Studying Characteristics of Transmission Lines with Help of Computer Simulation in the Matlab Environment

Use of transmission lines in telecommunications is considered. It is stressed that signals' behavior in the lines exerts considerable influence on the characteristics of telecommunication networks. Analytical methods of studying signals' behavior in the telecommunication lines is shown to encounter substantial difficulties. It is proposed to use computer simulation of the lines in Matlab environment. For a long line with distributed parameters, its simplified equivalent circuit with lumped components is introduced. It is shown that the circuit can be described using Kirchhoff's laws and relationship between voltage and current for the individual elements of the equivalent circuit. Systems of differential equations that determine the behavior of the line are obtained. To facilitate digital computer simulation, transition from the system of differential equations to the system of difference equations is performed. As an example, behavior of the beforehand charged telecommunication line with twenty typical elements is studied for the case of its discharge on a resistive load. Simulation results prove that the corresponding model in Matlab environment correctly reflects all the underlying electromagnetic processes in the line as well as helps to elucidate some aspects that are not possible to observe in real-life experiments. The proposed method can be effectively used to study any telecommunication lines that can be reduced to the equivalent circuits with lumped parameters.