High-performance groundless EEG/ECG capacitive electrodes

An improved non-contact and groundless EEG/ECG biopotential acquisition system is presented. The system consists in a set of capacitive electrodes and a feedback electronic circuit that provides a way to build an appropriate electronic common, quashing the need for a ground electrode. The circuit also implements a dynamic interference rejection using feedback to control the amount of probed noise that is subtracted. This allows for the capability to provide direct interference canceling, mitigating the mains noise, both 50 Hz/60 Hz and harmonics. We further delve into the design of the electrodes and its impact on the sensitivity, spatial selectivity and distance attenuation.