Carrier wave

In <a href="/facts/Telecommunications/vxoj1cxR">telecommunications</a>, a carrier wave, carrier signal, or just carrier, is a periodic <a href="/facts/Waveform/yAskMREw">waveform</a> (usually <a href="/facts/Sinusoidal/mD1CB09M">sinusoidal</a>) that conveys information through a process called <a href="/facts/Modulation/aAXPjINv">modulation</a>. One or more of the wave's properties, such as amplitude or frequency, are modified by an information bearing signal, called the message signal or modulation signal. The carrier frequency is usually much higher than the message signal <a href="/facts/Frequency/QUSbPaW8">frequency</a>; this is because it is usually impractical to transmit signals with low frequencies over long distances (due to attenuation).
The purpose of the carrier is usually either to transmit the information through space as an <a href="/facts/Electromagnetic_wave/Ynx7ujCW">electromagnetic wave</a> (as in <a href="/facts/Radio_communication/XFr909M2">radio communication</a>), or to allow several carriers at different frequencies to share a common physical transmission medium by <a href="/facts/Frequency_division_multiplexing/lgj6TMU1">frequency division multiplexing</a> (as in a <a href="/facts/Cable_television/GzXa4pbW">cable television</a> system). 
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 <a href="/facts/Emission_(electromagnetic_radiation)/fxumR717">emission</a> in the absence of any modulating signal.
In <a href="/facts/Music_production/RcLFfQKL">music production</a>, carrier signals can be controlled by a modulating signal to change the sound property of an audio recording and add a sense of depth and movement.

Carrier wave open-in-new

Carrier wave