Fully-passive and wireless detection of very-low-power brain signals

A fully-passive and wireless neurosensing system is presented for acquisition of very-low-power brain signals. The system can detect neuropotentials as low as 50μV_pp in frequency-domain. This is an improvement of up to 22dB in sensitivity compared to previously reported neuropotentials. Importantly, it implies reading of most known and useful brain signals. Currently, the system can also recover neuropotentials down to 200μV_pp in time-domain. This remarkable sensitivity is enabled by: (a) an anti-parallel diode pair (APDP) implanted mixer that performs harmonic mixing with high conversion efficiency, and (b) a pair of highly-coupled interrogator and implanted antennas. The proposed neurosensing system creates transformational health-status monitoring possibilities for a very wide range of applications.