1.2.2      Normal incidence of a plane wave on a perfect conductor surface

In this case an envelope of a standing wave will be demonstrated. Assuming that a plane wave incidents normally on a perfect metal (perfect electric conductor – PEC) with impedance equal to 0, reflection coefficient is equal:


The SWR in this case equals to:


According to SWR value, the wave in a first medium (air) is a standing wave. No energy is transferred through the media boundary and the fields in envelope nodes have values equal to 0.

The above values and conclusions may be confirmed in electromagnetic simulation. Open the ready to run ppw6.QWpro model in QW-Modeller or open ppw5.QWpro and modify it adequately performing the following:

-         Remove the LoadPort port since it is not required in this case. Pick the LoadPort port on the project tree (see Fig. 15) and remove with Delete option available under right mouse button.

-         Change the medium of section 2 to metal by editing Medium parameter of the section2 object (see Fig. 16).

-         Save the project with a new name.

 

Fig 15 How to delete port (element) from the project.

 

Fig 16 Element properties edition.

 

Run the simulation by pressing  button in Simulation tab. Open 1D display window using  button in 1D Fields tab. Switch to excisting field component i.g. Hy. Fig. 17 shows the display that should be seen.

Fig 17 Magnetic field envelope of a wave normal to PEC surface.

It can be seen that there is no propagation in perfect metal. The values of magnetic field in the envelope nodes are close to 0. The values are not 0 due to the numeric accuracy limit – the smaller the mesh cell dimension will be, the closer field value to 0 would be.