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|[[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]]
Electric and magnetic field plots of the circular loop antenna.
=== Visualizing 3D Radiation Patterns ===
[[File:wire_pic37.png|thumb|300px|[[MoM3D Module]]'s radiation pattern dialog]]
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|[[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.}}
The RCS of the wire-plate structure: (Left) σ<sub>θ</sub>, (Center) σ<sub>φ</sub> and (Right) total RCS..
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=== Customizing 3D Plots ===
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Similar to the current distribution and field sensor plots, [[EM.Cube|EM.CUBE]]'s 3-D radiation pattern plots are interactive. When you move the mouse over a pattern plot, tiny dots appear on its surface. These dots correspond to the theta-phi angle pairs on the surface of the unit sphere where the far field data have been calculated. Upon mouse-over, you can highlight one of these points. A small tooltip appears on the plot that shows the normalized far field value in that direction.
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[[File:wire_pic41_tn.png]]
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Reading far field values from a 3-D radiation pattern plot by mouse-over.
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You can change the type of the 3-D radiation pattern plot through the '''Radiation Pattern Dialog'''. The plot type change applies to all the three nodes: theta component, phi component and total field patterns. In the 3D Display Type section of this dialog you can choose from three options: '''3D Polar''', which is the default choice, '''Spherical Map''' and '''Cone'''. In the last two cases, the far field values are plotted on the surface of the unit sphere, where each point correspond to a (θ, φ) pair. In the spherical map, the curved cells of the unit sphere are colored based on their field value. In the cone-type plot, a vectorial visualization of the far fields is generated. In the last case, you can also set the size of the cones that represent the far field vectors.
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[[File:wire_pic42_tn.png]] [[File:wire_pic43_tn.png]]
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The spherical map and cone (vectorial) versions of the radiation pattern show in the previous figure.
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Just like current distribution and field sensor plots, each individual 3-D radiation pattern plots has an '''Output Settings Dialog''', from which you can further customize the plot's scale (linear vs. dB), lower and upper limits and color map type.
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