Antenna design and placement options for an implantable wireless medical telemetry system

The main aim of our research is to convert an existing ultra-high frequency (UHF) telemetry system, operating in free space, to an implantable telemetry system. This system, based on active radio-frequency identification (RFID) technology, will be initially implanted in rats for transmission of physiological signals to a monitoring station outside the cage. Designing an implantable compact antenna to suit the space available in the active RFID tag is the most important step in this conversion. In this paper, two placements options are considered - on the ground-plane side and on the component-side of the tag. Novel implantable planar inverted-F antennas (PIFAs) with biocompatible material coatings were designed for each case. The ground plane of the antenna, together with the tag circuit ground, helped to reduce radiation into the rat´s body. A rat tissue model is considered and the critical design parameters such as biocompatible coating permittivity, that have a profound effect on antenna performance, are identified. The input reflection coefficient, radiation pattern and efficiency are presented.