Suppose that the modulating signal is m(t)=2cos(2πfmt) and the carrier signal is xc(t) = Ac cos(2πfct). Which one of the following is a conventional AM signal without over-modulation?
1
x(t) = Acm(t)cos(2πfct)
2
x(t) = Ac[1 + m(t)]cos(2πfct)
3
\(x(t) = A_c cos(2πf_ct) + \frac{A_c}{4} m(t) cos(2\pi f_c t)\)
4
x(t) = Ac cos(2πfmt) cos(2πfct) + Ac sin(2πfmt)sin(2πfct)