Amplitude Modulation Circuit Implementation for use in a Communication Course for Electrical Engineering Students

Modern descriptions of analog communication schemes are mathematics based using transform theory and block diagrams. This presentation style leaves undergraduate students with the challenge of relating these theories to real world circuit implementations. This is particularly true if the lecture class does not have a complementary laboratory component. This paper attempts to bridge this gap by presenting a basic yet comprehensive project that can be used to demonstrate amplitude modulation and demodulation theory. It is specifically designed to stir the interest of junior or senior level electronics minded electrical engineering students. In this project, a double sideband large carrier waveform is produced using a simple switching modulator circuit. The resulting amplitude modulation (AM) waveform is then demodulated using an envelope detector circuit. The proposed project requests that students perform a circuit simulation as well as an actual circuit implementation. The circuit behavior is studied via both analysis using software tools and measurement using hardware components. The project further requires that the electrical signals are visualized in both the time and frequency domain to enhance concept understanding. The paper outlines an introduction to the modulation theory along with an overview of the necessary circuits and concepts. Additionally, suggested student activities, project assignment alternatives, along with detailed mathematical solutions are provided.