Demodulator

Article By:

White, Stanley A. Signal Processing and Controls Engineering, San Clemente, California.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.185200

A device that recovers from a transmitted signal information that has been embedded in the signal by a process of modulation. The modification of a usually sinusoidal electrical carrier signal (or simply carrier) for the purpose of transmitting information that is carried on a second electrical modulating signal or information signal is called modulation. The device or circuit that performs the modulation is called a modulator. The information may be from any of a variety of sources such as sensor data, speech signals, or image data. The modulator varies the carrier in amplitude, frequency, phase, or some combination to embed the information for efficient transmission. After reception, this information is recovered from the received signal by a demodulator. During modulation, information is shifted in frequency from baseband to the carrier frequency for efficient transmission. Demodulation is the reverse process by which the information is restored in frequency to its baseband. See also: Carrier (communications); Modulation; Modulator

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