The remaining curves are parts of circles representing reactance. The R = 1 circle passes through the center of the R line. Resistance values are plotted on the resistance circles, all of which are tangent to one another at the far right of the resistance line. A horizontal line through the center of the main circle represents the resistance with R = 0 at the far left of the line and infinite resistance at the far right. The Smith chart is made up of multiple circles, and segments of circles arranged in a way to plot impedance values in the form of R ± jX (Fig. If you have avoided the Smith chart in the past, here’s a primer on how to take advantage of it. And as you will find out, it’s useful for working out transmission-line problems and in designing impedance-matching circuits. How he came up with this is an untold story, but he provided a solution to the complex calculations on transmission lines. The intimidating graph, developed by Philip Smith in 1939, is just about as bad as it looks. Most of you have probably heard of the Smith chart. Identify impedance-matching component values from the Smith chart.Determine the impedance of a load at the end of a transmission line.Plot complex impedances on a Smith chart.
Members can download this article in PDF format. This article is part of the Analog Series: Back to Basics: Impedance Matching
