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:
    • a1 = 15.8 (width of Ku section.)
    • b1 = 7.9 (height of Ku section.)
    • l1 = 12 (length of Ku section.)
    • a2 = 22.9 (width of X section.)
    • b2 = 10.2 (height of X section.)
    • l2 = 12 (length of X section.)
    • fmin = 9.4872e9 (minimum calculation frequency.)
    • fmax = 15e9 (maximum calculation frequency.)
    Note: fmin is just above the cutoff frequency for the Ku band waveguide section.
  3. Create the Ku band section.
    1. Create a cuboid
      • Base corner (C): (-a1/2, -l1, -b1/2)
      • Width (W): a1
      • Depth (D): l1
      • Height (H): b1
  4. Create the X band section.
    1. Create a cuboid.
      • Base corner (C): (-a2/2, 0, -b2/2)
      • Width (W): a2
      • Depth (D): l2
      • Height (H): b2
  5. Union both cuboids.
  6. Set the both regions to free space.
  7. Simplify the part.
    Tip: The simplify tool will remove the face at the junction between the two cuboids. Alternately, use face selection to manually delete this face. The free space setting will change the region from solid PEC to vacuum.
  8. Rename the face at the end of the Ku band section to Port1 and the face for the X band section to Port2.
  9. Add waveguide ports to the faces with labels Port1 and Port2.
    Tip: To calculate the magnitude of the coupling, the phase is not required. For accurate phase results the reference vector needs to be set with the same orientation for both ports.
  10. Check that the propagation direction of each waveguide port is set inwards.
  11. Set the frequency.
    • Continuous interpolated range.
    • Start frequency (Hz): fmin
    • End frequency (Hz): fmax
  12. Set magnetic symmetry in the X=0 plane and electric symmetry in the Z=0 plane.