The Smith chart is a chart of normalized impedances (or admittances) in the reflection coefficient plane. This has been accomplished in a rather general tool called the Smith chart. Thus, the following proposition: Build a graphical chart (or an equivalent computer program) capable of representing the reflection coefficient as well as load impedances in some general fashion and you have a simple method of designing transmission line circuits without the need to perform rather tedious calculations. You may also recall, perhaps with some fondness, the complicated calculations which required, in addition to the use of complex variables, the use of trigonometric and hyperbolic functions. The reflection coefficient, in turn, was defined in terms of the load and line impedances (or any equivalent load impedances such as at a discontinuity). Voltage, current, and power were all related to the reflection coefficient.
The reflection coefficient was used to find the conditions on the line, to calculate the line impedance, and to calculate the standing wave ratio. A look back at much of what we did with transmission lines reveals that perhaps the dominant feature in all our calculations is the use of the reflection coefficient.
