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A high-efficiency asymmetric Doherty power amplifier has been developed. This study proposed a harmonic suppressing technique at the second and the third harmonics and an impedance converting technique at a fundamental frequency with a T -shaped stub. Amplification efficiency was improved by a two-power-level impedance optimisation and harmonic treatment for the carrier amplifier and peaking amplifier on an asymmetric Doherty power amplifier circuit. The 10-W and 45-W GaN HEMTs released by Cree/Wolfspeed are respectively used for the carrier amplifier and the peaking amplifier. The fabricated asymmetric Doherty power amplifier with 58.6 % drain efficiency at a saturated output power of 46.3 dBm was achieved at 2.19 GHz. It achieved a 72.1 % drain efficiency at 8 dB output back-off condition from the saturation. Furthermore, the second and third harmonic spurious levels were reduced to −58.1 dBc and −62.8 dBc, respectively.

In this work, a 2-dimensional phased-array antenna is proposed for microwave power transfer. The purpose of this antenna design is to simplify the phase control system for beam steering. In this paper, we design and fabricate two-stage phase shifters and $3\times 3$ antenna array. The demonstration of 2-D beam steering based on only two dc sources was tried. According to a demonstration, the 2-D beam steering of 15.5° and 16.5° in azimuth and elevation axis are confirmed.

This work targets microwave power transfer to a flying drone. The rf transmitter is assumed to use a magnetron unit array. Each magnetron transmitter is attached to large-aperture antennas. Beam steering is provided by phased-array systems or mechanical gimbals on each antenna. The beams generated by the phase-controlled magnetrons and radiated from the transmitters are combined in free space. This report discusses the 5.8 GHz phase-locked magnetron characteristics. 60 % dc-rf conversion efficiency and 1 kW output are confirmed in a demonstration if self-excited oscillation. The phase-locked magnetron demonstration also confirms phase shifting of the output signal by controlling the phase of the injection signal.

Stratospheric platform attracts attention as a new communication infrastructure for expanding the communication area in many countries. In stratospheric platform, the unmanned airplanes stay at the stratosphere(an altitude of about 20km) and use as a communication relay station. In this concept, it is important to get a light and stable power supply for long term operation. Microwave power transfer is proposed as one solution. By using radio waves, microwave power transfer can transmit wirelessly and efficiently even at long distances. However, considering the shape of the airplane, it is desirable for the receiving antenna to be an elongated rectangle. An antenna shape such as rectanglar or circular affects the transmission efficiency even though the antenna aperture area is even. Therefore, when the receiving antenna becomes rectangular, it is confirmed that the transmission efficiency improves if the transmitting antenna is elongated according to its shape. Furthermore, we estimate the transmission efficiency including the attenuation of the atmosphere and the rainfall. In addition, since the airplane is assumed to move along the flight path, it is necessary to obtain how much power can be obtained over the entire flight path. Therefore, we also examined the received power in the entire flight path.

The two-dimensional phased-array antenna for microwave-power transfer is proposed in this work. The antenna designed in small-scale units based on traveling-wave feed technique contributes to scalably expand the antenna aperture. In addition, the number of phase control systems for beam steering is drastically reduced by the proposed feed technique contributes. In this paper, we compare and clear the circuit loss of the parallel and traveling-wave feed line and the limited number of series elements. In addition, we calculate and analyze the beam angle of two-way antenna units in circuit and EM cooperation simulation.

Here, we report an electrochemical biosensor aimed at daily self-check of salivary uric acid (UA). For this purpose, a paper-based sampling device and an amperometric biosensor with a reaction chamber designed for inserting the sampling device were employed. Our sampling device was made of a flexible material based on filter paper and it is possible to collect certain amount of saliva with sufficient reproducibility by gently putting it on the salivary gland for about 5 seconds. The biosensor measures UA contained in the sampling device by inserting it into the reaction chamber, filled with phosphate buffer saline (PBS). The output current of the biosensor was proportional to the concentration of UA, which contained in the solution collected by the sampling device, from 10 μM – 400 μM. As a real sample test, the biosensor was used for the measurement of UA levels of a healthy male volunteer. The output current increased immediately when the sampling device containing saliva was inserted to the reaction chamber. Concentration of salivary UA was estimated to 150 μM, which value was compatible to the reported UA levels in saliva.

In this paper, we attempt to design variable amplitude undulation motion in which the input speed and force are bounded, on the basis of the kinematics and inverse dynamics. To realize this motion, we used a snake-like robot with controllable side-thrust links, which was proposed in our previous research. The driving principle of this robot can be considered to correspond to avariable speed transmission system, i.e., this robot moves slowly for a large amplitude of undulation, and it moves fast for small amplitude of undulation. By using this characteristic, we propose a control design method in which the amplitude is varied with respect to time; the corresponding motion is termed as variable undulation motion, and is illustrated by a numerical simulation.

In this paper, we propose a novel kind of snakelike mobile robot as well as a new example of nonholonomic systems. The proposed robot consists of multiple links connected to each other by passive joints, which have active omnidirectional wheels at their center to drive sideways. The head and tail links are prohibited to move in the lateral direction due to the attachment of passive ordinary wheels. We derive the kinematic model of the robot and clarify its singular posture. Based on analysis of controllability Lie algebra and corresponding holonomy, we clarify the locomotion principle of the robot and propose translation, rotation and transformation control strategies. The proposed strategies are tested with numerical simulations.

A 4.5–4.9-GHz high-efficiency GaN HEMT amplIfier has been developed based on a dual-band design regarding a multi-harmonic treatment technique considering up to third-order harmonics. To prevent narrowing of the high-efficiency bandwidths due to many reactance control transmission lines connected in cascade for the harmonics, T-shaped stubs which terminate four harmonics at one point on a transmission line were used instead of λ/4 open-ended stubs terminating the harmonics for each of the reactance control lines. The fabricated GaN HEMT amplifier exhibited a maximum power-added efficiency of 65% and a maximum drain efficiency of 71% at 4.6 GHz with a saturation output power of 36 dBm. In addition, a drain efficiency of more than 60% was obtained over a wide frequency range from 4.52 to 4.94 GHz.

Due to the recent popularization of the Internet, continuous media data broadcasting such as audio or video have attracted great attention. Although continuous media data broadcasting can reduce the more necessary bandwidth than conventional on-demand delivery, waiting time from requesting data to playing it increases. In division-based broadcasting, many researches have proposed scheduling methods to reduce the waiting time. Although a division-based broadcasting system has also been proposed to evaluate these methods, this system does not consider the case of wireless LAN environment. In wireless LAN environment, we have to consider such problems as a communication protocol and a packet loss. In this paper, we propose a division-based broadcasting system to solve the problem in the conventional system. In our proposed system, we can evaluate the effectiveness for reducing the waiting time using the scheduling method.

Wireless body area network (BANs) have attracted a lot of attention as a future technology of wireless networks. Wireless BANs are generally divided into two kinds of groups, i.e., on-body BANs and in-body BANs. However, the performance requirements and channel propagation characteristics of the two BANs are quite different from each other, that is, wireless signals are approximately transmitted along the human body as a surface wave in on-body BANs, on the other hand, the signals are transmitted through the human tissue in in-body BANs. As a solution for this problem, this paper develops a structure of dual-mode transceivers, which is composed of transmitters for in-body and on-body communications and a receiver for the both communications. Then, we evaluate the communication performance of the dual-mode transceivers via a computer simulation with realistic channel models, which can well represent the propagation characteristics of on-body and in-body communications. Our computer simulation results demonstrate the feasibility of the dual-mode transceiver structure in wireless BANs.

One of promising transmission technologies in wireless body area networks (BANs) is ultra wideband-impulse radio (UWB-IR) transmission, which can provide high data rate for real-time transmission, and extremely low power consumption for increasing device longevity. Moreover, energy detection scheme in UWB-IR transmission is advantageous in terms of simple implementation. On the other hand, UWB-IR signals suffer from large attenuation in wireless BANs, so it is important to secure high quality of UWB-IR transmission performance. In this paper, we pay attention to optimization for energy detection duration of the UWR-IR transmission to solve this problem. For this purpose, in addition to an experiment and a computer simulation, we derive the bit error rate (BER) performance by a theoretical analysis with Gaussian approximation. From the investigations, we have come to a conclusion that nevertheless several conditions are required, the theoretical analysis with Gaussian approximation can work well, that is, we achieve good agreements between the results by the experiment, the computer simulation and the theory. Furthermore, the UWB-IR transmission performance can be improved by using an optimal energy detection duration.