title: A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.
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.
authors.affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. diwei.he@nottingham.ac.uk.
authors.forename: Diwei
authors.initials: D
authors.lastname: He
authors.affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. steve.morgan@nottingham.ac.uk.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Morgan
authors.affiliation: Keysight Technologies Belgium NV, Kortrijksesteenweg 1093 B, 9051 Sint Denijs Westrem, Belgium. dimitrios.trachanis@keysight.com.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Trachanis
authors.affiliation: Keysight Technologies Belgium NV, Kortrijksesteenweg 1093 B, 9051 Sint Denijs Westrem, Belgium. jan.vanhese@keysight.com.
authors.forename: Jan
authors.initials: J
authors.lastname: van Hese
authors.affiliation: Keysight Technologies Belgium NV, Kortrijksesteenweg 1093 B, 9051 Sint Denijs Westrem, Belgium. Dimitris.Drogoudis@cirrus.com.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Drogoudis
authors.affiliation: EDALab-Networked Embedded Systems, Ca Vignal, 2-Strada Le Grazie, 15-37134 Verona, Italy. franco.fummi@edalab.it.
authors.forename: Franco
authors.initials: F
authors.lastname: Fummi
authors.affiliation: EDALab-Networked Embedded Systems, Ca Vignal, 2-Strada Le Grazie, 15-37134 Verona, Italy. francesco.stefanni@edalab.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Stefanni
authors.affiliation: EDALab-Networked Embedded Systems, Ca Vignal, 2-Strada Le Grazie, 15-37134 Verona, Italy. valerio.guarnieri@edalab.it.
authors.forename: Valerio
authors.initials: V
authors.lastname: Guarnieri
authors.affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. barrie.hayes-gill@nottingham.ac.uk.
authors.forename: Barrie R
authors.initials: BR
authors.lastname: Hayes-Gill
keywords: CMOS sensor; SpO2; heart rate monitor; lock-in; photoplethysmography; pulse oximetry; smart sensor