Variation of the frequency of a carrier wave (commonly a radio wave) in accordance with variations in the audio signal being sent. Developed by American electrical engineer Edwin H. Armstrong in the early 1930s, FM is less susceptible to outside interference and noise (e.g., thunderstorms, nearby machinery) than is AM. Such noise generally affects the amplitude of a radio wave but not its frequency, so an FM signal remains virtually unchanged. FM is also better able to transmit sounds in stereo than AM. Commercial FM broadcasting stations transmit their signals in the frequency range of 88 megahertz (MHz) to 108 MHz. For more information on FM, visit Britannica.com. Britannica Concise Encyclopedia. Copyright © 1994-2008 Encyclopædia Britannica, Inc. (1) An earlier magnetic disk encoding method that places clock bits onto the medium along with the data bits. It was superseded by MFM and RLL.FM
in full frequency modulationfrequency modulation
(2) Varying the frequency of the waves of a carrier in order to transmit analog or digital data. Frequency modulation (FM) is widely used in audio transmission, not only for its namesake FM radio, but for the audio channels in television. See modulation and carrier.Vary the Angle In FM modulation, the frequency of the carrier wave is varied by the incoming signal. In this example, the modulating wave implies an analog signal. Digital Frequency Shift Keying (FSK) For digital signals, frequency shift keying (FSK) uses two frequencies for 0 and 1 as in this example.
Saturday, June 20, 2009
Frequency modulation
Posted by M. USMAN SAJJAD at 6:16 AM
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