Implantable Semi-Active UHF RFID Tag With Inductive Wireless Power Transfer

The objective of this letter was to design a compact, battery-less system for an implantable semi-active UHF radio frequency identification (RFID) tag with inductive wireless power transfer for the human body. An RFID chip of the tag, combining powering from a reader by communication and from another source through inductive wireless power transfer, was used. Tag sensitivity for communication was increased by about 21 dB with the help of wireless inductive powering when compared to tags that did not employ this system. Communication and powering circuits were integrated within compact structures on the sides of the reader and the tag. The structure for communication and powering on the side of the reader consists of a center-excised Archimedes spiral antenna and a circular loop, respectively. Similarly, the structure on the side of the tag consists of a folded dipole antenna for communication and a rectangular loop for powering.