frequency modulation


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Related to frequency modulation: phase modulation, amplitude modulation

frequency modulation:

see modulationmodulation,
in communications, process in which some characteristic of a wave (the carrier wave) is made to vary in accordance with an information-bearing signal wave (the modulating wave); demodulation is the process by which the original signal is recovered from the wave
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; radioradio,
transmission or reception of electromagnetic radiation in the radio frequency range. The term is commonly applied also to the equipment used, especially to the radio receiver.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Frequency Modulation

 

a method of modulating oscillations, in which the frequency of the high-frequency carrier oscillations is varied over time according to a law that corresponds to the signal being transmitted. A feature of frequency modulation is its high immunity to noise. Frequency modulation is used for high-quality transmission of information: in radio broadcasting (in the very-high-frequency band), for the audio signal of television programs, in voice-frequency telegraphy, in radiotelephone communications, and in other fields.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

frequency modulation

[′frē·kwən·sē ‚mäj·ə‚lā·shən]
(communications)
Modulation in which the instantaneous frequency of the modulated wave differs from the carrier frequency by an amount proportional to the instantaneous value of the modulating wave. Abbreviated FM.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Frequency Modulation

(communications)
(FM) A method of encoding data by varying the frequency of a constant amplitude carrier signal.

Contrast Amplitude Modulation.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

frequency modulation

(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 It was superseded by MFM and RLL.

(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.








A Sad Tale of FM Origins


FM radio was invented in the early 1930s by Edwin Howard Armstrong, who years earlier had made a fortune selling RCA his amplifier technology. When he asked RCA to license his FM in 1933, RCA turned it down and pursued its own research. Seven years later, RCA offered him USD $1 million for outright purchase, but Armstrong declined. He was angry at the long hiatus and thought the offer too low. Later, Armstrong sued for patent infringement when he discovered RCA was using his technology, but RCA's legal tactics kept him at bay for so many years that the patents expired. Fighting the company also depleted his wealth. In 1954, Armstrong wrote a note to his wife, walked over to his bedroom window and jumped 13 stories to his death. Eventually, his wife received millions in back royalties from the company.
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References in periodicals archive ?
At intermediate pressures, extensive frequency modulation was produced in proportion to pressure.
The frequency modulation law obtained by solving through numerical methods of the equations [T.sub.gT](f) = t, is depicted in Fig.
On the contrary, instantaneous spatial frequency estimates suffer from the abrupt spatial transitions in the test image: Estimates of vertical frequency modulation, even though flattened, are wrong, whereas horizontal ones are correct outside the space between horizontal parts of letter C (see the profiles in column E).
Frequency modulation of a 4.43-MHz subcarrier transmits the picture information.
The EL6119C incorporates two separate high frequency modulation (HFM) oscillators for up to 500 MHz and 100 mA, peak to peak, per output.
It's designated "FM." Not quite "frequency modulation," although one could argue that by placing the vehicle's V6 engine so that its center of gravity is located just behind the front axle there's not only a 52:48 front/rear weight distribution, but that there's improvement in handling, stability, and ride quality.
The composers of spectral music have been influenced by several electronic processes besides additive synthesis: filtering, ring modulation, and frequency modulation among others.
But in fact, the halftone screening methods used in any process reduce the tonal range, detail reproduction and color palette available to a printer and consequently the degree of fidelity to a photographic original.With advances in photographic, electronic and print reproduction technologies as well as innovative software engineering, frequency modulation screening techniques or stochastic screening has emerged as a method that can equal direct engraving gravure printing.
Frequency modulation, a new method of radio transmission and reception, was developed by Edwin H.
Traditional broadcast radio modulation schemes like FM (frequency modulation) or AM (amplitude modulation) are used because signals are picked up by many receivers.

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