34.6 EEG Dust: A BCC-Based Wireless Concurrent Recording/Transmitting Concentric Electrode

EEG recording technology creates the opportunity to sense and discover potential fluctuation in the human brain [1]. Quantitative analysis based on various EEG sensor nodes provide vital information on the patient's mental and physiological status. However, conventional multi-channel work requires wire connections and thus suffers from huge environmental interference, which makes it difficult to be wearable and durable for daily EEG monitoring. Some work [2] tried to solve the problem of common mode interference from power line coupling by using a common mode charging pump (CMCP) technique, which cancels out a certain amount of common mode voltage. However, the charging speed of the capacitor makes it unsuitable when coupled common mode potential changes over time and environment. Some work [3] proposed a floating power system with an on-chip frequency-controlled LDO, while it requires all channels tied together to average out the common mode potential and forced a power plane to be shared by all of them, which works for implantable neural recording system instead of a widespread distributed EEG recording system. Moreover, a conventional EEG recording system requires a separate reference electrode, which introduces more connection wires and extra interferences. For the active electrode [4], which removes the input connection wires to reduce common mode interference, the potential difference between circuit ground and human body is another essential issue, a driven-right leg circuit is used in [4] leads to extra wire/interference and stability issue. Work in [5] proposed in-ear EEG AFE with BCC transmission, however, concurrent signal recording/BCC transmission is not reported.