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Carrier wave
 
 
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In telecommunications, a carrier wave, or carrier is a waveform
Waveform

Waveform means the shape and form of a signal such as a wave moving in a solid, liquid or gaseous medium.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form....
 (usually sinusoidal) that is modulated
Modulation

In telecommunications, modulation is the process of varying a Periodic function waveform, i.e. a tone, in order to use that signal to convey a message, in a similar fashion as a musician may modulate the tone from a musical instrument by varying its volume, timing and Pitch ....
 (modified) with an input signal
Signal (electrical engineering)

In the fields of telecommunications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
 for the purpose of conveying information. This carrier wave is usually of much higher frequency
Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
 than the input signal.

Frequency modulation
Frequency modulation

In telecommunications, frequency modulation conveys information over a carrier wave by varying its frequency . In analog signal applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal....
 (FM) and amplitude modulation
Amplitude modulation

Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave....
 (AM) are commonly used methods to modulate the carrier. In the case of single-sideband modulation
Single-sideband modulation

Single-sideband modulation is a refinement of amplitude modulation that more efficiently uses electric power and bandwidth . It is closely related to vestigial sideband modulation ....
 (SSB) the carrier is suppressed (and in some forms of SSB eliminated).






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Encyclopedia


In telecommunications, a carrier wave, or carrier is a waveform
Waveform

Waveform means the shape and form of a signal such as a wave moving in a solid, liquid or gaseous medium.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form....
 (usually sinusoidal) that is modulated
Modulation

In telecommunications, modulation is the process of varying a Periodic function waveform, i.e. a tone, in order to use that signal to convey a message, in a similar fashion as a musician may modulate the tone from a musical instrument by varying its volume, timing and Pitch ....
 (modified) with an input signal
Signal (electrical engineering)

In the fields of telecommunications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
 for the purpose of conveying information. This carrier wave is usually of much higher frequency
Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
 than the input signal.

Frequency modulation
Frequency modulation

In telecommunications, frequency modulation conveys information over a carrier wave by varying its frequency . In analog signal applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal....
 (FM) and amplitude modulation
Amplitude modulation

Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave....
 (AM) are commonly used methods to modulate the carrier. In the case of single-sideband modulation
Single-sideband modulation

Single-sideband modulation is a refinement of amplitude modulation that more efficiently uses electric power and bandwidth . It is closely related to vestigial 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
Beat frequency oscillator

A beat frequency oscillator or BFO in radio telegraphy, is a dedicated oscillator used to create an audio frequency signal from carrier wave transmissions to make them audible, as they are not Broadcasting as such....
 (BFO).

The frequency for a given radio or television station is actually the carrier wave's center frequency
Center frequency

In electrical engineering and telecommunications, the center frequency of a filter or channel is a measure of a central frequency between the upper and lower cutoff frequency....
.

Modern modulation systems & the carrier wave

Newer forms of radio communication, such as spread spectrum
Spread spectrum

Spread-spectrum techniques are methods by which electromagnetic radiation generated in a particular Bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth....
 and ultra wide band, do not transmit a conventional carrier wave, nor does COFDM, which is used in DSL and in the European standard for HDTV
High-definition television

High-definition television is a digital television broadcasting system with higher than traditional television systems . HDTV is digitally broadcast; the earliest implementations used analog broadcasting, but today digital television signals are used, requiring less Bandwidth due to digital video compression....
.
  • COFDM should be thought of as an array of symmetrical carrier waves. The rules governing carrier wave propagation affect COFDM differently than 8VSB
    8VSB

    8VSB is the 8-level vestigial sideband modulation method adopted for terrestrial broadcast of the ATSC digital television standard in the United States, Canada, and other countries....
    .
  • Some forms of spread spectrum
    Spread spectrum

    Spread-spectrum techniques are methods by which electromagnetic radiation generated in a particular Bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth....
     transmission and most forms of ultra wide band transmission are mathematically defined as being devoid of carrier waves.


Definition of carrier waves

In telecommunication
Telecommunication

Telecommunication is the assisted Transmission of Signal over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, Drum , Semaphore line, flag signals or heliograph....
, the term carrier (cxr) or carrier wave has the following meanings:

  1. A waveform
    Waveform

    Waveform means the shape and form of a signal such as a wave moving in a solid, liquid or gaseous medium.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form....
     suitable for modulation
    Modulation

    In telecommunications, modulation is the process of varying a Periodic function waveform, i.e. a tone, in order to use that signal to convey a message, in a similar fashion as a musician may modulate the tone from a musical instrument by varying its volume, timing and Pitch ....
     by an information
    Information

    Information as a Conveyed concept has a diversity of meanings, from everyday usage to technical settings. Generally speaking, the concept of information is closely related to notions of constraint, communication, control system, data, form, instruction, knowledge, Meaning , stimulation, pattern, perception, and knowledge representation....
    -bearing signal.
  2. An unmodulated emission
    Emission (electromagnetic radiation)

    In physics, emission is the process by which the energy of a photon is released by another entity, for example, by an atom whose electrons make a transition between two electronic energy levels....
    . Note: The carrier is usually a sinusoidal wave
    Sine wave

    The sine wave or sinusoid is a function that occurs often in mathematics, physics, signal processing, hearing , electrical engineering, and many other fields....
     or a uniform or predictable series of pulses. Synonym: carrier wave.
  3. Sometimes employed as a synonym
    Synonym

    Synonyms are different words with identical or very similar meanings. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy....
     for a carrier system
    Carrier system

    In telecommunication, a carrier system is a multichannel telecommunications system in which a number of individual channels are multiplexed for transmission ....
    , or a synonym
    Synonym

    Synonyms are different words with identical or very similar meanings. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy....
     for a telecommunications provider company (operator), such as a common carrier
    Common carrier

    A common carrier is a business that transports people, goods, or services and offers its services to the general public under license or authority provided by a regulatory body....
    .


Source: Federal Standard 1037C
Federal Standard 1037C

Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended....
 and MIL-STD-188
MIL-STD-188

MIL-STD-188 is a series of U.S. military standards relating to telecommunications....


See also

  • Carrier recovery
    Carrier recovery

    A carrier recovery system is a Electronic circuit used to estimate and compensate for frequency and phase differences between a received signal's carrier wave and the receiver's local oscillator for the purpose of coherent demodulation....
  • Carrier system
    Carrier system

    In telecommunication, a carrier system is a multichannel telecommunications system in which a number of individual channels are multiplexed for transmission ....
  • Carrier tone
  • Frequency-division multiplexing
    Frequency-division multiplexing

    Frequency-division multiplexing is a form of signal multiplexing which involves assigning non-overlapping frequency ranges to different signals or to each "user" of a medium....