- Carrier wave
telecommunications, a carrier wave, or carrier is a waveform(usually sinusoidal) 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 by radioor light. This carrier wave is usually of much higher frequencythan the basebandmodulating signal (the signal which contains the information). Frequency modulation(FM) and amplitude modulation(AM) are commonly used to modulate the carrier. In the case of single-sideband modulation(SSB) the carrier is suppressed (and in some forms of SSB eliminated). The carrier must be reintroduced at the receiver by a beat frequency oscillator(BFO).
The frequency for a given radio station is actually the carrier wave's
Modern modulation systems & the carrier wave
Newer forms of radio communication, such as
spread spectrumand ultra wide band, do not transmit a conventional carrier wave, nor does COFDM, which is used in DSLand in the European standard for HDTV.
COFDMshould be thought of as an array of symmetrical carrier waves. The rules governing carrier wave propagation affect COFDMdifferently than 8VSB.
* Some forms of
spread spectrumtransmission and most forms of ultra wide bandtransmission are mathematically defined as being devoid of carrier waves.
Definition of carrier waves
telecommunication, the term carrier (cxr) or carrier wave has the following meanings:
waveformsuitable for modulationby an information-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 a
synonymfor a carrier system, or a synonymfor a telecommunications provider company (operator), such as a common carrier.
Federal Standard 1037Cand MIL-STD-188
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