Key result
The proposed low-noise photoplethysmography sensor achieved a mean absolute error of 6.2 ms for heartbeat interval acquisition with a total current consumption of 28.2 μA.
Why the study?
Heartbeat monitoring in daily life requires accurate heartbeat interval acquisition with low power consumption, but lowering sampling rates reduces accuracy through signal-to-noise ratio degradation and sampling errors.
Does a low-noise PPG sensor using correlated double sampling and error compensation improve heartbeat interval acquisition accuracy at low power consumption in healthy subjects?
Does a low-noise PPG sensor using correlated double sampling and error compensation improve heartbeat interval acquisition accuracy at low power consumption in healthy subjects?
A novel PPG sensor design utilizing correlated double sampling and error compensation enables accurate heartbeat interval acquisition with ultra-low power consumption, suitable for wearable devices.
This study designs a low-power photoplethysmography (PPG) sensor based on the error compensation method for heartbeat interval acquisition. To perform heartbeat monitoring in daily life, it is necessary to obtain long-term and accurate heartbeat interval data with low power consumption, because of the limited size and battery capacity of the PPG sensor. Effective reduction in the power consumption of the sensor requires the duty-cycled LEDs and lowering pulse repetition frequency (PRF), i.e., decreasing the sampling rate. However, these methods reduce the accuracy of the heartbeat interval measurement because of signal-to-noise ratio (SNR) degradation and sampling errors. We propose an algorithm for heartbeat interval error compensation and incorporate a low-noise readout circuit to improve SNR. The readout circuit uses current integration to achieve low duty-cycle LED driving. A correlated double sampling (CDS) is introduced to minimize the random noise arising from the switching operation of the integration circuit. An error compensation method based on the PPG waveform similarity is also introduced using the autocorrelation and linear interpolation. The measurement results obtained from nine subjects show that a total current consumption of 28.2 μA is achieved with a 20-Hz PRF and 0.3% LED duty cycle. The proposed design effectively reduces the mean absolute error (MAE) of the heartbeat interval to an average of 6.2 ms.
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Watanabe et al. (2019) studied Healthy (n=9). Low-noise PPG sensor using correlated double sampling and error compensation vs. Conventional PPG sensor and ECG reference was evaluated on Mean absolute error (MAE) of heartbeat interval. The proposed low-noise photoplethysmography sensor achieved a mean absolute error of 6.2 ms for heartbeat interval acquisition with a total current consumption of 28.2 μA.
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