A novel gain and maximum oscillation frequency (fmax) enhancement method for GaN high-electron-mobility transistors (HEMTs) was developed using a standing wave-controlled gate (SC-gate). By intentionally modifying the fingertip termination condition, drastic gain and fmax improvements were achieved in the millimeter-wave frequency band without changing the manufacturing process of the GaN HEMTs. This study reviews the SC-gate technology and previous prototype evaluation results and reports additional analysis results. Furthermore, a W-band amplifier, MMIC, was designed and fabricated based on the S-parameter measurement data of the SC-gate GaN HEMT. The maximum available gain (MAG) of the SC-gate GaN HEMT used in this amplifier MMIC was 10 dB at 80 GHz, whereas the MAG in a conventional GaN HEMT without an SC-gate was 4.5 dB. The maximum gain of the fabricated amplifier MMIC was 6.3 dB at 80.6 GHz. This value is higher than that of the conventional GaN HEMT, which confirms the effectiveness of the SC-gate technology in the W band.

Two-dimensional electron gases (2DEGs) are essential not only for modern electronics but also for the advancement of next-generation communication technologies and quantum computing. Here, we report a non-contact method for characterizing material parameters of 2DEGs using circularly polarized TE_11n modes. By developing an excitation method utilizing a circular patch antenna with an adjustable coupling hole, we enable the use of higher-order modes up to TE₁₁₇, while minimizing the effects of cylindrical symmetry breaking. This method is demonstrated by measuring the magnetic field dependence of microwave conductivities in a GaAs/AlGaAs heterojunction at 300 K and 77 K. The electron mobility obtained by fitting to the Drude model is in good agreement with the results from standard Hall measurements. Additionally, the signature of cyclotron resonance is clearly observed at 77 K, and the effective electron mass is successfully estimated. The present method could accelerate fundamental research and device development using various 2DEGs.

In this paper, we propose a sensor node using a unidirectional harmonic antenna that can acquire remote sensor information without complex digital circuits. The antenna suitable for the harmonic sensor node is characterized by utilizing a wideband E-shaped element to suppress pattern degradation at harmonic frequencies. First, through basic investigations where the sensor is modeled as a variable voltage source, we demonstrate that sensor voltage information can be remotely detected based on the transmission zero frequency. Next, using a sensor node incorporating a temperature sensor and energy harvesting circuit as an example, we show that the temperature in a remote location can be detected from the stopband frequency, thereby verifying the effectiveness of the proposed method. These findings are validated through harmonic balance analysis, electromagnetic field simulations, and RF circuit simulations.

We developed the stable, ultra-fast vertical polyimide capacitive-type humidity sensor with a response time of 10 ms order using fluorinated polyimide with a multi-walled carbon nanotube (CNT) gas permeable upper electrode. On the basis of the diffusion model, the response time is reduced to less than 0.1s by reducing the hydrophobic partially fluorinated polyimide dielectric layer to ca. 100 nm. Although the sensitivity increases with the reduction of polyimide (inversely proportional) thickness, the recovery time increases and non-linear sensitivity are observed after the exposure to a high-humid air (>80 %RH). The slow recovery and instability were improved by the insertion of ultra-thin perfluoro polymer (Cytop).

In order to improve the immunity and stability of dc-dc converters in industrial production, a discrete adaptive super-twisting sliding mode algorithm is proposed in this paper. Firstly, a linear gain term is introduced into the conventional algorithm to improve discrimination accuracy of the system. Secondly, for the complexity and constraints of the gain parameters in the sliding mode algorithm, this paper designs a voltage-based time-varying function instead of multiple gains in the model, and demonstrate the stability of the proposed finite-time observer algorithm through Liapunov stability theorem. Finally, simulations and experiments were conducted on the proposed algorithm, demonstrating that the finite time super twist sliding mode control algorithm proposed in this paper can effectively reduce the impact of load changes on the output voltage.

This paper presents topology optimization of microstrip lines using twin deep neural networks (DNNs) for prediction of scattering parameters and its accuracy evaluation. Topology optimization can be accelerated by using a DNN that acts as a surrogate model for time-consuming EM simulations. However, if the prediction accuracy of the DNN for performance prediction is not high enough, the optimization will fail due to misleading caused by prediction errors. To reduce the risk of optimization failure, the present method introduced an additional DNN to evaluate the accuracy of the performance prediction. The proposed method is shown to be effective in avoiding misleading and speeding up the optimization process through numerical and experimental results.

To address the issue of low conversion efficiency in DC-DC Boost converters under heavy load, this paper utilizes a technique of adaptive on-resistance control for power MOSFETs. By setting different drive voltages in different load ranges, the on-resistance of power MOSFETs is reduced, addressing the issue of significant conduction loss at heavy loads. In addition, using pulse skipping modulation (PSM) and partially turning off power MOSFETs can improve the system's conversion efficiency at light loads. Based on 0.18μm BCD technology, specific verification of this method was completed in an actual chip. The results show that with an input voltage of 3.7V, output voltage of 5V, and operating frequency of 1.5MHz within a wide load range from 10mA to 900mA, the system can adaptively adjust the on-resistance of power MOSFETs. This increases efficiency from 83% to 91.7% when the load current equals 900mA and achieves efficiencies above 90% across the entire load range, with a peak efficiency reaching 96.5%.

In this paper, we have investigated the integration process at room temperature and device characteristics of 1 transistor type nonvolatile memory with organic semiconductor field-effect transistor (OFET) integrated with resistive random access memory (ReRAM). The threshold voltage (V_TH) of pentacene-based OFET with LaB_xN_y gate insulator is controlled by the ReRAM characteristics of LaB_xN_y gate insulator. The bottom-gate type pentacene-based OFET was fabricated on SiO₂/Si(100) substrate. The nitrogen-doped LaB₆ bottom gate electrode was deposited by RF sputtering and patterned. Then, LaB_xN_y gate insulator was deposited by the RF sputtering followed by the pentacene and Au source and drain electrode deposition by the evaporation. The Set/Reset operations of ReRAM were confirmed by the drain voltage sweep of ± 2 V. Furthermore, V_TH shift of -0.9 V was observed by the Set operation of ReRAM so that the nonvolatile memory characteristics were realized for the 1 transistor type ReRAM/OFET.

We report on low-power operation of the half-flux-quantum (HFQ) shift-register circuit. We used a superconducting quantum interference device composed of two conventional switching junctions (0-junctions) and one π-shifted non-switching magnetic Josephson junction (π-junction) as a switching element, called 0-0-π SQUID. Because the π-shift assists switching by inducing a spontaneous current, the 0-0-π SQUID shows a nominal small critical current value and is easily switched by a weak driving force. This feature allows us to significantly reduce static and dynamic power consumption at junctions and bias-feeding resistors. We carefully designed the HFQ circuit elements using a circuit parameter optimization tool and introducing additional non-switching 0-0-π SQUIDs to compensate for superconductor phase shifts. We fabricated the test circuit of the 4-bit shift-register by forming Nb/PdNi/Nb π-junctions on the Nb four-layer, 10-kA/cm² device. We successfully obtained correct operation with measured power consumption of 0.12-0.18 μW/bit, which was about 1/10 of the conventional single-flux-quantum shift-register designed with the 0-junctions of the same critical currents and the standard bias voltage.

We report a hybrid fabrication process for superconductor large-scale integrated circuits (ICs) with ferromagnetic π-shifted Josephson junctions (π junctions) and conventional 0 junctions. π junctions have a Nb/PdNi/Nb sandwich structure and are formed on the reliable Nb four-layer structure used for Nb/AlO_x/Nb 0-junction-based ICs. The additional process for making π junctions causes little damage to the 0 junctions. The π phase shift for the superconducting macroscopic wave function is confirmed by forming 0-0-π SQUIDs that have two 0 junctions and one π junction in a superconducting loop. The π junction serves as the π phase shifter because the critical currents of the π junctions are much larger than those of the 0 junctions. The modulation patterns of the 0-0-π SQUIDs show a clear shift by the magnetic field corresponding to the half flux quantum (HFQ). The critical currents of the 0-0-π SQUIDs without fields, which are referred to as the nominal critical currents, are reduced depending on the product of the loop inductance and the critical current of the 0 junction. The nominal critical current reaches 1/5 of the critical current of the single 0 junction. The small values of the nominal critical currents contribute to the reduction of the power consumption in the HFQ circuit directly.

In order to reduce the fluctuation range of output speed and torque of permanent magnet synchronous motor at high speed, this paper proposes an improved flux-weakening control method of single current regulator of permanent magnet synchronous motor. Based on chaotic mapping and Monarch Butterfly Optimization, an adaptive chaos monarch butterfly optimization is proposed to use for online parameter identification. This algorithm generates a chaotic sequence distributed according to a specific pattern through a single chaotic mapping, and combines it with the results of the previous parameter identification to generate an initialized population. Secondly, the impact mechanism of different load curve positions on the smoothness and efficiency of motor operation was analyzed, and the influence of motor parameters on voltage limited elliptical distortion was analyzed. Finally, a method of giving the cross-axis voltage considering motor parameters is designed. The simulation and experimental results show that the parameters of the motor can be accurately identified online based on ACMBO. When the load is 85N⋅m, the range of motor torque output error is effectively reduced.

Fiber reinforced materials are widely used in many products because of their excellent mechanical and chemical properties. The fiber types include rebar, wire, polypropylene fiber and carbon fiber, etc., and the fiber diameter ranges from millimeter to micrometer level. However, fiber reinforced materials are followed by a large number of electromagnetic shielding problems, especially for products in aerospace and other fields. And the reflection characteristics greatly affect the shielding performance of the material. Therefore, it is very important to evaluate the reflection characteristic of products by electromagnetic simulation. Due to the complex microstructure of fiber reinforced materials, direct modeling is very difficult and computationally expensive. Based on the existing multi-layer equivalent modeling method, this paper optimizes the layered method, and proposes an equivalent layer model modeling method when the number of layers is small. The idea of this method is to minimize the difference between the equivalent model and the actual structure through non-uniform thickness stratification, so as to improve the equivalent accuracy under the condition of the same number of segmentation layers. Finally, a series of simulations based on selected structural parameters and frequency range are carried out to compare the simulation results of the proposed method with those of the existing methods, and the results prove the effectiveness of the proposed method. Moreover, the conclusion obtained by this method is still valid when the structure size parameters, wavelength and electrical conductivity are proportionally changed according to the theory of electromagnetic wave propagation.

Optical correlation-domain reflectometry (OCDR), widely recognized for its ability to pinpoint the locations and reflectivities of faulty connections and other reflective points along optical fibers, offers the advantages of random accessibility, real-time operation, and cost-effectiveness. In Brillouin OCDR, commonly employed for distributed strain and temperature sensing, a well-known challenge is the trade-off between spatial resolution and measurement range. To overcome this limitation, a double-modulation scheme has been introduced. Recent research has shown that this trade-off is also present in simplified OCDR systems without a frequency shifter, making it crucial to develop methods that can extend the measurement range while preserving spatial resolution. In this study, we experimentally validate the ability of the double-modulation scheme to effectively enhance the measurement range in simplified OCDR.

In this paper, we propose a method to quantify the nonlinearity of the quantizer, which is one of the key nonlinear blocks in Delta-Sigma analog-to-digital converter (ΔΣ ADC) and the only one that is inherently nonlinear. By deriving the histogram of the components at the quantizer input other than the signal, it is possible to quantify the effective non-linearity in ΔΣ ADC, and quantify the effect of scaling factors such as the gains of the integrators on non-linearity. Quantizer non-linearity is evaluated through numerical calculations, complemented by analytical investigations with practical approximations. The comparison with the behavioral simulation results demonstrates the feasibility of the proposed analysis.

We focus on modifying Au surface with UiO-66-NH₂ for heavy metal detection via surface plasmon resonance (SPR) technique. Two conditions were tested for the deposition of UiO-66-NH₂, i.e., spin-coating immediately after dropping the UiO-66-NH₂ dispersion solution on the surface (0-minute) and spin-coating after incubating for 15 min. (15-minute). The 0-minute condition resulted in a more uniform UiO-66-NH₂ distribution, thus selected for further investigation of heavy metal ion adsorption. The SPR signal showed a response to As(V) ion adsorption on UiO-66-NH₂ layer in aqueous solution, demonstrating a novel and effective method for As(V) detection in the 10 to 50 mg mL^-1 range. This modified sensor exhibited improved sensitivity for detecting As(V) ions.

Many studies have been conducted on the application of microneedles (MNs) for drug administration in the medical field. In medical applications, large amounts of drugs need to be administered. We investigated the method of melting and diffusing a solidified regent on the punctured MN inside human skin by ultrasonic heating. This was because when the MN was punctured into human skin, the liquid did not migrate along the needle groove into the skin. As a countermeasure, the following method was adopted: after transporting liquid to the needle tip owing to capillary force, the liquid was solidified. Then the MN was punctured pseudo human skin (gel), and the solidified liquid was melted and diffused by ultrasonic heating. Temperature characteristics of the MN was investigated changing the needle material, needle diameter, and ultrasonic wave direction. In addition, the behavior of the liquid in the gel was observed under ultrasonic heating.

An enzymatic biofuel cell (EBFC) that uses lactic acid as fuel to generate electricity is an attractive power source for wearable devices. Power density of an EBFC was improved by using two paired electrodes: LOD (anode)-BOD (cathode) and LDH+NAD (anode)-BOD (cathode). The purpose was to reduce the pyruvic acid produced by LOD at anode. The enzymes that generate power output were LOD at the anode and BOD at the cathode, and the additional electrode pair modified with LDH and NAD at the anode and BOD at the cathode was placed near the power output electrodes. The combination of LDH and NAD can perform both oxidation and reduction. Therefore, the pyruvic acid produced at the anode can be reduced. The output of the single pair electrodes (LOD-BOD) was increased from 25 μW/cm² to approximately 43 μW/cm² (1.7 times) with the additional paired electrodes.

LIDARX, an optical pulse detection integrated circuit (IC), has been developed for LIDAR receivers onboard planetary explorers. JAXA developed the IC, based on the experience of the Hayabusa and Hayabusa2 projects, to reduce the circuit size of the receiver, shorten the development period, and improve sensitivity. This IC has been implemented as the core device for the receiver circuit of the LIDAR installed in the explorer of the Japanese Martian Moons eXploration (MMX) mission. The explorer will perform close-up remote sensing and in situ observations of both moons and collect a sample from one of the moons to bring back to Earth.

LIDARX is not a simple time-to-digital converter circuit but a sophisticated IC with micro-signal amplification, timing detection, wave height measurement, and clock interpolation functions. Furthermore, LIDARX has a wide dynamic range of 60 dB for light intensity to accommodate distance changes of about three orders of magnitude, which is expected when LIDAR is used as a navigation sensor during landing. The CMOS process is a conventional 0.35 μm, which has been well-tested in high-energy physics, to ensure radiation resistance. This report describes the details, functions, and calibration method of LIDARX's peripheral circuits and the circuits inside the IC, and evaluates its dynamic range and measurement accuracy. In addition, test results are reported for resistance to single-event effects and total ionization dose, which are essential for onboard spacecraft components.

There is an increasing request for interfacing high input common mode (CM) voltages in voltage or current sense such as battery management system. This paper proposes a capacitive gain amplifier (CGA) designed to sample the differential mode (DM) voltage of signals with a CM voltage that varies from 0 to 90V. A control strategy that integrates chopping and auto zero (AZ) is used to reduce the input offset voltage. This control strategy also accelerates the CM voltage establishment of the CGA. A high-voltage switch (HV Switch) has been designed to ensure that the CM voltage of the input signal reaches 90V, while the DM voltage reaches 5V. A linear trim method is proposed to reduce gain error. The CGA has been manufactured in the DBhitek 0.18-μm CMOS process. As the Vcm varies from 0 to 90V, the circuit has an offset voltage of 3.8μV, an output noise of 71.8nV/Hz^1/2 and a gain error of 0.0056%.

The diffraction of an H-polarized plane electromagnetic wave by a perfectly conducting rectangular cylinder is rigorously investigated using the Wiener-Hopf technique. Exact and approximate solutions of the Wiener-Hopf equations are obtained. The scattered field is evaluated explicitly using the saddle point method. Representative numerical examples of the radar cross section are presented. Some comparisons with the existing results are also provided.

The diffraction by a semi-infinite parallel-plate waveguide with partial material loading is rigorously analyzed using the Wiener-Hopf technique. In solving the Wiener-Hopf equations, the Modified Residue Calculus Technique (MRCT) is applied to obtain a highly accurate solution. The scattered field inside and outside the waveguide is evaluated explicitly. Representative numerical examples on the radar cross section are presented for various physical parameters and the scattering characteristics of the waveguide are discussed in detail.

Wired-logic processor architecture is a promising technology for energy-efficient computing. They have achieved several orders of magnitude higher energy efficiency than conventional FPGA-based deep neural network (DNN) processors by eliminating DRAM/BRAM access. The technical challenge of the wired-logic architecture is a huge amount of hardware resources to implement all weights and processing elements as wired-logic circuits. While the non-linear neural network (NNN) was proposed which can save hardware resources by a ternary weight, highly sparse neural network, the area overhead is still large for non-linear function implementation of NNN. Here we developed a coarse- and fine-grained lookup table (LUT) segmentation technique for resource-efficient FPGA-based NNN wired-logic processors. Two techniques are designed and analyzed: (1) an LUT segmentation technique based on coarse and fine granularity, and (2) accuracy optimization through the incorporation of redundant bits. The application of these proposed techniques to state-of-the-art wired-logic processors markedly enhances the scalability achievable with a single FPGA, thereby facilitating the implementation of larger-scale neural networks across various tasks, including CIFAR-10 classification and keyword spotting. The hardware resource requirements for non-linear functions in processing elements decreased by 94.4%, and 95.4%, respectively. Notably, the recognition accuracy for both CIFAR-10 and the keyword spotting task decreased by less than 0.2%, a negligibly small degradation.

We demonstrated a coincidence circuit based on single flux quantum (SFQ) circuits with high-time accuracy for a two-photon interferometer using superconducting nanostrip photon detectors (SNSPDs). The coincidence circuit was designed to have 3 different time windows of 30 ps, 100 ps, and 200 ps, which can be selectable on demand. Furthermore, each time window can be fine-tuned by changing the applied bias currents. The circuit was fabricated by the AIST high-speed standard process based on Nb/AlO_x/Nb junctions with critical current density of 10 kA/cm². We experimentally evaluated the time window of the coincidence circuit at temperatures below 2.4 K in a 0.1-W Gifford-McMahon (GM) cryocooler.

With the growth of deep learning and machine learning applications, an efficient processing element array (PEA) has become increasingly important. To address this need, this paper introduces a quantized bit-serial PEA, which improves data reusability by integrating a weight ring (WR) dataflow mechanism and increases operation frequency through the use of bit-serial circuits. This design substantially reduces the number of feature map accesses, thereby optimizing data processing efficiency. A key aspect of our approach is the use of quantization techniques. By converting floating-point values to signed 8-bit fixed-point numbers, we reduce computational complexity and ease memory bandwidth pressure. We briefly discuss that ignoring bias terms may not impact model inference accuracy when the appropriate neural network type and dataset are chosen. Our proposed WR dataflow, inspired by the weight stationary (WS) dataflow, only updates the outdated row with a new row. This not only boosts data reuse rates but also diminishes costly data access operations. Notably, the 3×3 WR PEA requires 38.54% of the off-chip accesses per second as compared to the 3×3 WS PEA and merely 11.25% compared to its no local reuse (NLR) PEA counterpart. Empirical results show its excellent trade-off between area, power, and speed, ensuring robust data reuse efficiency. By combining quantization and WR dataflow, our high-reuse, quantized bit-serial PEA offers a fresh perspective on deep learning hardware design.

In order to achieve a compact robot vision system that can perform object identification in real environments exposed to large changes in illumination, it is essential to consider both the algorithm and the hardware architecture. In this study, we have developed a compact and low-power image recognition system that is robust to illumination changes, consisting of a CMOS image sensor, field-programmable gate array (FPGA), and graphics processing unit (GPU) for embedded devices. To minimize the effects of changes in the illumination, our system uses the center/surround (C/S) retinex model, which is a color constancy model of the visual nervous system. Since the C/S retinex model involves large-scale spatial filtering with high computational costs, we compared the processing speeds of different hardware implementations of this model. This comparison showed that the FPGA implementation of the C/S retinex model used in this study is more than 10 times faster than the GPU implementation. Using the output of this efficiently processed C/S retinex model, a relatively small convolutional neural network (CNN), which runs on a GPU for embedded devices, performs object classification. We also investigated the impact of the spatial parameters of the C/S retinex model on the classification accuracy of CNNs using a dataset of images acquired under various lighting conditions. This investigation revealed parameters that provide better classification accuracy, and these parameters were largely independent of the CNN architecture used. This system performed object classification under various illumination colors at 52.1 frames per second with a power consumption of approximately 10.9 W.

This paper proposes an optoelectronic architecture of Convolutional Recurrent Neural Network (C-RNN in short). It employs RNN layers that replace area-consuming fully connected (FC) layers in typical convolutional neural network (CNN) architectures. The convolution and RNN layers in this architecture process input data in a pipelined manner that improves the throughput of the inference processing. It takes advantage of both the high input compression capabilities of CNNs and the compact and power-efficient nature of RNNs. The proposed optoelectronic C-RNN architecture achieves over 97.8% accuracy on the MNIST dataset while maintaining the advantages of power-efficient and high-speed characteristics of photonics. Our proposed optoelectronic C-RNN architecture can reach 240 TOPs/W, which is ten times more efficient than CMOS-based dedicated CNN accelerators.

The I-V measurement results of poly(vinyl alcohol)/ITO triboelectric generators are reported and discussed with a focus on the orientational ordering of molecular dipoles as electrical power sources induced by mechanical rubbing. The results showed that the rubbing induces dc current flowing through the ammeter in the direction from the poly(vinyl alcohol) to the cotton rubbing cloth. The polarity of induced current is opposite to what is expected from triboelectric series table, where poly(vinyl alcohol) is listed in the negative side relative to cotton. Assuming that the OH molecular groups are orientationally ordered in the direction away from the rubbing surface, and the current is induced through depolarization from the ordered state, the current direction is well explained. The results suggest that the molecular orientational ordering induced by rubbing is key for the operation of triboelectric generators using polar materials.

Organic multifunction diodes (MFDs) with light-emitting, photovoltaic, and photo sensing functions were demonstrated using a stack of N, N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C₁₃) and 2,7-di(9H-fluoren-2-yl)benzo[lmn][3,8]-phenanthroline-1,3,6,8(2H,7H)-tetraone (HFl-NDI) as an electron transporter/acceptor and 5,6,11,12-tetraphenylnaphthacene (rubrene) as an emitter/donor. Polyethylenimine ethoxylated (PEIE) as an electron injection layer was introduced in an inverted-structured device. By using the inverted structure and introducing HFl-NDI to reduce the absorption in the acceptor layer, an increase in the emission of EL and an increase in the short-circuit current density in the OSC were obtained.

We describe the operation of a rapid-single-flux-quantum (RSFQ) hardware random number generator comprising two Josephson oscillators, an XOR gate, and a non-destructive read-out (NDRO) cell. Single-flux-quantum (SFQ) pulse trains fed to the input terminals of the XOR gate contain timing jitters due to thermal noises. Then, the output of the XOR gate becomes random, which is stored in the NDRO cell and fetched by the trigger signal. We experimentally evaluated the output randomness of a test circuit fabricated using a 10 kA/cm² Nb/AlO_x/Nb integration process. For evaluation, the NIST FIPS 140-2 test suite was used. 24 random number sequences of 20 kb length were acquired with the trigger signal of 1 MHz, and evaluated for each operation condition. Relationships between the output randomness and operation conditions were obtained. In addition, numerical simulation demonstrated true random number generation at 20 GHz.

This paper presents a broadband high-efficiency power amplifier (PA) based on a series of continuous modes (SCMs). A novel filtering matching network is proposed for realizing the output matching network (OMN) of the PA. The network consists of a branch-loaded cascade-coupled microstrip line structure (BLCCMLS) and a harmonic control network (HCN). The cascaded coupled microstrip line extends the bandwidth of the filter, and this filtering OMN has high bandpass selectivity and high out-of-band rejection, which improves the efficiency of the PA. For demonstration, a 10W GaN HEMT device is used to design and implement a PA. The measurement results indicate that the designed PA achieved an output power (Pout) of 38.7-42 dBm, a drain efficiency (DE) of 60.5%-74.1%, and a gain of 8.7-12 dB at 2.05-2.7 GHz.

S-shaped current (I)-voltage (V) characteristics are routinely observed in emerging photovoltaic cell research. The opposed twodiode equivalent circuit model can reproduce such characteristics. The present study demonstrates Bayesian estimation of equivalent circuit parameters of a photovoltaic cell from S-shaped I-V characteristics with affordable computational cost below 15 min. The demonstration codes have been made publicly available on GitHub to cultivate transparency and facilitate reproducibility. This initiative aims not only to advance the understanding of photovoltaic cell behaviors but also to provide a practical, accessible tool for researchers in the field.

Naphthalenediimide (NDI) derivatives without or with one or two vinyl groups were synthesized to prepare thin films by the vapor deposition. NDI with larger number of vinyl substitution tends to form thin films with poorer crystallinity and lower electrical conductivity. On the other hand, the vinyl modification is effective in improving film morphology and temporal stability. Electron-assisted deposition of the vinyl-substituted NDIs produces smooth and stable amorphous polymer films with a lower conductivity. The vinyl substitution brings about contradictory effects of improving film morphology and stability at a cost of reducing crystallinity and conductivity. The vinyl modification also enables controlling the film/substrate interface by covalent tethering via a self-assembled monolayer.

An optical resonator with two waveguide discontinuities constructed by a metal-dielectric-metal plasmonic waveguide has been analyzed using the finite-difference time-domain (FD-TD) method with the piecewise linear recursive convolution (PLRC) method. The waveguide discontinuity has been expressed as an equivalent transmission line circuit whose circuit parameters are estimated from the reflection coefficients analyzed by the FD-TD method. We have confirmed the validity of the circuit configuration because the reflection characteristics of the equivalent circuit with the circuit parameters agree with those of the FD-TD method. Next, we have analyzed a resonator structure with two waveguide discontinuities and shown that the equivalent circuit gives a good approximation for the structure with a large difference in waveguide width at the discontinuities, in which conventional equivalent circuits had large errors.

This paper describes the high-precision electromagnetic field analysis methods that the author has developed (point matching method considering edge condition and Modified Fourier series expansion method) and research on their applications. In addition, as a new application of periodic structures, it is discuss a new method for solving scattering problems involving arbitrarily shaped objects in inhomogeneous media.

This paper presents an extension of the Kelvin transformation for high-frequency electromagnetic problems. The Kelvin transformation is a coordinate transformation that maps infinite space to a finite space, acting as a conformal transformation of Maxwell's equations. We apply concepts of differential geometry to derive the material constant's metric and spatial dependence in the exterior domain, which was originally proposed for low-frequency eddy current problems. This paper extends the conformal transformation concept to high-frequency problems by introducing a Perfectly Matched Layer (hereafter referred as to PML) in the exterior domain. This technique makes it easy to apply a simple Maxwellian PML.

In this study, the scattering fields by multi-window buildings have been analyzed by using the Kirchhoff approximation method. The scattering fields are obtained by the radiation integrals due to the equivalent current sources excited by the incident plane wave on the exterior of the building and the virtually closed window apertures. The fields in the window region are represented by rectangular waveguide modes, then the reflected fields from window glasses are also converted to the equivalent currents. The validity of our formulation has been confirmed by numerical comparison with the physical optics method and by measurements on scale models. Discussions have been made on the impact of window glass in the context of high-frequency wireless communications.

This paper proposes directivity synthesis for multimode horns with square-waveguide aperture based on quadratic programming approach using radiation patterns for each mode for obtaining axial-symmetric beam and low cross-polarization components, and also for realizing desired constant beamwidth. As a design example, we present a 11/14/20/30-GHz primary horn with square aperture and also show effectiveness of the proposed method by evaluating electric force lines of aperture distribution and 15-dB beamwidth of radiation patterns.

Power line communication (PLC) technology utilizes the alternating current distribution network to transmit signals, enabling high-speed information exchange in photovoltaic (PV) power systems without the need for additional wiring, thereby saving costs. The use of PV PLC technology may potentially cause radiated emissions that interfere with wireless radiocommunications, consequently leading to electromagnetic compatibility issue. Additionally, conducting accurate radiated emission measurements on-site in PV power systems can be challenging. The paper proposes a methodology utilizing a scaled model for the equivalent radiated emissions of PV PLC. This approach facilitates the execution of equivalent testing for PV PLC radiated emissions under controlled laboratory conditions. Conducting a simulation study using CST to determine the equivalent simulation of actual long-line model through scaled short-line model, three scaled short-line models with different diameters were selected for comparison with the simulated radiated emission results of long-line model. After that, the optimal scaled short-line model was determined, followed by practical testing of the scaled short-line model in an anechoic chamber. Finally, by comparing the results, the accuracy of the simulation model was validated, this further substantiates the feasibility of the research methodology employed in this study. The study serves as a reference for achieving accurate prediction of PV PLC radiated emissions and the determination of associated limits in the future.