William S. Brinson and Brent R. Petersen, "Java(TM) applet for teaching transmission lines in steady state," in Conf. Rec. 2001 Canadian Conference on Computer Engineering Education, vol. 1, (Fredericton, NB, Canada), May 31-June 1, 2001.


Teaching electromagnetics often involves spatial visualisation of theory and problems. Traditional teaching methods are effective, but can be augmented with the use of animation.

One specific electromagnetic situation is considered, transmission lines carrying one frequency in steady state. An applet in java(TM) was developed to demonstrate by animation the transmission line concepts. This applet is presented to the students in a junior course in electromagnetic fields and waves. This particular applet demonstrates forward and reverse travelling waves, partial reflections, total reflections, matched loads, and standing waves.

The transmission line applet alone is insufficient to demonstrate the theory. However, the theory presented in a lecture is reinforced by the applet.

One technical issue that arose is spatial and temporal aliasing. Since the applet displays the animated and travelling waves within a limited resolution and display time, aliasing may occur. This situation is detected by the applet and the user is informed. Even though aliasing may occur, the applet displays the aliased waveform. One noticeable effect of aliasing that can occur is the forward and reverse travelling waves travelling in the wrong direction.

The time to design and develop the applet is relatively high. The time for one developer to learn java(TM) would only occur once. However, the development time for each engineering application is nevertheless relatively high. The relative productivity in terms of course development time is lower with the java(TM) applet than that based on traditional teaching methods, such as lectures, laboratories, and assignments. However, the cost may eventually be recovered by repeated use of the applet in augmenting traditional teaching methods.

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