Read range study of energy-harvested implanted NFC sensors with commercial NFC ICs and smartphones

The present work deals about the study of the depth and the read range of implanted sensors based on battery-less Near-Field Communication (NFC) integrated circuits (IC) using as a reader the smartphone with NFC. The performance of NFC ICs with energy harvesting capability from different manufactures is compared. The conventional system based on resonant 2-coils topology, and an improved one based on 3 resonant coils are studied. In the latter a relay antenna is implemented on a patch and attached on the skin. From the experimental results it can be concluded that the system based on 3-coils presents a much better robustness. The measurements have been performed using a prototype of the implanted tag consisting of a 15×15 mm antenna with a commercial NFC IC with energy harvesting that is able to read up to 16 mm inside the body using commercial smartphones.