[[EM.Cube]]âs [[MoM3D Module|MoM3D module]] offers two distinct 3D MoM simulation engine. The first one is a Wire MoM solver that can be used to simulate wireframe models of metallic structures. This solver is particularly useful for modeling wire-type antennas and arrays. The second engine features a powerful surface MoM solver. It can model metallic surfaces and solids as well as solid dielectric objects. The Surface MoM solver uses a surface integral equation formulation of Maxwell's equations. In the case of solid dielectric objects, equivalent electric and magnetic currents are assumed on the surface of the dielectric object to formulate the interior and exterior boundary value problems.
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Click here to learn more about the theory of [[3D Method of Moments]].
=== Free Space Greenâs Function ===
Ports are used to order and index gap sources for S parameter calculation. They are defined in the '''Observables''' section of the Navigation Tree. Right click on the '''Port Definition''' item of the Navigation Tree and select '''Insert New Port Definition...''' from the contextual menu. The Port Definition Dialog opens up, showing the total number of existing sources in the workspace. By default, as many ports as the total number of sources are created. You can define any number of ports equal to or less than the total number of sources. This includes both gap sources and active lumped elements (which contain gap sources). In the '''Port Association''' section of this dialog, you can go over each one of the sources and associate them with a desired port. Note that you can associate more than one source with same given port. In this case, you will have a coupled port. All the coupled sources are listed as associated with a single port. However, you cannot associate the same source with more than one port. Finally, you can assign '''Port Impedance''' in Ohms. By default, all port impedances are 50Σ. The table titled '''Port Configuration''' lists all the ports and their associated sources and port impedances.
{{Note|In [[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|EM.CUBE]]]]]]]]]]]]]]]] you cannot assign ports to an array object, even if it contains sources on its elements. To calculate the S [[parameters]] of an antenna array, you have to construct it using individual elements, not as an array object.}}
[[File:port-definition.png]]
The radiation patterns of antenna arrays usually have a main beam and several side lobes. Some [[parameters]] of interest in such structures include the '''Half Power Beam Width (HPBW)''', '''Maximum Side Lobe Level (SLL)''' and '''First Null [[Parameters]]''' such as first null level and first null beam width. You can have [[EM.Cube|EM.CUBE]] calculate all such [[parameters]] if you check the relevant boxes in the "Additional Radiation Characteristics" section of the '''Radiation Pattern Dialog'''. These quantities are saved into ASCII data files of similar names with '''.DAT''' file extensions. In particular, you can plot such data files at the end of a sweep simulation.
{{Note|Defining an array factor in the radiation pattern dialog simply performs a post-processing calculation. The resulting far field obviously do not take into account any inter-element coupling effects as [[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|[[EM.Cube|EM.CUBE]]]]]]]]]]]]]]]] does not construct a real physical array in the project workspace.}}
{{Note|Using an array factor for far field calculation, you cannot assign non-uniform amplitude or phase distribution to the array elements. For this purpose, you have to define an array object.}}