Carrier wave
In
This carrier wave usually has a much higher frequency than the message signal does. This is because it is impractical to transmit signals with low frequencies.
The purpose of the carrier is usually either to transmit the information through space as an
The term originated in radio communication, where the carrier wave creates the waves which carry the information (modulation) through the air from the transmitter to the receiver. The term is also used for an unmodulated
In
Overview
The term carrier wave originated with radio. In a
Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) to add information to the carrier. The frequency spectrum of a modulated AM or FM signal from a radio transmitter is shown above. It consists of a strong component (C) at the carrier frequency with the modulation contained in narrow sidebands (SB) above and below the carrier frequency. The frequency of a radio or television station is considered to be the carrier frequency. However the carrier itself is not useful in transmitting the information, so the energy in the carrier component is a waste of transmitter power. Therefore, in many modern modulation methods, the carrier is not transmitted. For example, in 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).
Carriers are also widely used to transmit multiple information channels through a single cable or other
Carrierless modulation systems
The information in a modulated radio signal is contained in the
Carrier leakage
Carrier leakage is interference caused by crosstalk or a DC offset. It is present as an unmodulated sine wave within the signal's bandwidth, whose amplitude is independent of the signal's amplitude. See frequency mixers.
See also
References
- University Of Texas. Archived from the originalon 2008-04-14. Retrieved 2008-05-30.
- ^ Federal Standard 1037C and MIL-STD-188
- ^ Rory PQ (May 8, 2019). "What Is Modulation and How Does It Improve Your Music". Icon Collective. Retrieved August 23, 2020.
The dictionary definition of carrier wave at Wiktionary