In this note, we are going to Define Amplitude Modulation. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.
Author Name: Arun Paul.
Define Amplitude Modulation
Amplitude Modulation or AM is the process of changing the amplitude of a high frequency carrier wave in response to the intensity of the input signal.
Waveform of Amplitude Modulation
In amplitude modulation, only the amplitude of the carrier wave is modified in response to the signal’s strength. However, the modified waves’ frequency, or carrier frequency, remains constant. The figure represents the principle of amplitude modulation.
Fig (i) shows the audio electrical signal whereas Fig (ii) shows a carrier wave of constant amplitude. Fig (iii) shows the amplitude modulated wave.
It is worth noting that the amplitudes of both positive and negative half-cycles of the carrier wave vary in response to the signal. For example, when the positive signal increases, so does the amplitude of the carrier wave. However, during the signal’s negative half-cycle, the amplitude of the carrier wave falls. Amplitude Modulation is carried out via an electrical circuit known as a modulator.
The following points are interesting to think about in amplitude modulation –
- The amplitude of the carrier wave changes according to the intensity of the signal.
- The amplitude variations of the carrier wave is at the signal frequency fs.
- The frequency of the amplitude modulated waves remains the same i.e. carrier frequency fc.