A multi-channel EEG system featuring single-wire data aggregation via FM-FDM techniques

Conventional EEG systems are extremely power hungry due to a reliance on high resolution analog-to-digital converters (ADCs) to cover their required dynamic range. This paper presents a novel architecture for acquiring multi-channel high-resolution EEG using low power techniques. Instead of digitizing the output of each analog front-end (AFE) amplifier with an individual ADC, a voltage-controlled oscillator is used to generate an up-converted frequency-modulated (FM) signal at a unique carrier frequency. All channels then share a single wire via frequency-domain multiplexing (FDM), enabling a rugged mechanical design. The composite FM signal is then digitized with a single ADC optimized for time-domain resolution (1 MHz, 12 bits) rather than employing multiple ADCs optimized for voltage-domain resolution (1 kHz, 16–24 bits), thereby enabling a low-power implementation. To validate this approach, a discrete prototype is developed and achieves 75 dB of dynamic range per channel.

I. Introduction

Electroencephalogram (EEG) monitoring has wide range of applications — from the diagnosis and treatment of a number of brain-related diseases and disorders to brain-computer interactive technologies for every-day application. Ideally, patients suffering from a number of neurological conditions such as epilepsy, post-traumatic brain injury, Alzheimer's disease, and more would benefit from continuous, noninvasive, and high-resolution measurement of EEG during activities of daily living (ADL) [1]. Interactive systems that maximize the flexibility of the human brain with the efficiency of computer technology such as search target recognition, drowsiness detection, and human-robot interaction will require minimal intrusion upon and maintenance from the user [2], [3]. Figure 1

Traditional multi-channel EEG acquisition approach