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Torben Voigt

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Everything posted by Torben Voigt

  1. Hi @Kuzi, To save time it would be good to also have these files: fek, bof, out.
  2. Hi @Kuzi, this doesn't seem to be the correct model. In your pics I see an antenna structure and also a polar plot of far field results. In the attached model only a plane wave excitation is present and the far field request is set to "Calculate fields in plane wave incident direction". Could you please check?
  3. Hi @bouvy, Does running a simulation from CADFEKO work?
  4. Hi @Kuzi, I think there are methods to calculate the RCS based on radiated near field results (near field to far field transformation). I don't know details about it, but Dr. Andre Rennings may have some knowledge here.
  5. Hi @designer, I don't see a problem here. When you select all your mesh parts in CADFEKO and then go to Export -> Mesh -> Gerber mesh, the exported *.gbr file seems to be correct:
  6. Hi @SUG, FEKO assumes wires to be thin. This means that a segment (= mesh part of a wire) should not be shorter than 5 times the radius of the wire. Else using cylinders is recommended. Looking at your screenshot, you should clearly model the coil as a cylinder. The attached model shows the idea. coil.cfx
  7. Hi @Kuzi, I can only see a small part of the polar plot. Are you sure that the main lobes are in the theta = 180° direction? Could you attach the files (cfx, fek, bof, out)?
  8. Hi @SUG, New FEKO user will find very helpful examples in the ExampleGuide.pdf and basic knowledge in the GettingStarted.pdf:
  9. Hi @Dimon, Presently diffraction effects from edges and wedges of RL-GO PEC faces meshed with curvilinear triangles are supported.
  10. Hi @Yasaman, the layered dielecrics are very thin comared to the wavelength: I don't think you will be successful wit MoM. It may be feasible to use FEM instead. I attach a FEM version of the model but you will need to see if reducing the mesh size of the thin dielectric layers changes the results. full_turnstile_fixed_FEM.zip
  11. Hi @Kuzi, You may use a Parameter Sweep for the varying height. In POSTFEKO the horizontal axis could then be height.
  12. Hi @Marcus Chang, No, in FEKO you will always have one mesh (= one geometry) per model. You can of course use the Parameter Sweep to automatically create different models.
  13. Hi @Lydia He, these are just comments (not warnings). They say that you can increase the speed of your simulations by activating parallel computation and also that the former *.str file has been re-written. FEKO stores the currents in *.str files so that they can be re-used in later simulations of the same model, if e.g. different requests are made.
  14. Hi @Marcus Chang, I don't think that the extension (efe / hfe) are needed. However, you can do it like this: properties.EFieldFilename = "02_NF source_PEC corner reflector_190406_sphere placed 72 lambda_alt_NearField_"..i..".efe" properties.HFieldFilename = "02_NF source_PEC corner reflector_190406_sphere placed 72 lambda_alt_NearField_"..i..".hfe"
  15. Hi @Marcus Chang, the code temp.lua seems to work. It successfully adds 3 NearFieldData in CADFEKO: What's still missing is the "Start reading from line" which is 1 in all cases. You should change line 15 properties.ReadFromLine = "1" to properties.ReadFromLine = "1+(20*20)*"..(i-1) 20 is the number of field points in x and y, so this will ensure that the starting number will be like 1, 401, 801. Hope this helps!
  16. Hi @Marcus Chang, Here you go: 2018.zip Please install FEKO 2019 soon. It's hard to provide support for different versions.
  17. Hi @Marcus Chang, It's not necessary to use EDITFEKO for this anymore. In principle you need one configuration per frequency. Also you need one Field data per configuration. Please have a look at the attached CADFEKO script. It imports field data and makes sure that the "start reading from line" is correct It creates near field sources it sets the right frequency ... It was all created using Macro recording and a little editing. You can use it and fit it to your model. Open base_model.cfx and run the script from there, it should give you some insight in the process. base_model.cfx MacroRecording_1.lua antenna_only_nf_export.efe antenna_only_nf_export.hfe
  18. Hi @Roberto7, Incident electromagnetic beam: Unfortunately I don't think the simulation files from the video are available for download. The principle workflow is Open POSTFEKO and create a time signal (Gaussian pulse). This will allow you to determine fmin and fmax for the simulation in the frequency domain. (see this video for a quick introduction to FEKO time analysis: https://securefiletransfer.altair.de/link/yczV6Lp0HH6ObscNdRiyBF) Create the model in CADFEKO, use a plane wave excitation. Set fmin = duration of timesignal and fmax = fmin * no. of samples Use continuous frequency range, ideally this will decrease the runtime for large frequency ranges. Note, your model will be electrically large, so expect large memory usage and long runtime with full wave solvers (e.g. MLFMM). You will probably have to switch to asymptotic solvers (PO, LE-PO, RL-GO or UTD). Note, this doesn't seem like a beginner's application, but still doable Anechoic chamber: Simulating an anechoic chamber is a very demanding task, due to the excessive geometry and highly lossy media. Especially at higher frequencies you will quickly reach hardware limitations. You may just give it a try by modelling afew of the pyramids and investigate the computational requirements. In many cases the reflection coefficient of absorbing walls is -40 dB and less and so they can probably be neglected in the model. Of course OPTFEKO (built-in optimiser) can be used on building scale as well. PS: Talking of buildings, maybe WinProp is the better suited software for you? -> WinProp
  19. Hi @YMERGURRA, If you only have access to the Student version, I'm afraid you won't be able to export the geometry in any other format than Parasolid. Maybe you find some converter tool Parasolid -> Gerber in the internet?
  20. Hi @Kuzi, the original element in the center will not be considered in the simulation. You can see it as a template for the array elements. If you have a look at POSTFEKO you can see it's not visualized:
  21. Hi @sutton304803, You might want to try modelling the twisted pair cable like in the attached example (helix + coating): patch_twisted_pair.cfx
  22. Hi @Marcus Chang, For the corner reflector you're using PO, but with PO no multi-reflections between PO faces are taken into account. A corner reflector is THE classical example where PO is not feasible. Furthermore, the asymptotic methods (PO, LE-PO, RL-GO and UTD) are only feasible if the model is electrically very large, e.g. 20 lambda, bigger is better, but the corner reflector is only around 4 lambda. You should definitele use MoM / MLFMM here. Same goes for the sphere, which is only 3 lambda in radius. When calculating the scattered field of the reflector and the sphere correctly (MoM), the received power of the reflector is around 10 times higher than that of the sphere.
  23. Hi @Marcus Chang, If you get identical far field results for both, then I assume you have in addition "Calculate only the scattered part of the field" activated: This will in this model of course give the same results, as the sphere is the only scattering object. So, in both cases you will get the scattered field from the sphere surface.
  24. Hi @Marcus Chang, Unfortunately I'm not sure about the Matlab code. Maybe someone else (@mel, @JIF) could have a look? You can get the far field pattern of the reflected field of sphere by doing this: This will then only use the contribution of the surface currents of the sphere.
  25. Hi @Marcus Chang, Let check what you did: In horn_X band_190309.cfx you calculate and save the near field and the far field of the horn antenna. In FF source_PEC sphere_sphere surface NF source_190312.cfx you replace the horn by the near field data from 1. and to illuminate a PEC sphere. Here's mistake #1: The orientation of the near field is wrong (the horn is looking downwards): This would be correct: Mistake #2: The near field data is placed at z=0, while in model 1. it is placed at z=0.2138m. Around the PEC sphere you request a new near field to capture the radiated field from that sphere. Here's the mistake #3: The near field request has the same radius as the sphere, so the near field point are calculated exactly on the PEC surface. For acurate near field results a field point should not be closer than 1.5 x the edge length of the surface mesh. In temp_190313.cfx you compare the received power of an RX near field antenna and an RX far field antenna. The results are different because of mistake #2 and also because of warning WARNING 39270: A receiving antenna described by a far field pattern is positioned too close to a scatterer, far field condition not met. It says that that a source (the field of the PEC sphere) is too close to the RX far field receiving antenna. In general for far field sources (or receiving antennas) a far-field radius should be considered. I also decreased the increment beween the near field points of model 1. to ensure accuracy. The final results agree quite well: Note, with larger distance between source and RX antenna (or plane wave instead of the near field of the PEC sphere) the difference would be around 0.2 dB, because of omitting Warning 39270. The three new model files are attached: NF_vs_FF_RX_antenna.zip
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