Modulation Calculator
Calculate modulation parameters for AM and FM signals
Leave empty for AM (modulation index = 1)
How to Use This Calculator
Enter Carrier Frequency
Input the carrier frequency (fc) in Hz. This is the main frequency being modulated.
Enter Modulation Frequency
Input the modulation frequency (fm) in Hz. This is the frequency of the signal modulating the carrier.
Enter Modulation Index (Optional)
For FM, enter the modulation index (m). For AM, leave empty (defaults to 1).
Calculate
Click calculate to get the bandwidth, sideband frequencies, and other modulation parameters.
Formulas
AM Bandwidth: BW = 2 × fm
FM Bandwidth (Carson's Rule): BW ≈ 2 × fm × (1 + m)
Sidebands: fc ± fm
where fc = carrier frequency, fm = modulation frequency, m = modulation index
Example (AM):
Carrier: 1,000,000 Hz, Modulation: 1,000 Hz
Bandwidth = 2 × 1,000 = 2,000 Hz
Upper Sideband: 1,001,000 Hz, Lower Sideband: 999,000 Hz
Example (FM):
Carrier: 100 MHz, Modulation: 5 kHz, m = 5
Bandwidth ≈ 2 × 5,000 × (1 + 5) = 60,000 Hz
About Modulation Calculator
The Modulation Calculator determines key parameters for amplitude modulation (AM) and frequency modulation (FM) signals, including bandwidth, sideband frequencies, and modulation characteristics. Understanding these parameters is essential for radio communications, signal processing, and telecommunications.
When to Use This Calculator
- Radio Engineering: Design AM and FM radio systems
- Telecommunications: Calculate signal bandwidth requirements
- Signal Processing: Analyze modulated signals
- RF Design: Determine spectrum requirements for transmitters
- Broadcasting: Calculate channel spacing and bandwidth
- Education: Learn about modulation theory
Why Use Our Calculator?
- ✅ Quick Calculations: Get modulation parameters instantly
- ✅ Both AM and FM: Supports amplitude and frequency modulation
- ✅ Bandwidth Calculation: Uses Carson's rule for FM
- ✅ Sideband Frequencies: Shows upper and lower sidebands
- ✅ Free Tool: No registration required
Understanding Modulation
Modulation is the process of encoding information onto a carrier wave. AM varies the amplitude of the carrier, while FM varies the frequency. Both create sidebands around the carrier frequency.
- AM (Amplitude Modulation): Bandwidth = 2 × fm, creates two sidebands
- FM (Frequency Modulation): Bandwidth depends on modulation index
- Sidebands: Frequencies at fc ± fm carry the modulation information
- Bandwidth: Determines the spectrum width needed for transmission
Modulation Types
- AM: Simple, bandwidth = 2fm, used in broadcast radio
- FM: More complex, bandwidth depends on modulation index, better noise immunity
- PM (Phase Modulation): Similar to FM, varies phase instead of frequency
Frequently Asked Questions
What is modulation?
Modulation is the process of encoding information onto a carrier wave by varying one of its properties (amplitude, frequency, or phase). This allows the signal to be transmitted efficiently over long distances.
What is the difference between AM and FM?
AM (Amplitude Modulation) varies the amplitude of the carrier wave, while FM (Frequency Modulation) varies the frequency. FM generally provides better noise immunity but requires more bandwidth.
What are sidebands?
Sidebands are frequencies that appear above and below the carrier frequency during modulation. They contain the modulation information and are located at fc ± fm.
What is Carson's rule?
Carson's rule approximates FM bandwidth as BW ≈ 2fm(1 + m), where fm is the modulation frequency and m is the modulation index. This gives a practical estimate of the spectrum width needed.
How does modulation index affect bandwidth?
In FM, higher modulation index (m) increases bandwidth. For m < 1 (narrowband FM), bandwidth ≈ 2fm. For m > 1 (wideband FM), bandwidth increases significantly according to Carson's rule.