An ultrasound-based laboratory experience to illustrate the maximum power transfer theorem

This paper aims to tackle both the challenge of illustrating the maximum power transfer theorem in a first-year course and the challenge of organizing courses with an extensive program that must be completed in a rather short time. This is the case for the three-year degree program leading to the Diploma in Electronic Systems for Telecommunications offered by the Technical University of Catalonia (UPC). In this degree program, an ultrasound-based laboratory experience was developed primarily to cover the topic of maximum power transfer in the second-semester Circuit Analysis course. In this experience, the range of an ultrasonic transmitter/receiver system, which starts out rather short, is improved by using an LC matching network. The measurement setup uses low-cost circuitry and standard instrumentation available in any basic electronics laboratory. During this experience, we realized that other topics could easily be introduced, including some related to the third-semester Radiofrequency course. Therefore, we added a largely descriptive section to illustrate some of the following topics: wavelength and propagation-speed measurement, directivity, standing waves, pulse-echo distance measurement and the effect of air movement and temperature on the propagation speed.