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Online Simulator for Amplitude Modulation & Demodulation


Amplitude Modulation (AM)


Change the parameter values to see the effect. See Mathematical Background =>

Message Frequency (Hz)

Carrier Frequency (Hz)

Message Signal Amplitude

Carrier Signal Amplitude


Mathematical Background of Amplitude Modulation (AM)


sAM(t) = Ac[1 + kam(t)] cos(ωct)

where ω = 2πf & ka = Amplitude Sensitivity

Modulation index, μ = kaAm or Am/Ac
where Am and Ac are amplitudes of the message and carrier respectively

The amplitude of the carrier signal varies in accordance with the message signal's amplitude.

Read more about Amplitude Modulation and demodulation


🧪 Experiment for Students:

"Set the Carrier Amplitude to 1 and the Message Amplitude to 1. This produces a modulation index of 1 (100% modulation). Observe the modulated waveform and envelope. Next, keep the Carrier Amplitude at 1 and increase the Message Amplitude to 1.5. This produces a modulation index greater than 1 (overmodulation), causing envelope distortion and making accurate signal recovery difficult."

Amplitude Modulation Knowledge Check

What happens when the modulation index of an AM signal exceeds 1?

Understanding AM Performance

Modulation Index (m)

The modulation index determines the depth of modulation. For standard AM, 0 ≤ m ≤ 1 produces a clean envelope. When m > 1, overmodulation occurs, resulting in envelope distortion and poor signal recovery at the receiver.

Bandwidth Requirement

An AM signal occupies twice the highest message frequency. If the message bandwidth is B, the required AM bandwidth is 2B because both upper and lower sidebands are transmitted.

Noise Sensitivity

AM is highly susceptible to amplitude noise because information is carried in the signal envelope. Electrical interference and fading directly affect the received audio quality, which is why FM generally provides better noise performance.

MATLAB Codes for Modulation

View MATLAB Codes for Amplitude Modulation (AM) =>

Try Other Interactive Online Simulators

📻 Analog Modulations

📻 Digital Modulations (Basics)

🔢 M-ary QAM & PSK Modulations

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Instructions for Amplitude Demodulation

  • Step 1: Tunable LPF's Cutoff frequency works in accordance with the Message frequency
  • Step 2: You can Demodulate the AM Signal clicking on the 'Perform AM Demodulation' button
  • Step 3: Click on the 'Show Frequency Spectrums' button above to see spectrums of the message, AM modulated and demodulated signal. The frequency spectra is shown for a modulation index of 1.

Cut-off Frequency

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