John R. Carson

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John R. Carson
Pittsburgh, PA, USA
Death date
Associated organizations
Fields of study
Morris N. Liebmann Memorial Award


John Renshaw Carson was a transmissions theorist who worked to develop early communication systems. He was also the inventor of the single-sideband modulation.

Carson was born on June 28, 1886 in Pittsburgh. He received his bachelor's of science degree from Princeton University in 1907, and went on to attend the Massachusetts Institute of Technology in 1907. Carson decided to return to Princeton after spending one school year at MIT. He received his engineering degree in 1909 and a master's of science degree in 1912. Upon graduation, Carson worked as an instructor in Electrical Engineering and Physics at Princeton. He remained there until he joined American Telephone and Telegraph (AT&T) in 1914.

Much of Carson's research at AT&T focused on early radio telephone experiments. In 1915, in invented the single-side modulation. This technology allowed for the transmission of multiple telephone calls simultaneously within one electrical circuit. Carson installed this system, the first of its kind, between Pittsburgh and Baltimore. Between 1917 and 1925, Carson also studied the effects of filters on amplitude modulation, which would allow telephone system designers to predict whether or not crosstalk would occur between multiple calls over a single set of wires. In 1922, Carson introduced the Carson Bandwidth Rule, which presented a mathematical analysis of frequency modulation (FM). Four years later, he published his book, Electrical Circuit Theory and Operational Calculus. Carson left AT&T in 1925 and joined Bell Laboratories as a mathematician and electrical engineer. One of his most notable accomplishments at Bell Labs was his mathematical analysis of George C. Southworth's 1932 waveguide experiments. Carson remained at Bell Labs until 1940.

Carson received the IRE Morris N. Liebmann Memorial Award in 1924 for "his valuable contributions to alternating current circuit theory and, in particular, to his investigations of filter systems and of single side band telephony." In 1939, he received the Elliott Cresson Medal from the Franklin Institute. He was also the recipient of an honorary Doctor of Science degree from the Brooklyn Polytechnic Institute (1937). Carson died on October 31, 1940.