Harry Nyquist

Harry Nyquist was a Swedish-born American electrical engineer whose studies of signal transmission and noise became groundwork for information theory and digital communication. Born in Nilsby, Sweden, in 1889, he emigrated to the United States in 1907 and earned his doctorate at Yale University in 1917. He then worked for the American Telephone and Telegraph Company and, from 1934 to 1954, for Bell Telephone Laboratories, where he rose to Assistant Director of Systems Studies and held 138 United States patents. His best known result, the Nyquist sampling theorem, states that a signal must be sampled at no less than twice its highest frequency if it is to be reconstructed, a rule that underlies every analog to digital converter. He also explained thermal noise mathematically, devised the vestigial sideband system used in television broadcasting, and gave control engineers the Nyquist diagram for judging the stability of feedback systems. In 1960 he received the IRE Medal of Honor.