Modulation is a technique which modifies waves of high frequency by the wave of low frequency.
Consider the carrier signal:
Vc(t)=Vcsin(ωct), the modulating signal:
Vm(t)=Vmsin(ωmt), and the signal after modulation look like
V(t)=[Vc+Vm(t)]sin(ωct). Putting this all together gives
V(t)=Vcsin(ωct)+2Vmcos(ωct−ωmt)−2Vmcos(ωct+ωmt). Now multiply the terms with cosines by Vc/Vc:
V(t)=Vcsin(ωct)+
+2VmVcVccos(ωct−ωmt)−2VmVcVccos(ωct+ωmt), and substitute Vm/Vc with ma - the amplitude modulation index.
V(t)=Vcsin(ωct)+2Vcmacos(ωct−ωmt)−2Vcmacos(ωct+ωmt). The sideband components are
2πωc−ωm=fc−fm and
2πωc+ωm=fc+fm.The single-sideband transmission reduces the bandwidth transmitted and it allows to double the number of channels within the same frequency band.
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