Amplitude-modulated – Definition & Meaning

Amplitude modulation, commonly known as AM, is a type of modulation technique used in radio communication to transmit signals. It is one of the oldest and simplest modulation techniques, which has been in use since the early days of radio communication. In this article, we will discuss the definition and meaning of amplitude-modulated in detail.


Amplitude modulation is a process of varying the amplitude of a carrier wave in proportion to the amplitude of the modulating signal. The modulating signal can be an audio signal, video signal, or any other signal that needs to be transmitted. The amplitude of the carrier wave is varied by adding or subtracting the modulating signal from it.


The concept of amplitude modulation was first proposed by John Renshaw Carson in 1915. He demonstrated that a modulating signal could be transmitted by varying the amplitude of a carrier wave. The first AM radio broadcast was made in 1920, and since then, AM has been the primary modulation technique used in radio communication.

Meaning in different dictionaries

According to the Oxford English Dictionary, amplitude modulation is “a method of transmitting a radio signal in which the amplitude of a high-frequency carrier wave is varied in accordance with the amplitude of a low-frequency signal.”
Merriam-Webster defines amplitude modulation as “a system of radio transmission in which the amplitude of a high-frequency wave is varied in accordance with the amplitude of a low-frequency signal.”


Amplitude modulation is commonly associated with radio communication, especially in the medium-wave and short-wave frequency bands. It is also used in some types of radar systems and for transmitting signals over long distances.


Some synonyms of amplitude modulation include AM, amplitude shift keying (ASK), and on-off keying (OOK).


The antonyms of amplitude modulation are frequency modulation (FM), phase modulation (PM), and pulse modulation.

The same root words

The root words of amplitude modulation are amplitude and modulation. Amplitude refers to the maximum displacement or distance moved by a wave from its rest position, while modulation refers to the process of varying a signal in order to transmit information.

Example Sentences

  1. The AM radio station broadcasts its signal using amplitude modulation.
  2. The radar system uses amplitude modulation to detect the distance and speed of objects.
  3. The on-off keying modulation technique is a type of amplitude modulation used in digital communication systems.
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