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 centimeters.
  2. Define the following variables.
    • epsr_a = 10.2 (The relative permittivity of the bottom layer.)
    • epsr_b = 2.54 (The relative permittivity of the top layer.)
    • f_min = 2.1e9 (The minimum frequency.)
    • f_max = 2.3e9 (The maximum frequency.)
    • lambda_a = c0/f_max/sqrt(epsr_a)*100 (The wavelength in the bottom layer.)
    • lambda_b = c0/f_max/sqrt(epsr_b)*100 (The wavelength in the top layer.)
    • d_a = 0.16 (The height of the bottom layer.)
    • d_b = 0.16 (The height of the top layer.)
    • patch_l = 4.0 (The length of the patch antenna.)
    • patch_w = 3.0 (The width of the patch antenna.)
    • grnd_l = 2*patch_l (The length of the substrate.)
    • grnd_w = 2.5*patch_w (The width of the substrate.)
    • feed_l = lambda_a (The length of the microstrip feed line.)
    • feed_w = 0.173 (The width of the microstrip feed line.)
    • stub_l = 1.108 (Length of the matching stub on the microstrip feed line.)
    • ap_l = 1.0 (The length of the aperture.)
    • ap_w = 0.11 (The width of the aperture.)
  3. Create a dielectric medium, bottom_layer.
    • Relative permittivity: epsr_a
    • Dielectric loss tangent: 0
    • Label: bottom_layer
  4. Create a dielectric medium, top_layer.
    • Relative permittivity: epsr_b
    • Dielectric loss tangent: 0
    • Label: top_layer
  5. Create the aperture.
    1. Create a rectangle.
      • Definition method: Base centre, width, depth.
      • Base centre (C): (0, 0, 0)
      • Width (W): ap_l
      • Depth (D): ap_w
      • Label: aperture
  6. Create the finite ground plane.
    1. Create a rectangle.
      • Definition method: Base centre, width, depth
      • Base centre (C): (0, 0, 0)
      • Width (W): grnd_w
      • Depth (D): grnd_l
      • Label: ground
  7. Create the aperture in the ground.
    1. Subtract aperture from ground.
    2. Rename Subtract1 to slotted_ground.
    The finite ground plane now has a hole at the centre where the aperture plate was defined.
  8. Create the patch.
    1. Create a rectangle.
      • Definition method: Base centre, width, depth.
      • Base centre (C): (0, 0, d_b)
      • Width (W): patch_w
      • Depth (D): patch_l
      • Label: patch
  9. Create the microstrip feed line.
    1. Create a rectangle.
      • Definition method: Base corner, width, depth
      • Base corner (C): (-feed_w/2, -feed_l/2 + stub_l, -d_a)
      • Width (W): feed_w
      • Depth (D): feed_l
      • Label: feed

An edge feed will be used to excite the model.

  1. Create a plate (via) that connects the ground plane and feed line.
    1. Create a rectangle at the end of the feed line in the XZ plane.
      1. Change the workplane origin to (-feed_w/2, feed_l/2 + stub_l, -d_a).
      2. Rotate the workplane by 90° around the U axis to create the rectangle in the XZ plane.
      3. Base corner (C): (0, 0, 0)
      4. Width (W): feed_w
      5. Depth (D): d_a
      6. Label: feedPort

A positive terminal and a negative terminal are required for the edge source.

  1. Split feedPort in the UV plane at (0, 0, -d_a/2).
    1. Rename the two resulting components to port_bottom and port_top.
  2. Union the parts and rename the resulting part to conducting_elements.
  3. Set all faces to PEC.
    Note: This step ensures that the faces will remain PEC after future union operations.
  4. Create the bottom dielectric layer.
    1. Create a cuboid.
      • Base centre (C): (0, 0, -d_a)
      • Width (W): grnd_w
      • Depth (D): grnd_l
      • Height (H): d_a
      • Label: bottom_layer
  5. Create the top dielectric layer.
    1. Create a cuboid.
      • Base centre (C): (0, 0, 0)
      • Width (W): grnd_w
      • Depth (D) (H): grnd_l
      • Height: d_b
      • Label: top_layer
  6. Union all parts.
  7. Set the region of the bottom layer to bottom_layer.
  8. Set the region of the top region to top_layer.
  9. Add an edge port between the two split components of feedport.
    • The positive face correspond to the face attached to the ground plane.
    • The negative face correspond to the face adjacent to the positive face.
  10. Create a voltage source. Add a voltage source to the port. (1 V, 0°, 50 Ω).
  11. Set a continuous frequency range from f_min to f_max.
  12. 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.