Fundamental Limits for Implanted Antennas: Maximum Power Density Reaching Free Space

Skrivervik, Anja K.; Bosiljevac, Marko; Šipuš, Zvonimir

doi:10.1109/tap.2019.2891697

Cited by 58 publications

(80 citation statements)

References 30 publications

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“…In Fig. 3 is shown a comparison of the optimal normalized absorption cross section Q opt a given by (50), the absorption of a homogeneous sphere made of gold Q Au a (full Mie solution) obtained by normalization of (42) with the intensity I i of the plane wave at the origin (29) and the geometrical area cross section πa 2 , and the corresponding variational bound Q var a for a homogeneous object given by (31). The background relative permittivity is b = 1 + i b with various levels of background loss: b ∈ {10 −9 , 10 −3 , 10 −1 }.…”

Section: Numerical Examplesmentioning

confidence: 99%

“…(55)). The optimal normalized absorption cross section Q opt a is given by (50), Q opt a,2 and Q opt a,21 denote the corresponding electric multipole contribution (τ = 2, l = 1, 2, 3, . .…”

Section: Numerical Examplesmentioning

confidence: 99%

“…However, some of the substances that are used can also show significant losses such as with z-doped PMMA materials 3 . Another important medical application is concerned with implantable antennas that are used in telemetry applications as a part of communication link of health-monitoring and healthcare systems 28,50 . The presence of losses in the background medium affects the reliability of such links, especially the performance of in-body antennas.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Optical theorems and physical bounds on absorption in lossy media

Ivanenko¹,

Gustafsson²,

Nordebo³

2019

Opt. Express

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Two different versions of an optical theorem for a scattering body embedded inside a lossy background medium are derived in this paper. The corresponding fundamental upper bounds on absorption are then obtained in closed form by elementary optimization techniques. The first version is formulated in terms of polarization currents (or equivalent currents) inside the scatterer and generalizes previous results given for a lossless medium. The corresponding bound is referred to here as a variational bound and is valid for an arbitrary geometry with a given material property. The second version is formulated in terms of the T-matrix parameters of an arbitrary linear scatterer circumscribed by a spherical volume and gives a new fundamental upper bound on the total absorption of an inclusion with an arbitrary material property (including general bianisotropic materials). The two bounds are fundamentally different as they are based on different assumptions regarding the structure and the material property. Numerical examples including homogeneous and layered (coreshell) spheres are given to demonstrate that the two bounds provide complimentary information in a given scattering problem.

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Section: Numerical Examplesmentioning

confidence: 99%

Section: Numerical Examplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optical theorems and physical bounds on absorption in lossy media

Ivanenko¹,

Gustafsson²,

Nordebo³

2019

Opt. Express

View full text Add to dashboard Cite

show abstract

“…From the applications point of view, antennas embedded in lossy media have received attention in geophysics, marine technology [3], [13], [14], medical engineering [15]- [17], etc. Hence, it is worthy to develop a thorough understanding of radiation from the Hertzian dipole which is placed in a lossy medium.…”

Section: Introductionmentioning

confidence: 99%

Physical Meaning of the Dipole Radiation Resistance in Lossless and Lossy Media: What is the Radiation Resistance of Antennas in Lossy Media?

Mirmoosa

Nordebo

Tretyakov

2020

IEEE Antennas Propag. Mag.

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In this tutorial, we discuss the radiation from a Hertzian dipole into uniform isotropic lossy media of infinite extent. If the medium is lossless, the radiated power propagates to infinity, and the apparent dissipation is measured by the radiation resistance of the dipole. If the medium is lossy, the power exponentially decays, and the physical meaning of radiation resistance needs clarification. Here, we present explicit calculations of the power absorbed in the infinite lossy host space and discuss the limit of zero losses. We show that the input impedance of dipole antennas contains a radiation-resistance contribution which does not depend on the imaginary part of the refractive index. This fact means that the power delivered by dipole antennas to surrounding space always contains a contribution from far fields unless the real part of the refractive index is zero. Based on this understanding, we discuss the fundamental limitations of power coupling between two antennas and possibilities of removing the limit imposed by radiation damping.

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“…A wide range of RF antennas has been proposed for body-implantable applications [4]- [15]. Yet, establishing robust links between an in-body capsule and external equipment remains a major challenge because of too low efficiencies (< 0.1%) of the antennas operating in lossy media with uncertain electromagnetic (EM) properties [16], [17]. Considering typical maximum input power levels ranging from a few to about 50 mW [18] (limited by safety standards) and Rx sensitivities, this efficiency provides an operating range up to only a few meters [19].…”

Section: Introductionmentioning

confidence: 99%

Influence of Body-Implanted Capsule Dimensions and Materials on Achievable Radiation Efficiency

Nikolayev

Joseph

Sauleau

et al. 2019

2019 IEEE Asia-Pacific Microwave Conference (APMC)

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Fundamental bounds on achievable radiation efficiency serve as the design quality gauge, facilitate the choice of the antenna type considering the available dimensions, and provide simple rules to check the feasibility of a given design. This study quantifies the effect of body-implanted capsule dimensions and materials on achievable radiation efficiency. We also show that a dielectric-loaded electric antenna operating close to the optimal frequency can radiate more efficiently than a magnetic one. The latter, however, is more efficient when electrically small.

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Fundamental Limits for Implanted Antennas: Maximum Power Density Reaching Free Space

Cited by 58 publications

References 30 publications

Optical theorems and physical bounds on absorption in lossy media

Optical theorems and physical bounds on absorption in lossy media

Physical Meaning of the Dipole Radiation Resistance in Lossless and Lossy Media: What is the Radiation Resistance of Antennas in Lossy Media?

Influence of Body-Implanted Capsule Dimensions and Materials on Achievable Radiation Efficiency

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