Immune-to-Detuning Wireless In-Body Platform for Versatile Biotelemetry Applications

Antennas Wirel. Propag. Lett.

Joseph

Skrivervik

et al. 2019

Self Cite

Wireless implantable bioelectronics and accurate in vivo characterization of path loss require efficient and robust in-body antennas. Loading electric antennas with the effective permittivities higher than that of surrounding tissues is a promising solution. In this study, proof-of-concept conformal microstrip antennas are proposed. The antennas are optimized for a standard impedance of 50 Ω and operate in all high-watercontents tissues. Integral ground plane shields the antenna from inner circuitry. The radiation efficiencies are 0.4%, 2.2%, and 1.2% for the (434, 868, and 1400)-MHz designs, respectively, when computed in a 100-mm spherical phantom with muscleequivalent properties. The efficiencies are compared to the fundamental limitations and closely approaches them. Specific absorption rates are evaluated, and the corresponding maximum input power levels are established. Prototypes are fabricated and characterized to validate the design.

Section: Discussionmentioning

confidence: 99%

Section: Antenna Designmentioning

confidence: 99%

Dielectric-Loaded Conformal Microstrip Antennas for Versatile In-Body Applications

Antennas Wirel. Propag. Lett.

Joseph

Skrivervik

et al. 2019

Self Cite

“…Here, we consider Γ A = 0. The mismatch-loss immunity of in-body antennas was addressed previously in [16].…”

Section: B Realistic Full-wave 2d-axisymmetric Modelmentioning

confidence: 99%

Optimal Frequency of Operation and Radiation Efficiency Limitations of Implantable Antennas

2020 14th European Conference on Antennas and Propagation (EuCAP)

Šipuš

Bosiljevac

et al. 2020

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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.

“…In this study, we consider ΓA = 0. Impedance detuning issues of in-body antennas were addressed in [32], [33].…”

Section: Formulation Of the Problemmentioning

confidence: 99%

Radiation Performance of Highly Miniaturized Implantable Devices

2019 49th European Microwave Conference (EuMC)

Joseph

Martens

et al. 2019

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Miniature wireless implantable bioelectronics provide powerful capabilities for biotelemetry, therapeutics, and neural interfacing. These technologies rely on antennas to communicate with external receivers, yet existing systems suffer from poor radiation performance. We address this issue by studying the through-tissue propagation, deriving the optimal frequency range, and obtaining the maximum achievable farfield radiation efficiency. Three problem formulations are considered with increasing complexity and anatomical realism. Polarization effects of TM and TE modes are investigated using an infinitesimal magnetic dipole and a magnetic current sources, respectively. The optimal operating frequency is found within the [10 8 , 3 × 10 9 ]-Hz range and can be roughly approximated as f ≈ 2.2 × 10 7 /d for deep implantation (i.e. d ≳ 2 cm). Considering the implantation depth, the operating frequency, the polarization, and the directivity, we show that about an order-of-magnitude efficiency improvement is achievable compared to existing devices.