``Classic'' Amplitude Modulation

Classic amplitude modulation (AM) is more general.

Modulating signal includes a constant (DC offset):

$$x(t) = \left(A_0 + \cos(2\pi f_\Delta t)\right)\cos(2\pi f_c t),$$

(where the first term is the modulating signal.)

DC component $>= 1$ makes the modulating signal unipolar, i.e., the entire signal is greater than zero.

Figure 6: A unipolar signal.