Radio-frequency (RF)-based wireless power transfer method is highly desirable to power deep-body medical implants, such as cardiac pacemakers. The antenna is one of the essential components of such system; however, it poses significant design challenges for deep-body applications and must be modeled and characterized correctly to achieve the required performance. In this paper, design and validation of a novel wideband numerical model (WBNM) are proposed for deeply implantable antennas and to enable RF-powered leadless pacing. In particular, we acquired a wideband tissue simulating liquid (TSL) and fully characterized it using a dielectric probe. Based on the measured properties of the TSL, the design and numerical characterization of the WBNM were performed using a hybrid simulation method, i.e., by employing the finite-element method and method of moment. The proposed WBNM was validated experimentally as well as analytically using a reference microstrip antenna. Good agreement between the simulated, measured, and analytical results validated the proposed model. Furthermore, the application of this model and the TSL was demonstrated by the design, development, manufacture, and measurement of a novel metamaterial-based conformal antenna at 2.4 GHz. Moreover, good agreement was found between the simulated and measured results of the proposed conformal antenna. It is evident from the results that the proposed numerical model can be used to design deeply implantable antennas for any frequency, ranging from 800 to 5800 MHz. Finally, the proposed miniature conformal antenna and its successful integration with a leadless pacemaker model present a great potential for future RF-powered leadless pacemakers and other deep-body medical implants. INDEX TERMS Tissue simulating model, numerical model, leadless pacemakers, implantable antennas, implantable medical devices, energy harvesting, deep-body implants.

HS, including S3 amplitude and HSTIs, may be measured using PG-embedded circuitry at implant sites without special purpose leads. Further study is warranted to determine if relative changes in heart sounds measurements can be effective in applications such as remote ambulatory monitoring of HF progression and the detection of the onset of HF decompensation.

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Specific Absorption Rate (SAR) is a measure of safety and a requirement for portable radio frequency devices which are regulated mainly by the standards recommended by the Institute of Electrical and Electronics Engineers (IEEE) and International Commission on Non-Ionizing Radiation Protection (ICNIRP).Accurate approximation of SAR is therefore important for safety as well as for compliance purposes. This paper presents the analytical representation and derivation of the SAR from the basics of electromagnetic theory, Maxwell Equations, and law of conservation of energy in electromagnetic theory. It is shown, analytically, that for a time harmonic electromagnetic wave propagating in a homogeneous lossy medium having permittivity ϵ, permeability µ, and conductivity σ, the time rate change of electric and magnetic energy densities at steady state inside a given volume is zero. It is also shown that at the steady state, the net power flowing through a volume, bounded by a surface is equal to the power dissipated in that volume. Furthermore, this work demonstrates that at the steady state, SAR can be represented in terms of power density or in terms of power dissipated in the given volume. Moreover, calculation of SAR for a 1 mm × 1 mm × 0.01 m box having the dielectric properties of human skin was performed using the derived formulas and then compared with the numerical results, 1 This article is protected by copyright. All rights reserved. This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as