Editing Smith chart (section)

{{Short description|Electrical engineers graphical calculator}}
{{For|other uses of the term Smith diagram|Smith diagram (disambiguation)}}
{{Redirect|Volpert diagram|the similar term Volpert graph|Volpert graph (disambiguation)}}
{{Use British English|date=August 2017}}
{{Use dmy dates|date=June 2023|cs1-dates=y}}
{{Use list-defined references|date=June 2023}}
The '''Smith chart''' (sometimes also called '''Smith diagram''', '''Mizuhashi chart''' ({{lang|ja|水橋チャート}}), '''Mizuhashi–Smith chart''' ({{lang|ja|水橋<!--・-->スミス<!--・-->チャート}}),<ref name="Okamura_1959"/><ref name="Kenichi_1999"/><ref name="Mori_2013"/> '''Volpert–Smith chart'''<!-- also "Volpert–Smith diagram" --> ({{lang|ru|Диаграмма Вольперта—Смита}})<ref name="Kurochkin_2009"/><ref name="Salov_2022"/> or '''Mizuhashi–Volpert–Smith chart''') is a graphical calculator or [[nomogram]] designed for [[electrical engineering|electrical and electronics engineers]] specializing in [[radio frequency]] (RF) engineering to assist in solving problems with [[transmission line]]s and [[impedance matching|matching]] circuits.<ref name="Ramo-Whinnery-Duzer_1965"/><ref name="Ramo-Whinnery-Duzer_1994"/><ref name="Smith_1969"/><ref name="Smith_1995"/><ref name="MAX_2012"/>

It was [[simultaneous invention|independently]]<ref name="Voltmer_2007"/><ref name="Kurochkin_2009"/><ref name="ETHW_2018"/><ref name="Salov_2022"/> proposed by [[Tōsaku Mizuhashi]]<!-- also transscribed as "Tōsaku Mizuhasi" --> ({{lang|ja|水橋東作}}) in 1937,<ref name="Mizuhashi_1937"/> and by {{ill|Amiel Rafailovich Volpert|ru|Вольперт, Амиэль Рафаилович|lt=Amiel R. Volpert}} ({{lang|ru|Амиэ́ль Р. Во́льперт}})<!-- many third-party sources state 1939 suggesting that there are earlier sources than 1940 --><ref name="Volpert_1940"/><ref name="Kurochkin_2009"/> and [[Phillip Hagar Smith|Phillip H. Smith]] in 1939.<ref name="Smith_1939"/><ref name="Smith_1944"/> Starting with a rectangular diagram<!-- according to <ref name="Inan_2005"/> "in 1931", but I could not find a more authorative source for this so far -->, Smith had developed a special [[polar coordinate]] chart by 1936, which, with the input of his colleagues [[Enoch B. Ferrell]] and [[James W. McRae]], who were familiar with [[conformal mapping]]s, was reworked into the final form in early 1937, which was eventually published in January 1939.<ref name="Smith_1939"/><ref name="Smith_1995"/><ref name="Inan_2005"/> While Smith had originally called it a "''transmission line chart''"<ref name="Smith_1939"/><ref name="Smith_1944"/> and other authors first used names like "''reflection chart''", "''circle diagram of impedance''", "''immittance chart''" or "''Z-plane chart''",<ref name="Smith_1995"/> early adopters at [[MIT]]'s [[MIT Radiation Laboratory|Radiation Laboratory]] started to refer to it simply as "''Smith chart''" in the 1940s,<ref name="Smith_1995"/><ref name="Inan_2005"/> a name generally accepted in the Western world by 1950<!-- possibly earlier? -->.<ref name="Linton_1950"/><ref name="GeneralRadio_1950"/>

The Smith chart can be used to simultaneously display multiple parameters including [[electrical impedance|impedances]], [[admittance]]s, [[reflection coefficient]]s, <math>S_{nn}\,</math> [[scattering parameters]], [[noise figure]] circles, constant gain contours and regions for [[stability theory|unconditional stability]].<ref name="Pozar_2005"/><ref name="Gonzalez_1997"/>{{rp|pages=93–103}} 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 [[electronic oscillator|oscillator]] design and [[stability theory|stability]] analysis.<ref name="Gonzalez_1997"/>{{rp|pages=98–101}} 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 chart is still a very useful method of showing<ref name="Bevelacqua_2013"/> how RF parameters behave at one or more frequencies, an alternative to using [[table (information)|tabular]] information. Thus most RF circuit analysis software includes a Smith chart option for the display of results and all but the simplest impedance measuring instruments can plot measured results on a Smith chart display.<ref name="Tektronix_2017"/>
[[File:Smith chart3.svg|thumb|290x290px|An impedance Smith chart (with no data plotted).]]