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amplitude modulation

   Also found in: Dictionary/thesaurus, Medical, Financial, Acronyms, Wikipedia, Hutchinson 0.06 sec.
amplitude modulation: see modulation modulation, 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
..... Click the link for more information. ; radio radio, 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.
..... Click the link for more information. .

Varying the voltage of a carrier or a direct current in order to transmit analog or digital data. Amplitude modulation (AM) is the oldest method of transmitting human voice electronically. In an analog telephone conversation, the voice waves on both sides are modulating the voltage of the direct current loop connected to them by the telephone company.

Modulate a Carrier
Amplitude modulation (AM) is also widely used to alter a carrier wave to transmit data. For example, in AM radio, the voltage (amplitude) of a carrier with a fixed center frequency (the station's channel) is varied (modulated) by the analog audio signal.

AM is also used for digital data. In quadrature amplitude modulation (QAM), both amplitude and phase modulation are used to create different binary states for transmission (see QAM). AM is also used to modulate light waves in optical fibers. See modulation and carrier.

Vary the Amplitude
In AM modulation, the voltage (amplitude) of the carrier is varied by the incoming signal. In this example, the modulating wave implies an analog signal.


Digital Amplitude Shift Keying (ASK)
For digital signals, amplitude shift keying (ASK) uses two voltage levels for 0 and 1 as in this example.

(communications)Amplitude Modulation - (AM) A method of encoding data by varying the amplitude of a constant frequency carrier.

Contrast Frequency Modulation.
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The company's radio stations consist of 40 frequency modulation (FM) and 12 amplitude modulation (AM) stations located in Arizona, California, Colorado, Florida, Nevada, New Mexico and Texas.
Entravision Communications Corp. (EVC) by Los Angeles Business Journal
The phase control and amplitude modulation of separated oscillatory fields are discussed for the measurement of the T-odd correlation term.
A Ramsey's method with pulsed neutrons for a T-violation experiment by Skoy, V. / Journal of Research of the National Institute of Standards and Technology
The entire suite of audio effects includes: Amplitude Modulation, Chorus, Delay/Echo, Distortion, Dynamics, Compression, Enveloping, Flange/Wah-Wah, Gapper/Snipper, Noise Gate, Pitch Bend/Shift, Reverb, and Vibrato; three Eqs--Graphic, Parametric, and Paragraphic and Time Compression/Expand.
SONIC FOUNDRY ANNOUNCES SOUND FORGE 5.0 by EDP Weekly's IT Monitor
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