FM Modulation Online Simulator

Frequency Modulation (FM) Simulator

In Frequency Modulation, the frequency of the carrier signal varies in accordance with the message signal's amplitude. See Mathematical Background=>

Change the parameter values to see the effect.

Message Frequency (fm): Hz
Carrier Frequency (fc): Hz
Carrier Amplitude (Ac):
Modulation Index (β):

Frequency deviation
Δf = β × fm

sFM(t) = Ac cos(ωct + kf∫m(t)dt)
where ω = 2πf & kf = Frequency Sensitivity
Modulation index, β = (kf * Am) / fm
    

FM Modulation & Demodulation Online Simulator →

🧪 Experiment for Students:

"Changing carrier amplitude affects only the displayed signal magnitude and transmitted power. It does not change the frequency deviation, modulation index, or bandwidth of an ideal FM signal. In another simulator, set the Message Amplitude to 1 and Frequency Sensitivity ($k_f$) to 5. Observe how the wave 'stretches' and 'squeezes'. Next, increase the Message Amplitude to 2.5. Notice that the frequency swings become much wider because the peak frequency deviation ($\Delta f = k_f \cdot A_m$) has increased."

Understanding Frequency Modulation (FM) Performance

Modulation Index ($\beta$)

The FM modulation index ($\beta$) is defined as the ratio of peak frequency deviation to the message frequency. Unlike Amplitude Modulation (AM), the modulation index in FM can be significantly greater than 1. A small value ($\beta < 1$) corresponds to Narrowband FM (NBFM), while larger values produce Wideband FM (WBFM).

Bandwidth and Carson's Rule

An FM signal theoretically contains an infinite number of sidebands. In practice, the required transmission bandwidth is estimated using Carson's Rule: $BW \approx 2(\Delta f + f_m)$. Therefore, FM bandwidth depends on both the peak frequency deviation ($\Delta f$) and the highest modulating frequency ($f_m$).

Noise Immunity

Frequency Modulation offers excellent resistance to noise compared with AM. Because information is carried by frequency variations rather than amplitude changes, FM receivers can use limiter circuits to suppress amplitude-based noise and interference while preserving the original information.

Read More about Narrowband vs. Wideband Signals (Click here) | BPSK vs BFSK: Understanding the 3dB Power Gain

MATLAB Codes for Modulation

View MATLAB Codes for Frequency Modulation (FM) =>

How is an FM Signal Generated?

An FM signal can be generated using various methods. Here, we will discuss how to generate an FM signal practically using a VCO (Voltage-Controlled Oscillator).

A VCO is an electronic oscillator whose output frequency changes according to the applied input voltage. To generate an FM signal, the message signal is applied to the VCO's control input. As the amplitude of the message signal varies, the instantaneous frequency of the VCO output varies accordingly, producing a frequency-modulated (FM) signal.

Read More about VCO (Click here)

Power of an FM Signal

Try Other Interactive Online Simulators

📻 Frequency Demodulations

• Frequency Modulation (FM) and Demodulation

📻 Other Analog Modulations

• Amplitude Modulation (AM) and Demodulation
• Phase Modulation (PM) and Demodulation

📻 Digital Modulations (Basics)

• Amplitude, Frequency, and Phase Shift Keying

🔢 Continuous Phase Modulations

• MSK (minimum shift keying)
• GMSK (gaussian minimum shift keying)
• BPSK vs MSK (phase comparison)
• BPSK vs MSK vs GMSK (Spectral and Phase comparison)

🔢 M-ary QAM & PSK Modulations

• QAM Constellation (4, 16, 64, 256)
• M-ary PSK Constellation Diagrams
• Interactive BER vs SNR Simulator for m-ary PSK & QAM
• Advanced M-ary Modulation Simulator: Constellation, min dist, Efficiency, SER, EVM (RMS)

Further Reading (Theory)

📚Amplitude, Frequency and Phase Modulation Techniques (Analog)

• Amplitude Modulation (AM) and Demodulation
• Frquency Modulation (FM) and Demodulation
• Phase Modulation (PM) and Demodulation

📚Amplitude, Frequency and Phase Shift Keying (Digital)

• Amplitude Shift Keying
• Frequency Shift Keying
• Phase Shift Keying