Signal modulation

Signal modulation encodes information by varying a signal’s properties, such as amplitude, frequency, phase, or pulse timing. It enables information to be transmitted over physical channels.

Amplitude modulation: A modulation method that encodes information by varying a carrier wave’s amplitude. It represents information through the signal property named in this concept’s definition.
Analog signal: A signal whose values vary continuously over time or another continuous domain. Analog modulation varies continuous signal properties to represent information.
Quadrature amplitude modulation: A digital modulation method that encodes symbols through combinations of amplitude and phase changes. It combines two signal properties to carry multiple bits per symbol.
Multiplexing: The combining of multiple signals for transmission over a shared communication channel. It shares channel capacity among signals, while modulation encodes each signal onto a carrier.
Frequency modulation: A modulation method that encodes information by varying a carrier wave’s instantaneous frequency. It changes frequency rather than amplitude to carry the message.
Digital signal: A signal that represents information using a finite set of distinct values. Digital modulation maps discrete symbols onto distinguishable signal states.
Orthogonal frequency-division multiplexing: A multicarrier transmission method that sends data over many closely spaced orthogonal subcarriers. It applies digital modulation across parallel subcarriers in modern broadband links.
Line coding: The representation of digital data as voltage or light-level patterns on a transmission medium. It encodes bits directly as signal patterns rather than modifying a carrier wave.
Phase modulation: A modulation method that encodes information by varying a carrier wave’s phase. It conveys information through shifts in the carrier’s phase.
Information theory: The mathematical study of information, compression, and reliable communication over noisy channels. It provides measures for how much information a modulated signal can convey.

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