DSB AM Modulator Passband

Modulate using double-sideband amplitude modulation

• 

Libraries:
Communications Toolbox / Modulation / Analog Passband Modulation

Description

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

Examples

DSB-Modulate and -Demodulate Passband Signal in Simulink

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

In — Input signal

scalar

Input signal, specified as a scalar.

This port is unnamed on the block.

Data Types: double

Output

Out — Output signal

scalar

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

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 — Input signal offset factor

1 (default) | scalar

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 (Hz) — Carrier frequency in Hz

300 (default) | positive scalar

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 / T_s > (2 × f_c), where T_s represents the sample time of the input signal. For more information, see Baseband vs. Passband Simulation.

Initial phase (rad) — Initial phase offset in radians

0 (default) | scalar

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

$$(u(t)+k)\cos (2\pi f_{c}t+\theta )$$

where:

• k represents the Input signal offset parameter.

• f_c represents the Carrier frequency (Hz) parameter.

• θ represents the Initial phase (rad) parameter.

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

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

Version History

Introduced before R2006a