= Suppressed-carrier amplitude modulation
{title2=$s(t)=m(t)\cos(2\pi f_ct)$}
In <suppressed-carrier amplitude modulation>, a message $m(t)$ multiplies a carrier without adding a large standalone carrier term. The double-sideband form is $s(t)=m(t)\cos(2\pi f_ct)$, with spectrum $[M(f-f_c)+M(f+f_c)]/2$. Multiplying by a phase-aligned local oscillator $2\cos(2\pi f_ct)$ and low-pass filtering recovers $m(t)$ under appropriate bandwidth separation. A phase error $\phi$ instead scales the recovered message by $\cos\phi$. Thus ordinary envelope detection is not generally enough; coherent carrier phase information matters. Suppressing the carrier changes power allocation without removing both sidebands.
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