Creating the Model

Create the model in CADFEKO. Define any ports and sources required for the model. Specify the operating frequency or frequency range for the model.

  1. Set the model unit to millimeters.
  2. Define the following variables:
    • epsr = 9.5 (The relative permittivity of the substrate.)
    • r = 0.63 (The radius of the feed element.)
    • hBig = 1 (The height of the feed base.)
    • rBig = 2.25 (The radius of the feed base.)
    • rDisk = 60 (The radius of the ground.)
    • rDome = 12.5 (The radius of the inner dome.)
    • rDomeBig = rDome + 5.5 (The radius of the outer dome.)
    • h = 7 (The height of the feed element.)
    • fmin = 3e9 (The minimum frequency.)
    • fmax = 6e9 (The maximum frequency.)
    • lambda = c0/fmax * 1000 (The wavelength in free space. [mm])
  3. Define a named point:
    • excite_b: (0, 6.5, -1)
  4. Define a dielectric medium, air.
    • Relative permittivity: 1
    • Dielectric loss tangent: 0
    • Label: air
  5. Define a dielectric medium, dome.
    • Relative permittivity: epsr
    • Dielectric loss tangent: 0
    • Label: dome
  6. Define a dielectric medium, isolator.
    • Relative permittivity: 2.33
    • Dielectric loss tangent: 0
    • Label: isolator
  7. Create a new workplane.
    • Origin: excite_b
    • Set the new workplane as the default workplane.
  8. Create the outer conductor for the feed pin.
    1. Create a cylinder.
      • Radius (R): rBig
      • Height (H): hBig
      • Label: FeedBase
  9. Create the inner conductor for the feed pin.
    1. Create a cylinder.
      • Radius (R): r
      • Height (H): hBig + h
      • Label: FeedPin
  10. Union the two cylinders.
  11. Set the regions that make up the central feed pin to air.
  12. Set the region that makes up the feed base to isolator.
  13. Set the default workplane to Global XY.
  14. Create the finite ground plane.
    1. Create an ellipse.
      • Radius (U): rDisk.
      • Radius (V): rDisk.
  15. Create the outer dome.
    1. Create a sphere.
      • Radius: rDomeBig.
      • Label: OuterDome.
  16. Create the inner dome.
    1. Create a sphere.
      • Radius: rDome.
      • Label: InnerDome.
  17. Union all parts and rename Union to DRA.
  18. Delete the bottom halves of the dome.
  19. Set the region of the inner dome to dome.
  20. Set the region of the outer dome to air.
  21. Set the solution method for all regions to FEM.
    Tip: Open the Region properties dialog and click the Solution tab. From the Solution method list, select Finite Element Method (FEM).
  22. Set all faces in the model to PEC.
  23. Set the following faces to the Default face medium.
    • The top and bottom faces of FeedBase.
    • The remaining faces of the dome.
    • The single face inside Feedpin.
  24. Use the Simplify transform to remove redundant faces and edges in the model.
  25. Add a FEM modal port to the bottom face of FeedBase.
  26. Add a FEM modal source to the FEM modal port.
  27. Set a continuous frequency range from fmin to fmax.
  28. Specify the symmetry about the X=0 plane as Magnetic symmetry.
    Tip: Exploit model symmetries (if it exists) in a large or complex model to reduce computational costs.