amplitude modulation

Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent. For example, changes in the signal strength can be used to reflect the sounds to be reproduced by a speaker, or to specify the light intensity of television pixels. (Contrast this with frequency modulation, also commonly used for sound transmissions, in which the frequency is varied; and phase modulation, often used in remote controls, in which the phase is varied.)
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Noun
1. modulation of the amplitude of the (radio) carrier wave
(synonym) AM
(hypernym) modulation

Modulation in which the amplitude of a carrier wave is varied in accordance with some characteristic of the modulating signal . (188 ) Note: Amplitude modulation implies the modulation of a coherent carrier wave by mixing it in a nonlinear device with the modulating signal to produce discrete upper and lower sidebands, which are the sum and difference frequencies of the carrier and signal. The envelope of the resultant modulated wave is an analog of the modulating signal. The instantaneous value of the resultant modulated wave is the vector sum of the corresponding instantaneous values of the carrier wave, upper sideband , and lower sideband. Recovery of the modulating signal may be by direct detection or by heterodyning.

<communications> (AM) A method of encoding data by varying the amplitude of a constant frequency carrier.
Contrast Frequency Modulation.
(2001-04-30)

amplitude modulation
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