Incorporating Back Telemetry in a Full-Wave CMOS Rectifier for RFID and Biomedical Applications

We have incorporated back telemetry mechanism within the circuitry of an integrated full-wave CMOS rectifier for RFID and implantable biomedical applications. The new rectifier saves silicon area by eliminating the need for additional large switches and provides more flexibility in choosing the most appropriate load shift keying mechanism by having the capability of both shorting and opening the transponder coil. This would result in a more robust back telemetry link with improved reading range and higher data rate. A prototype version of the rectifier was implemented in AMI 0.5-mum standard CMOS process, occupying -0.25 mm². The back telemetry rectifier was powered through an inductive link and proved to be fully functional in its three modes of operation: rectification, open coil (OC), and short coil (SC).