A carrier wave
c(t) = AC sin (ωct)
is amplitude modulated by a message signal
m(t) = Amsin (ωmt)
The amplitude modulated wave can be regarded as made up of the
(1) original carrier wave of frequency ωc and amplitude Ac and two sinusoidal waves, each of amplitude (Am/2) and frequencies (ωc ± ωm).
(2) original carrier wave of frequency ωcand amplitude (Ac + Am) and two sinusoidal waves, of amplitude Am each and frequencies (ωc ± ωm).
(3) modified carrier wave of frequency (ωc + ωm) and amplitude Ac and two sinusoidal waves, of amplitude (Am/2) each and frequencies (ωc ± ωm).
(4) modified carrier wave of frequency (ωc - ωm) and amplitude Ac and two sinusoidal waves, of amplitude Am each and frequencies (ωc ± ωm).
