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<html><head><meta http-equiv="Content-Language" content="en-us"><meta http-equiv="Content-Type" content="text/html; charset=windows-1252"><meta name="GENERATOR" content="Microsoft FrontPage 4.0"><meta name="ProgId" content="FrontPage.Editor.Document"><title>2D FDTD</title></head><body><h2>2D FDTD+PML to simulate EMAG fields in medium</h2><p>FDTD is a very popular method for EMAG analysis and simulation. Andboundarycondition is used to terminate the infinite computation region. In thecalculation of photonic band gap material, periodic boundary condition(PBC),Mur's 2nd absorption boundary condition (ABC) and Perfectly matched layer(PML)are often used and implemented in my program. They can be verified eachotherand they are good for different purposes.</p><p>In this section, we will present some demonstration calculated by usingFDTDand PML boundary conditions. Any introduction of PML and implementationdetailsare not listed here, please refer any references about them.</p><p>The biggest advantage of PML is its very low reflection from theboundary andgood for high quality simulations. However, it uses much more memory andcomputation time than other methods. Fortunately, the computer is gettingfasternowadays.</p><h3>Point source in vacuum</h3><p>Here is a simulation of vacuum with 201x201 grids, a point source atthecenter emits a sine wave (with a power of 6 to make it sharper). Theanimationof the simulation is shown as the GIF.</p><p><img border="0" src="vacuum/vacuum.gif" width="201" height="201"><ahref="vacuum/vacuum.gif"></a></p><h3>Plane wave source in vacuum</h3><p>Here is a simulation of plane wave source in a 201x201 vacuum, a linesourceon the left side is emitting a sine wave (with a power of 6).</p><p><img border="0" src="planewave/pw.gif" width="201" height="201"></p><h3>A GaAs disk in vacuum radiated by a plane wave source</h3><p>A GaAs (dielectric constant is 13.0) disk with a radius of 15 grids ina201x201 vacuum is incident by a plane wave source. The incident field willbescattered by the disk. The total field is shown in the animationbelow.</p><p>A similar case is shown right to it with a perfect conductor disk(PEC) atthe same location.</p><p><imgborder="0" src="disk/disk.gif" width="201" height="201"> <img border="0" src="mdisk/mdisk.gif" width="201" height="201"></p><h3>The 2-hole interference experiment</h3><p>In the 201x201 vacuum space, a perfect conductor line is placed in thecenter, it has two holes in it. A plane wave is incident on it. We can seetheinterference pattern after the PEC rod.</p><p><imgborder="0" src="metalhole/mholes.gif" width="201" height="201"></p><p> </p><h2>How well is PML? </h2><p>You can see our experiment using a plane wave source at the left side,apoint source at the center. Both cases, a Gaussian band pass pulse isused. Thepropagation of the pulse along the cells in x-direction is shown ingraph. A 101x101 cell is used and free space is studied. 10 PML layers isued in this calculation. Inour test, the reflection is estimated to be smaller than 1e-7. Thisshows PMLis much better than Mur's 2nd ABC.</p><p>Click here to see how a plane wave pulse evolves: <ahref="plane_pulse.bmp">plane_pulse.bmp</a></p><p>Click here to see how a point source pulse propagates in vacuum: <ahref="point_pulse.bmp">point_pulse.bmp</a></p><p>Update will continue........</p><p>Binary files on Solaris and simple document and examples are availableusing tar -xvf *.tar to uncompress the filesFor 2D TM mode, <a href=../pml2dtm.tar>here to download</a>For 2D TE mode, <a href=../pml2dte.tar>Here to download</a><p> </p><p> </p><p> </p></body></html>⌨️ 快捷键说明
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