), in a group of prominent scientists at a demonstration of RCA's trans-ocean communication at the
New Brunswick Marconi Station, April 23, 1921.
Albert Einstein is 8th from left, and
Charles Steinmetz is at center, in light-colored suit. Carson was born in
Pittsburgh, Pennsylvania, and, together with his twin brother Joseph, attended
Princeton University, graduating in 1907 with a Bachelor of Science degree. John attended the
Massachusetts Institute of Technology from 1907 to 1908, before returning to Princeton to receive his
electrical engineering degree in 1909 and a Master of Science degree in 1912. From 1912 to 1914, Carson was an instructor in Electrical Engineering and Physics at Princeton. However, in 1913, he was offered a position at
American Telephone & Telegraph (AT&T), and left the university in 1914. At AT&T, Carson was involved in early
radio telephone experiments. In 1915, he invented
single-sideband modulation to transmit multiple telephone calls simultaneously on a single electrical circuit, and was responsible for installing the first such system between
Pittsburgh and
Baltimore. In 1922, he defined
instantaneous frequency in a mathematical treatment of
frequency modulation (FM), and introduced the
Carson bandwidth rule. In his 1922 paper, Carson presented a negative opinion of narrowband FM, which occurs when the maximum frequency swing is made narrower than the audio bandwidth. Later,
Edwin Armstrong managed to demonstrate that FM can be advantageous if the frequency swing is significantly wider than the audio bandwidth. From 1917 to 1925, Carson analyzed the effects of filters on
amplitude modulation via
operational calculus, thus allowing telephone system designers to predict
crosstalk in multiple calls over a single pair of wires. He published a series of papers on this subject in the
Bell System Technical Journal, culminating in his 1926 book
Electrical Circuit Theory and Operational Calculus. From 1925 to 1940, Carson worked for
Bell Telephone Laboratories as a mathematician and electrical engineer. Notable work during this era included his mathematical analysis of
George C. Southworth's 1932
waveguide experiments. Carson received the 1924
IRE Morris N. Liebmann Memorial Award "in recognition of his valuable contributions to alternating current circuit theory and, in particular, to his investigations of filter systems and of single side band telephony." He received an honorary Doctor of Science degree from
Brooklyn Polytechnic Institute in 1937 and the 1939
Elliott Cresson Medal from the
Franklin Institute. His undergraduate letters are archived at
Princeton University. ==Patent==