Figure 3From: Detection of a and b waves in the acceleration photoplethysmogram Fourier transform of noisy PPG signals: (a) PPG signal and (b) Fourier transform (spectrum) of the PPG signal. The spectrum illustrates peaks at the fundamental frequency of 50 Hz, as well as the second and third harmonics at 100 Hz. The spectrum shows that the main energy of the PPG signal lies below 20 Hz.Back to article page