=== Huygens Sources ===
[[File:po_phys17.png|thumb|300px|PO Module's Huygens Source dialog]]
At the end of a full-wave simulation in the EM.Cube's FDTD, MoM3D, Planar or Physical Optics Modules, you can generate Huygens surface data. According to Huygens' principle, if one knows the tangential electric and magnetic field components on a closed surface, one can determine the total electric and magnetic fields everywhere inside and outside that closed surface. Huygens surfaces are defined around a structure for recording the tangential components of electric and magnetic fields at the end of full-wave simulation of the structure. The tangential electric and magnetic fields are saved into ASCII data files as magnetic and electric currents, respectively. These current can be used as excitation for other structures. In other words, the electric and magnetic currents associated with a Huygens source radiate energy and provide the excitation for the PO Module's physical structure.
* You can open the property dialog of a Huygens source by right clicking on its name in the Navigation Tree and selecting '''Properties...''' From this dialog you can change the color of the Huygens source box as well as its location and orientation. You can enter new values for the X, Y, Z '''Center Coordinates''' and '''Rotation Angles''' of the Huygens box. You can also view the dimensions of the box.
* By default, the Huygens data are imported as a single Huygens source. You can create an arbitrary array of Huygens sources for your PO project. To do so, in the "Create Array" section of the Huygens source dialog, enter desired values for the '''Number of Elements''' and '''Element Spacing''' along the X, Y and Z directions. You will see an array of wire-frame box appear in the project workspace.
[[File:po_phys17.png]]
Figure: PO Module's Huygens Source dialog.
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