Hitoshi Hayashi

Abstract The shape of conductive filaments in CBRAM is important for resistance switching and conductance modulation, especially in applications like neuromorphic and reservoir computing that use conductance as weight. We report on RF-induced modulation of CBRAM using Ge₂Sb_3.4Te_6.2 with sheet-like filaments and compared it to those with dendritic filaments. RF input below 100 MHz reduced SET and RESET voltages, similar to CBRAM with dendritic filaments, but showed significantly different resistance changes. Repeated RF on/off input gradually increased the resistance of low-resistance state, unlike the dendritic filament CBRAM, where the resistance decreased. The increased resistance suggests RF-induced denser sheet-like filaments. Furthermore, the resistance of the high-resistance state showed a peculiar RF-induced resistance change not observed in dendritic filaments. The resistance decreased during RF input and increased to nine times the initial value when RF was switched off. The results show that the conductance modulation by RF input strongly depends on the filament type.

This letter shows a compact planar microstrip crossover. The crossover design employs a microstrip to coplanar waveguide transition. The crossover is fabricated on a low cost and readily available FR-4 substrate, and simulation and measurement responses in the low frequency band have been shown. The number of GND vias forming a quasi-coaxial section that confined the electric field around the signal via was increased to improve impedance matching. The core size of the circuit is as compact as 20 mm × 10 mm even in the low frequency band. The crossover operates in the low frequency band with insertion loss of less than 1 dB, return loss of more than 10 dB, and isolation of more than 15 dB.

A new wideband 3-dB tandem coupler is presented that has wide bandwidth using four 90° short stubs. The proposed tandem coupler does not require a higher transmission line impedance or a narrower coupling gap than conventional couplers. Measurements of the fabricated tandem coupler operated at a center frequency of f0 = 1 GHz are presented as verification of the design concept. The fractional bandwidth (FBW) at which the return loss is suppressed to a level better than 15 dB was 71%. Theoretical calculations and measurements of the tandem coupler were in good agreement.

This paper proposes a new 3-branch-line coupler with harmonic suppression. We achieved harmonic suppression by using 90° short stubs. The proposed 3-branch-line coupler with harmonic suppression has the same circuit size as the conventional circuit by arranging 90° short stubs in the space between transmission lines of the conventional 3-branch-line coupler. To verify the design concept, a measurement of a fabricated 3-branch-line coupler with harmonic suppression operating at f0=1 GHz is shown. The measurement results of the branch-line coupler designed at 1 GHz showed good harmonic suppression at 2 GHz.

We propose a new activation function and verify its performance in a deep image prior network. The new activation function is RSwish, which is Swish with a random slope for x < 0 assuming that the input value of the activation function is x. In addition, we manipulate the probability of the random number and observe the effect. As a result, we found that RSwish can perform better than Swish by manipulating probabilities according to the degree of color change in the image.

We present an evaluation of the bit error rate performance of a newly proposed high-speed startup and low-power encoding method in an additive white Gaussian noise environment. The Manchester code currently used for the non-contact IC card requires a phase-locked loop because the intervals of the state transition change. On the other hand, in the proposed encoding method, state transitions occur periodically at the center of a waveform.

To estimate muscle pain, data from Twitter posts, or tweets, with and without symptomatic remarks were collected using the Twitter API. We performed morphological analysis, weighting by TF‐IDF, and calculation of the cosine similarity between the tweets, and then used the results to estimate muscle pain. Evaluation experiments were conducted to examine whether tweets with symptomatic remarks shared higher cosine similarity among all tweets combined. The results indicate that Twitter data could be used to characterize muscle pain symptoms.

In this letter, a microstrip dual-band band-pass crossover is proposed. By reducing the number of inner open stubs, miniaturization of a window-shaped crossover without reducing bandwidth can be achieved. An electromagnetic simulation and measurements are used to validate the compact (0.35λ × 0.35λ) crossover with a wide bandwidth.

In this paper, we compare the performance of activation functions on a deep image prior. The activation functions considered here are the standard rectified linear unit (ReLU), leaky rectified linear unit (Leaky ReLU), and the randomized leaky rectified linear unit (RReLU). We use these functions for denoising, super-resolution, and inpainting of the deep image prior. Our aim is to observe the effect of differences in the activation functions.

This paper presents a miniaturized Wilkinson power divider with DC isolation. By using parallel coupled lines, we can achieve DC isolation while maintaining good RF bandwidth. We compare the proposed design with the previously proposed design. The measurement results of the fabricated Wilkinson power divider exhibit good isolation and return losses at the frequency range between 1.6 GHz and 2.2 GHz.

This paper presents a miniaturized branch-line coupler with harmonic suppression. By using a combination of a 45° open stub and a 45° short stub instead of using a 90° short stub, we can achieve harmonic suppression while maintaining good RF bandwidth. We compare the proposed design with the conventional design. The measurement results of the fabricated branch-line coupler designed at 1 GHz exhibit good harmonic suppression at the frequency of 2GHz.

We propose a Wilkinson power divider that suppresses harmonics using radial open stubs. By combining quarter-wavelength coupled lines and radial open stubs, broadband harmonic suppression can be realized. Simulation of the proposed configuration showed promising results.

We report on a novel fabrication of nanostructures of silver (Ag) germanium telluride (GeTe) at room temperature and the control of resistive switching using them. We systematically fabricated Ag seed nanoparticles of various sizes by thermal annealing and demonstrated that deposition of GeTe by RF sputtering onto the Ag seed nanoparticles spontaneously produced nanostructures including broccoli-like, hollow nanostructures comprised predominantly of nanocrystalline grains of Ag, Ag3Ge, Ag2Te, and Ag5Te3. The nanostructure shape and the constituent crystalline phases depend on the amount of Ag used for the seeds. The nanostructure formation followed nanoscale phase separation and crystallization into an unexpected phase from the phase diagram, including a metastable state. The structural changes were characteristic of the Ag nanoparticles no significant structural changes occurred for GeTe deposition onto Ag films. As an application of the spontaneously formed nanostructures, we demonstrated a control resistive switching when a voltage was applied with a lateral Ag electrode pair deposited onto the top. We found that the Ag amount used for the seed formation determined the polarity of resistive switching and the SET/RESET voltages. By increasing the Ag amount, the resistive switching turned from the clockwise direction to the counter-clockwise direction, and the SET/RESET voltages were lowered.

This paper presents broadband 4-way power divider with 45 degrees phase differences between output ports. The divider is developed by combining a broadband 45 degrees power divider and 90 degrees power dividers, and is implemented on a 4-layer FR4 substrates, by using inner-layer crossovers, instead of conventional bonded crossovers. Over the frequency range from 400 to 700 MHz, the fabricated power divider exhibits power splits of -6.8 +/- 0.9 dB and return losses of greater than 14 dB Furthermore, isolation between the output ports is greater than 16dB, and the phase differences between output ports are within 5 degrees of the desired values (90 degrees, -45 degrees, and -135 degrees). (C) 2017 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.

This letter presents miniaturized Gysel power dividers using lumped-element components. The characteristic impedances of all the equivalent transmission lines in these dividers are fixed to the same values based on even and odd mode analysis, thus simplifying the design procedure and miniaturizing the Gysel power dividers. The ideal divider designed at a frequency of 590 MHz exhibits power splits of -3.2±0.2 dB and return losses of greater than 15 dB for the frequency range of 460 to 650 MHz. Furthermore, isolation between output ports is greater than 15 dB for the frequency range of 500 to 680 MHz. The fabricated miniaturized Gysel power divider achieves broadband characteristics and is very compact, occupying only about 15% of the area of a conventional Gysel power divider.

A broadband power divider using Lange couplers and short-circuited stubs is described. The divider comprises three Lange couplers, two short-circuited stubs, and a delay line. Fabricated power divider on an FR4 substrate exhibits a coupling of 3.6 ± 0.7 dB and a phase difference of 45 ± 2° from 0.4 to 0.74 GHz.

A simple design of a four-element planar Butler matrix is proposed, comprising two-section branch-line hybrids to enhance broadband characteristics obtained by 90 degrees short stubs used to improve relative-phase characteristics between output ports. Over the frequency range from 2.2 to 2.6 GHz, the experimental matrix exhibits phase errors (in the desired phase differences between output ports) and couplings of within 6 degrees and -7.2 +/- 1 dB, respectively. (C) 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Indoor systems cannot obtain a precise estimate of the location, due to unstable signals. In this paper, we use realistic wireless data from the IEEE International Conference on Data Mining (ICDM) dataset and Azure Machine Learning Studio to perform Bagging (also called bootstrap aggregating). By using the machine leaning technique in the Azure Machine Learning Studio, we can obtain more than 69 percent precision in identifying the correct area among 247 areas with only 505 training data. This result is equivalent to the second place entry in the IEEE ICDM Data Mining Contest. We show that this can achieve a highly accurate location estimation.

This letter presents two novel prototypes of reduced-size Gysel power dividers using 90 degrees and +/- 180 degrees lumped-element components. The first design is a Gysel power divider using 90 degrees and 180 degrees lumped-element components. The ideal divider designed at a frequency of 590 MHz exhibits power splits of -3.2 +/- 0.2 dB and return losses of greater than 15 dB for the frequency range of 530 to 710 MHz. The second design is a Gysel power divider using 90 degrees and -180 degrees lumped-element components. The ideal divider designed at a frequency of 590 MHz exhibits power splits of -3.2 +/- 0.2 dB and return losses of greater than 15 dB for the frequency range of 520 to 700 MHz. To verify the purposed designs, two miniaturized broadband Gysel power dividers were simulated, fabricated, and measured. The sizes of both proposed Gysel power dividers are reduced to 3.1 cm x 3.2 cm. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2341-2344, 2016

Harmonic resistive multipliers that exploit the unique current-voltage (I-V) characteristics of Ag/Ge-(Sb)-Te/Pt resistive-switching devices are demonstrated. For a Ge17Sb29Te54-based device, an antisymmetric non-linear I-V curve with a hump-like structure at +/- 0.4 V is obtained, whereas for a Ge51Te49-based device, an asymmetric non-linear I-V curve with SET switching at +0.4 V and RESET switching at -0.1 V is observed. The Ge17Sb29Te54-based device performs third harmonic multiplication for a 160 MHz input at 0 dBm, and sixth harmonic multiplication at 5 dBm under unbiased conditions without any matching circuit. For the latter device, biasing at a voltage of +/- 0.4 V leads to fifth harmonic multiplication, which is absent for a 0 dBm input under unbiased conditions. No harmonic multiplication is observed for an unbiased Ge51Te49-based device due to its high resistance, but biasing at the switching voltage of 0.4 V leads to fourth harmonic multiplication for a 0 dBm input. The unique non-linear characteristics of these devices suggest their potential for radio frequency applications.

This letter presents the simulation and measurement results for a miniaturized rat-race hybrid using six lumped-element components. The hybrid was implemented on an FR4 substrate using chip inductors and chip capacitors. For the 530- to 620-MHz frequency range, the rat-race hybrid exhibited power splits of -3.4+/-0.7 dB, return losses of &gt;18 dB, an isolation between output ports of &gt;24 dB, and errors in the desired relative phase difference between output ports of &lt;58. (C) 2016 Wiley Periodicals, Inc.

This paper presents a miniaturized broadband three-way power divider with 120 degrees phase differences between output ports. The divider is developed by using a cascade connection of 90 degrees Lange couplers and is implemented on an FR4 substrate. For the frequency range of 440-770 MHz, which corresponds to a relative bandwidth of more than 54%, the divider exhibits power splits of -5.3 +/- 0.6 dB, return losses greater than 20 dB, and isolation between output ports greater than 19 dB. Furthermore, for the frequency range of 560-580 MHz, the divider exhibits errors in the desired relative phase difference between output ports of less than 4 degrees. The measurement results reveal the feasibility of the proposed power divider configuration for broadband circuit applications with the output ports located well away from each other.

A high-speed start-up and low-power decoding circuit for wireless sensor networks is presented. The Manchester code that is currently used for Ethernet (10BASE-T), noncontact IC cards, and RFID systems requires a phase-locked loop because the intervals of the state transition change. In the proposed circuit, state transitions occur periodically at the center of a waveform owing to the use of an encoding method involving several waveforms.

Although the Miller encoding method has the advantages of distinguishing bits and recognizing transmission and reception signals easily, similar to the FM0 encoding method, it generates DC offsets. This letter presents an evaluation of a novel Miller encoding method that reduces DC offsets in an Additive White Gaussian Noise (AWGN) environment.

This paper proposes a method for determination of adjacent nodes to facilitate the formation of power-efficient wireless sensor networks that are robust to channel variations caused by movement in the surrounding communication environment. Whereas conventional methods determine adjacent nodes in wireless sensor networks using one ID packet, our proposed method uses several ID packets that are collected in link investigation cycles. This method improves the battery life of the overall network system and thereby facilitates highly-reliable communication networks. (C) 2015 Wiley Periodicals, Inc.

This paper proposes the optimization of power-efficient wireless mesh networks in outdoor and indoor environments, particularly for gas metering in Japan. We investigate the effect on total power consumption by changing the output power and allocated frequency band of a gas metering system. From the simulation results, we show that these changes are effective in achieving low power consumption. (c) 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

This paper proposes the optimization of power-efficient wireless mesh networks in outdoor and indoor environments, particularly for gas metering in Japan. We investigate the effect on total power consumption by changing the output power and allocated frequency band of a gas metering system. From the simulation results, we show that these changes are effective in achieving low power consumption.

Bad posture while working on VDT (Visual Display Terminals)-based systems can cause negative effects, such as stoop. However, it is difficult to notice such negative effects on our own. This letter presents a system to determine the postures of workers using a 3D (three-dimensional) camera (Microsoft Kinect). Experimental results show that the system can determine particular postures.

Smart Grid, which is an enhanced power system with ICT, has been expected as a means of de-carbonizing, realizing reliable supply of electricity, and conserving energy usage. In Japan, the Great East Japan Earthquake has spurred the strong attention to demand response and counter measures against disaster. To develop service business for electricity demand-side, ICT infrastructure of services for electricity customers is required so as to establish information exchanges between electricity supply and demand sides.This technical report investigates the Smart Grid ICT infrastructure systems focused on demand-side technologies.

This paper presents a miniaturized broadband three-way power divider. The divider is developed by using a cascade connection of 90 degrees Lange couplers and is implemented on an FR4 substrate. For the frequency range of 460-710 MHz, which corresponds to the relative bandwidth of more than 42%, the divider exhibits power splits of -5.1 +/- 0.6 dB, return losses greater than 20 dB, and isolation between output ports greater than 23 dB. The measurement results reveal the feasibility of the proposed power divider configuration for broadband circuit applications with the output ports located well away from each other.

This paper presents the simulated and measured results for a miniaturized broadband rat-race hybrid for UHF biomedical and healthcare applications and TV white space systems. The hybrid was implemented on an FR4 substrate using spiral inductors and chip capacitors. For the frequency range of 430-710 MHz, which corresponds to the relative bandwidth of more than 49%, the rat-race hybrid exhibits power splits of -3.5 +/- 0.7 dB, return losses greater than 14 dB, isolation between output ports greater than 21 dB, and errors in the desired relative-phase difference between output ports less than 4 degrees.

We present a high-speed start-up and low-power decoding circuit for body-centric communications. The Manchester code that is currently used for Ethernet (10BASE-T), noncontact IC cards, and RFID systems, requires a phase-locked loop because intervals of the state transition change. In the proposed circuit, state transitions occur periodically at the center of a waveform owing to the use of an encoding method involving several waveforms.

We investigated the following three important issues after the Great East Japan Earthquake: (1) the logistics of relief supplies to the disaster area, (2) the recovery process of transportation, and (3) the corporate structure of the insurance company. Based on these results, we consider the applicability of “the logistics of emergency relief supplies,” which the insurance company can offer as a new service to assist in the early disaster recovery after an earthquake.

This paper proposes the optimization of power-efficient wireless mesh networks in outdoor environment, particularly for gas metering in Japan. We investigate the effect on the total power consumption by changing the output power and allocated frequency band of the gas metering system. From the simulation results, we show that these changes are effective in achieving low power consumption.

We propose a novel encoding method for non-contact IC card or RFID systems. The Manchester code that is currently used for non-contact IC card or RFID systems requires a phase-locked loop (PLL) because intervals of the state transition change. In our novel encoding system, state transitions occur periodically at the center of a waveform through the use of an encoding method involving three waveforms.

This paper describes a miniaturized lumped-element in-phase power divider with a simple layout. We first propose a miniaturized lumped-element in-phase power divider composed of two inductors, a resistor, and three capacitors. The simulation and experimental results reveal that the proposed power divider will be effective in maintaining isolation between output ports.

This paper proposes a method for determination of adjacent nodes to facilitate the formation of power efficient wireless sensor networks that are robust to channel variations caused by movement in the surrounding communication environment. Whereas conventional methods determine adjacent nodes in wireless sensor networks using one ID packet, our proposed method uses several ID packets that are collected in link investigation cycles. This method improves the battery life of the overall network system and thereby facilitates highly-reliable communication networks. © 2014 The Institute of Electrical Engineers of Japan.

The "U-Bus Air" system is a state-of-the-art, next-generation centralized utilities telemetering system that has been newly developed by the Japan Utility Telemetering Association (JUTA), with the support of the Japanese government. The members of JUTA include leading Japanese utility supplying companies, communication equipment manufacturers, communication business operators, and meter manufacturers. The "U-Bus Air" system utilizes a multi-hopping wireless network that consumes low power. This system can be integrated with a variety of smart meters, including city gas, LP gas, water, and electric power meters.

This paper presents a miniaturized 4-way power divider with 45 degrees phase differences between output ports. The divider is developed by combining a 90 degrees Lange coupler and broadband 45 degrees power dividers, and is implemented on an FR4 substrate. The measurement results reveal the feasibility of the proposed power divider configuration for effectively reducing transmitter intermodulation.

This paper presents a tandem Lange 3-dB 90 degrees hybrid. The hybrid consists of two 8.34-dB Lange couplers connected in tandem and is implemented on a 4-layer flame resistant laminate, composed of woven fiberglass cloth with an epoxy resin binder (FR4) substrate, by using inner-layer crossovers, instead of conventional bonded crossovers. Owing to its optimized tandem structure and inner-layer crossovers, for operating characteristics within the frequency range 440-760 MHz, the hybrid exhibits a power coupling of 3.5 +/- 0.6 dB and return losses greater than 23 dB. Furthermore, isolation and phase difference between the output ports is greater than 29 dB and 90 degrees +/- 1 degrees, respectively.