Implantable antennas for medical wireless telemetry systems operating in the 900 MHz ISM band

This thesis focuses on the development of a compact and efficient antenna as the most important factor in an implantable wireless biomedical telemetry system. Significant challenges exist in the UHF implementation because of the electromagnetic (EM) wave interactions with the surrounding biological tissue, complexity of the biological tissue, the need for antenna miniaturization, and power minimization of the implantable device and biocompatability requirements. This dissertation presents the designs, implementations and validations of a few implantable planar inverted-F antennas (I-PIFAs). They all have full ground planes, as opposed to the partial ground plane of the original free-space antenna for a RFID system under development, to maximize the energy radiated out of the body and to minimize that into the body. Yet the developed antennas are much smaller than the original free-space antenna located on a RFID tag. The antennas performance were evaluated by studying the bandwidth impedance, radiation pattern and input reflection coefficient characteristics inside the rat body model. To monitor a physiological signal (temperature) from rat skin remotely, one of the proposed antennas was attached to the implantable RFID tag circuit board. In addition, proximity feed technique was applied to the antennas for widening bandwidth (BW) as detuning of the operational frequency of the implanted antenna occurs due to the effect of bio-compatible coating material as well as rat tissue.