Work

An Embedded Auto-Calibrated Offset Current Compensation Technique for PPG/fNIRS System

Year: 2025

Type: article

Abstract: Optical sensors play a critical role in biomedical monitoring systems, enabling non-invasive measurement of physiological parameters. However, these systems face a persistent challenge: the small amplitude of physiological signals is often overshadowed by a dominant DC offset current. This offset combines the dark current, ambient light, and reflections from fat and skull. This limits the amplification of signals and degrades the sensitivity of PPG/fNIRS systems. This letter presents a mixed-signal auto-calibrated offset compensation technique using dual discrete loops for PPG and fNIRS systems. Two specialized prototypes -a dedicated PPG system and an fNIRS system -were validated using a 3.3 V supply. The results show that the proposed system can effectively compensate for the offset currents within a range of 1lA to 100 lA. We have recorded PPG and fNIRS signals and performed breathing experiments to validate the results. The results show that the proposed system is able to record the signal accurately.

Source: IEEE Embedded Systems Letters

DOI: 10.1109/les.2025.3550393

Authors: Sadan Saquib Khan, Pratyush Kumar Padhi, Shufali Ashraf Wani, Meraj Ahmad, Laxmeesha Somappa, Shahid Malik

Institutions: Indian Institute of Technology Delhi, University of Glasgow, Indian Institute of Technology Bombay

Language: English

Topic: Non-Invasive Vital Sign Monitoring

Subfield: Biomedical Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: green

Funder: Science and Engineering Research Board

Award: G4740963517