FIG. 1.

Amplitude-modulated signal. (A) 6 Hz (modulation frequency, f_m) sine wave with an amplitude of 0.5, offset constant of 1, and phase offset (ϕ₁) of zero is multiplied with (B) a 40 Hz (carrier frequency, f_c) sine wave with a phase offset (ϕ₂) of zero. (C) The result is a 40 Hz sine wave amplitude modulated at 6 Hz with a depth of modulation equal to M/A=0.5 or 50%. (D) The Fourier representation of the amplitude-modulated signal shows a peak at the 40 Hz carrier frequency, with sidebands at±6 Hz around the center carrier signal. Color images available online at www.liebertpub.com/brain