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This letter proposes a new wireless power transfer mechanism named the directly-strong-coupling.It adopts only two resonators and it achieves strong-coupling performances. Asymmetric sizes of antennas are designed to reduce the receiver's size for indoor applications. The mechanism remains a power efficiency of 35.6% over a distance of 1 m. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:250–253, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27315

This paper proposes a new wireless power transfer (WPT) system for the endoscopic capsule. In the system, a group of vertically segmented primary coils around the human body are adopted as the transmitting coils. According to the position of the endoscopic capsule, one of the transmitting coils is intelligently selected to transfer the power with the highest efficiency. This paper also presents a coil selection and control algorithm for the unique WPT system. Compared with the conventional design, the calculated transmission efficiencies of the new solution at the best and worst points of the body are enhanced by 53.5% and 138% respectively. And the average efficiency of the proposed solution is about 3.8%.

The wireless power antenna plays an important role in the wireless power transfer. To reduce the system size, realize the full directionality, improve the coupling efficiency and other parameters, various kinds of power antenna techniques have been proposed in recent years. Accordingly, these techniques constitute many wireless power transfer structures. In this chapter, we firstly give an overview to the power antenna techniques in the wireless power transfer, introduce their classification and detailed catalogs, and discuss their design considerations. Second, four kinds of transfer structures are presented with details. They are the LC-pair, the Multiple-resonators, the Quad-loops, and the Helix-derivatives. Both basic design methods and advanced optimizations are to be proposed or explained. Although the transfer structures share the same physical principles, they have entirely different performances and application conditions.

This paper presents a wireless power transfer system for a motion-free capsule endoscopy inspection. Conventionally, a wireless power transmitter in a specifically designed jacket has to be connected to a strong power source with a long cable. To avoid the power cable and allow patients to walk freely in a room, this paper proposes a two-hop wireless power transfer system. First, power is transferred from a floor to a power relay in the patient's jacket via strong coupling. Next, power is delivered from the power relay to the capsule via loose coupling. Besides making patients much more conformable, the proposed techniques eliminate the sources of reliability issues arisen from the moving cable and connectors. In the capsule, it is critical to enhance the power conversion efficiency. This paper develops a switch-mode rectifier (rectifying efficiency of 93.6%) and a power combination circuit (enhances combining efficiency by 18%). Thanks to the two-hop transfer mechanism and the novel circuit techniques, this system is able to transfer an average power of 24 mW and a peak power of 90 mW from the floor to a 13 mm × 27 mm capsule over a distance of 1 m with the maximum dc-to-dc power efficiency of 3.04%.

This paper proposes an omnidirectional wireless power receiving IC for implanted biomedical applications. The IC consists of new power receiving circuits (switch-mode CMOS Rectifier) and new power combination circuits (Skipping Booster). By predicting the coming of the current zero-cross-point (ZCP), the proposed CMOS rectifier switches current with more precise timing. By skipping the rectification in some certain periods, the proposed Skipping Booster combines energy from all rectifiers together. Thanks to the two new circuits, the wireless power receiving IC could receive omnidirectional wireless power with a peak efficiency of 93.6%, which is higher than the conventional results (30%∼80%). It has been verified with a prototype of a batteryless endoscopic capsule.

This paper proposes a new Wireless-Powered Micro-Ball Endoscopy system, in which wireless power is emitted from an emitter array embedded in a floor and resonantly relayed by a passive wireless power jacket on patients. Comparing to other wireless powering endoscopy systems, both the patients' freedom of movement and the power efficiency are improved. To enhance the power efficiency, an End-Fire Helix Emitter is proposed, which is a fundamentally novel structure used for generating near field alternative magnetic field with high efficiency. This paper also proposes a Load-Adaptive power converter circuit to keep optimal power efficiency by matching the varied load impedance. A prototyping design is fabricated. At the frequency of 24.05MHz, the power efficiency of transmission from floor to wireless jacket is 44.6%, and the overall energy efficiency from floor to Endoscopic Micro-Ball is 2.5% at best.

This paper investigates the design and optimization of a wireless power transmission link targeting Micro-Ball Endoscopy applications. A novel asymmetric resonant coupling structure is proposed to deliver power to an endoscopic Micro-Ball system for image read-out after it is excreted. Such a technology enables many key medical applications with stringent requirements for small system volume and high power delivery efficiency. A prototyping power transmission sub-system of the Micro-Ball system was implemented. It consists of primary coil, middle resonant coil, and cube-like full-direction secondary receiving coils. Our experimental results proved that 200mW of power can be successfully delivered. Such a wireless power transmission capability could satisfy the requirements of the Micro-Ball based endoscopy application. The transmission efficiency is in the range of 41% (worst working condition) to 53% (best working condition). Comparing to conventional structures, Asymmetric Resonant Coupling Structure improves power efficiency by 13%.