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A Short Explanation of Smith Charts

The following short explanation does not intend to replace even a single page of a textbook on reflection coefficients. It is just given to make usage of TSmitchChart clear.

Basically, the domain of definition of the reflection coefficient is a circle of radius 1 in the complex plane:

Now, we can ask the question: what is a particular (line/load) impedance in the coordinate system of the reflection coefficient circle. Therefore we normalize the impedance to a given value (e.g. 50 Ohms). It turns out that the entire range of possible impedances can be projected onto the coordinate system of the reflection coefficient. The following figure shows the lines of constant resistance and constant reactance.

Combining both family of curves results in the Smith Chart:



Last Update: 2012-Oct-20