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.
- Set the model unit to millimetres.
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Define the following variables.
- d1 = 2.22 (Distance between apertures.)
- d2 = 12.51 (Distance between apertures.)
- epsr = 2.2 (The relative permittivity of the substrate.)
- s = 10 (Length of the aperture.)
- w = 4.6 (Width of the microstrip.)
- strip_feed_arc_radius = 2*s (The radius of curved microstrip line.)
- strip_length = 2* s + d2 + d1 (The straight section length of the microstrip line.)
- substrate_depth = 50 (The substrate depth.)
- substrate_height = 1.58 (The substrate height.)
- substrate_width = 140 (The substrate width.)
- f_max = 5e9 (The maximum frequency.)
- f_min = 2.5e9 (The minimum frequency.)
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Create a dielectric medium.
- Dielectric loss tangent: 0
- Relative permittivity: epsr
- Label: substrate
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Create the straight section of the microstrip line.
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Create the feed section of the microstrip.
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Create the arc section of the microstrip.
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Create a line.
- From: (0, -strip_feed_arc_radius-w/2, 0)
- To: (0, -strip_feed_arc_radius+w/2, 0)
- On the Workplane tab set the Origin: (strip_length, strip_feed_arc_radius, substrate_height
- Pathsweep Line1 on outer_circle.
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Union all parts.
The resulting geometry represents half of the top microstrip section.
Figure 1. Geometry after Union operation.
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Copy and rotate Union1 by 180°
around the U axis.
Note: The new part represents half of the bottom microstrip.
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Create the ground plate.
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Create an aperture.
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Create a second aperture.
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Subtract aperture_1 and
aperture_2 from ground_plate.
The resulting geometry is a ground plane between two microstrip lines with two square holes.
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Copy and mirror all geometry around the VN plane.
Figure 2. Geometry after the copy and mirror operation.
- Union all the parts.
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Set all faces to perfect electric conductor (PEC).
Tip: Faces set to PEC remain PEC when becoming faces of a dielectric region.
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Add edge ports.
- Port1
- Define an edge port between the bottom microstrip feed on the negative X side and the ground plate.
- Port2
- Define an edge port between the bottom microstrip feed on the positive X side and the ground plate.
- Port3
- Define an edge port between the top microstrip feed on the negative X side and the ground plate.
- Port4
- Define an edge port between the top microstrip feed on the positive X side and the ground plate.
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Create two substrate layers.
- Union all the parts in the model.
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Activate the FDTD solver.
Tip: Open the Solver settings dialog and click the FDTD tab. Select the Activate the finite difference time domain (FDTD) solver check box.
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Set the frequency.
- Linearly spaced discrete points
- Start frequency (Hz): f_min
- End frequency (Hz): f_max
- Number of frequencies: 101