In this article, we will compute the bi-static radar cross-section (RCS) of a Dassault Mirage III type fighter aircraft at 850 MHz with [[EM.Tempo]]. Throughout the article, we will discuss a few challenges involved in working with electrically-large models.
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{{Note| For an in-depth tutorial related to computing RCS in [[EM.Tempo]], please review [[EM.Tempo Tutorial Lesson 2: Analyzing Scattering From A Sphere]]}}
== Computational Environment ==
The CAD model used for this simulation was found on [https://grabcad.com/ GrabCAD], an online repository of user-contributed CAD files and models. [[EM.Cube]]'s IGES import was then used to import the model. Once we import the model, we move the Mirage to a new PEC material group in [[EM.Tempo]].
<div><ul> <li style="display: inline-block;"> [[Image:glass.png ââ|thumb|left|200px|Selecting glass as cockpit material for the Mirage model.]]</li><li style="display: inline-block;"> [[Image:Mirage image.png ââ|thumb|left|200px|Complete model of Mirage aircraft.]]</li></ul></div>
For the present simulation, we model the entirety of the aircraft, except for the cockpit, as PEC. For the cockpit, we use [[EM.Cube]]'s material database to select a glass of our choosing.
===Planewave Source===
Since we're computing a Radar Cross Section, we also need to add a planewave source. For this example, we will specify a TMz planewave with k = sqrt(2)/2 x - sqrt(2)/2 z, or θ = 135 degrees, φ = 0 degrees., or:Â :<math> \hat{k} = \frac{\sqrt{2}}{2} \hat{x} - \frac{\sqrt{2}}{2} \hat{z} </math>
===Mesh Settings===
For the mesh, we use the "Fast Run/Low Memory Settings" preset. This will set the minimum mesh rate at 15 cells per lambdaλ, and permits grid adaptation only where necessary. This preset provides slightly less accuracy than the "High Precision Mesh Settings" preset, but results in smaller meshes, and therefore shorter run times.
At 850 MHz, the resulting FDTD mesh is about 270 million cells. With mesh-mode on in [[EM.Cube]], we can visually inspect the mesh.
<li style="display: inline-block;"> [[Image:Large struct article mesh detail.pngâ|thumb|left|300px|Mesh detail near the cockpit region of the aircraft.]] </li>
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===Engine Settings===
[[Image:Large struct article ScreenCapture3.png|thumb|left|300px|RCS pattern of the Mirage model at 850 MHz in dBsm.]]
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</ul></div>Â <div><ul> <li style="display: inline-block;"> [[Image:RCS XY.pngâ|thumb|left|300px|XY cut of RCS]]</li><li style="display: inline-block;"> [[Image:RCS ZX.pngâ|thumb|left|300px|ZX cut of RCS]]</li><li style="display: inline-block;"> [[Image:Large struct article RCS YZ.pngâ|thumb|left|300px|YZ cut of RCS in m^2.]]</li>
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<div><ul>
<li style="display: inline-block;"> [[Image:Large struct article ScreenCapture2ScreenCapture1.png|thumb|left|300px]] </li><li style="display: inline-block;"> [[Image:Large struct article ScreenCapture1ScreenCapture2.png|thumb|left|300px]]</li></ul></div>Â <div><ul> <li style="display: inline-block;"> [[Image:RCS XY Polar.png||thumb|left|300px| XY Cut of RCS is dBsm]]</li><li style="display: inline-block;"> [[Image:RCS ZX Polar.png||thumb|left|300px| ZX Cut of RCS is dBsm]] </li><li style="display: inline-block;"> [[Image:RCS YZ Polar.png||thumb|left|300px| YZ Cut of RCS is dBsm]] </li>
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