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DSB AM Modulator Passband

Modulate using double-sideband amplitude modulation

  • DSB AM Modulator Passband block

Libraries:
Communications Toolbox / Modulation / Analog Passband Modulation

Description

The DSB AM Modulator Passband block modulates a signal using double-sideband amplitude modulation.

Examples

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Sample a 100 Hz input signal at 8000 samples per second. Modulate the input signal using the double-sideband amplitude modulation method with a Hilbert transform filter of order 100. Demodulate the signal. Plot the input signal, the modulated signal, and the demodulated signal.

The dsb_moddemod_passband model modulates a signal using double-sideband amplitude modulation with a Hilbert transform filter and a carrier frequency of 2000 Hz and then demodulates the signal. When the model runs, it plots the signals. The model samples a 100 Hz linear frequency sweep chirp with a 400 Hz target frequency at 8000 samples per second. This configuration ensures the Hilbert transform filter operates in the flat section of the magnitude response and that the modulated signal has the desired magnitude and form.

Plot the input signal, the modulated sidebands, and the demodulated signal by using a spectrum analyzer.

Limitations

  • This block does not work inside a triggered subsystem.

Ports

Input

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Input signal, specified as a scalar.

This port is unnamed on the block.

Data Types: double

Output

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Output signal, returned as a scalar. The output is a passband representation of the modulated signal.

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.

Input signal offset factor, specified as a scalar. This value should be greater than or equal to the absolute value of the minimum of the input signal.

Carrier frequency in Hz, specified as a positive scalar.

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.

Block Characteristics

Data Types

double

Multidimensional Signals

no

Variable-Size Signals

no

Algorithms

The DSB AM Modulator Passband block transmits the lower and upper sideband signal. For an input signal u(t), as a function of time t, the output is

(u(t)+k)cos(2πfct+θ)

where:

It is common to set the value of k to the maximum absolute value of the negative part of the input signal u(t).

Extended Capabilities

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

Version History

Introduced before R2006a