Arduino-based investigation of transmission lines and impedance matching

Abstract

Transmission lines play a crucial role in radio-frequency energy transmission between source and load. These systems connect essential physical phenomena like the formation of standing waves and the attenuation of electromagnetic waves in material media with practical considerations such as impedance matching and signal integrity. Understanding these systems requires knowledge of fundamental concepts like inductance, capacitance, and impedance. The absence of impedance matching between the line and load leads to a modulated amplitude in the resulting signal owing to interference between the injected and reflected signals. Here, we present an experiment utilizing an Arduino platform as a signal generator and a data acquisition interface to analyze a radio frequency transmission line. By employing a few-meter-long coaxial cable as the transmission line and a digital oscilloscope with a high sampling rate (several giga-samples per second), we demonstrate how to determine the reflection coefficient as a function of the load impedance. The reflection coefficient enables determination of the return loss, underscoring the significance of impedance matching for optimal performance among the source, transmission line, and the load.