A near-threshold, multi-node, wireless body area sensor network powered by RF energy harvesting

A wirelessly-powered, near-threshold, body area network SoC supporting synchronized multi-node TDMA operation is demonstrated in 65nm CMOS. A global clock source sent from a base-station wirelessly broadcasts at 434.16MHz to all sensor nodes, where each individual BAN sensor is phase-locked to the base-station clock using a super-harmonic injection-locked frequency divider. Each near-threshold SoC harvests energy from and phase locks to this broadcasted 434.16MHz waveform, eliminating the need for a battery. A Near-V_T MICS-band OOK transmitter sends the synchronized local sensor data back to the base-station in its pre-defined TDMA slot. For an energy-harvested local V_DD=0.56V, measurements demonstrate full functionality over 1.4m between the base-station and four worn sensors, including two that are NLOS. The sensitivity of the RF energy harvesting and the wireless clock synchronization are measured at -8dBm and -35dBm, respectively. ECG Lead-II/Lead-III waveforms are experimentally captured, demonstrating the end-to-end system application.