The trademark on the Smith Chart recently expired, and Ms. Be sure to check out our entry on Philip Smith in our Microwave Hall of Fame! Phil's widow until recently operated Analog Instruments, the company that sold the official Smith chart for many, many years. The Smith chart was developed by Philip Smith at Bell Telephone's Radio Research Lab during the 1930s. Click here to go to our main page on S-parametersĬlick here to go to a page on plotting Smith Charts with ExcelĬlick here to learn about a three-dimensional Smith ChartĬlick here to go to our Smith Chart tribute page (new for November 2023)