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FieldForcer

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  1. Hi Torben, Thanks for the reply. Because original signal is a 2 ms, and the pulse is only 290 us. Reducing signal duration is not a design option. Multiplication of time signal with rect window (though a Bartlet window is preferable) can be done, if there is a predefined rect() function in POSTFEKO.
  2. Hi Mel, I converted surface mesh (stl) model of BrainWhiteMatter to tetrahedral mesh(wrl) in Gmsh. Following were the options to export volume mesh: Then I imported BrainWhiteMatter.wrl mesh in FEKO. and received following error: Clearly this wasn't a good format for volume mesh. Which format should I use? It seems that Gmsh can import other formats. If I want to select few elements, and measure total volume, it might be possible to do it in Gmsh.
  3. Hi Torben, I attempted suggested method, and results of surface current density get inconsistent. The method yields inaccurate results. Most importantly, from simulation viewpoint, it requires lot of core hours to re-run entire simulation to estimate surface area. I am wondering if there are any freewares where I can export result file, and pick elements to calculate surface area.
  4. Hi Torben, When I click on mesh, these do not show as triangles, rather as quadrilaterals. How is triangles ID related to quads? How can this be done? Please elaborate method.
  5. Hi Torben, I want to know the vertices because l wish to calculate area of triangles with red color in POSTFEKO. To this end, I can find triangle ID in POSTFEKO. Next I look for their vertices in some FEKO file, and write a subroutine to calculate area occupied by these triangles. How can this be done? Also faces can be selected in CADFEKO. So I already know face number. Here I used selection tool to select an arbitrary face, and I can read face number is 30890. Still there is no information about area of selected face. When I choose multiple faces, I still can't measure combined face area. Do you understand ?
  6. As I understand, each triangle is made by three vertices. For each triangle ID, there should be three X, Y, and Z coordinates. Here there is only one X, Y and Z coordinates for each triangle ID. Earlier you mentioned that these coordinates represent center point of each triangle. Is it possible to directly measure area of triangles in POSTFEKO by sequentially selecting them ?
  7. Hi Torben, Area covered by each triangle can be computed from three points that form each triangle. These are not equilateral triangles. Location of three vertices is not mentioned in Currents.os file. How to obtain location of three vertices/points that form each triangle in POSTFEKO? Vielen Dank, FieldForcer
  8. Dear all, I have Currents.os file. First column contains triangle element number. These are present in increasing order in Currents.os as shown in an image excerpt below. Next three columns contain X-, Y- and Z-position of triangles. What location in triangles do these X-, Y- and Z-position refer to? Also I have attached complete file in the post. Thanks, FieldForcer Currents.tar.xz
  9. Hi mel, I don't have wave-guide port, and video suggests using FEM modal port. Does it mean I change voltage port to FEM modal port? Also video mentions applying FEM to dielectric regions, but that option is unavailable in Properties of brainwhitematter mesh. What am I missing? Is there a method to define better mesh, and apply FEM/MoM solver? Figures8Coil_MIDA.cfx
  10. Hi Torben, With Use model mesh option, remeshed geometry has too many triangles. I agree with mel. This simulation will require enormous RAM. When I executed simulation, I received following error: I tried to find if something is wrong with geometry, and if mesh could be repaired with following options. No clashes were detected.
  11. Hi mel, Your presumption is correct. I changed Front medium to Free Space, and turned off Low Frequency Stabilization in Solver Settings because low frequency stabilization and dielectric bodies (SEP) are not allowed in the same model. Mesh gives same warning as before meaning I dont' have control over mesh of BrainWhiteMatter. When I execute simulation, solution requires enormous memory because BrainWhiteMatter mesh is too fine. I used coarse mesh for wires, and can't play with White_Matter mesh. How to scale down memory requirement? Thanks, FieldForcer P.S.: Attached is updated cfx file. Figures8Coil_MIDA.cfx
  12. Hi, I executed a time-domain simulation on a brain skull. And I get following result. In POSTFEKO, I want to select elements that have magnetic field value above a threshold. How can elements above a threshold value be selected in POSTFEKO? How can surface area and volume of these elements be calculated in POSTFEKO? Units of Surface Current Magnitude can't be displayed in POSTFEKO. 3.How can units of surface current be displayed? FieldForcer
  13. Hi, I imported a mesh from stl file in CADFEKO. When I right click on properties of this geometry, it shows that Front and Back medium are assigned White_matter property, but Face Medium is set to arbitrary Dielectric boundary. I didn't define Dielectric boundary, but I did define White_matter property. Problem is Face medium drop down list does not show White_matter, and I can't select it. As a result mesh has some arbitrary Dielectric boundary. When I mesh model, I receive a Warning 16097. Next, I executed a frequency sweep solution with following option: CEM validate didn't detect any issue. After execution, the solution obtained doesn't show any mesh. What is solution to such a problem? I have attached both cfx, pfs, and stl file. Thanks in advance, FieldForcer P.S.: Earlier Peter Futter suggested I write lua script. I don't understand workflow of writing such a file to solve mesh issue. Figures8Coil_MIDA.cfx Figures8Coil_MIDA.pfs Brain_White_Matter.stl
  14. Hi Torben, Wires thinner than 0.8mm are not used in antenna design. I can't think of a reason to used 0.25mm wire unless there is a bundle of 8 such wires. Loop implies a closed circuit. Antenna examples (ref. FEKO user manual) directly apply voltage source, without closing circuit for feed-wire. I did the same, if that is what you referring to being unrealistic. By default, PEC ground plane is created at z=0 only. I can't create a PEC plane at side of the port. This time again CEM validate didn't detect any error. But while execution, job was terminated with ERROR 39138: Invalid specification of an infinite ground plane: geometry not allowed below the plane surface I had to shift entire model above z=0 plane, and then I didn't receive any error. Addition of PEC plane didn't affect surface current, and gain increased to 10. Still origin of lobes is by default at center of coordinate system, and not center of reflector. Antenna can't gain from receiving direction. Can antenna designer here on Forum, help with realistic design in CADFEKO ? Thanks, FieldForcer
  15. Hi Torben, That's a good suggestion. Currently lambda ≈ 29.9mm, and segment length = lambda/12 ≈ 2.5mm. That gives wire radius of 1mm < 2.5mm. CEM Validation works for 0.7mm radius, but not for 0.8mm. What wire radius will be realistic? I do want to make it realistic. I guess you are suggesting that loop should close for current to return back. However I checked back with design given to me, and it doesn't have a path for return current. I looked at the result for wire-radius = 0.7mm, and x=0 geometric symmetry. Lobes indicate that there is minimum total gain along x-axis, and maximum total gain along z-axis. I would expect that when feed-wire is excited, electromagnetic waves travel towards reflector, and as a result, there should have been minimum gain along y-axis. I am missing out sth crucial. Why don't simulation give zero gain along y-axis? Thanks, FieldForcer
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