  # bobo44

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1. Hi, I have a question about C-3.1 Infinite cylinder from Feko ExampleGuide. When i change the media from Pec to dialectric i become an error in runfeko. Why doesnt it work? Infinite_Cylinder_r06diel.cfx Infinite_Cylinder_r06pec.cfx
2. Hello, I have a question about Sparameters in Feko. I have an infinite medium in x,y direction, in z direction it has the thickness d. The plane wave is normally incident on this medium. I additionly calculated the Sparameters in Matlab with NRW Method, thought the permittivity is right, S Parameters dont match. For example i have a medium(lossless) permittivity er = 20 S11 = (1 - Z^2) * Г / ((1 - Г^2) * Z^2) = -0.904 - j0.000 /abs = 0.904 S12 = 0.000 - j0.425 /abs = 0.425 (Г(refl coeff ideal for d = infinity) = (n2 - n1)/(n2 + n1) n1 = 1, n2 = sqrt(er) d = lambdas/4 Z = exp(-j ks d) = -j) In feko i have at 10 lambda S11 8.67303E-01 -159.80 S12 4.49503E-01 -87.71 though they shouldnt be different, i wonder why https://arxiv.org/ftp/arxiv/papers/1206/1206.4801.pdf (NRW) er20.cfx er20.out
3. you can make a lua script, that executes the feko solver, it is possible with for example a script like this, but if the conductivity and permittivity are changed with frequency, you should better define a frequency dependant medium, you can either define it as debye relaxation or some other or setting the values from a file or typing them manually in dielectric medium properties. if i got you right, but anyway, there are this lua scripting possibilities in cadfeko and postfeko you can use. app = cf.GetApplication() project = app.Project --do smth in script for example --request near field --simulate results -- Mesh the model project.Mesher:Mesh() --set another frequency, material properties here -- Set the frequency to single frequency. StandardConfiguration1 = project.SolutionConfigurations["StandardConfiguration1"] FrequencyRange1 = StandardConfiguration1.Frequency properties = FrequencyRange1:GetProperties() properties.Start = n1 FrequencyRange1:SetProperties(properties) -- Save project app:Save() -- RunFEKO project.Launcher:RunFEKO()
4. What are the reasons, why the reflected coefficient (Er/Ei) is too law? Can it be because of reflection coefficient is per definition the maximum amlitude of Er devided to maximum amplitude of Ei and my scattered near field at that point is not necessarily equal to the max. Amplitude. (i have drawn it in the picture with Vin and Vref) ------ I calculated only scattered near field. r - reflected, i -incident I have three mediums, the red one in the middle has the eff. permitivity of 18 at GHz, the 2 on the sides the eff. permitivity of 1(air) according to Fresnel Equations r = (n2 - n1) / (n2 + n1) = 0.8947 if i just take my nearfield data at the boundary and divide it with 1V/m incident field, i become r = 0.2
5. Why do i need periodic boundary conditions in order to calculate reflection. coefficient? I dont have a periodic or infinite structure, i want to calculate it for cube. But when i run feko solver, it requests me to set some periodic boundary conditions. I dont get it.I use a plane wave as a sourse. Should the plane position for phase reference be by (0,0,0)? (because it should be orthogonal to k propagation direction)
6. As i know, if two volumes intersect in Feko, i have to cut one from another, then create the one i cutted once again and unite them with unity. I create 1000 Spheres, some of them intersect. What would be right in Feko? Can i go through each Sphere i add and cut it from previous cubes and then add them as unity, even if they dont intersect or Is it needed to determine Volume Intersections generically and only in this case cut the one volume, then create it again and unite How can I detect volume intersection in Feko? or I should better add a Matlab Scipt for determining intersections?
7. thank you andries, it helped a lot, the model wasnt supposed to be symmetrical, i just edited existing feko eample with my model, that as it.
8. I want to mesh and get error Sphere1.Region58 breaks the symmetry definition. Either it does not have a symmetrical counterpart, or it is not symmetrical around the plane. How can i remove those planes?
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