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Wireless charging technology for heavy-duty vehicles, such as electric buses, has been actively investigated with a view to accelerating deployment of an important form of eco-friendly transportation. We have been developing a wireless power transfer (WPT) system for rapid charging of electric buses. Most of the performance targets were achieved: the maximum electric power received was 44 kW or more,...
A 44 kW wireless power transfer (WPT) system is being developed for rapid contactless charging in an electric bus in the 85 kHz band, the candidate frequency for a wireless charging system for light-duty vehicles that is currently undergoing standardization. A two-channel WPT system with currents of opposite phase in the two transmit pads of the channels is introduced to reduce radiated emissions...
A 44 kW wireless power transfer (WPT) system is being developed for rapid contactless charging in an electric bus in the 85 kHz band, the candidate frequency for a wireless charging system for light-duty vehicles that is currently undergoing standardization. For field operation of this WPT system using the 85 kHz band in Japan, permission for use as industrial facilities emitting radio waves is required...
Transmitting and receiving resonators for 7 kW-class wireless power transfer/transmission (WPT) systems operating at 85 kHz have been developed for contactless Electric Vehicle (EV) / Plugin Hybrid EV (PHEV) charging. The light weight and small volume of the on-board receiving resonator to be mounted on the vehicle are required attributes. A thickness and a shape of the core in the resonance coil...
This paper presents a novel control method for wireless power transmission (WPT). The proposed method can maximize the power efficiency only by controlling the voltage ratio between the primary and the secondary side. Experimental measurement results of the prototype system with 3 kW power transmission show the efficiency difference between the proposed control method and the available maximum value...
Wireless power transfer technology is expected to be one of key technologies to offer easy and safe power supply as well as battery charging and thus to contribute to smart community through various kinds of products, such as portable digital devices and electrical vehicles. This paper mainly focuses on EMC issues on wireless power transfer, including emission which may cause the interference to other...
Built-in antennas in mobile equipments are often subject to changes in input impedance due to the proximity of objects, e.g. a user's hand/head, a desk, etc. The resulting mismatch can lower the efficiency of the RF power amplifiers (PAs), will reduce battery life, cause low communications quality, etc. To mitigate these problems, a novel automatic tunable antenna system using a probe is proposed...
A single-layer antenna composed of four subarrays and compact low-loss feed-line structures connecting to an RF-module for 77 GHz automotive radar systems is presented. This antenna is based on a slotted post-wall waveguide array, which is integrated in a ceramic-filled PTFE substrate. The antenna gain is higher than 16 dBi relative to the maximum available directivity of 20.4 dBi at 76.5 GHz. The...
<?Pub Dtl?>High-speed short-range wireless communication systems are expected to utilize the 60-GHz band. This paper presents a bonding wire loop antenna in a standard ball grid array (BGA) package for 60-GHz short-range wireless communication. The proposed antenna has a loop shape and consists of two bonding wires connecting to a complementary metal–oxide–semiconductor (CMOS) chip and a metal...
Recently the number of operating frequency bands for a single mobile terminal has been increasing, while the size reduction for a built-in antenna is required. Therefore, it has become more difficult for the antennas built-in mobile terminal to cover all frequency bands with high efficiency. Moreover, the body of the user and the other objects in the vicinity of the mobile terminal usually detune...
In wireless electric power transmission employing magnetic resonant coils, objects or debris in the vicinity of the coil cause impedance mismatching. The mismatching will decrease the transmission efficiency at the frequency for performing electric power transmission. We have investigated the efficiency improvement by impedance matching adjustment using variable lumped capacitors. In the present work,...
A wireless power transfer system using both a resonant coil and a loop element has been reported. In this report, both a transmitter and a receiver are composed of a resonant coil and a loop element. In another report, only a loop element is employed for a receiver, and the configuration of the receiver is simplified. If there is a mutual coupling between the resonant coil and a surrounding object,...
Most of the recent wireless communication systems have adopted MIMO (Multi-Input Multi-Output). The MIMO performance of the multiple antennas mounted or even built in a wireless terminal depends on not only the mutual local relationship but also the housing and the printed circuit boards used in the terminal. Moreover, besides the performance metrics for the antennas like directional gain or radiation...
The spread of small mobile terminals, such as cell phones, is spurring interest in Wireless Body Area Network (WBAN), including intrabody communication [1] utilizing electromagnetic field on human body surface. In order to generate or detect the change in the EM field on human body surface, intrabody communication usually utilizes a pair electrode, instead of antenna. The pair electrode consists of...
A 77-GHz slot array antenna with a single-mode post-wall waveguide is presented for automotive radars. First, transmission losses and fabrication costs of various transmission lines in millimeter-wave band are compared. The measured transmission loss in the 77-GHz post-wall waveguide integrated in a PTFE substrate at 77 GHz is shown 0.20 dB/cm, which is less than that of the microstrip line. Then,...
The transfer efficiency between a transmission coil and a reception coil for wireless power transfer via magnetic resonance is a function of the orientation between the coils. When two coils share a single axis, the transfer efficiency is maximal, but otherwise the efficiency becomes lower. In this paper, a wireless power transfer system via magnetic resonance using a transmission coil array is proposed...
The unlicensed 60 GHz frequency band is suitable for high-speed wireless systems with transmission rates of 1 Gbps or more. In this paper, we propose a bonding wire antenna built into a BGA package for 60 GHz short-range wireless communication. This antenna utilizes two bonding wires and a metal plate on an interposer in a BGA package and has a loop shape. The proposed antenna is built into a standard...
It is required to work in various surrounding environments in order that the small antennas used for mobile terminal and RFID tag are located in the vicinity of various objects including the human body and the metal. H-shaped antenna has been proposed to obtain the characteristics not to be changed by circumference environment. The H-shaped antenna has been designed by adjusting offset position and...
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