Modulation

: For the musical use of "modulation", see modulation (music).

Related Topics:
Music - Modulation (music)

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Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information. One of the three key characteristics of a signal is usually modulated: its phase, frequency or amplitude. A device that performs modulation is known as a modulator and a device that performs demodulation is known as a demodulator. A device that can do both operations is a modem (a contraction of the two terms).

Related Topics:
Carrier signal - Sinusoidal - Information - Phase - Frequency - Amplitude - Modem

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In digital modulation, the changes in the signal are chosen from a fixed list (the modulation alphabet) each entry of which conveys a different possible piece of information (a symbol). The alphabet is often conveniently represented on a constellation diagram.

Related Topics:
Digital - Constellation diagram

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In analogue modulation, the change is applied continuously in response to the data signal. The modulation may be applied to various aspects of the signal as the lists below indicate.

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Modulation is generally performed to overcome signal transmission issues such as to allow

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• Easy (low loss, low dispersion) propagation as electromagnetic waves
• Multiplexing — the transmission of multiple data signals in one frequency band, on different carrier frequencies.
• Smaller, more directional antennas

Carrier signals are usually high frequency electromagnetic waves.

Related Topics:
Carrier signals - Electromagnetic waves

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Modulation: Analogue Modulation Techniques ►