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PM Demodulator Passband

Demodulate PM-modulated data

  • PM Demodulator Passband block

Libraries:
Communications Toolbox / Modulation / Analog Passband Modulation

Description

The PM Demodulator Passband block demodulates a signal that was modulated using phase modulation. The input is a passband representation of the modulated signal. Both the input and output signals are real scalar signals.

Examples

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Sample a 100 Hz linear frequency sweep chirp with a 400 Hz target frequency at 4 kilosamples per second. Modulate the input signal using the phas modulation method. Demodulate the signal. Plot the input signal, the modulated signal, and the demodulated signal.

The pmmoddemod_passband model modulates the input linear frequency sweep chirp signal using the PM method at a carrier frequency of 1.5 kHz with pi/2 phase deviation and then demodulates the signal. When the model runs, it plots the signals. This configuration ensures the Hilbert transform filter operates in the flat section of the magnitude response and that the demodulated signal has the desired magnitude and form.

The spectrum analyzer plot shows input signal, the modulated signal, and the demodulated signal.

Limitations

  • This block does not work inside a triggered subsystem.

Ports

Input

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Input signal, specified as a scalar. The input is a passband representation of the modulated signal.

This port is unnamed on the block.

Data Types: double

Output

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Demodulated output signal, returned as a scalar.

This port is unnamed on the block.

Data Types: double

Parameters

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To edit block parameters interactively, use the Property Inspector. From the Simulink® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Carrier frequency in Hz, specified as a positive scalar.

Due to the implementation of the Hilbert transform by means of a filter, for best results, choose a carrier frequency, fc, that exceeds the sample rate of the input signal by at least 10%.

Typically, an appropriate carrier frequency is a much higher than the highest frequency of the input signal. By the Nyquist sampling theorem, 1 / Ts > (2 × fc), where Ts represents the sample time of the input signal. For more information, see Baseband vs. Passband Simulation.

Initial phase offset of the carrier in radians, specified as a scalar.

Phase deviation of the carrier frequency in radians, specified as a scalar. Also known as the variation in the phase.

Hilbert transform filter order, specified as an even, positive scalar with a value greater than 2. This parameter value defines the length of the FIR filter used to compute the Hilbert transform.

Block Characteristics

Data Types

double

Multidimensional Signals

no

Variable-Size Signals

no

More About

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Extended Capabilities

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C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a