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.

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.

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.