Low-leakage differential-drive rectifier as 13.56 MHz inductive energy harvester for deep medical implants with field exposure compliance

Abstract

In this paper, we present a 13.56 MHz energy harvester for arterial pressure measurement implants placed at deep distances in human bodies. A 50 µm diameter thin wire is used to fabricate a 150-turn solenoid coil around a PCB stripe with a cross-sectional area of 1.35×1 mm 2 . The solenoid has a length of 12 mm, low-frequency inductance of 4.75 µH, and series resistance of 8 Ω. With this coil and an 11-stage modified differential-drive rectifier, our harvester achieved 698 nW (−31.56 dBm) sensitivity for unloaded output voltage of 1.88 V and maximum receiver efficiency of >72% at −23.5 dBm available power using 0.0228 mm 2 silicon area in 180 nm technology. A transmission distance of 21 cm was reached under compliance with the field exposure levels set by the IEEE Std. C95.1-2019.