Click here to learn the basics of the Smith Chart
Click here to see some Smith Chart tributes
Click here to download a (bootleg) copy of the Smith Chart
The Smith Chart was the brainchild of Phillip H. Smith back in the 1930s; he is in our humble Microwave Hall of Fame. One of the unique things about his work is that both axes (real and imaginary) go all the way to infinity. Following his retirement from Bell Labs, Smith's company, Analog Instruments, marketed copies of the chart starting in the 1970s. Smith passed away in 1987, leaving his widow Anita to run Analog Instruments. As of February 2024, Analog Instruments is still listed on Manta.com with one employee (presumably, Anita).
In 2015, IEEE MTT-S bought the trademark from Anita Smith. Here is an article about that acquisition, on IEEE Xplore. It is one of those rare IEEE articles that they don't try to monetize, you can download it for free.
Does that mean MTT-S will knock on your door if you use the Smith Chart inappropriately? So far we have not heard of that happening. You may notice that the borders of Microwaves101 are filled in with Smith Chartage, which was a gift from MTT-S back when we were partnered with them. As of 2023, we are not in any form of partnership with MTT-S. And you can download and print out a copy of the chart with Microwaves101 embroidered across the top!
Reference
T. Lee, "The Smith Chart Comes Home [President's Column]," in IEEE Microwave Magazine, vol. 16, no. 10, pp. 10-25, Nov. 2015.