Reflection coefficients can be read directly from the chart as they are unit-less parameters. Once an answer is obtained through the graphical constructions described below, it is straightforward to convert between normalised impedance (or normalised admittance) and the corresponding unnormalized value by multiplying by the characteristic impedance (admittance). The Smith chart is usually normalized to a terminating impedance Z0 ( real). The most commonly used normalization impedance is 50 ohms. 1: Schematic view of a measurement setup used to determine the reflection. The image below shows an example Smith chart used to plot the impedance Z 1.2 - i0.7 Ohms. Suppose our unmatched load impedance is Z 60 - i35 Ohms if the system impedance is 50 Ohms, then we divide the load and system impedances, giving a normalized impedance of Z 1.2 - i0.7 Ohms. Normalised scaling allows the Smith chart to be used for problems involving any characteristic or system impedance which is represented by the center point of the chart. The system impedance might be a 50 Ohm transmission line. These are often known as the Z, Y and YZ Smith charts respectively. The Smith chart is plotted on the complex reflection coefficient plane in two dimensions and is scaled in normalised impedance (the most common), normalised admittance or both, using different colours to distinguish between them.
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