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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.

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.

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.

Frequency Modulation

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

Contrast Amplitude Modulation.

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 It was superseded by MFM and RLL.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.
References in periodicals archive ?
Koo, "Sidelobes reduction using simple two and tri-stages nonlinear frequency modulation (NLFM)," Progress In Electromagnetics Research, Vol.
Side Effects Evaluation of Switching Frequency Modulation in Power Converters // Proceedings of 32nd Annual IEEE IECON, 2006.
The real-time synthesis unit performs additive synthesis with frequency modulation on sixty-four simultaneous oscillators at 44.
Vibrato-like frequency modulation can also be produced electronically, but generally is not needed if resonances in the voice-electronic resonator system can be arbitrarily produced.
Examination of influence of periodic switching frequency modulation in dc/dc converters on power quality on a load // Proceedings of the 11th Biennial Baltic Electronics Conference.
The military's Single-Channel Ground-Air Radio System very high frequency frequency modulation radio system is limited to line-of-sight propagation.
Types of frequency modulation supported include CW, constant, frequency modulation on pulse (FMOP) and agile (pulse-to-pulse, and switch and dwell).
This modulation can be frequency modulation (chirp) or phase reversals (binary-phase-shift keying) as explained in a previous column about pulse compression (see "Radar, Part 5 -- Pulse Compression," JED, September 2000, p.
The combination of a Silent Switcher topology and spread spectrum frequency modulation minimizes EMI concerns.
It requires parsing out two factors, (1) the psychophysics of pitch perception with and without frequency modulation, and (2) the motor control for producing a constant fundamental frequency ([F.
But the team still faced the problem of reliability, so they turned to optical frequency modulation.
As a result of the switching frequency modulation (SFM), energy of discrete harmonics of unmodulated switching frequency is spread over a wider frequency range, thus peak EMI levels are significantly reduced [2] as it is shown in Fig.

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