frequency modulation

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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 It might be outdated or ideologically biased.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 It was superseded by MFM and RLL.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 ?
Since the switching delays are very problematic in SFM buck converters in CCM [3,4], effect of SFM on the boost converter output voltage ripples is to be evaluated considering turn-on and turn-off switching delays ([t.sub.don] and [t.sub.doff] respectively) between frequency modulated control signal and the power MOSFET drain-to-source voltage.
Beauchaine recommends using an FM (frequency modulated) system.
It uses frequency modulated radio waves in definite frequency channels of 300 mega-cycles or higher.
Frequency Modulated Continuous Wave (FMCW) radars are a fast expanding area in radar technology due to their stealth features, extremely high resolutions, and relatively clutter free displays.
The solid-state Blighter passive electronically scanned array (PESA) radar detects small and slow-moving targets - even in cluttered environments - due to the radar's coactive frequency modulated continuous wave (FMCW) Doppler fast-scan processing.
[K.sub.i] = [B.sub.i]/[T.sub.i] is the frequency modulated rate.
The Centerwave 6000 is said to be key technology for quality assurance during the extrusion of big tubes, and features several transceivers arranged around the circumference of a tube, sending and receiving continuous frequency modulated millimeter waves for a non-contact and [micro]m-precise online measurement of diameter, ovality and wall thickness for larger tubes during the extrusion.
The rate of frequency modulated in azimuth at the center of azimuth beam denoted as [K.sub.a] can be expressed approximately as Equation (6) [4].
According to [4], for the majority of frequency modulated signals, the quality of the approximations achieved by stationary phase method increases in the same time with the increasing of the product between time width (T) and bandwidth (B) assigned to these (radar) signals.

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