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oussama1

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  1. oussama1 liked a post in a topic by Derek Campbell in How can we add an aperture into curvature surface?   
    You could project a slanted rectangle onto the outer cylinder. Select and copy the new face. Sweep the face to create a volume and subtract that volume from the cylinder. Repeat with an orthogonal rectangle. This should naturally leave you with the diamond shaped faces. Next, subtract a cylinder with a smaller radius from the bigger cylinder. Repeat with slanted rectangles on the inside. Finally, select, copy and sweep the diamond-shaped faces even deeper than the slanted rectangles to cut a hole through the outer conductor.
     
    Once you have swept a single diamond-shaped face, I would try copy and translating that volume down the length of the cylinder. Ideally, that volume would perfectly overlap the other diamond-shaped faces. This allows you to subtract the volumes from the outer conductor, but more importantly it could all be automated with a Lua script.
  2. oussama1 liked a post in a topic by Derek Campbell in How can we add an aperture into curvature surface?   
    I would suggest creating a circle on the Construct tab in CADFEKO and then use the Copy + Rotate feature to replicate the circle around the circumference of the cylinder. You could then use the Copy + Translate feature to replicate the circles along the length of the cylinder. If you want to get fancy, you could write a Lua script that Copies, Translates and Rotates each set of circles. The circles can be Projected onto the cylinder and finally deleted. Please note there will be some warping, because the Project feature is not a Bend feature.
  3. oussama1 liked a post in a topic by mel in The terminals of shielded cable   
    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.)

  4. oussama1 liked a post in a topic by mel in The terminals of shielded cable   
    >> 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.
  5. oussama1 liked a post in a topic by mel in The terminals of shielded cable   
    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.
  6. oussama1 liked a post in a topic by JIF in Simulating 4D antenna array (time modulated array)   
    Hi
    This is possible and is exactly what time analysis in POSTFEKO does. The analysis is based on FFT/IFFT and thus the signal is inherently periodic (you can't avoid it).
  7. MvdM liked a post in a topic by oussama1 in microstrip antenna array simulation   
    thank you so much, I really appreciated your help  and suggestions
  8. oussama1 liked a post in a topic by MvdM in microstrip antenna array simulation   
    To answer the second question in your original post:
     
    At the moment, for touching elements you need to build the geometry without using the array tool. Union the parts to ensure mesh connectivity. You can use copy and translate, but you would have to define the individual ports and voltage sources for each element.
    See this example for 2 elements: E_antenna_arra_2_elements_shared_dielectric.cfx.
     
    It would be easy to automate this process in a more current version of Feko.
  9. oussama1 liked a post in a topic by MvdM in microstrip antenna array simulation   
    The problem, for the version you are using, is the dielectric. The Domain Green's function method for fast array synthesis initially did not support dielectrics. This method was extended in Feko 14.0.430 to support dielectrics modelled with the Method of Moments using the surface equivalence principle (SEP).
  10. oussama1 liked a post in a topic by MvdM in microstrip antenna array simulation   
    No error appears in my simulation of your model, E_antenna_arra_1.cfx. I used version 2018.1.2.
     
    To solve this model in an older version, you cannot use the fast array method.
     
    On the ribbon in CADFEKO, go to the Solve/Run tab and select "Solver settings". Deactivate "Solver model with the Domain Green's Function Method (DGFM)".
     

     

     

     
  11. oussama1 liked a post in a topic by mel in Calculating the capacitance and inductance in FEKO   
    You can export these parameters to the *.out file.
     
    Presently this option can only be enabled in EDITFEKO under the CS card. 
    Basically after setting the up your model and meshing it in CADFEKO, from there, run EDITFEKO. Find the CS card(s), click on them and hit F1 to edit, and check the box "Export cable parameters to *.out file", save and run FEKO.
     

  12. oussama1 liked a post in a topic by JIF in How can we use FEM line port   
    Hi
    Based on your image, it looks like the source you are looking for is the "impressed current source" or a wire with a voltage source on it. As Peter said, have a look at the examples.
  13. oussama1 liked a post in a topic by Peter Futter in How can we use FEM line port   
    Hi @oussama1
     
    The FEM line port is to be used with the FEM solver. If you want to excite an wire/edge and are not using FEM then you can use the Edge port. Have a look through the example guide for more examples covering this. 
  14. oussama1 liked a post in a topic by Peter Futter in Field-to-Wire-Coupling without Modeling the input and output terminals   
    hello,
    thanks for sharing the additional detail.
    I think that your original approach was correct - using general networks. Simulate the S-parameters for the terminal geometry, export the touchstone file and use this in a general network connected to the wires for the simulation with the plane wave.
    have a look at the Examples guide for a similar workflow: E-4 Subdividing a model using non-radiating networks
     

  15. oussama1 liked a post in a topic by Peter Futter in Field-to-Wire-Coupling without Modeling the input and output terminals   
    Hi @oussama1
     
    to clarify my understanding of your question - what is the incident waves that you refer to, is the circuit exposed to an external plane wave source? It might help if you attach the .cfx file.
  16. oussama1 liked a post in a topic by mel in MoM singularities problems   
    Remove the infinite ground. For the FDTD boundary set a PEC boundary at the bottom and the other ends of the bounding box keep on default.
    You will need a fine mesh to ensure enough voxels due to the small wire-wire spacing.
    I used a GPU, else the solution time would be a few hours. Memory was about 2.5 to 3.5 GB depending on the mesh.
  17. oussama1 liked a post in a topic by mel in MoM singularities problems   
    Have refined the MoM mesh and also used the FDTD solver (not necessarily the best mesh solved, since server time is limited) but results are in reasonable agreement. 
     
    I concur with JIF. This is a characteristic of the model. See attached image.
     
     

  18. oussama1 liked a post in a topic by JIF in MoM singularities problems   
    oussama1,
     
    I think these resonances are "real" and this is not a problem in the MoM. I can't think what would be causing them, but if I think of something, I'll let you know. Maybe someone else on the forum has an explanation for you.
  19. oussama1 liked a post in a topic by JIF in MoM singularities problems   
    Could you add the model(s) to the forum? That saves me time, since I don't have to rebuild the models (and I could make an error while building them). Once you have added the models, I'll have a closer look.
  20. oussama1 liked a post in a topic by JIF in MoM singularities problems   
    Hello oussama1,
     
    If you would like us to take a look, the best is to provide the model so that we can do investigations.
     
    Since I don't see the model on the issue, I'll make suggestions for you to investigate.
    Zoom in on the area that you suspect has a problem (around 150 MHz, 440 MHz), etc. - you only need to investigate one of these for now. Reduce the frequency range around the "problem area" and increase the number of frequency points. Keep zooming in in by reducing the frequency range more and more. If there seems to be a jump in the results from one frequency to the next, it could be a solver problem, but if the results remain the same, it might not be a solver problem at all. (We have seen cases in the past where users think there is a problem with the solver and then it turns out to be a physical phenomenon.) Have you performed a mesh conversion study? Refine the mesh and see if the results remain the same. As I said, if you provide the model, we can have a closer look.
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