Effective Midrange Wireless Power Transfer with Compensated Radiation Loss

Abstract

In conventional inductive wireless power devices, the energy is transferred via only reactive near fields, which is equivalent to nonradiative Förster energy transfer in optics. Radiation from transmitting and receiving coils is usually considered as a parasitic effect that reduces the power-transfer efficiency. As long as the distance between the two antennas is small compared to the antenna size, conventional wireless power-transfer devices offer rather high power-transfer efficiency, of the order of 80%-90%. However, for larger distances, the transfer efficiency dramatically drops, making such devices impractical. In this paper, we develop a dynamic theory of wireless power transfer between two small loop antennas, clarify the role of far-field radiation, and find a possibility to realize efficient wireless power transfer at large distances utilizing the regime of radiation suppression due to optimized mutual dynamic interactions between the transmitting and receiving antennas. The analytical results are validated by simulations and measurements, and they open a possibility to greatly expand the range of distances of compact wireless power-transfer devices. The developed theory can also be applied to coupling between antennas of different types and to energy transfer between nano-objects.

The Magnetic Field from Cylindrical Arc Coils and Magnets: A Compendium with New Analytic Solutions for Radial Magnetization and Azimuthal Current

“…To form a compact expression 𝜐(𝜈) is defined in-lieu of a conditional statement for the cases ( 67) and (68). Of interesting note, the summation of 𝛽 (1) is independent of azimuthal source terms, and the summation of 𝛿 (1) only contains radial source terms within the argument of the regularized beta function. An alternate form of Equation ( 75) is given in Equation ( 103).…”

“…To highlight and quantify the robustness of the solutions presented in this article, in this section we consider the asymptotic expansion of the integrals: 𝛽 (1) , 𝛿 (1) (74); 𝛽 (2) , 𝛿 (2) (82); 𝛽 (3) , 𝛾 (3) (85). For classical electromagnetic formulations, previous work has not quantified the convergence of hypergeometric (now shown to be of the beta type) series solutions in the near-field, or the error with summing a finite number of terms.…”

“…The hypergeometric functions F(a, b, c, sin 2 𝛷 q ) all → 0 as 𝜈 → ∞. For the 𝛿 (1) series we have the limits lim 𝜈→∞ (109) that are equivalent to the 𝛽 (1) series (93), albeit the total remainder is now a sum of three remainders.…”

“…𝛽 (1) , ϑ B z (228) 𝛽 (2) , 𝛿 (2) , 𝛽 (3) , 𝛾 (3) D2, D3 Bz (237) 𝛽 (2) , 𝛽 (3) Volume M 𝜌 B z (304) 𝛽 (1) , 𝛿 (1) D1 Bz (313)…”

“…A vast number of engineering-relevant analytic formulations exist in literature for calculating the magnetic field from particular shaped coils and permanent magnets with various current densities or magnetization directions, respectively. Collections of these elemental solutions, with superposition and without loss of generality, are useful towards the modeling and subsequent DOI: 10.1002/apxr.202300136 optimization in a range of systems or applications, such as: wireless power transfer, [1,2] energy recovery, [3] magnetic imaging, [4] magnetic levitation, [5] or electric machines. [6] Description and computation of the analytic magnetic field solutions, due to a constant and uniform Cartesian magnetization, is well-understood for cuboid [7][8][9] and polyhedron geometries.…”