Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering


Communication is an inherent characteristic of the human species. Man has continually strived to improve his methods of communicating with his fellow man. With the understanding of electricity and its subsequent control, a powerful tool became available; one important use of this tool is in the field of communications. First applications of electricity to communications involved physical connections between sending and receiving instruments. When scientists desired to eliminate the direct connections between the communicators, new methods had to be devised. The new methods which were developed involved the transmission of electromagnetic energy through space. One of the basic electrical waveforms used was a sine wave; the sine wave by itself, however, contains no information. Therefore, some characteristic of the wane must be varied in order that the wave can carry information. There are three fundamental qualities of a wave that can be altered – the amplitude, the frequency, and the phase. “Modulation” is the word which was adopted to denote the variation of one of these characteristics of a wave. Early work was directed toward the perfection of amplitude modulation systems. But amplitude modulation has certain limitations, among which is a noise problem. Therefore, in the early 1920’s frequency modulation (F-M) was proposed. In 1922 J. R. Carlson published a paper which was unfavorable towards frequency modulation, and the result was a decline of interest for several years. E. H. Armstrong soon discovered that F-M would actually result in less noise, and it was not long before F-M came into wide use.

Library of Congress Subject Headings

Radio frequency modulation




South Dakota State University