Carrier wave

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In telecommunications, the carrier wave , carrier signal , or just carrier , is a modulated (modulated) modular (usually sinusoidal) waveform with an input signal for the purpose of conveying information. This carrier wave usually has a much higher frequency than the input signal does. Carrier objectives are usually good for transmitting information through space as electromagnetic waves (as in radio communications), or to allow multiple operators at different frequencies to share common physical transmission media with multiplexed frequency division (eg, cable television systems). The term is also used for unmodulated emissions in the absence of modulating signals.

Video Carrier wave

Overview

Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) to add information to the operator. The frequency spectrum of the modulated AM or FM signal from the radio transmitter is shown above. It consists of a strong component (C) at the carrier frequency $Â\; Â{\displaystyle Â\; Â\; Â\; Â\; Â\; Â\; Â}$ _{           f                                           {\ displaystyle f_ {C}}  Â} with modulations contained in the narrow sidebands (S) above and below the carrier frequency. Radio frequency or television stations are considered as carrier frequencies. However the carrier itself is not useful in transmitting information, so the energy in the carrier component is a waste of transmitter power. Therefore, in many modern modulation methods, carriers are not transmitted. For example, in single-sideband modulation (SSB), the operator is pressed (and in some form of SSB, omitted). The carrier must be reintroduced at the receiver by a pulse frequency oscillator (BFO).

Maps Carrier wave

Unobstructed modulation system

Newer forms of radio communications (such as spread spectrum and ultra-wideband) do not use conventional sinusoidal carrier waves, nor OFDM (used in DSL and in European standards for HDTV).

• OFDM can be regarded as an array of symmetric carrier waves. The rules governing carrier wave propagation affect OFDM differently from 8VSB.
• Some forms of spectrum spectrum spread (and most ultra-wide forms) are mathematically defined as having no carrier waves. Implementation of the transmitter usually produces residual carriers that may (or may not) be detected or transmitted.

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Carrier

Leak carrier is a disturbance caused by cross-talk or DC offset. It is present as an unmodulated sine wave in the signal bandwidth, whose amplitude does not depend on the signal amplitude. See frequency mixer, to read more about carrier leakage or local oscillator feedback.

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See also

• Recovery operator
• Operator system
• Operator tone
• Frequency-division multiplication
• Sideband

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References

Source of the article : Wikipedia