John Renshaw Carson
Encyclopedia
John Renshaw Carson who published as J. R. Carson, was a noted transmission theorist for early communications systems. He invented single-sideband modulation
.
Carson was born in Pittsburgh, Pennsylvania
, graduated from Princeton University
in 1907 with a bachelors of science degree, and attended Massachusetts Institute of Technology
1907-1908 before returning to Princeton to receive his electrical engineering
degree in 1909 and a master of science degree in 1912. From 1912-1914 Carson was an instructor in Electrical Engineering and Physics at Princeton, but in 1913 was offered a position at American Telephone & Telegraph
(AT&T), and in 1914 left the university.
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 published a mathematical treatment of frequency modulation
(FM), which 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 1917-1925 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 1925-1940 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
.
Single-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....
.
Carson was born in Pittsburgh, Pennsylvania
Pittsburgh, Pennsylvania
Pittsburgh is the second-largest city in the US Commonwealth of Pennsylvania and the county seat of Allegheny County. Regionally, it anchors the largest urban area of Appalachia and the Ohio River Valley, and nationally, it is the 22nd-largest urban area in the United States...
, graduated from Princeton University
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....
in 1907 with a bachelors of science degree, and attended Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
1907-1908 before returning to Princeton to receive his electrical engineering
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
degree in 1909 and a master of science degree in 1912. From 1912-1914 Carson was an instructor in Electrical Engineering and Physics at Princeton, but in 1913 was offered a position at American Telephone & Telegraph
American Telephone & Telegraph
AT&T Corp., originally American Telephone and Telegraph Company, is an American telecommunications company that provides voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agencies. AT&T is the oldest telecommunications company...
(AT&T), and in 1914 left the university.
At AT&T Carson was involved in early radio telephone experiments. In 1915 he invented single-sideband modulation
Single-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....
to transmit multiple telephone calls simultaneously on a single electrical circuit, and was responsible for installing the first such system between Pittsburgh and Baltimore
Baltimore
Baltimore is the largest independent city in the United States and the largest city and cultural center of the US state of Maryland. The city is located in central Maryland along the tidal portion of the Patapsco River, an arm of the Chesapeake Bay. Baltimore is sometimes referred to as Baltimore...
. In 1922 he published a mathematical treatment of frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
(FM), which introduced the Carson bandwidth rule
Carson bandwidth rule
In telecommunication, Carson's bandwidth rule defines the approximate bandwidth requirements of communications system components for a carrier signal that is frequency modulated by a continuous or broad spectrum of frequencies rather than a single frequency. Carson's rule does not apply well when...
. 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
Edwin Armstrong
Edwin Howard Armstrong was an American electrical engineer and inventor. Armstrong was the inventor of modern frequency modulation radio....
managed to demonstrate that FM can be advantageous if the frequency swing is significantly wider than the audio bandwidth. From 1917-1925 Carson analyzed the effects of filters on amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
via operational calculus
Operational calculus
Operational calculus, also known as operational analysis, is a technique by which problems in analysis, in particular differential equations, are transformed into algebraic problems, usually the problem of solving a polynomial equation.-History:...
, 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
Bell System Technical Journal
The Bell System Technical Journal was the in-house scientific journal of Bell Labs that was published from 1922 to 1983.- Notable papers :...
, culminating in his 1926 book Electrical Circuit Theory and Operational Calculus.
From 1925-1940 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
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
experiments.
Carson received the 1924 IRE Morris N. Liebmann Memorial Award
IEEE Morris N. Liebmann Memorial Award
The initially called Morris Liebmann Memorial Prize provided by the Institute of Radio Engineers , the IEEE Morris N. Liebmann Memorial Award was created in 1919 in honor of Colonel Morris N. Liebmann. It was initially given to awardees who had "made public during the recent past an important...
"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
Elliott Cresson Medal
The Elliott Cresson Medal, also known as the Elliott Cresson Gold Medal, was the highest award given by the Franklin Institute. The award was established by Elliott Cresson, life member of the Franklin Institute, with $1,000 granted in 1848...
from the Franklin Institute
Franklin Institute
The Franklin Institute is a museum in Philadelphia, Pennsylvania, and one of the oldest centers of science education and development in the United States, dating to 1824. The Institute also houses the Benjamin Franklin National Memorial.-History:On February 5, 1824, Samuel Vaughn Merrick and...
. His undergraduate letters are archived at Princeton University
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....
.
Patent
: John Carson/AT&T: "Method and Means for Signaling with High Frequency Waves" filed on December 1, 1915; granted on March 27, 1923Selected works
- "Wave Propagation over Parallel Wires: The Proximity effect", Philosophical Magazine, volume IXLI, June 1921, pages 607-633.
- "Notes on the Theory of Modulation", Proceedings of the Institute of Radio Engineers, volume 10, issue 1, February 1922, pages 57–64.
- "A Generalization of Reciprocal Theorem," Bell System Technical Journal, volume 3, pages 393-399, 1924.
- "Selective Circuits and Static Interference", Bell System Technical Journal, volume 4, page 265, 1925.
- "Wave Propagation in Overhead Wires with Ground Return", Bell System Technical Journal, volume 5, page 539, 1926.
- Electrical Circuit Theory and Operational Calculus, New York : McGraw-Hill, 1926.
- J. R. Carson, S. P. Mead, and S. A. Schelkunoff, "Hyper-Frequency Waveguides: Mathematical Theory", Bell System Technical Journal, volume 15, pages 310-333, 1936.