Smith chart
The Smith chart (sometimes also called Smith diagram, Mizuhashi chart (水橋チャート), Mizuhashi–Smith chart (水橋スミスチャート), Volpert–Smith chart (диаграмма Вольперта—Смита) or Mizuhashi–Volpert–Smith chart) is a graphical calculator or nomogram designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assist in solving problems with transmission lines and matching circuits. It was independently proposed by Tōsaku Mizuhashi (水橋東作) in 1937, and by Amiel R. Volpert (Амиэ́ль Р. Во́льперт) and Phillip H. Smith in 1939.