Communications Blockset

SSB AM Modulator Baseband

Modulate using single-sideband amplitude modulation

Library

Analog Baseband Modulation, in Modulation

Description

The SSB AM Modulator Baseband block modulates using single-sideband amplitude modulation with a Hilbert transform filter. The output is a baseband representation of the modulated signal. The input signal is real, while the output signal is complex. The input must be a sample-based scalar signal.

SSB AM Modulator Baseband transmits either the lower or upper sideband signal, but not both. To control which sideband it transmits, use the "upper" sideband or "lower" sideband parameter.

If the input is u(t) as a function of time t, then the output is

where is the Initial phase parameter and û(t) is the Hilbert transform of the input u(t). The plus sign indicates the upper sideband and the minus sign indicates the lower sideband.

Hilbert Tranform Filter Parameters

This block uses a Hilbert transform filter, possibly with a compensator. The filter produces a Hilbert transform of its input signal. These mask parameters relate to the Hilbert transform filter:

• The Time delay for Hilbert transform filter parameter specifies the delay in the filter design. You should choose a value of the form

• (N+1/2)*(Sample time parameter)

  where N is a positive integer.

• The Bandwidth of the input signal parameter is the estimated highest frequency component in the input message signal. This parameter is used to design a compensator for the Hilbert transform filter, which would force the message signal amplitude to remain within the assigned range.

• If this parameter is either 0 or larger than 1/(2*Sample time), then the block does not generate a compensator.

This block uses the hilbiir function in the Communications Toolbox to design the Hilbert transform filter.

Dialog Box

Initial phase (rad)

The phase offset, , of the modulated signal.

Bandwidth of the input signal (Hz)

The highest frequency component of the message signal. To avoid using a compensator in the Hilbert transform filter design, set this to 0.

Time delay for Hilbert transform filter (s)

The time delay in the design of the Hilbert transform filter.

Sample time

The sample time of the Hilbert transform filtering.

"upper" sideband or "lower" sideband

A string that specifies whether to transmit the upper or lower sideband. Choices are 'upper' and 'lower'.

Pair Block

SSB AM Demodulator Baseband

See Also

DSB AM Modulator Baseband, DSBSC AM Modulator Baseband

References

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

SSB AM Demodulator Passband

SSB AM Modulator Passband