A Low-Voltage CMOS Rectifier with On-Chip Matching Network and a Magnetic Field Focused Antenna for Wirelessly Powered Medical Implants.

In this work, we present a CMOS rectifier and its associated external transmitting antenna that are designed for wirelessly powered implantable devices in general, and for a smart medical stent interface, in particular. The detailed characterization and modelling procedures of the "smart stent'' implant are presented, and the extracted circuit model of the stent is used for stent-rectifier co-optimization. A fully on-chip transformer-based tunable matching network is co-designed with the differential cross-coupled rectifier. At the external side, a four-port driven antenna is designed to focus the magnetic field in tissue as well as enhance the power density around the implant. As a proof-of-concept, the rectifier is fabricated in a 0.13 μm CMOS process and the measurement results show that it can generate more than 500 mV DC voltage on a 2 kΩ load when the available power of the stent is greater than -2 dBm, corresponding to 34% power conversion efficiency (PCE). Finally, the "smart stent" system is tested in-vitro. The results of the wireless power transfer experiments show that with 480 mW transmitting power and 53 mm separation distance (including 33 mm phantom tissue), more than 350 μW is delivered to the rectifier's 2 kΩ load.