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A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.

He D, Morgan SP, Trachanis D, van Hese J, Drogoudis D, Fummi F, Stefanni F, Guarnieri V, Hayes-Gill BR - Sensors (Basel) (2015)

Bottom Line: The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations.With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise.The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

View Article: PubMed Central - PubMed

Affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. diwei.he@nottingham.ac.uk.

ABSTRACT
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

No MeSH data available.


(a) Red λ = 660 nm (top) and IR λ = 940 nm (bottom) PPG signals taken in reflectance mode from the finger of a healthy volunteer; (b) Frequency spectrum of the Red PPG signal (DC removed) and system noise floor.
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sensors-15-17076-f006: (a) Red λ = 660 nm (top) and IR λ = 940 nm (bottom) PPG signals taken in reflectance mode from the finger of a healthy volunteer; (b) Frequency spectrum of the Red PPG signal (DC removed) and system noise floor.

Mentions: The CMOS sensor was then applied in vivo to a healthy volunteer in both transmission and reflectance mode. After CMOS on chip digital demodulation, typical red and IR PPG signals can be captured and displayed. Figure 6a shows the typical output PPG signal obtained in reflectance mode with the frequency spectrum of the red channel plotted in Figure 6b from which a heart rate of 1.1 Hz (~66 bpm) can be clearly observed with associated harmonics. The noise floor obtained from a static tissue phantom is also plotted for comparison.


A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.

He D, Morgan SP, Trachanis D, van Hese J, Drogoudis D, Fummi F, Stefanni F, Guarnieri V, Hayes-Gill BR - Sensors (Basel) (2015)

(a) Red λ = 660 nm (top) and IR λ = 940 nm (bottom) PPG signals taken in reflectance mode from the finger of a healthy volunteer; (b) Frequency spectrum of the Red PPG signal (DC removed) and system noise floor.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541923&req=5

sensors-15-17076-f006: (a) Red λ = 660 nm (top) and IR λ = 940 nm (bottom) PPG signals taken in reflectance mode from the finger of a healthy volunteer; (b) Frequency spectrum of the Red PPG signal (DC removed) and system noise floor.
Mentions: The CMOS sensor was then applied in vivo to a healthy volunteer in both transmission and reflectance mode. After CMOS on chip digital demodulation, typical red and IR PPG signals can be captured and displayed. Figure 6a shows the typical output PPG signal obtained in reflectance mode with the frequency spectrum of the red channel plotted in Figure 6b from which a heart rate of 1.1 Hz (~66 bpm) can be clearly observed with associated harmonics. The noise floor obtained from a static tissue phantom is also plotted for comparison.

Bottom Line: The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations.With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise.The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

View Article: PubMed Central - PubMed

Affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. diwei.he@nottingham.ac.uk.

ABSTRACT
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

No MeSH data available.