). Accept the changes by pressing OK button and save the project with a new name.1.1.4 Envelope shape in lossy media
In the scenarios considered above the medium in which a plane wave propagated was a lossless medium. The observed fields' envelope was a straight line. In this paragraph a lossy medium will be considered and its influence on envelope shape will be observed.
Open example ppw4.QWpro in QW-Modeller or modify ppw1.QWpro in the following way. Open the Project Media dialogue (Fig. 8) as it was done before and add the "dielectric" medium. The window as in Fig 9 will appear. Modify the Sigma parameter to be equal to 0.1 (it is expressed in ). Accept the changes by pressing OK button and save the project with a new name.
The attenuation coefficient a, determining the envelope shape, can be calculated analytically using the following formula for the propagation constant:
Real part 
The attenuation coefficient may be also calculated from the simulation data in the 1D display window following the below formula:
where:
· x1 first marker localisation (in mm) (e.g. at the beginning of guide)
· x2 second marker localisation (in mm) (e.g. at the end of guide)
· E(x1) electric field magnitude read for x1 position
· E(x2) electric field magnitude read for x2 position
The display showing exemplary makers’ position for attenuation coefficient calculation together with their values is shown in Fig 12.
Fig 12 Electric field envelope for lossy medium.
The calculated attenuation coefficient a value is:
Good agreement between theoretical calculations and simulation data is achieved.
It is recommended to change s parameter to 1 and observe the envelope shape change.