SSB AM Demodulator Passband

Demodulate SSB-AM-modulated data

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  • SSB AM Demodulator Passband block

Libraries:
Communications Toolbox / Modulation / Analog Passband Modulation

Description

The SSB AM Demodulator Passband block demodulates a signal that was modulated using single-sideband amplitude modulation. Both the input and output signals are real scalar signals.

Examples

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This example uses:

Open Model

Sample a 100 Hz input signal at 8000 samples per second. Modulate the input signal using the single-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 ssb_response model modulates a signal using single-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.

Run the model with the SSB AM Modulator Passband block configured to modulate the upper sideband. Plot the input signal, the modulated upper sideband, and the demodulated signal by using a spectrum analyzer.

Reconfigure the SSB AM Modulator Passband block to modulate the lower sideband and plot the signals again.

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 positive scalar. Match the carrier frequency, fc, to the corresponding SSB 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 / 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 modulated signal in radians, specified as a scalar.

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

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 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.

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.

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

Dependencies

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

Block Characteristics

Data Types

double

Multidimensional Signals

no

Variable-Size Signals

no

References

[1] Peebles, Peyton Z, Jr. Communication System Principles. Reading, MA: Addison-Wesley, 1976.

Version History

Introduced before R2006a

See Also

Blocks

Functions

Topics