15 Facts About Smith chart

Smith chart, invented by Phillip H Smith and independently by Mizuhashi Tosaku, is a graphical calculator or nomogram designed for electrical and electronics engineers specializing in radio frequency engineering to assist in solving problems with transmission lines and matching circuits.

The Smith chart can be used to simultaneously display multiple parameters including impedances, admittances, reflection coefficients, scattering parameters, noise figure circles, constant gain contours and regions for unconditional stability, including mechanical vibrations analysis.

The Smith chart is most frequently used at or within the unity radius region.

Smith chart is a mathematical transformation of the two-dimensional Cartesian complex plane.

The impedance Smith chart is then a Argand plot of impedances thus transformed.

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.

Smith chart has a scale around its circumference or periphery which is graduated in wavelengths and degrees.

Locus of points on a Smith chart covering a range of frequencies can be used to visually represent:.

Accuracy of the Smith chart is reduced for problems involving a large locus of impedances or admittances, although the scaling can be magnified for individual areas to accommodate these.

Smith chart is used with one frequency at a time, and only for one moment at a time, so the temporal part of the phase is fixed.

The Smith chart scaling is designed in such a way that reflection coefficient can be converted to normalised impedance or vice versa.

The Smith chart uses the same convention, noting that, in the normalised impedance plane, the positive -axis extends from the center of the Smith chart at to the point The region above the x-axis represents inductive impedances and the region below the -axis represents capacitive impedances .

Normalised impedance Smith chart is composed of two families of circles: circles of constant normalised resistance and circles of constant normalised reactance.

Smith chart is constructed in a similar way to the Smith chart case but by expressing values of voltage reflection coefficient in terms of normalised admittance instead of normalised impedance.

Smith chart appears like the normalised impedance, type but with the graphic nested circles rotated through 180°, but the numeric scale remaining in its same position as the chart.