NeuroMonitor: a low-power, wireless, wearable EEG device with DRL-less AFE

NeuroMonitor: a low-power, wireless, wearable EEG device with DRL-less AFE

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Electroencephalography (EEG) is an effective tool to non-invasively capture brain responses. Traditional EEG analogue front end (AFE) requires a driven right leg (DRL) circuit that restricts the number of channels of the device. The authors are proposing a new ‘DRL-less’ AFE design, and have developed a wearable EEG device (NeuroMonitor), which is small, low-power, wireless, and battery operated. The EEG device with two independent channels was fabricated on an 11.35 cm2 PCB that contained a system-on-a-chip microcontroller, a low-noise instrument amplifier, a low-power Bluetooth module, a microSD, a microUSB, and a LiPo battery. The DRL circuit was eliminated by utilising the high CMRR instrument amplifier with differential inputs, and followed by a modified high-Q active Twin-T notch filter ((fc Notch = 60 Hz,  − 38 dB). The signal was conditioned with a band-pass filter composed of a two-stage 2nd-order Chebyshev-I Sallen-Key low-pass filter cascaded with a passive 2nd-order low-pass filter (fc LP = 125 Hz) and a 1st-order passive high-pass filter (fc HP = 0.5 Hz). Finally, the signal was amplified to achieve an overall gain of 55.84 dB, and digitised with a 16-bit delta-sigma ADC (256 sps). The prototype weighs 41.8 gm, and has been validated against a research-grade EEG system (Neuroscan).


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