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 signal strength may be used to specify the sounds to be reproduced by a loudspeaker, or the light intensity of television pixels. Contrast this with frequency modulation, in which the frequency is varied, and phase modulation, in which the phase is varied.
In the mid-1870s, a form of amplitude modulation—initially called "undulatory currents"—was the first method to successfully produce quality audio over telephone lines. Beginning with Reginald Fessenden's audio demonstrations in 1906, it was also the original method used for audio radio transmissions, and remains in use today by many forms of communication—"AM" is often used to refer to the mediumwave broadcast band (see AM radio).
Other articles related to "amplitude modulation, modulation, amplitudes, amplitude":
... Quadrature amplitude modulation (QAM) is both an analog and a digital modulation scheme ... message signals, or two digital bit streams, by changing (modulating) the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or ... of both phase-shift keying (PSK) and amplitude-shift keying (ASK), or (in the analog case) of phase modulation (PM) and amplitude modulation ...
... Figure of merit for Amplitude modulation is given by Figure of merit for DSB-SC receiver or that of an SSB modulation is always unity ...
39 0 ... Minute mark no amplitude modulation ... The phase modulation generally encodes the same data as the amplitude modulation, but differs for bits 59 through 14, inclusive ... Bit 59 (no amplitude modulation) is phase-modulated as a 0 bit ...
... This occurs in Amplitude modulation (AM) ... Amplitude Modulation In Amplitude modulation the instantaneous change in the amplitude of the carrier Frequency with respect to the amplitude of the modulating or Base band signal ...
Famous quotes containing the words modulation and/or amplitude:
“Every accent, every emphasis, every modulation of voice, was so perfectly well turned and well placed, that, without being interested in the subject, one could not help being pleased with the discourse; a pleasure of much the same kind with that received from an excellent piece of music. This is an advantage itinerant preachers have over those who are stationary, as the latter can not well improve their delivery of a sermon by so many rehearsals.”
—Benjamin Franklin (17061790)
“Imagination, which in truth
Is but another name for absolute power
And clearest insight, amplitude of mind,
And reason, in her most exalted mood.”
—William Wordsworth (17701850)