Double-sideband suppressed-carrier transmission

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Double-sideband suppressed-carrier transmission (DSB-SC): transmission in which (a) frequencies produced by amplitude modulation are symmetrically spaced above and below the carrier frequency and (b) the carrier level is reduced to the lowest practical level, ideally completely suppressed.


In the double-sideband suppressed-carrier transmission (DSB-SC) modulation, unlike AM, the wave carrier is not transmitted; thus, a great percentage of power that is dedicated to it is distributed between the sidebands, which implies an increase of the cover in DSB-SC, compared to AM, for the same power used.


DSB-SC transmission is a special case of Double-sideband reduced carrier transmission.

[edit] How it works

This is best shown graphically. Below, is a message signal that one may wish to modulate onto a carrier, consisting of a couple of sinusoidal components.

Image:DSBSC_Message_Signal.png

The carrier, in this case, is a plain 10 kHz sinusoid -- pictured below.

Image:DSBSC_Carrier_Signal.png

The modulation is performed by multiplication in the time domain, which yields a 10 kHz carrier signal, whose amplitude varies in the same manner as the message signal.

Image:DSBSC_Modulated_Output.png

The name "suppressed carrier" comes about because the carrier signal component is suppressed -- it does not appear (theoretically) in the output signal. This is apparent when the spectra of the output signal is viewed:

TODO: figure out how to get this Matlab script to generate proper frequency domain spectra.


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