RF 003 - Patch antenna

Demo project

RF patch antennas are widely used in various modern wireless communication systems, from smartphones and laptops to satellites and radar systems. Their compact size, lightweight design, and ease of integration make them a popular choice for engineers. However, designing an efficient and reliable RF patch antenna requires careful consideration of various factors such as operating frequency, bandwidth, gain, and radiation pattern.

Simulation plays a crucial role in the design process, allowing engineers to virtually prototype and optimize antenna performance before physical fabrication. This example demonstrates how Quanscient Allsolve can be used to simulate an RF patch antenna, covering the entire workflow from modeling and simulation setup to running the simulation and analyzing the results. By following this example, you will gain valuable insights into the simulation of RF patch antennas and learn how to leverage Quanscient Allsolve’s capabilities to design and optimize your own antenna systems. This knowledge will enable you to tackle real-world antenna design challenges and develop innovative solutions for various wireless communication applications.

Simulation setup guide

Here you’ll find a simplified, example case level guide for setting up a patch antenna simulation in Quanscient Allsolve.

Step 1 - Define shared expressions

Start out in the Properties section by defining the following shared expressions:

Name	Description	Expression
Ls	Substrate length [m]	95.12e-3
hs	Substrate height [m]	1.57e-3
L50	50 ohm transmission line length [m]	15e-3
W50	50 ohm transmission line width [m]	4.84e-3
ht	Track height [m]	1e-4
Lqw	Quarter wavelength transformer line length [m]	24.05e-3
Wqw	Quarter wavelength transformer line length width [m]	0.72e-3
L	Patch length [m]	41.08e-3
W	Patch width [m]	L
epsilonR	Substrate dielectric constant (relative permittivity)	2.2
freq	Frequency [Hz]	2.35e-3

Step 2 - Build the geometry

1. In the Model section, start building the model by adding Box elements:

Name	Element type	Center point [m]	Size [m]	Rotation [deg]
substrate	Box	X: 0	X: Ls	X: 0
		Y: 0	Y: Ls	Y: 0
		Z: -hs/2	Z: hs	Z: 0

Name	Element type	Center point [m]	Size [m]	Rotation [deg]
50ohm	Box	X: -Ls/2+L50/2	X: L50	X: 0
		Y: 0	Y: W50	Y: 0
		Z: ht/2	Z: ht	Z: 0

Name	Element type	Center point [m]	Size [m]	Rotation [deg]
qw	Box	X: -Ls/2+L50+Lqw/2	X: Lqw	X: 0
		Y: 0	Y: Wqw	Y: 0
		Z: ht/2	Z: ht	Z: 0

Name	Element type	Center point [m]	Size [m]	Rotation [deg]
patch	Box	X: -Ls/2+L50+Lqw+L/2	X: L	X: 0
		Y: 0	Y: W	Y: 0
		Z: ht/2	Z: ht	Z: 0

2. Use the Surface rectangle operation to define a port on the substrate boundary in the negative X-plane. First, pick points for the local coordinate axes as shown below:

Name	Element type	Main axis	Secondary axis
port surface	Surface rectangle	Origin: left bottom corner point (12)	Point: right bottom corner (point 11)
		End point: left top corner (point 10)

To make a rectangle like above, use these values for offset and size:

Offset	Size
Main: 0	Main: W50
Secondary: -hs	Secondary: hs

3. Finally, add an airbox around the geometry:

Name	Element type	Center point [m]	Size [m]	Rotation [deg]
airbox	Box	X: 0	X: 0.2	X: 0
		Y: 0	Y: 0.2	Y: 0
		Z: 0.03	Z: 0.1	Z: 0

Finished geometry:

Step 3 - Define the materials

After confirming model changes, go to the Properties section to define model materials.

1. Assign Air to the airbox volume (38).
2. Assign Copper to the antenna track volumes (transmission line, quarter wavelength line and antenna patch, 13, 25, 37).
3. Assign FR-4 Dielectric to the substrate volume (1).
4. Set the Electric permittivity of FR4 to epsilonR*epsilon0.

Finished materials:

Step 4 - Define the physics

Go to the Physics section. Only the Electromagnetic waves physics is required for this simulation.

1. Add the Electromagnetic waves physics. Let EM waves target default to the whole geometry.

2. Add a perfect conductor interaction on the substrate plate bottom surface (83). This is done to ground the surface.

3. Add a perfect conductor interaction on the antenna track volumes (transmission line, quarter wavelength line and antenna patch, 13, 25, 37). This is done to prevent simulating electric losses, which are anyway minimal due to high conductivity of copper. If electric losses in the volumes are not interesting, the perfect conductor interaction can be used like this to reduce computational load.

4. Add a Lump V/I interaction for the port:

   Interaction	Port target	One volt electrode	Ground electrode
   Lump V/I	Port rectangle surface (54)	Top edge curve of port touching track (115)	Bottom edge curve of port, touching ground surface (112)

   Set lump Voltage to sn(1).

   

5. Add a Perfectly matched layer interaction on the airbox boundary. Set PML Type to Box PML and select all 6 boundary surfaces of the airbox (89-94).

   

Finished physics tree:

Step 5 - Generate the mesh

Proceed to the Simulations section and mesh the geometry with default settings. Check the preview:

Step 6 - Simulate

In the Simulations section, add a simulation:

• In Simulation settings:
  • Set Analysis type to Harmonic.
  • Set Fundamental frequency to freq.
  • Set Node count to 3. This ensures the solver has enough memory available to run the simulation.
• As Mesh, select the mesh you created.
• Inputs:
  • Add freq sweep with expression linspace(2.0e9, 5.0e9, 51)
• Outputs:
  • Add S-parameters
  • Add Radiation pattern
  • Add E harmonic 2
    • Select the substrate volume (1) as target.
    • Toggle on Skin only

Your simulation is now ready to run.

E field output targeting substrate

E field strength is 0 on the copper regions due to the perfect conductor interaction applied on them. Hence, the E harmonic 2 output is targeted on the substrate volume, so that E field results can be seen on the substrate top surface, where it is in contact with the copper volumes.

Skin only E field output

The E field output is toggled as Skin only for better visualizer performance. If field strength inside a volume is not of interest, then this option can be used to reduce computational load.

Step 7 - Results

In the Simulations section, you can add visualizations to see field output results (Radiation pattern, E field) and plots to see value output results (S-parameters):

• Radiation pattern at 2.36 GHz:
• E field harmonic 2 at 2.36 GHz:
• S-parameter plot made with external software:

References

[1] https://www.emtalk.com/mwt_mpa.htm