Design and characterization of bio-implantable antennas

Research on bio-implantable monitoring and/or medication delivery systems has experienced a large increase in interest in the last few years. Indeed, recent advances in technology have allowed for the miniaturization of such systems, making them small enough to be routinely implanted in patients. One key aspect of bio-implants is the telemetry, allowing for the wireless communication between the implant and an external base station. The antenna is a critical component of this communication system, as its size is set by physical factors (wavelength, data rate, etc.) rather than by the technology used. Designing antennas small enough to fit into miniature implants is thus a challenge, not very dissimilar to the design of miniature antennas for handhelds. In this contribution, we will first analyze the particularities of antenna design for implants, propose some design rules and finally dwell on the specific care to be taken when characterizing such antennas through measurements. All points will be illustrated by different examples.