Cell inconsistency can lead to poor performance and safety hazards. Therefore, cell equalizer is essentially required to prevent the series-connected cells from overcharging, undercharging, and overdischarging. Among current equalization schemes, passive equalizer has a continuously wasting energy with low equalization efficiency, and active equalizer has high cost with complex circuit structure. In this study, a novel composite equalizer based on an additional cell with low complexity is presented. This method combines a passive equalizer and an active equalizer. Firstly, the configuration and circuit of our proposed composite equalizer are introduced, and the equalization principle is analyzed. On this basis, the control strategy and algorithm of the composite equalizer are further proposed. Finally, the composite equalizer is verified through simulation and experiment in various cases. The study results show that this method improves both the consistency level and the available capacity of the battery pack. Moreover, our proposed equalizer can overcome the shortcomings of commonly used equalizer and combining the advantages of different equalizer to maximize the equalization efficiency with a simpler equalizer structure.

A dual-band focused transmitarray antenna designed by using frequency selective surfaces (FSS) technique is proposed in this paper. Compared with the traditional transmitarray antenna, the proposed antenna has advantages of good ability to focus electromagnetic wave in the dual-band, high resistant of poor measurement environment and easy to process. The transmitarray consists of four identical metal phase shift layers, each of which is separated by an air gap. The elements distributed on metal layer are composed of a I-shaped slot at the center and four L-shaped slots with central symmetry. The change of I-shaped slot length affects the change of phase in low frequency band and the change of L-shaped slot length affects the change of phase in high frequency band. The mutual coupling between the two kinds of slots can be neglected. The proposed antenna consisting of a transmitarray and a feed has been analysed, simulated, and measured. The results show that the average focal spot diameter (SD) is 35.2 mm at 12 GHz and 24.5 mm at 18 GHz, and the dual-band focused transmitarray antenna can operate in two frequency bands 11.8-12.2 and 17.8-18.1 GHz. Simulated and measured results show that the proposed antenna has good concordance, making it possible for various microwave measurements. INDEX TERMS Focused; all metal elements; dual-band; transmitarray antenna; frequency selective surfaces (FSS).

Coaxial coupled structure of wireless power transfer, applied to high-precision instruments in aerospace, can eliminate interference sources by spatial isolation. For the optimization of the electromagnetic structure, a C-shaped magnetic structure is presented for both shielding electromagnetic simulation and improving coupling. By comparing of spiral and coaxial structures, an analysis is presented and validated in the effect of positional offset on inductive coupling, voltage gain, and efficiency. To obtain a stable and sufficient power supply, the prototype is implemented based on primary series-secondary series compensation topology with a maximum output power of 200 W, and a DC-DC efficiency of 82% is achieved.

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The Internet of Things (IoT) connects billions of smart devices through wireless sensor networks (WSNs). However, to ensure the power supply for numerous passive devices in a WSN, it is necessary to replace batteries periodically, which will undoubtedly increase maintenance costs. This study proposes a capacitive coupling structure that is different from the previous capacitive power transfer (CPT) structures. The proposed structure can allow the positional variation of the receiver, and multiple receivers to be charged at the same time. Both theoretical and experimental results demonstrate that the power transmission is less affected by the positional variation of the pickup plates in the vertical and horizontal directions. In this study, all coupling capacitors between the plates are considered and the equivalent circuit model is derived. Further output characteristics of the circuit are derived and analysed. The dimensions of the structure are designed and simulated by using the EM full wave simulation. A prototype is designed to verify that a battery can be charged based on capacitive coupling. A 60 mAh rechargeable lithium-ion button battery is fully charged in 250 min, and the output power is ∼36 mW during charging.