=== Visualizing 3D Radiation Patterns ===
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[[File:PO45.png|thumb|300px|PO Module's Radiation Pattern dialog]]
Unlike the FDTD method, Physical Optics is an open-boundary technique. You do not need a far field box to perform near-to-far-field transformations. Nonetheless, you still need to define a far field observable if you want to plot radiation patterns. A far field can be defined by right clicking on the '''Far Fields''' item in the '''Observables''' section of the Navigation Tree and selecting '''Insert New Radiation Pattern...''' from the contextual menu. The Radiation Pattern dialog opens up. You can accept most of the default settings in this dialog. The Output Settings section allows you to change the '''Angle Increment''' in the degrees, which sets the resolution of far field calculations. The default value is 5 degrees. After closing the radiation pattern dialog, a far field entry immediately appears with its given name under the '''Far Fields''' item of the Navigation Tree.
The 3D plots can be viewed by clicking on their name in the navigation tree. They are displayed in [[EM.Cube]]'s project workspace and are overlaid on the project's structure. The view of a 3D radiation pattern plots can be changed with the available view operations such as rotate view, pan, zoom, etc. If the structure blocks the view of the pattern, you can simply hide the whole structure or parts of it. The fields are always normalized to the maximum of the total far field. A legend box appears in the upper right corner of the 3D radiation plot, which can be moved around by clicking and dragging with the left mouse button. The calculated Directivity of the radiating structure is displayed at the bottom of the legend box. It is important to note that if the PO structure is excited by an incident plane wave, the radiation patterns indeed represent the far-zone scattered field data.
<table><tr><td> [[FileImage:PO46PO37.png|500pxthumb|300px|EM.Illumina's Radiation Pattern dialog.]]</td>Â Figure<td> [[Image: PO46.png|thumb|500px|3D radiation pattern of a parabolic dish reflector excited by a short dipole at its focal point.]] </td></tr></table>
=== Radar Cross Section ===
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[[File:PO47.png|thumb|300px|PO Module's RCS dialog]]
When the physical structure is excited by a plane wave source, the calculated far field data indeed represent the scattered fields. [[EM.Cube]] calculates the radar cross section (RCS) of a target, which is defined in the following manner:
At the end of a PO simulation, the thee RCS plots σ<sub>θ</sub>, σ<sub>φ</sub>, and σ<sub>tot</sub> are added under the far field section of the Navigation Tree. These plots are very similar to the three 3D radiation pattern plots. You can view them by clicking on their names in the navigation tree. The RCS values are expressed in m<sup>2</sup>. For visualization purposes, the 3D plots are normalized to the maximum RCS value, which is also displayed in the legend box. Keep in mind that computing the 3D mono-static RCS may take an enormous amount of computation time.
<table><tr><td> [[FileImage:PO48PO47.png|500pxthumb|300px|EM.Illumina's Radar Cross Section dialog.]]</td>Â Figure<td> [[Image: PO48.png|thumb|500px|RCS of a PEC sphere illuminated by an laterally incident plane wave.]] </td></tr></table>
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