Amplitude modulation

Amplitude modulation encodes information by varying a carrier wave’s amplitude while keeping its frequency and phase fixed.

Carrier wave: A periodic signal that conveys information when one or more of its properties are varied. Amplitude modulation varies this periodic signal’s strength without changing its frequency or phase.
Frequency modulation: A modulation method that encodes information by varying a carrier wave’s instantaneous frequency. Unlike AM, it carries the message in frequency changes rather than amplitude changes.
AM broadcasting: Radio broadcasting that transmits audio using amplitude-modulated radio-frequency carriers. It is the best-known public use of conventional amplitude modulation.
Modulation: The process of varying a signal’s properties to encode information for transmission. Amplitude modulation is one specific way to vary a carrier to transmit a message.
Modulation index: A dimensionless measure of how strongly a modulating signal varies a carrier’s amplitude. It quantifies modulation depth and indicates whether the envelope can be recovered without distortion.
Phase modulation: A modulation method that encodes information by varying a carrier wave’s phase. It changes carrier phase instead of the amplitude varied in AM.
Amplitude-modulated radar: Radar that varies a transmitted carrier’s amplitude to convey information, including timing or ranging signals. AM waveforms can support radar measurements as well as radio communication.
Amplitude: The maximum magnitude of a wave’s oscillation relative to its reference level. AM encodes information in changes to this wave property.
Sideband: A frequency component produced when a carrier is modulated, located above or below the carrier frequency. Amplitude modulation places message information in sidebands surrounding the carrier.
Single-sideband modulation: An amplitude-modulation technique that transmits one sideband while suppressing the carrier and the other sideband. It preserves AM’s sideband-based information while using less bandwidth and transmitter power.

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