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

© The Institution of Engineering and Technology
Received 05/07/2016, Accepted 10/03/2017, Revised 08/02/2017, Published 16/03/2017

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).

Inspec keywords: frequency-domain analysis; band-pass filters; passive filters; time-domain analysis; low-power electronics; biomedical electronics; electroencephalography; notch filters; instrumentation amplifiers; high-pass filters; printed circuits; low noise amplifiers

Other keywords: delta-sigma ADC; low-power wireless module; EEG analogue front end; four-layer PCB; modified high-Q active twin-T notch filter; DRL-less AFE design; EEG data collection; gain 55.84 dB; DRL circuit; low-noise high CMRR instrument amplifier; cyber physical systems; time domain; mid-rail biasing; NeuroMonitor prototype; on-board analysis; electroencephalography; two stage 2nd-order Chebyshev-I Sallen-key low-pass filter; passive 2nd-order low-pass filter; AFE; data streaming; battery; band-pass filter; programmable system-on-a-chip microcontroller; bipolar montage; driven right leg circuit; frequency 125 Hz; word length 16 bit; PSoC microcontroller; referential montage; frequency 60 Hz; analogue MUX; Bluetooth; low-power wireless wearable EEG device; frequency domain; microUSB port; research-grade EEG system; interactive brain computer interface; 1st-order passive high-pass filter; mutex dual-buffer

Subjects: Passive filters and other passive networks; Bioelectric signals; Amplifiers; Printed circuits; Electrodiagnostics and other electrical measurement techniques

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