Philip H. Smith

Smith was a man of many achievements and contributions to electrical and microwave engineering. As a young engineer at Bell Laboratories in 1929, he worked on an antenna connected to the transmitter by a two-wire transmission line. In those days, the technique for matching the line to an antenna high up was a slow, primitive two-person job. One individual moved a cumbersome signal-sensing device along the line at the end of a pole, while a second read the signal through a telescope. To simplify this task, Smith developed a graphical solution that evolved from a rectangular plot accommodating only a limited range of data to a more practical diagram. Based on the principles of conformal mapping, the diagram accommodated data from zero to infinity. Introduced in 1939, the Smith Chart remains the basic tool for determining transmission-line impedance.