Coupling enhancement of planar spiral coils using planar ferrite for biomedical implants

Jiang, Hao; Ramirez, Marcella; Zhou, Shiyu; Liang, Shaobo; Lan, Di; Zhan, Junmin; Shahnasser, Hamid; Goldman, Ken; Roy, Shuvo

doi:10.1109/bmei.2012.6512947

Cited by 4 publications

(2 citation statements)

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“…The higher capacitance introduced lowered the antenna Q-factor, leading to a greater link bandwidth potential, while the lower self-resonant frequency can be leveraged to enhance coupling between the antenna terminals without the need for external tuning circuits. Ferrites have also been widely used to strengthen and focus the excited magnetic field in the desired direction [32], [33]. In some applications, helical coils have been wound around ferrite cores [11], while in others, ferrite sheets were placed behind the planar coil antenna [33], [34].…”

Section: Couplingmentioning

confidence: 99%

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Wireless Nonradiative Energy Transfer: Antenna performance enhancement techniques

Eteng

Rahim

Leow

2015

IEEE Antennas Propag. Mag.

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I n recent times, wireless nonradiative energy transfer has elicited considerable research interest. Its varied applications range from contactless battery charging and power delivery to sensors, near-field communications, and radio-frequency identification (RFID). Antenna performance plays a key role in the successful deployment of a wireless energy transfer strategy. This article presents an integrated survey of metrics and methods that have been employed to evaluate and improve antenna performance in nonradiative energy transfer schemes. Wireless NoNradiative eNergy traNsferWireless nonradiative energy transfer is a rapidly developing area of research interest. The application of this technology ranges from RFID systems [1], [2] and near-field communication networks [3], [4] to wireless charging [5]-[7], and wireless power delivery to biomedical sensor implants [8], [9]. Despite the recent attention given to this area, the concept has its origins in the past century. Some of the earliest well-known experimentation on the transmission of energy without wires was successfully carried out by Tesla, who focused on nonradiative transmission mechanisms. Although radiative techniques birthed modern wireless radio, not much interest was elicited by the proven nonradiative methods until quite recently [10].Nonradiative energy transfer is facilitated within the nearfield regions of electromagnetic sources, which, typically, are frequency dependent and located within a distance d 2 1 m r h from the source, where m is the wavelength [11]. The spatial range within which energy transfer is possible is typically short and comparable with the dimensions of the electromagnetic source. Energy exchange is more efficient when both the electromagnetic source and receiver share the same resonance frequency, as less energy is dissipated on nonresonant objects within the vicinity [12]. Consequently, the source and receiving electromagnetic terminals are sometimes referred to as resonators [4].Antenna theory reveals the presence of a reactive near-field region in close proximity to the surface of an antenna and a radiative near-field region in the transition zone between the near-and far-field regions [13]. Wireless nonradiative energy transfer primarily occurs in the reactive near-field region, where the electric and magnetic fields of an antenna are uncoupled and nonpropagating. Although the energy in any of these fields can be utilized, using the magnetic field ensures a lower interaction of the system with extraneous objects [12]. This requires the use of antennas that predominantly excite the TE 10 mode to enable the coupling of magnetic fields [14], [15]. Hence, in the literature, there is a preponderance of the use of spirals, helixes, coils, and other loop-inspired antenna geometries.Antennas used in wireless nonradiative applications require a different set of performance metrics than typical antennas for radiative applications. First, high radiation efficiency is not required to prevent eavesdropping in data-centric applicat...

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Section: Couplingmentioning

confidence: 99%

“…Ferrites have also been widely used to strengthen and focus the excited magnetic field in the desired direction [32], [33]. In some applications, helical coils have been wound around ferrite cores [11], while in others, ferrite sheets were placed behind the planar coil antenna [33], [34].…”

Section: Couplingmentioning

confidence: 99%