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Johan Huysamen

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  1. Dear @Haj Hassan I don't think it is currently possible to define SLL directly as an optimization goal in Feko, but it should be possible to define an indirect goal to achieve this. If you consider the gain of a 5-dipole linear array as in the graph above, you will see that the side lobe is defined as the maximum gain value outside the main beam. If we then minimize this value, we should reduce the SLL. We can achieve this by requesting a far field cut outside the main beam. In the example above this would be for Theta from 25 to 90 degrees. Let us call this far field request "Sidelobes": We can then define a goal as follows: This goal would then aim to reduce the highest peak outside the main lobe - which would reduce the SLL. It is important to note that the above goal does not consider the main beam gain value. If your optimization parameters might also affect your main beam gain, you would have to also include a goal to maximize your main beam gain or to optimize it to be equal to a required value. You might also have to play around with the "Weight" values of these two goals to achieve the best results.
  2. Dear Haj Hassan From your question I understand that you expect the near field and far field results to show the same type of behavior. In your model you request the near field values up to Z = 200mm. Given the size of your antenna (including the lens geometry), your near field request only covers the "near field" region surrounding the antenna. In the "reactive near field" close to the antenna you would not see radiating behavior in the fields and in the "radiating near field (or Fresnel) region" the fields would show radiating behavior, but the behavior would still vary based on the distance from the antenna. Only once you sample fields in the "far field" would the behavior show stable far field radiation. You would have to sample the fields at much higher Z values to see the "radiating far field" region that should then show similar behavior to the far field results. You could use a calculator such as the one below to determine the required distances. Remember to include the lens as part of your antenna when determining the antenna size dimension. https://www.everythingrf.com/rf-calculators/antenna-near-field-distance-calculator In the extreme case, if you were to request near fields with a spherical coordinate system at a radius of say 10m, you should see the same shape as for your far field request. Kind regards, Johan H
  3. Hi, You should be able to achieve this by setting the required geometry faces to have their "Face medium" as "Dielectric boundary"... For example: Create a Cuboid With the cuboid selected, expand the "Details tree" Set the cuboid region to be your dielectric Set the required PEC faces to be "Perfect electric conductor" Set the required dielectric-to-air interface faces to be "Dielectric boundary" The same process can be applied to your horn antenna geometry by first creating it as a solid (filled) geometry, setting the internal medium and then setting the required face properties. Kind regards, Johan H
  4. Dear ebdaculan (Provided that your antenna has a source applied) Efficiency is automatically available under the "Power" request data in POSTFEKO: You can add this request to a Cartesian graph and then select "Efficiency" under "Quantity" on the Result Palette (on the right-hand side in POSTFEKO). Note that the fficiency quantity would by default only include the effect of losses in the antenna. If you also want to see the effect of input mismatch on the efficiency, your should modify the "Power" settings (on the Source/Load tab in CADFEKO). Specifically you should select the "Incident power (transmission line model)" option and set the source power and the real and imaginary parts of the feed/source impedance: With these settings applied, the "Efficiency" quantity in POSTFEKO will include both the effect of losses and of mismatch. Kind regards, Johan H
  5. Hi Cris Yes, this is possible in CADFEKO. All (geometry) ports in Feko also have equivalent "mesh port" representations and you should be able to define these on your imported mesh. For example, if you have both geometry and an imported mesh in your CADFEKO model, and you select the option to create an "Edge port", CADFEKO would ask you if you want to create a "geometry port" or a "mesh port". If you only have an imported mesh, CADFEKO would open the mesh port creation dialog when selecting to create a port. One point to note is that the port creation requires mesh elements to be defined in the required labels. For example, to create an edge port on a mesh, you would have to have the mesh elements grouped into at least two "faces": one for the positive face of the port and one for the negative face. If you could provide more detail on your mesh and the type of port you are trying to create, we might be able to provide more detailed suggestions. Kind regards, Johan H
  6. Dear Haj Hassan I noticed in your CADFEKO model that the airplane id represented by separate (disconnected) faces. For accurate modeling, you would have to connect all these touching faces using the Union operation. The wing.stp file you included actually imports as a connected solid and you should therefore be able to use this geometry directly by simply importing and meshing it. At 10 GHz and using a "Coarse" mesh the airplane would require about 3.7 million mesh elements. Using the MLFMM for this model would require about 160 Gbytes of memory to solve. If you do not have access to a system with enough memory or if the run time requirement becomes prohibitive, you should consider using one of the high-frequency asymptotic solvers that Feko offers. You could consider the Physical Optics (PO), Large element Physical Optics (LE-PO), the Ray launching - geometrical optics (RL-GO) or even the Uniform theory of diffraction (UTD) options. These are applied under the Solution tab of the Face properties. Note that each of these solutions rely of different assumptions and the applicability of each technique would be affected by your application. It is not exactly clear from your CADFEKO model which results you would like to produce. Your current setup with the antenna illuminating the aircraft, would give you the radiation pattern of the antenna with some small perturbation due to the airplane. If you could clarify your application, we might be able to provide more detailed suggestions.
  7. Dear ankit321 For the CMA in Feko to calculate modal excitation coefficients (MECs) and modal weighting coefficients (MWCs), you must add a Characteristic Mode Configuration and select the Compute modal excitation coefficients (when sources are present) option: As these quantities are dependent on a source, also ensure that you have added a source to your Feko model. Note that MECs and MWCs were introduced in Feko with version FEKO Suite 6.3 and would therefore not be available in older version of Feko. Kind regards, Johan H
  8. Dear RF Engineer In your Feko model you are using the "Planar Multilayer Substrate" option to model an infinite substrate and ground plane. Could you please confirm that your CST results where also obtained using an infinite substrate/ground implementation? Kind regards, Johan H
  9. Hi celaleddin taylan From your three images it looks like you have changed the frequency ranges, but kept the number of frequency samples the same. If you then reduce the range, you sample the frequency more finely. The behavior you see is caused by the fact that the number of discrete frequency samples is insufficient to locate the minimum reflection coefficient. More samples (finer sampling) is required. I would suggest that you try the "Continuous (interpolated) range" option for the solution frequency: With this option Feko will automatically sample a sufficient number ot frequency points to accurately locate the minimum value (at the resonance point).
  10. Hi Kuzi From your description it sounds like you are trying to feed many antenna elements in an array. Please note that the SParameter configuration is specifically for requesting and calculating S-parameters between multiple ports. It is not intended for exciting antenna elements. This is done using a StandardConfiguration. For your application you should consider using the Finite Arrays tool: This allows you to create a single antenna element and then specific the number of array elements as well as the distribution (including the magnitude and phase of the element excitations). More information on this tool can be found under the Feko Help. You could also have a look at Example A17 of the Feko Example Guide. Kind regards, Johan H
  11. Dear sutton304803 Various options for infinite planes and (dielectric) half spaces can be selected through the "Plane / ground" option under the Construct tab in CADFEKO: This opens the "Plane / ground" dialog where you have various options. For your application you could use one of the two "Homogeneous half space in region Z<0" options or even the "Planar multilayer substrate" option if it is specifically required to have the top of the half space at any other value than Z=0. More information on these option can be found under the section "Infinite Planes and Half-Spaces" in the Feko Help (accessed by hitting <F1> in CADFEKO).
  12. Hi ynathan CADFEKO has an option to import one CADFEKO model into another. On the Home tab select Import -> CADFEKO model (*.cfx)... This will allow you to import various entities from one CFX file into your current model: There are also options to merge identical variables and media to ensure that you not have duplicate identical denifition as well as an option to add a prefix (text) to all the imported item labels to distinguish them from the original model items. Kind regards, Johan H
  13. Hi Patrick Theoretically a plane wave comes from infinity and is incident onto the geometry. The plane wave is applied as an excitation onto the geometry (mesh) in Feko. As such, it is applied to, and interacts with, the mesh where-ever there is a mesh element in the model. Similarly, when a (near) field result is requested, the plane wave will be considered in the calculation of that near field point where-ever required. Consider a Perfectly Electrically Conductive (PEC) sphere with radius r meshed into surface mesh triangles and solved with the default Method of Moments (MoM) in Feko. If we have an incident plane wave as excitation and we sample near fields say on a spherical surface at a radius of 2*r, the plane wave is applied as follows: Mathematically the plane wave excitation is evaluated at the positions of the mesh triangles and applied to the MoM solution matrix as an excitation (known as the right-hand side vector) The MoM is solved to compute the induced surface currents on the mesh triangles. The near fields are calculated by considering two contributions at each required near field request point: the (re)radiation of the induced surface currants and the contribution of the incident plane wave In effect then the plane wave does not have a physical extent. It is applied and evaluated by Feko where-ever it is required based on the mesh and requested results. Kind regards, Johan H
  14. Hi, You should set the thickness on each face to be the actual physical thickness of the conductor (and not half on each). Feko will model an equivalent surface current modified to account for the physical thickness as specified. Kind regards, Johan H
  15. Dear tmarinovic With your example I believe you are triggering: WARNING 40147: Near fields for spherical modes are computed in the cut-off region beta*R < N, reduce spherical wave order N or increase distance R Note that your OUT file should include details on the value for R for your specific example. In Feko the spherical mode source is intended as an option to represent an antenna installed on a large platform for efficient simulations of the installed performance of such an antenna. Here the focus is specifically on efficient far field calculations and not on near field sampling relatively close to the antenna. Details on Feko's implementation for spherical mode sources can be found under the "AS card" section starting on p986 of the Altair Feko User Manual. (UserManual.pdf located in the ..\help\feko\pdf folder of your Altair installation.) Unfortunately we are not able to go into more details regarding Feko's implementation - other than sharing this (publicly available) information. Kind regards, Johan H
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