Analog Front End for Capacitive Electrodes in Biomedical Applications

Capacitive non-contact electrodes have emerged as a promising solution for biomedical applications, particularly in electrocardiogram (ECG) monitoring, due to their ability to measure bioelectrical signals without direct skin contact. Despite their advantages, weak signal levels and high susceptibility to noise remain significant challenges, limiting their practical adoption. This article presents a novel Analog Front End (AFE) designed carefully stage-by-stage, with a focus on achieving high signal-to-noise ratio (SNR), and common-mode rejection ratio (CMRR), while maintaining a compact and power-efficient design. Experimental results demonstrate a marked improvement in SNR compared to conventional AFE designs, as well as min. 15 dB better suppression of the 50 Hz mains interference, validated through real-world scenarios and measurements on human subjects. The proposed AFE effectively mitigates environmental interference, particularly power-line network noise, ensuring robust ECG signal detection. This work advances the development of high-performance capacitive sensing technologies, enabling more reliable and non-invasive biomedical devices for continuous health monitoring.