A 30 μW remotely-powered implant with time-based voltage regulation

A time-interleaved wireless power transmission technique is presented to avoid interference between power transmission, sensor readout and communication operations. A time-based voltage control loop is also proposed to increase wireless power transmission efficiency. The control loop adjusts the duration of power transfer frames based on the coupling factor between the coils of the base station and the implantable device. An implantable chip with average RF power dissipation of 29.5 μW is fabricated using 0.18 μm CMOS technology. The chip records local body temperature with accuracy of ±0.05°C.