A high-sensitivity fully-passive wireless neurosensing system for unobtrusive brain signal monitoring

A high-sensitivity, fully-passive and wireless neurosensing system is presented for unobtrusive brain signal monitoring. The system is able to wirelessly detect neuropotentials down to 28 μV_pp in the frequency band of 100 Hz to 5 kHz. This is a 90-fold sensitivity improvement as compared to previous fully-passive implementations. Importantly, it implies detection of most neural signals generated by the human brain. The system consists of an implanted neurosensor and an exterior interrogator, and utilizes a highly-efficient microwave backscattering method for signal detection. High sensitivity is achieved via: (a) a sub-harmonic implanted mixer with high conversion efficiency, (b) a pair of highly-coupled implanted/interrogator antennas, and (c) a carefully matched interface between the implant antenna and mixer circuit. The proposed neurosensing system brings forward a new possibility of wireless neural signal detection using fully-passive technology.