Analyzing Transmission Lines

Summary

In deriving the inductance of a transmission line, there are two conceptual steps: first, to consider the magnetic field that results from current flowing in the wire, and second, the effect of that magnetic field in terms of linking that wire, or creating an inductive effect back onto it. While inductance deals with movement of charge and is mediated by magnetic fields, capacitance is based on the presence of charge per se, mediated by electric fields. The physical foundation for deriving the capacitance of a transmission line is Gauss's law, which relates the electric field across a surface to the electric charge enclosed by that surface. This chapter combines the resistive, inductive and capacitive properties of transmission lines into a complete model. It discusses four common types of transmission line models: long line model, medium line model, short line model, and lossless line model.