In 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,[1] for example voice or data, to be transmitted, for example by radio or light. waveformogg|right|a sine square and sawtooth wave at 440 hz]] Waveform means the shape and form of a signal such as a Wave moving in a solid liquid or gaseous In Telecommunications, modulation is the process of varying a periodic Waveform, i In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. This carrier wave is usually of much higher frequency than the baseband modulating signal (the signal which contains the information). Frequency is a measure of the number of occurrences of a repeating event per unit Time. In Signal processing, baseband is an adjective that describes signals and systems whose range of Frequencies is measured from zero to a maximum bandwidth In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity Frequency modulation (FM) and amplitude modulation (AM) are commonly used to modulate the carrier. Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave In the case of single-sideband modulation (SSB) the carrier is suppressed (and in some forms of SSB eliminated). Single-sideband modulation ( SSB) is a refinement of Amplitude modulation that more efficiently uses electrical power and bandwidth. The carrier must be reintroduced at the receiver by a beat frequency oscillator (BFO). A beat frequency oscillator or BFO in Radio telegraphy, is a dedicated Oscillator used to create an audio frequency signal from Carrier wave
The frequency for a given radio station is actually the carrier wave's 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
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Modern modulation systems & the carrier wave
Newer forms of radio communication, such as spread spectrum 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. Spread-spectrum techniques are methods by which Energy generated in a particular bandwidth is deliberately spread in the Frequency domain, resulting Ultra-wideband (aka UWB, ultra-wide band, ultraband, etc is a radio technology that can be used at very low energy levels for short-range high-bandwidth Orthogonal frequency-division multiplexing ( OFDM) — essentially identical to Coded OFDM ( COFDM) and Discrete multi-tone modulation ( High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition
- COFDM should be thought of as an array of symmetrical carrier waves. Orthogonal frequency-division multiplexing ( OFDM) — essentially identical to Coded OFDM ( COFDM) and Discrete multi-tone modulation ( The rules governing carrier wave propagation affect COFDM differently than 8VSB. Orthogonal frequency-division multiplexing ( OFDM) — essentially identical to Coded OFDM ( COFDM) and Discrete multi-tone modulation ( 8VSB is the 8-level Vestigial sideband modulation method adopted for terrestrial broadcast of the ATSC digital television standard in the United States,
- Some forms of spread spectrum transmission and most forms of ultra wide band transmission are mathematically defined as being devoid of carrier waves. Spread-spectrum techniques are methods by which Energy generated in a particular bandwidth is deliberately spread in the Frequency domain, resulting Ultra-wideband (aka UWB, ultra-wide band, ultraband, etc is a radio technology that can be used at very low energy levels for short-range high-bandwidth
Definition of carrier waves
In telecommunication, the term carrier (cxr) or carrier wave has the following meanings:
- A waveform suitable for modulation by an information-bearing signal. waveformogg|right|a sine square and sawtooth wave at 440 hz]] Waveform means the shape and form of a signal such as a Wave moving in a solid liquid or gaseous In Telecommunications, modulation is the process of varying a periodic Waveform, i Information as a concept has a diversity of meanings from everyday usage to technical settings In Telecommunication, signalling (UK spelling or signaling (US spelling has the following meanings The use of signals for controlling communications
- An unmodulated emission. 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 Note: The carrier is usually a sinusoidal wave or a uniform or predictable series of pulses. Synonym: carrier wave.
- Sometimes employed as a synonym for a carrier system, or a synonym for a telecommunications provider company (operator), such as a common carrier. This article deals with the general meaning of the term "synonym" In Telecommunication, a carrier system (loosely a synonym with carrier) is a Multichannel telecommunications System in which a number of individual This article deals with the general meaning of the term "synonym" 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 and MIL-STD-188
See also
References
- ^ Carrier wave with no modulation transports no information.. Federal Standard 1037C, entitled Telecommunications Glossary of Telecommunication Terms is a United States Federal Standard issued by the General Services Administration MIL-STD-188 is a series of US military standards relating to Telecommunications Purpose Faced with “past technical deficiencies in telecommunications A carrier recovery system is a circuit used to estimate and compensate for frequency and phase differences between a received signal's Carrier wave and the receiver's In Telecommunication, a carrier system (loosely a synonym with carrier) is a Multichannel telecommunications System in which a number of individual Frequency-division multiplexing ( FDM) is a form of signal Multiplexing where multiple Baseband signals are Modulated on different frequency University Of Texas. Retrieved on 2008-05-30. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1416 - The Council of Constance, called by the Emperor Sigismund a supporter of Antipope John XXIII burns Jerome of Prague following
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