April 2010 History

Scanning the Past: A History of Electrical Engineering from the Past
Submitted by Marc Bell, Editor

Copyright 1996 IEEE. Reprinted with permission from the IEEE publication, “Scanning the Past” which covers a reprint of an article appearing in the Proceedings of the IEEE Vol. 84, No. 9, September 1996.

Sergei A. Schelkunoff and Antenna Theory

Fifty-five years ago this month, the PROCEEDINGS OF THE RADIO ENGINEERS (IRE) included a paper by Sergei A. Schelkunoff on the theory of antennas. At the time, he was a member of the research staff at the Bell Telephone Laboratories (BTL) where he worked for about three decades. (See Fig. 1.) Schelkunoff made important contributions to the theory of coaxial cables and wave guides as well as to antennas.

Schelkunoff was born in Samara, Russia, in 1897. He was a student at the University of Moscow when his education was interrupted by the outbreak of World War I. He served in the Russian Army during the War before corning to the United States by way of Manchuria and Japan in 1921. He learned English and received both the B.A. and M.A. degrees in mathematics at the State College of Washington (now Washington University), Seattle. He worked in the Engineering Department of the Western Electric Company during 1923-1925 and spent a few months at the BTL in 1926. He taught at the State College of Washington from 1926-1929 and received the Ph.D. degree in mathematics at Columbia University in 1928 before returning to research at BTL.

2010_04-fig-1.JPG
Fig. 1.  Schelkunoff studying waveguide transmission in the early
1930’s.   (Reprinted from P. C. Mahon, Mission Communications:
 The Story of Bell Laboratories, 1975.)

One of Schelkunoffs early assignments was to investigate the theory of coaxial transmission lines. He published a paper on this topic in the Bell System Technical Journal in 1934. Subsequently, he studied the electromagnetic theory of wave guides for rnicrowaves and was coauthor with John R. Carson and Sallie P. Mead of a paper on that subject in the BSTJ in 1936. Schelkunoff s first IRE paper was on applications of the Summerfeld integral and appeared in the October 1936 PROCEEDINGS. He authored another IRE paper “Transrnission Theory of Pure Electromagnetic Waves,” published in November 1937. He treated the theory of spherical waves in a 1938 paper in the Transactions of the American Institute of Electrical Engineers and followed this with a 1939 IRE paper on the induced electromotive force method of computing radiation from antennas. In his September 1941 IRE paper, Schelkunoff addressed the ambitious topic of the “theory of antennas of arbitrary size and shape.” He explained that his mathematical analysis of antennas was “precisely the analysis appropriate to wave guides and electric horns.” He observed that:

We may also think of the antennas as the wall of an electric horn with an aperture so wide that one can hardly see the horn itself-just like a Cheshire cat: only the grin can be seen.

Schelkunoff suggested that the physical picture which emerged from his mathematical analysis was “attractive to an engineer.” He began his analysis with Maxwell’s equations and hypothetical conical antennas and went on to show how to apply the results to antennas of other shapes although they were “definitely more complicated.” He concluded that he believed that “the antenna theory is in such a shape that accurate results can be calculated if all visible factors such as base capacitance and antenna shapes are taken into consideration.”

Schelkunoff was awarded the Morris Liebmann Memorial Prize by the IRE in 1942 and was elected a Fellow of IRE in 1944. During World War ll, he served as a technical consultant to the National Defense Research Committee and to the U.S. Navy. He authored Electromagnetic Waves (1943), Applied Mathematics for Engineers and Scientists (1948), and Advanced Antenna Theory (1952). He retired from BTL in 1960 and subsequently taught electrical engineering at Columbia University. He died in 1992 at age 95.

James E. Brittain
School of History , Technology and Society
Georgia Institute of Technology