Harry Nyquist

Harry Nyquist (pron. [nʏ:kvɪst]) (Stora Kil, Sweden, February 7, 1889 – Harlingen, USA, April 4, 1976) was a physicist and Swedish-American engineer and contributor to Information Theory.

Biography

He was the son of Lars Jonsson Nyquist and Katrin Eriksdotter. His parents had seven children: Elin Teresia, Astrid, Selma, Harry Theodor, Aemelie, Olga Maria and Axel. Harry Nyquist immigrated to the United States in 1907, then entered the University of North Dakota in 1912 and received a bachelor's degree and a master's degree in electrical engineering in 1914 and 1915, respectively. He would later receive a PhD in physics at Yale University in 1917.

Upon receiving this degree, he began working in AT&T's Research and Development Department from 1917 to 1934, continuing when the company changed its name to Bell Telephone Laboratories in that year, until his retirement in 1954. Nyquist received the IEEE Medal of Honor in 1960 for his contributions to the quantitative understanding of thermal noise, data transmission, and negative feedback. In October 1960 he was awarded the Stuart Ballantine Medal from the Franklin Institute for his theoretical analyzes and practical inventions in the field of communication systems over the past forty years including, his work on the theories of telegraphic transmission, thermal noise in conductors electrical and feedback systems theory. In 1969 he was awarded by the National Academy of Engineering with its fourth Founders Medal “in recognition of his fundamental contributions to engineering.”

As an engineer at Bell Laboratories, Nyquist did important work on thermal noise, stability in feedback amplifiers, telegraphy, fax, television, and other important communication problems. Along with Herbert E. Ives, he helped develop AT&T's first fax machine, which was made public in 1924. In 1932 he published a paper on the stability of feedback amplifiers. The Nyquist stability criterion today appears in all feedback control theory texts.

His first theoretical work in determining bandwidth requirements to transmit information laid the foundation for later advances made by Claude Elwood Shannon, who developed Information Theory. In particular, Nyquist determined that the number of independent channels that can be put over a telegraph channel per unit of time is limited by twice the bandwidth of the channel, and published his results in the papers Certain Factors That affect the telegraph speed (“Certain factors affecting telegraph speed” of 1924) and Certain topics in telegraph Transmission Theory’; from 1928). This latter work is known today as the Nyquist-Shannon sampling theorem.