Oscillating Dipole Above Conducting Plane (emOscDipoleAboveConductorT.pre)


emOscDipoleAboveConductorT, radiation

Problem Description

This problem consists of an infintesimally short dipole located a variable height and orientation above a conducting plane. This simulation sets up a multifield, which can than have its electric and magnetic fields visualized to see how the distance between, and orientation of the dipole relative to the antenna effects these fields.

This simulation can be performed with a VSimBase license.

Opening the Simulation

The Dipole Above Conducting Plane 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 Basic Physics option.
  • Expand the Basic Examples (text-based setup) option.
  • Select Dipole Above Conducting Plane (text-based setup) 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.

The basic variables of this problem should now be alterable via the text boxes in the left pane of the Setup Window, as shown in Fig. 145.

image 1

Fig. 145 Setup Window for the Dipole Above Conducting Plane example.

Input File Features

This file has key parameters to adjust the antenna polarization, height and operating frequency. In addition the number of points per wavelength as well as simulation domain size and runtime can be adjusted. Finally the length of one timestep can be adjusted slightly. The input file itself consists of a multifield with 5 open boundary conditions, and one conducting boundary condition to simulate the ground plane.

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.
  • To run the file, 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 the window below.
image 2

Fig. 146 The Run Window at the end of execution.

Visualizing the Results

After performing the above actions, continue as follows:

  • Proceed to the Visualize Window by pressing the Visualize button in the left column of buttons.

The electric and magnetic field components can be found in the scalar data variables of the data overview tab.

  • Make sure the Data View drop down is set to Data Overview.
  • Here you can see Variables. Expand the Scalar Data.
  • Expand E
  • Select E_y
  • Check the box next to Display Contours and set the # of contours to 10

Initially, no field will be seen, as one is looking at Dump 0, the initial dump, when no fields are yet in the simulation. Move the slider at the bottom of the right pane to see the electric field at different times.

image 3

Fig. 147 The electric field

Further Experiments

In this example the “infinite” electric conductor is simulated by a physical conducting boundary at the bottom of the simulation. It would be possible to achieve the same results by having a second, equal infintesimal dipole placed the same height “below” the conducting plane.

The number of “lobes” visible in the far field is dependent on Antenna Orientation and height. If vertically oriented there will be 2*Height/Wavelength +1 lobes.A horizontally oriented dipole will produce 2*Height/Wavelength lobes. This can be a bit difficult to visualize using just E-field data as it must be properly thresholded. The lobes will be easier to see in the example Advanced Dipole Above Conductor, a part of the VSimEM package.

By adjusting the TIMESTEP_FACTOR timesteps can be made larger. If they get to large the simulation will become unstable.

To improve computational speed the size of the simulation domain can be optimized by adjusting LX/LY/LZ and PTS_PER_LAMBDA.