Signal Modulation Simulator
Visualize how AM, FM, and PM modulation schemes encode information onto carrier waves. Adjust carrier frequency, message frequency, modulation depth, and noise in real-time.
How to Use This Tool
- Select a modulation type (AM, FM, or PM) to switch modes
- Adjust sliders to see real-time waveform changes
- Toggle Message/ Spectrum to show or hide individual components
- Add noise to simulate real-world signal degradation
- Observe the spectrum to see frequency-domain effects of modulation
Information encoded in the amplitude of the carrier wave. Used in AM broadcast (530-1700 kHz), shortwave, and aviation.
Understanding the Waveforms
Top (green): The baseband message signal — the information you want to transmit. This could be audio, data, or any analog signal.
Middle (purple): The carrier wave — a high-frequency sinusoid that acts as the transport mechanism. It carries no information by itself.
Bottom (orange): The modulated signal — the carrier wave after the message has been encoded onto it. This is what actually gets transmitted through the air.
Spectrum: Shows the frequency content of the modulated signal. AM produces carrier + two sidebands. FM produces theoretically infinite sidebands spaced by the modulation frequency. PM shows similar spectral broadening.
Key Concepts
- Modulation Index: Measures how much the carrier is modified by the message. In AM, an index of 100% means full modulation; over 100% causes distortion (overmodulation).
- Bandwidth: AM bandwidth = 2 × message frequency. FM bandwidth ≈ 2(Δf + fm) per Carson's rule. Wider bandwidth generally means better signal quality but uses more spectrum.
- Noise Immunity: FM is inherently more noise-resistant than AM because noise primarily affects amplitude, which FM receivers can clip off. This is why FM sounds cleaner than AM.
- Power Efficiency: AM transmits the carrier plus two sidebands — the carrier carries no information but uses most of the power. SSB (Single Sideband) suppresses the carrier and one sideband, concentrating all power in the information-bearing signal.