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Derek Campbell

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Everything posted by Derek Campbell

  1. 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. 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. The airbox is definitely absorbing energy. The user is still required to verify accuracy. Users should always first work through a mesh convergence study to verify accuracy. Sometimes during this process the results do not converge regardless of how small the mesh elements become. One solution during this scenario is to enlarge the airbox. If the results change with respect to airbox dimensions, then this behavior is typically a clue that the airbox was too small.
  4. FEM uses an airbox that is called an Absorbing Boundary Condition (ABC). The air is responsible for absorbing all frequencies, all polarizations and all angles of arrival. MoM exploits the tangential component of the electric field converging to 0 as the field approaches a perfect electric conductor (PEC). The rule can also be massaged to account for dielectric materials and finite conductivity metals. The FEM airbox can have difficulty completely absorbing energy across all scenarios and especially grazing angles. Energy then reflects off the airbox and back into the simulation, which corrupts the results. The solution is to then make the airbox bigger at the cost of additional computational resources. MoM does not have this limitation and can handle propagation analytically exact.
  5. Hi pmcardle: When surrounding an FEM simulation with an airbox, you most likely did not intend to also have Method-of-Moments (MoM) activated. By default, Feko will solve FEM simulations with a MoM/FEM hybridization. I would suggest navigating to the Solve/Run tab in CADFEKO, selecting Solver Settings and switching to the FEM tab of the respective dialog box. There is a checkbox to decouple MoM. The resulting simulation will be a pure FEM analysis. Regards, Derek
  6. Hi riiily, I see both a warning and an error message. I will first address the error message you encountered and then also suggest a solution for the warning that you did not mention. The mesh for any solver can be easily defined by selecting "Coarse", "Standard", "Fine" from the Create Mesh dialog box. However, I rarely use these general settings because a custom mesh is almost always more efficient/accurate. A custom mesh can also be defined for any solver including RL-GO. Please switch to the Mesh tab in CADFEKO and select Create Mesh from the left-side of the ribbon. A dialog box will appear that allows a user to select "Custom". Users can then define global mesh settings for mesh elements, which in your case will be triangle edge lengths. The advanced tab on this dialog box also allows more customization with regard to curved surfaces including whether curvilinear elements should be used. Curvilinear elements are available for RL-GO with some hidden consequences. A flat triangle can be used to approximate a curved surface, but each local triangle does not know the radius of curvature being approximated. A curvilinear element does know the local radius of curvature, so diffractions from these curved surfaces can be computed. Curvilinear elements allow less triangles and less resources to be used, but including diffraction components increases the computational resources. The total resources tend to be about the same order of magnitude with curvlinear elements potentially providing a more accurate answer. I would also recommend you upgrade to the latest version of FEKO (currently 2017.2). There is an option available to automatically select the angular increments to launch rays with several other hidden features for efficiency. Several of these features have been refined in more recent versions. You can activate the Auto feature by switching to the Solve/Run tab in CADFEKO, select Solver Settings from the ribbon and then switching to the High Frequency tab in the respective dialog box. Toward the bottom is a radial option that enables Auto Settings for a more user friendly experience. This suggestion should eliminate the warning toward the top of your OUT file. There is also a note stating you are using sequential processing (a single core). Every solver available in FEKO has parallel processing efficiently implemented. I would suggest multiple cores to achieve faster results. Regards, Derek Campbell Senior Application Engineer
  7. Hi Cris, Lua capabilities continue to be developed. At the moment, Lua scripting can only be used to build geometry parts in CADFEKO. In the future, we will have the ability to define all aspects of simulations from a script as well as record mouse clicks to create macros. Regards, Derek
  8. Thank you, JIF. I posted this question to test whether me following the forum would in fact send me E-mail notifications. I have not received a notification for my question or your answers. I'm not following this specific thread, but rather the entire FEKO forum. Should this be sufficient to receive notifications for all threads and the respective answers? I have also verified the settings in my profile are set to E-mail me notifications. CJ has asked me to contact you regarding this issue.
  9. Do AEs receive E-mail notifications when someone posts a question?
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