adaptive brick mesh as well as a fixed-cell brick mesh for the FDTD simulation of your physical structure. [[EM.Ferma]] offers only a fixed-mesh brick mesh for the solution of electrostatic and magnetostatic Poisson equations.
 
<table>
<tr>
<td> [[Image:Mesh1.png|thumb|240px|The geometry of a metallic torus.]] </td>
<td> [[Image:Mesh2.png|thumb|240px|The brick volume mesh of the metallic torus.]] </td>
<td> [[Image:Mesh3.png|thumb|200px|The triangular surface mesh of the metallic torus.]] </td>
</tr>
</table>
 
== The Significance of Mesh Resolution ==
 
The objects of your physical structure are discretized based on a specified mesh density. The default mesh densities of [[EM.Tempo]], [[EM.Picasso]], [[EM.Libera]] and [[EM.Illumina]] are expressed as the number of cells per effective wavelength. Therefore, the resolution of the default mesh in these modules are frequency-dependent. You can also define the mesh resolution using a fixed cell size or fixed edge length specified in project units. The mesh density of [[EM.Terrano]] is always expressed in terms of cell edge length. The mesh resolution of [[EM.Ferma]] is always specified as the fixed cell size. All of [[EM.Cube]]'s computational modules have default mesh settings that usually work well for most simulations.
 
The accuracy of the numerical solution of an electromagnet problem depends greatly on the quality and resolution of the generated mesh. As a rule of thumb, a mesh density of about 10-30 cells per effective wavelength usually yields satisfactory results. Yet, for structures with lots of fine geometrical details or for highly resonant structures, higher mesh densities may be required. Also, the particular simulation data that you seek in a project also influence your choice of mesh resolution. For example, far field characteristics like radiation patterns are less sensitive to the mesh density than the near-field distributions on a structure with a highly irregular shape and a rugged boundary.
Kazem Sabet
28,333
edits