Amplitude Modulation

This tutorial demonstrates how mathematics is applied in communication systems. Use the interactive simulator below to explore how varying modulation parameters alter signal behavior.

What is Amplitude Modulation?

Amplitude modulation is a technique used to transmit electric signals containing information using radio waves. Let \(f(t)\) be the electric signal to transmit (representing information via a mathematical function) and \(\cos(\omega t)\) be the carrier signal. Let the amplitude of the carrier change in terms of \(f(t)\) as follows:

\[ F(t) = (1 + f(t)) \cos(\omega t) \]

This is called amplitude modulation since the amplitude of the carrier changes according to \(f(t)\). To understand this precisely, let the signal to transmit be a simple sinusoidal signal of the form \(f(t) = m \cos(s t)\). Hence, \(F(t)\) becomes:

\[ F(t) = (1 + m \cos(s t)) \cos(\omega t) \]

The applet below helps you explore the amplitude modulated signal \(F(t)\) when the modulation index \(m\) changes from zero to larger positive values.

Interactive Simulation on Amplitude Modulation

  1. Click the "Plot Signal" button above to refresh/start.
  2. Set parameter m to zero (no modulation). Explain the graph obtained.
  3. Set parameter m to 1. Explain the graph obtained.
  4. Set parameter m to values larger than 1. Explain the graph obtained.

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