A co-planar, near field communication telemetry link for a fully-implantable glucose sensor using high permeability ferrites

This paper presents a ferrite based telemetry system for use to link an Near Field Communication (NFC) based, fully implantable glucose sensor with a wearable external transmitter system that enables a continuous monitoring glucose system. This telemetry system has been developed both for optimal performance, in terms of power and data transfer, but also for practical system form factor and patient use. The core of the inductive link utilizes two ferrite based antennas that form a loosely coupled transformer. To optimize coupling and form factor, the sensor uses directly printed, high permeability NiZn based ferrite substrate for the 13.56MHz coupling to the 130mil diameter by 620mil long sensor. The internal transmitter antenna is embedded within a microcontroller based system. The traces and the packaging for the internal antenna help to form strong magnetic field that is co-planar to the skin and directed towards the sensor. The results of characterization of the power coupled system by software simulations and direct sensor measurements are shown.