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Torben Voigt

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Posts posted by Torben Voigt


  1. Hi @lostarmour,

     

    You should make all regions PEC and then use "Simplify". This deletes 24 (small) redundant faces:

    image.thumb.png.24f1e2de68d80b4ae68fdfa60e8b45b2.pngimg_057.png.2def504f26ca9a92784beec7d487a190.png

     

     

     

     

     

     

     

     

     

    Then I found out that these areas are the tricky parts:


    img_060.png.2131db4714bb816544205faf955b2df6.png        img_061.png.8565b0dd9cefc5940aedc83714896ef8.pngimg_059.png.43d6aa2e41dc730f008af4811ae9881b.png

    I closed these two and now it works 9,072 triangles (compared to 51,554 in the original model): 08262019_Feko_two_blades_alt.cfx

     

    It solves in a couple of minutes. Please make sure to refine the mesh slightly and compare the results. This is just an example.


  2. Hi @Marcus Chang,

     

    20 lambda is just a rough estimation for RL-GO, it always depends on the model.

    Your model seems ideal for PO or LE-PO (only one interaction on the reflector). The solution should be quite accurate. RL-GO would work but it will require much more time because the near field source will be transformed into a spherical modes source first (and same for the Rx antenna). 

    Just apply PO (full ray tracing) to the reflector face and you should be good. Also compare with LE-PO (full ray tracing).


  3. Hi @Haj Hassan,

     

    interpreting the far field in a lossy halfspace unfortnately isn't easy. When using the Reflection Coefficient Approximation for example, FEKO deactivates the computation of far fields below z=0 completely. In principle the far field in FEKO is computed in an infinite distance by neglecting the term exp(-j*beta*r)/r. bet however is different for the two media..

     

    I would suggest to rather calculate near field values in a certain distance if you're really interested in the field below ground.


  4. 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?


  5. 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.

    image.png.c24502627dbf028f2eb3ef25c07179b6.png


  6. Hi @Marcus Chang,

     

    the code temp.lua seems to work. It successfully adds 3 NearFieldData in CADFEKO:

    image.thumb.png.cf66ed0fb86a48afa0ac85c9ad8b63d7.png

    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!

     


  7. 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


  8. 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

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