"Modulation of a radio frequency carrier can be defined as the variation of some wave parameter such as amplitude, frequency, or phase, in accordance with intelligence to be transmitted. An unmodulated carrier is simply a continuous sine wave and contains no information other than the fact that the transmitter has been turned on. The spectrum of an unmodulated signal consists of a single frequency. Any type of modulation is characterized by the appearance of additional frequencies, known as sidebands. One of the fundamental problems in radio engineering is to reduce the number of sidebands to a minimum and still adequately represent the information to be transmitted. The large number of radio facilities required by modern civilization can be accommodated in the radio spectrum only if each facility uses bandwidth as sparingly as possible. Reduction of bandwidth inevitably results in lower quality service so that final designs are compromises between conflicting considerations. The purpose of any modulation study are to provide an understanding of the modulation process and a basis for reducing bandwidth. Obviously, the engineer cannot efficiently take measures to reduce bandwidth until he knows the ideal bandwidth requirement for a system.
A study of square wave modulation is of importance in the field of radio telegraphy; telegraphic signals are characterized by sudden transitions between two signal conditions in both on-off keying and frequency shift keying. It is the purpose of this paper to study the signal spectra resulting when a carrier amplitude is modulated by a square wave. These two types of modulation correspond to on-off keying and frequency shift keying, respectively"--Introduction, pages 1-2.
Lund, Louis H., 1919-1998
M.S. in Physics
Missouri School of Mines and Metallurgy
iii, 39 pages
© 1951 Richard H. Duncan, All rights reserved.
Thesis - Open Access
Radio frequency modulation
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Duncan, Richard Henry, "Square wave modulation" (1951). Masters Theses. 3028.