Optimal Frequency of Operation and Radiation Efficiency Limitations of Implantable Antennas

Abstract

Fundamental limits on radiation performance of implantable antennas serve as the design quality gauge, facilitate the choice of the antenna type, and provide simple design rules to maximize the radiation performance. This study obtains the limits using two formulations: 1) theoretical spherical-wave expansion using elementary magnetic and electric dipoles and 2) realistic full-wave 2D-axisymmetric models of TM10 and TE10 mode capsule antennas. Using both formulations, the optimal radiation conditions are investigated, the effects of antenna dimensions and its implantation depth are quantified. The results also demonstrate that an electric antenna operating close to the optimal frequency could achieve higher efficiency than a magnetic one. The latter, however, is more efficient below the optimal frequency range.

Physical Bounds on Implant Powering Efficiency Using Body-Conformal WPT Systems

“…There, an electric implantable source shows a higher peak efficiency than a magnetic one for a range of scenarios. This is indeed a fundamentally different problem as the implant radiation into free space implies interaction of the source with the tissue-air boundary and consequent re-radiation of induced surface currents (the reader is referred to [11], [13], [20] for more information on this topic).…”