Yagi-Uda (YagiUda2p4.sdf)

Keywords:

yagiUdaArrayWireModel, yagiT, far field, radiation

Problem description

A Yagi-Uda array is a directional antenna consisting of several parallel dipole elements. Only one of these dipole elements is driven, the other elements being parassitic . Directionality is acheived by requiring that there be one longer element adjacent to the source element, which is refereed to as the reflector. The rest of the elements beginning adjacent to the source but opposite to the reflector are shorter than the source element, these are called directors. Yagi antennas are ubiquitous and as such optimal parameters for dipole lengths and separations have been established, we go with values one would typically find in any text covering the matter. This example illustrates how to obtain the far field radiation pattern of a Yagi-Uda array.

This simulation can be performed with a VSimEM license.

Opening the Simulation

The Yagi-Uda example is accessed from within VSimComposer by the following actions:

  • Select the NewFrom Example… menu item in the File menu.
  • In the resulting Examples window expand the VSim for Electromagnetics option.
  • Expand the Antennas option.
  • Select 2.4 GHz Yagi Uda Antenna and press the Choose button.
  • In the resulting dialog, create a New Folder if desired, and press the Save button to create a copy of this example.

All of the properties and values that create the simulation are now available in the Setup Window as shown in Fig. 166. You can expand the tree elements and navigate through the various properties, making any changes you desire. The right pane shows a 3D view of the geometry, if any, as well as the grid, if actively shown. To show or hide the grid, expand the Grid element and select or deselect the box next to Grid.

Setup Window

Fig. 166 Setup Window for the Yagi-Uda example.

Simulation Properties

This file allows the modification of the antenna operating frequency, antenna dimensions, and simulation domain size.

By adjusting the dimensions any sized Yagi-Uda array can be simulated.

Note

To obtain good far field resolution generally four or more antenna elements is desirable (One source, one reflector, two or more directors).

Running the Simulation

After performing the above actions, continue as follows:

  • Proceed to the Run Window by pressing the Run button in the left column of buttons.
  • Here you can set run parameters, including how many cores to run with (under the MPI tab).
  • When you are finished setting run parameters, click on the Run button in the upper left corner of the Logs and Output Files pane. You will see the output of the run in the right pane. The run has completed when you see the output, “Engine completed successfully.” This is shown in Fig. 167.
Run Window

Fig. 167 The Run Window at the end of execution.

Analyzing the Results

Click the Show All Analyzers button in the bottom left of the window, select “computeFarFieldFromKirchhoffBox.py” from the list, and click “Open.”

Next, select the computeFarFieldFromKirchhoffBox.py analysis script from the Active Analyzer drop down.

The default parameters are sufficient for this problem. Input 10.0 for the farFieldRadius parameter and run the analyzer by clicking the “Analyze” button.

Analysis Window

Visualizing the results

To view the near field pattern, do the following:

  • Expand Scalar Data
  • Expand E
  • Select E_x
  • Expand Geometries
  • Select poly (YagiUda2p4PecShapes)
  • Select Clip All Plots
  • Move the dump slider forward in time
Visualize Window

Fig. 169 The electric field near-field pattern.

The far field radiation pattern can be found in the scalar data variables of the data overview tab underneath the farE field. Check the farE_magnitude box.

Visualize Window

Fig. 170 The electric field manifestation of the far field pattern.

Further Experiments

Try adding more directors and changing their dimensions to see the affect on the far field pattern.