Detuning study of implantable antennas inside the human body

Abstract

This study quantifies the detuning and impedance mismatch of antennas implanted inside the human body. Maximum frequency shifts caused by variations in the electrical properties of body tissues and different anatomical distributions were derived. The results are relevant to the design of implantable antennas. They indicate the bandwidth enhancement and initial tuning necessary for correct functioning. The study was carried out using electromagnetic modeling based on the finite-difference time-domain method and high- resolution anatomical models. Four anatomical computer models of two adults and two children were used. The implanted antennas operated in the Medical Implant Communication Service band. The most important detuning and impedance mismatch was found for subcutaneous locations and in areas where a layer of fat tissue was present. The maximum frequency shift towards higher frequencies was 70 MHz. The frequency shift did not occur symmetrically around 403 MHz, but was shifted towards higher frequencies.