== Excitation Sources ==
EM.Illumina provides three types of sources for the excitation of your physical optics simulation (click on each type to learn more about it):
* {| class="wikitable"|-! scope="col"| Source Type! scope="col"| Applications! scope="col"| Restrictions|-| '''[[Glossary of EM.Cube's Excitation Sources#Hertzian Short Dipole Sources Source | Hertzian Short Dipole SourcesSource]]'''* | style="width:300px;" | Almost omni-directional physical radiator| style="width:300px;" | None, stand-alone source|-| '''[[Glossary of EM.Cube's Excitation Sources#Plane Wave Sources | Plane Wave SourcesSource]]'''* | style="width:300px;" | Used for modeling scattering | style="width:300px;" | None, stand-alone source|-| '''[[Hybrid_Modeling_using_Multiple_Simulation_EnginesGlossary of EM.Cube's Excitation Sources#Working_with_Huygens_Sources Huygens Source | Huygens SourcesSource]]''' | style="width:300px;" | Used for modeling equivalent sourced imported from other [[EM.Cube]] modules | style="width:300px;" | Imported from a Huygens surface data file|} Click on each category to learn more details about it in the [[Glossary of EM.Cube's Excitation Sources]].
A short Hertzian dipole is the simplest way of exciting a structure in EM.Illumina. A short dipole source acts like an infinitesimally small ideal current source. The total radiated power by your dipole source is calculated and displayed in Watts in its property dialog. Your physical structure in EM.Illumina can also be excited by an incident plane wave. In particular, you need a plane wave source to compute the radar cross section of a target. The direction of incidence is defined by the θ and φ angles of the unit propagation vector in the spherical coordinate system. The default values of the incidence angles are θ = 180° and φ = 0° corresponding to a normally incident plane wave propagating along the -Z direction with a +X-polarized E-vector. Huygens sources are virtual equivalent sources that capture the radiated electric and magnetic fields from another structure that was previously analyzed in another [[EM.Cube]] computational module.