Implantable Antennas: A Tutorial on Design, Fabrication, and In Vitro/In Vivo Testing

Implantable medical devices (IMDs) are medical devices that are implanted inside the patient´s body by means of a surgical operation and can be used for a number of diagnostic, monitoring, and therapeutic applications. Typical examples include implantable pacemakers, defibrillators, glucose monitors, cochlear implants, drug infusion pumps, intracranial pressure monitors, neurostimulators, etc. [1]. To be truly beneficial while preserving patient comfort, IMDs need to wirelessly exchange data with exterior monitoring/control equipment. Low-frequency inductive links have traditionally been used for wireless telemetry of IMDs [2], [3]. However, in an attempt to overcome their inherent limitations related to low data rate, restricted communication range, and sensitivity to inter-coil misalignment, recent focus is on antenna-enabled medical telemetry for IMDs. Wireless transmission is most commonly performed in the 402-405 MHz frequency band, which has been exclusively allocated for medical implant communications systems (MICSs), is internationally available and feasible with low-power circuits, falls within a relatively low-noise portion of the spectrum, and allows for acceptable propagation through human tissue [4]. Nevertheless, other radio-frequency (RF) bands might also be used, such as those defined in the recent IEEE 802.15.6 standard [5].