- Carrier wave
In
telecommunications , a carrier wave, or carrier is awaveform (usuallysinusoidal ) that is modulated (modified) with an input signal for the purpose of conveying information, [citeweb|title=Carrier wave with no modulation transports no information.|url=http://www.utexas.edu/research/cemd/nim/Agif/CarrWave.html|publisher="University Of Texas "|accessdate=2008-05-30] for example voice or data, to be transmitted, for example byradio or light. This carrier wave is usually of much higherfrequency than thebaseband modulating signal (the signal which contains the information).Frequency modulation (FM) andamplitude modulation (AM) are commonly used to modulate the carrier. In the case ofsingle-sideband modulation (SSB) the carrier is suppressed (and in some forms of SSB eliminated). The carrier must be reintroduced at the receiver by abeat frequency oscillator (BFO).The frequency for a given radio station is actually the carrier wave's
center frequency .Modern modulation systems & the carrier wave
Newer forms of radio communication, such as
spread spectrum andultra wide band , do not transmit a conventional carrier wave, nor doesCOFDM , which is used inDSL and in the European standard for HDTV.
*COFDM should be thought of as an array of symmetrical carrier waves. The rules governing carrier wave propagation affectCOFDM differently than8VSB .
* Some forms ofspread spectrum transmission and most forms ofultra wide band transmission are mathematically defined as being devoid of carrier waves.Definition of carrier waves
In
telecommunication , the term carrier (cxr) or carrier wave has the following meanings:# A
waveform suitable formodulation by aninformation -bearing signal.
# An unmodulated emission. "Note:" The carrier is usually a sinusoidal wave or a uniform or predictable series of pulses. "Synonym:" carrier wave.
# Sometimes employed as asynonym for acarrier system , or asynonym for a telecommunications provider company (operator), such as acommon carrier .:Source:
Federal Standard 1037C andMIL-STD-188 See also
*
Carrier recovery
*Carrier system
*Frequency-division multiplexing References
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