Smith chart and how to use it

-May 24, 2012

An indispensible tool for solving transmission line and waveguide problems, the Smith chart was invented in 1939 by Phillip H. Smith as a graph-based method of simplifying the complex math (that is, calculations involving variables of the form x + jy) needed to describe the characteristics of microwave components.

Although calculators and computers can now make short work of the problems the Smith chart was designed to solve, the Smith chart, like other graphical calculation aids remains a valuable tool.

According to Smith himself, “From the time I could operate a slide rule, I’ve been interested in graphical representations of mathematical relationships.” It’s the insights you can derive from the Smith chart’s graphical representations that keep the chart relevant. On instruments, for example, Smith chart displays can provide an easy-to-decipher picture of the effect of tweaking the settings in a microwave network; in an EDA program, a Smith chart display can graphically show the effect of altering component values.

Download your Smith chart by clicking on the image.

For more on Smith charts and how to use them, including a pretty funny story about Phillip Smith himself, see: How does a Smith Chart work? For other useful resources, as well as some background, on Smith charts, I’d recommend The Smith chart society reference page

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