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mel

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Everything posted by mel

  1. The scope tab only operates on surface currents. So you should specify the Faces not the Regions to include in the near field calculation.
  2. You can add the inductance to a port on the wire that connects to the ground. For a port on the cylinder, you can use the edge port. See e.g here below an edge port for a cylinder dipole. (Or you can make a small gap and use a short wire with a wire port.)
  3. >> However, how can we mesh the cylinder into triangles with the edge lengths the same as the spacing between the inner and outer conductor Just apply a local mesh size on the inner cylinder face. >> what about the outer conductor connection to the ground? should i use wire approximation or cylindrical? You can use either. You will be adding stray inductance to ground with either of them. But at low frequencies this inductance will be very small.
  4. Feko uses the thin wire approximation. You will not necessarily get accurate results by just specifying the wire radius. It only modifies the self impedance of the wires and will not necessarily accurately model the coupling to the shield, which is critically based on the physical spacing between the inner and outer conductors. It would be better, although computationally more expensive, to model the center conductor as a cylinder meshed into triangles. You must ensure that the meshed triangle edge lengths are roughly the same as the spacing between the inner and outer conductor. Secondly the radiation from the terminations can become significant if the the electrical length of the termination segments become large (so at high frequencies). This electrical length is not modeled in the MTL terminations. At higher frequencies you can compensate for the inductive effect by adding an equivalent capacitance.
  5. That problem was fixed in a later version of Feko. Please download and install version 2019.
  6. Hi Lostarmour. Could you please attach the .out file as well. Thanks.
  7. Feko does not support anisotropic Green's functions.
  8. If the imaginary part of the impedance is positive then you will get the inductance. E.g. Impedance in Ohm 1.4910E+03 9.1526E+02 1.7495E+03 31.54 Inductance in H 3.1862E-06
  9. This problem was fixed in Feko 2019.2. Please update. Else disable the MLFMM to use FEM/MoM instead of FEM/MLFMM.
  10. You can plot the 1000 discrete samples that were calculated already. They will be correct. In POSTFEKO you can set the graph to plot as follows (Trace, Sampling Settings): The interpolated data could be inaccurate but only in some areas of the frequency range where there may be e.g. some numerical noise - the interpolation could have tried to interpolate that unsuccessfully. If the temporary files of a continuous run have been kept a continuous run can be resumed by setting the start frequency to the last incomplete frequency. Also see the User Manual - search for ADAPTFEKO.
  11. The error is referring to the fact that the MLFMM is only for ELECTRICALLY large models, so models with at least 5 or more wavelengths in a direction. For the model you attached just switch off MLFMM. This will then be a standard MoM solution. P.S. You could do with finer meshing - maybe set a local mesh size on the metallic faces of the patches since they are the critical radiators.
  12. The Planar Multilayer Green's function is used to model your substrates and MLFMM is not supported together with the Green's Function. If you want to use MLFMM, you would have to use a finite substrate instead of infinite.
  13. If you add any voltage or current source the results will be available in POSTFEKO under Source data. It will also be in the OUT file. If not, please provide an example of where this data is not given?
  14. Inserting a capacitor onto a wire loop is very simple. Add a wire port and then add a load. You may need to split the loop and then Union the two parts again (or create multiple sections of loop which are Unioned together) to ensure you a vertex at the exact position where you want to place the port (load).
  15. The Output tab has more information: It seems your cir file does not meet the requirements. Have you worked through the ExampleGuide example "E.3.1 Dipole Matching Using a SPICE Network?"
  16. Yes, see "Automatic Meshing for Regions" in the Altair_Feko_User_Guide.pdf
  17. Feko will mesh the FEM tets according to the wavelength inside the medium, so definitely defining a conductivity will reduce the mesh size.
  18. You will need to do a full wave solution, so either MoM/FEM/MLFMM. Some suggestions: 1 Do a mesh convergence test on the reflector and target to determine what the coarsest mesh is you can use. You can vary the mesh sizes across the different parts/faces by using local mesh settings. I would suggest trying a mesh size of lambda/6.5 or maybe coarser. 2 It should be possible to replace the absorber with an equivalent cuboid of the same width and length but with some thickness inbetween the cone base and cone tip. The cones individual surface areas add many expensive dielectric triangles to the model. A single cuboid with width/length/height will be computationally cheaper. 3. Instead of running every model with all the available cores, rather run 2 models over half the angles with half the cores each. The model is not very large and the parallel efficiency is not perfect for increasing number of processes.
  19. Hi Marcus Is the reflector and sphere in a static position? So only the horn and absorber is moving?
  20. Hi Marcus Previously you stated:"To clarify the problems we face, please see attached .cfx (similar to our case), in such simulation, we spent several hours to simulate it." Today you stated:"Please see attached .out file run in our sever with 256 RAM. Even though we spent 1 hrs to solve it faster than our expectation." The *.out file shows a 1.1 hour solve time. Is this too long? Note that for S-parameters if you do not need S12 and S22 you can set the 2nd port on the S-parameter request to inactive. This will save you 1470.531 seconds (see out file) for the 2nd solution. The 2nd port will only act as a sink port then. Regarding the hallow sphere, I see stabilized MLFMM is activated. Note that it only applies to the metallic parts of the model and will run longer than for the case where stabilization is not active.
  21. Please attach the *.out file too.
  22. The workflow is not ideal. Let me not rather use that dreaded term:"...in the next version..." The solver runs a more in depth check of the whole mesh while Cadfeko does a very quick check and often misses these triangles. The workflow is to find the triangle numbers in the postprocessor (POSTFEKO) and go back to the preprocessor (CADFEKO) to find and fix them. Often the poor mesh is caused by poor CAD. Fixing the CAD is first prize, else you will need to fix the mesh. This video and this video should help.
  23. There was an issue with previous versions where a certain number of parallel processes did not report the triangle numbers to the out file. Please try a different number of parallel processes or just run the model with 1 process only. Then check the out file again if it reports the triangle numbers and find/view them in POSTFEKO.
  24. Are you sure you want to solve a model of size of around 17 mm from 16 to 23 Hz? Did you perhaps mean GHz? If so, then use 16e9 to 23e9 for the frequency.
  25. You can enable the Domain Green's Function (DGFM).
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