page_title: Smith chart
section_title: Mathematical basis
hierarchical_section_title: Smith chart / Mathematical basis
context_page_description: The Smith chart, invented by Phillip H. Smith, and T. Mizuhashi, 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. However, the remainder is still mathematically relevant, being used, for example, in oscillator design and stability analysis.
  While the use of paper Smith charts for solving the complex mathematics involved in matching problems has been largely replaced by software based methods, the Smith charts display is still the preferred method of displaying how RF parameters behave at one or more frequencies, an alternative to using tabular information.
caption: Most basic use of an impedance Smith chart. A wave travels down a transmission line of characteristic impedance Z0, terminated at a load with impedance ZL and normalised impedance z=ZL/Z0. There is a signal reflection with coefficient Γ. Each point on the Smith chart simultaneously represents both a value of z (bottom left), and the corresponding value of Γ (bottom right), related by z=(1 + Γ)/(1 − Γ).