Performance of Frequency Translation in Separating a Photoplethysmographic Signal from an Additive Motion Artifact

New pulse oximetry detection based on the light absorbance ratio as determined from amplitude modulation indexes in the time and frequency domains

“…In the frequency domain, the AC component is the magnitude of the cardiac-frequency signal, and the DC component is the magnitude of the zero-hertz signal. Recently, a method of shifting the frequency band of a PPG signal from a low-frequency location to a higher-frequency location has been proposed [31] , [32] , [33] . These methods use a sinusoidal wave instead of a square wave signal to drive a dual light source.…”

“…These methods use a sinusoidal wave instead of a square wave signal to drive a dual light source. In the past, square wave control signals have been used to drive the dual light source, causing the signals at the light detector to be two pulse amplitude modulated (PAM) signals in the time-division multiplexing (TDM) form; in contrast, under two sinusoidal control signals of different frequencies, the obtained signals are two amplitude modulated signals (AM) of different carrier frequencies, corresponding to frequency-division multiplexing (FDM) [32] , [33] . To calculate from such a FDM signal, bandpass filters (BPFs) and demodulators have been used to recover the normal PPG signals and calculate in either the time domain or the frequency domain as described above.…”