A plot of complex reflection overlaid with an impedance and (or) admittance grid referenced to a 1-ohm characteristic impedance. The Smith chart, invented by Phillip H. Smith is a graphical aid designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assist in solving problems with transmission lines and matching circuits. Use of the Smith chart utility has grown steadily over the years and it is still widely used today, not only as a problem solving aid, but as a graphical demonstrator of how RF parameters behave at one or more frequencies, an alternative to using tabular information. The Smith chart can be used to represent many parameters including impedances, admittances, reflection coefficients, S_{nn}\, scattering parameters, noise figure circles, constant gain contours and regions for unconditional stability. The Smith chart is most frequently used at or within the unity radius region. However, the remainder is still mathematically relevant, being used, for example, in oscillator design and stability analysis. Smith Chart is a registered trademark of Analog Instruments Company, New Providence, NJ.

Smith Chart Resource:

Free Smith Chart for Excel by RF Cafe – two unique spreadsheets that allow entering either S-parameters or complex numbers