=== Plane Wave Sources ===
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[[File:PMOM77.png|thumb|[[Planar Module]]'s Plane Wave dialog]]
You can excite a planar structure with an incident plane wave to explore its scattering characteristics such as radar cross section (RCS). Exciting an antenna structure with an incident plane wave is equivalent to operating it in the "receive" mode. Plane wave excitation in the [[Planar Module]] is particularly useful for calculation of reflection and transmission coefficients of periodic surfaces. Note that the incident plane wave in your project bounces off the layered background structure and part of it also penetrates the substrate layers. The total incident field that is used to calculate the excitation vector of the MoM linear system is a superposition of the incident, reflected and transmitted plane waves at various regions of your planar structure:
[[File:PMOM111.png]]<math> \mathbf{E^{inc}(r)} = E_0 (\mathbf{\hat{e}_1} e^{ -jk_0 \mathbf{\hat{k}_1\cdot r} } + R \mathbf{\hat{e}_2} e^{ -jk_0 \mathbf{\hat{k}_2\cdot r} } ) </math>
where η:<submath>0\mathbf{H^{inc}(r)} = \frac{E_0}{\eta_0} ( \mathbf{\hat{k}_1 \times \hat{e}_1} e^{-jk_0 \mathbf{\hat{k}_1 \cdot r} } + R \mathbf{\hat{k}_2 \times \hat{e}_2} e^{-jk_0 \mathbf{\hat{k}_2\cdot r} } ) </submath> <!--[[File:PMOM111.png]]--> where <math>\eta_0 = 120&\pi; </math> is the characteristic impedance of the free space, '''k<sub>1</sub>''' and '''k<sub>2</sub>''' are the unit propagation vectors of the incident plane wave and the wave reflected off the topmost substrate layer, respectively, and '''ê<sub>1</sub>''' and '''ê<sub>2</sub>''' are the polarization vectors corresponding to the electric field of those waves. R is the reflection coefficient at the interface between the top half-space and the topmost substrate layer and has different values for the TM and TE polarizations.
EM.Cube's [[Planar Module]] provides the following polarization options:
* In the Field Definition section of the dialog, you can enter the '''Amplitude''' of the incident electric field in V/m and '''Phase''' in degrees. The default field Amplitude is 1 V/m, with a zero Phase.
* The direction of the Plane Wave is determined by the incident '''Theta''' and '''Phi''' angles expressed in the spherical coordinate system in degrees. You have to choose the '''Polarization''' of the plane wave from the four options: '''TM<sub>z</sub>''', '''TE<sub>z</sub>''', '''LCP<sub>z</sub>'''and '''RCP<sub>z</sub>'''. The components of the unit propagation vector are shown based on your choice of the angles of incidence. The components of the normalized E- and H-field vectors are also displayed based on your choice of polarization.
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[[File:PMOM77.png]]
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Figure 1: [[Planar Module]]'s Plane Wave dialog.
== Running Planar MoM Simulations ==