Remote Powering Realization for Smart Orthopedic Implants

This paper presents a remote powering realization for smart orthopedic implants with a full-wave rectifier and a voltage doubler. The measured power efficiency of the rectifier at 13.56 MHz is 80% for an output power of 20 mW with 2.2 V output. The rectifier consists of two cross coupled PMOS transistors, and two NMOS switches with two comparators. The power efficiency of the voltage doubler is measured to be higher than 85% for output powers from 2 mW to 20 mW. Both circuits are fabricated by using 0.18 mu m standard CMOS process. The remote powering is realized by using two spiral coils and a class-E type power amplifier working at 13.56 MHz.