DSB AM Demodulator Passband

R2026b

Demodulate DSB-AM-modulated data

• 

DSB AM Demodulator Passband block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Communications Toolbox / Modulation / Analog Passband Modulation

Description

The DSB AM Demodulator Passband block demodulates a signal that was modulated using double-sideband amplitude modulation. The block uses the envelope detection method. The input is a passband representation of the modulated signal. Both the input and output signals are real scalar signals.

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. The input is a passband representation of the modulated signal.

This port is unnamed on the block.

Data Types: double

Output

Out — Demodulated output signal

scalar

Demodulated output signal, returned as a scalar.

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, k, specified as a scalar. This value should be greater than or equal to the absolute value of the minimum of the input signal. Set this parameter to the input signal offset value in the corresponding DSB AM Modulator Passband block.

Carrier frequency (Hz) — Carrier frequency in Hz

300 (default) | positive scalar

Carrier frequency in Hz, specified as a positive scalar. Match the carrier frequency, f_c, to the corresponding DSB AM Modulator Passband block.

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.

Lowpass filter design method — Design method for lowpass filter

Butterworth (default) | Chebyshev type I | Chebyshev type II | Elliptic

Design method for the lowpass filter, specified as Butterworth Chebyshev type I, Chebyshev type II, or Elliptic.

Filter order — Order of lowpass filter

4 (default) | positive scalar

Order of the lowpass filter, specified as a positive scalar in the range [1, 500]. This parameter value defines the order of the filter specified by the Lowpass filter design method parameter.

Cutoff frequency — Cutoff frequency in Hz

300 (default) | positive scalar

Cutoff frequency in Hz, specified as a positive scalar. This parameter value defines the cutoff frequency of the filter specified by the Lowpass filter design method parameter.

Passband ripple (dB) — Peak-to-peak passband ripple in dB

0.1 (default) | positive scalar

Peak-to-peak passband ripple in dB, specified as a positive scalar.

Dependencies

To enable this parameter, set Lowpass filter design method to Chebyshev type I or Elliptic.

Stopband ripple (dB) — Peak-to-peak stopband ripple in dB

0.1 (default) | positive scalar

Peak-to-peak stopband ripple in dB, specified as a positive scalar.

Dependencies

To enable this parameter, set Lowpass filter design method to Chebyshev type II or Elliptic.

Block Characteristics

Data Types	double
Multidimensional Signals	no
Variable-Size Signals	no

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"commanapbnd3/DSB AM Demodulator Passband"

Example: add_block("commanapbnd3/DSB AM Demodulator Passband","myModel/myBlock",MakeNameUnique="on")

Version History

Introduced before R2006a