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FM Demodulator Baseband

Demodulate using FM method


Modulation > Analog Baseband Modulation


The FM Demodulator Baseband block demodulates a sample- or frame-based complex input signal. The block returns a real output signal.


Frequency deviation (Hz)

Specify the frequency deviation of the modulator in Hz as a positive real scalar. The system bandwidth is equal to twice the sum of the frequency deviation and the message bandwidth.

Simulate using

Select the type of simulation to run.

  • Code generation. Simulate model using generate C code. The first time you run a simulation, Simulink generates C code for the block. The C code is reused for subsequent simulations, as long as the model does not change. This option requires additional startup time but provides faster simulation speed than Interpreted execution.

  • Interpreted execution. Simulate model using the MATLAB interpreter. This option shortens startup time but has slower simulation speed than Code generation.


This block implements the algorithm, inputs, and outputs described on the comm.FMDemodulator reference page. The object properties correspond to the block parameters.


FM Modulation and Demodulation

The example, doc_fmmoddemod, shows how the FM Modulator Baseband and FM Demodulator Baseband blocks are used to modulate and demodulate a sinusoidal signal.

The input data is a sine wave of frequency 4 Hz and amplitude 1 V. The frequency deviation is set to 50 Hz. The Modulated Signal scope illustrates that the frequency of the modulator output, Mod Sig, varies with the amplitude of the input data.

The Demodulated Signal scope demonstrates that the output of the demodulator, Demod Sig, is perfectly aligned with the input data.

Supported Data Types

PortSupported Data Types
Signal Input
  • Double-precision floating point

  • Single-precision floating point

Signal Output
  • Double-precision floating point

  • Single-precision floating point

Selected Bibliography

[1] Chakrabarti, I. H., and Hatai, I. “A New High-Performance Digital FM Modulator and Demodulator for Software-Defined Radio and Its FPGA Implementation.” International Journal of Reconfigurable Computing. Vol. 2011, No. 10.1155/2011, 2011, p. 10.

[2] Taub, Herbert, and Donald L. Schilling. Principles of Communication Systems. New York: McGraw-Hill, 1971, pp. 142–155.

Introduced in R2015a

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