Search Results (385)

Relaxor ferroelectric single crystals, such as Pb(In₁/₂Nb₂/₃)O₃–Pb(Mg₁/₂Nb₂/₃)O₃–PbTiO₃, possess extraordinary electro-optic (EO) coefficients, offering immense potential for next-generation integrated modulators. However, the application of PIN-PMN-PT in fiber-optic gyroscopes (FOGs) is hindered by the challenge of fabricating high-quality optical waveguides with strict mode selectivity, as conventional diffusion typically excites multi-mode propagation. Here, the fabrication of high-quality, mode-selective waveguides is achieved in rhombohedral PIN-PMN-PT via a nickel in-diffusion technique. The resulting graded-index structures exhibit a Gaussian profile with a maximum refractive index change (∆n) of 1.53% while preserving the single crystal structure. Under specific processing conditions, we achieve precise mode selectivity, enabling exclusive transverse electric (TE) mode transmission. This mode selectivity fulfills the requirements for single-mode Y-branch geometries, establishing a robust platform for ultra-compact, low driving voltage modulators and advancing the miniaturization of inertial navigation and integrated photonic systems. Full article

This article presents the design and characterization process of a lightweight Vivaldi antenna for high-voltage ultra-wideband systems. The proposed antenna consists of two radiating arms with different exponential curves on their inner and outer edges fed with an insulated-coplanar-plates transmission line. Weight reduction is achieved by implementing the antenna with sheets composed of a polyester layer between two aluminum layers, with a polylactic acid insulator inserted between the arms. The reflection coefficient of the implemented antenna demonstrates an impedance bandwidth ranging from 0.61 GHz to 3.44 GHz. High-voltage operation of up to 12.4 kV is also experimentally demonstrated. In addition to satisfying the high-voltage and ultra-wideband operational requirements, the proposed antenna is shown to achieve, among antennas with comparable characteristics, the most effective combination of low minimum operating frequency and low weight. The transfer function between the voltage applied to the antenna, $V_s$, and the radiated electric field, $E_r$, is measured. Using this transfer function, the radiated electric field is calculated for an input voltage pulse with a rise time of 110 ps to confirm the antenna’s capability of producing radiated pulses with low distortion. The calculated radiated electric field pulse closely matches the results obtained with full-wave simulation. To assess the similarity between the radiated and applied pulses, the pulse width stretch ratio is calculated, yielding a variation of 3.86% for the direction of maximum gain and 9.36% for 30° in the H-plane of the antenna. This feature is desirable for EMC, EMI and sensing applications. The antenna is also characterized in the frequency domain, achieving a maximum gain of 10.09 dBi at 3.63 GHz and a 30° 3 dB beamwidth for ultra-wideband pulses. Full article

This paper proposes a non-overlapping planar cross-arranged ultra-wideband shared-aperture base station antenna array targeting the 2 to 6 GHz application bandwidth. The low-frequency module (double-layer parasitic coupling) and the high-frequency module (chamfered slotted patch) are independently designed, and metal baffles are introduced around the antenna elements to reshape the boundary conditions and physically block the electromagnetic coupling paths. Both simulation and experimental results demonstrate that the fabricated prototype successfully exceeds the targeted 2–6 GHz spectrum, achieving an actual continuous coverage from 1.84 to 6.3 GHz. Specifically, the antenna achieves a gain higher than 5.9 dBi in the measured low-frequency band (1.84–3.72 GHz) and higher than 6.1 dBi in the high-frequency band (3.63–6.3 GHz), with a voltage standing wave ratio (VSWR) below 2 across the entire band. The metal baffles successfully correct the high-frequency radiation pattern distortion and ensure stable directional radiation over the full operating bandwidth. This design provides an efficient, robust, and manufacturable solution for 5G offshore wind power multi-band base station antennas. Full article

Edge intelligence is often limited by the computation–energy trade-off in resource-constrained devices. Boltzmann machines (BMs) provide strong unsupervised learning capability, yet their reliance on Gibbs sampling makes digital implementations costly in both computation and energy. In this paper, we present a voltage-controlled magnetic anisotropy magnetic tunnel junction (VCMA-MTJ)-based MRAM system that performs in-memory stochastic sampling for state generation and updates in restricted/deep Boltzmann machines (RBMs/DBMs). By exploiting the intrinsic stochastic switching of VCMA-MTJs, the proposed system achieves probabilistic sampling with an energy as low as ∼10 fJ per sample. Implemented on a microcontroller-based edge platform, it enables real-time multi-sensor anomaly detection with an F1-score of 0.9854 and stable operation. The proposed hardware–algorithm co-design achieves in situ stochastic computing and storage within a single MRAM cell, providing an ultra-low-power substrate for probabilistic inference at the edge. Full article

A 0.3 V nanowatt CCII⁻ is presented in 0.18 $\mathsf{\mu }$m TSMC CMOS, targeting ultra-low-power current-mode interfaces. Post-layout extracted simulations demonstrate correct conveying operation with a total DC power consumption of less than 2.40 nW. The low-frequency tracking factors evaluated at 1 Hz are ${\beta }_0=0.9452$ (−0.48 dB) and ${\alpha }_0=0.9609$ (≈−0.35 dB), with $-3$ dB bandwidths of 22.95 kHz and 63.95 kHz for the voltage and current transfers, respectively. Small-signal extraction confirms the intended impedance profile, yielding $R_X=46.73$ M$\mathsf{\Omega }$, $R_Z=1.204$ G$\mathsf{\Omega }$, and a very high input resistance $R_Y=392$ G$\mathsf{\Omega }$. Robustness is verified through full PVT and mismatch analyses, showing stable functionality across process corners, a 0–80 °C temperature range, and 270–330 mV supply variations while maintaining nanowatt-level dissipation. Full article

The gimbal servo system in a control moment gyroscope (CMG) is critical for high-precision spacecraft attitude control, where comprehensive performance testing and evaluation are essential for ensuring spacecraft reliability and service life. Traditional motor testbenches exhibit limitations, whereas the electric motor emulator (EME) based on power electronic converters is a promising alternative for testing extreme operating conditions, such as ultra-low speed operation and fault scenarios. However, existing EME control methods suffer from limited system bandwidth and insufficient emulation accuracy, which limits their applicability. To address these issues, this paper proposes an improved current control strategy for the ultra-low speed permanent magnet synchronous motor (PMSM) emulator. First, a mathematical model of the EME based on the topology of the voltage source converter is established. Then, based on the deadbeat control concept, a deadbeat predictive current control (DPCC) strategy is developed to enhance the dynamic performance. Furthermore, to suppress the parameter mismatch disturbance, an optimization scheme based on a cascaded extended state observer (CESO) is introduced. The first-stage ESO is applied to estimate and compensate for total disturbances, while the second-stage ESO is a supplement to suppress the remaining disturbances in the EME system, which improves the robustness of the DPCC controller. Finally, the effectiveness of the improved emulation accuracy of the proposed method is verified through experiments. Full article

The accelerating adoption of electric vehicles (EVs) is driving the demand for next-generation wide-bandgap (WBG) power devices that can deliver high efficiency, high power density, and robust operation under stringent electrical and thermal stress. Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) have emerged as a leading WBG technology due to their high breakdown voltage, ultrafast switching capability, and low conduction and switching losses relative to silicon devices, enabling high-performance EV power converters such as on-board chargers, DC-DC converters, and traction inverters. This review provides a comprehensive device-level assessment of GaN HEMTs, emphasizing advanced device architectures, state-of-the-art discrete transistors, and their implications for high-frequency, high-efficiency power conversion. Critical performance and reliability challenges, including current collapse, self-heating, and gate degradation, are analyzed in the context of their physical mechanisms and operational behavior under realistic conditions such as elevated junction temperatures, high switching frequencies, and dynamic load profiles. Furthermore, emerging opportunities in ultra-wide-bandgap semiconductor technologies beyond GaN are discussed, providing insights to guide the design, optimization, and robust integration of WBG devices into next-generation EV power electronic systems. Full article

Single-crystal 4H-SiC, as a wide-bandgap semiconductor material, has become a key substrate for high-power electronics and radio frequency devices due to its outstanding characteristics such as high-voltage tolerance, high-temperature stability, high-frequency efficiency and low loss. However, its inherent properties of high hardness and low fracture toughness also pose severe challenges to the ultra-precision processing of wafer substrates. In this study, through molecular dynamics methods, the influence of diamond abrasive grains with different sharpness on the processing of 4H-SiC at different grinding speeds was simulated, with a focus on analyzing its surface morphology, material removal behavior and subsurface damage characteristics. The structural evolution of 4H-SiC workpieces and diamond abrasive grains was identified through the radial distribution function, and the dynamic changes in temperature and stress during processing were further investigated to clarify the mechanism of abrasive wear and graphitization phenomena. The results show that regular octahedral abrasive grains with higher sharpness have better material removal efficiency, but they also cause more significant subsurface damage. Increasing the grinding speed helps to reduce the depth of subsurface damage. In addition, high temperature and high stress are the key factors leading to the transformation of diamond into graphite. Even under low-speed grinding conditions, the edges of the abrasive grains may still undergo graphitization due to stress concentration. The above findings have theoretical significance for an in-depth understanding of the material removal mechanism of 4H-SiC nano-grinding, and can also provide an important reference for the development of high-performance grinding wheels for SiC grinding. Full article

Droplet manipulation constitutes a fundamental operation in numerous bio-microfluidic applications, including but not limited to medical diagnostics and targeted drug delivery. Among the various technologies developed for this purpose, magnetic digital microfluidics (MDMF) has emerged as a compelling approach due to its inherent advantages of contamination-free actuation, low cost, and configurational flexibility. Nevertheless, conventional MDMF remains constrained by its reliance on bulky instrumentation and substantial power consumption for generating controllable magnetic fields, which limit its in-field applications. To address these limitations, this work presents a programmable and portable electromagnetic microfluidic droplet manipulation platform that synergistically integrates static and dynamic magnetic fields to enable non-contact, high-precision droplet control under ultra-low power conditions. The proposed system comprises an electromagnetic actuation module, a permanent magnet, and a glass substrate coated with Teflon film. The entire system is secured by a PMMA support structure, within which a glass substrate is mounted and spatially separated from the permanent magnet. The PMMA support is fabricated using a milling process, offering a simple manufacturing procedure and high structural reusability and reproducibility. The control logic is implemented on a field-programmable gate array (FPGA) development board, facilitating fully autonomous operation powered by a standard battery. The platform operates at a low voltage of 3.5 V and a driving current of 180 mA, corresponding to a total power consumption of merely 0.63 W, while achieving robust manipulation of droplets in the volume range of 0.5 to 5 μL. A maximum average droplet velocity of up to 0.6 cm/s was attained under optimal conditions. The proposed platform offers a scalable and energy-efficient solution for portable droplet-based assays and holds significant promise for integration into point-of-care diagnostic tools and field-ready biochemical analysis systems. The platform demonstrates excellent operational stability and reproducibility, as validated by repeated actuation experiments with a positioning deviation of approximately 0.1 mm under optimized conditions. The fabrication process also exhibits high reliability with consistent performance across multiple experimental runs. Full article

Wind energy harvesting based on triboelectric nanogenerators (TENGs) is a promising solution for powering distributed Internet of Things (IoT) nodes, yet its practical efficiency and stability are often hindered by the fluctuating and unpredictable nature of wind. Here, we propose a self-regulating TENG (SR-TENG) that leverages the synergistic effects of centrifugal, elastic, and frictional forces to automatically switch between non-contact and contact modes based on wind speed. This configuration achieves an ultra-low start-up wind speed of 0.86 m/s, ensures sustainable high-performance output across a broad wind speed range, and exhibits excellent durability with no observable performance degradation during 23,000 s of continuous operation at 375 rpm. Systematic structural optimization enables the SR-TENG to reach a peak open-circuit voltage of 140 V, a short-circuit current of 12.5 μA, and a transferred charge of 300 nC at 375 rpm. When integrated with a customized power management circuit, the system delivers a 30.39-fold increase in effective output power at a 1 MΩ load and a 4-fold faster charging rate for a 10 μF capacitor. For practical validation, the harvested ambient wind energy successfully powers a wireless temperature-humidity sensor for real-time cloud data transmission. These results highlight that the SR-TENG holds great potential for advanced wind energy harvesting and self-powered sensing applications in distributed IoT systems. Full article

In this study, an ultra-low-voltage operational transconductance amplifier (OTA) operating from a 0.3 V supply, designed in a 45 nm CMOS process, is presented. To overcome the severe headroom constraints, the design employs a bulk-driven differential input stage combined with a current-reuse strategy, effectively enhancing transconductance while operating all transistors in the subthreshold region. This approach enables a rail-to-rail input common-mode range. A multipath Miller zero cancellation compensation technique ensures stability. The resulting OTA achieves an open-loop gain of 44.2 dB and a remarkable common-mode rejection ratio (CMRR) of 87.5 dB, all while consuming 23.3 nW of power. With a gain–bandwidth product of 9.9 kHz, a power supply rejection ratio (PSRR) of 41.1 dB, and an input noise of 1.0 μV/√Hz, this design is highly suitable for energy-constrained, low-frequency applications such as biomedical sensor interfaces and IoT nodes. Full article

Buildings account for approximately 40% of global energy consumption, with heating, ventilation and air conditioning systems being the primary contributor. Building management systems offer a promising solution for enhancing energy efficiency, particularly in retrofitting older or protected buildings. However, powering numerous wireless sensors required by BMS remains a logistical challenge. This study investigates the feasibility of harvesting thermal energy lost through windowpanes to power ultra-low-power IoT sensors, a concept that was not previously explored in the literature. A thermoelectric energy harvester was developed using a TEC1-12710 thermoelectric module and an EM8900 ultra-low-voltage DC-DC boost converter. Laboratory and field experiments were conducted to evaluate the system’s performance under various thermal conditions, with electrical energy accumulated in a 0.01 mF capacitive energy storage. In laboratory conditions, a temperature difference of ~1 °C enabled the system to generate up to 3.24 V with a power density of 3 mW/m². Field tests during winter yielded lower performance (1.43 V, 1.9 mW/m²), which was attributed to suboptimal thermal gradients and operating points. It was thus experimentally shown that windowpane heat losses can be effectively harnessed for indoor energy harvesting. While the current efficiency is limited, the approach shows promise for powering battery-free IoT devices. Full article

Memristors are valuable elements with very good memory and switching features. They have minimal power consumption, nano-scale sizes, and a possibility for integration with high-density Complementary Metal Oxide Semiconductor (CMOS) integrated circuits. They are applicable in neural networks, memory crossbars, and different electronic devices. This work considers some improved and existing models for memristors, functioning at high-frequency signals with a high speed and very good effectiveness. The main parasitic parameters—series resistance, capacitance, and small-signal direct current (DC) voltage and current shifting signals—are taken into account. An additional leakage conductance is analyzed as a parasitic component. The influence of the parasitic parameters on the normal functioning of memristor-based circuits is analyzed and evaluated at hard-switching and soft-switching modes. For investigations of the main characteristics of the considered models and their applicability in memory arrays, Linear Technology Simulation Program with Integrated Circuits Emphasis (LTSPICE) library models are generated and analyzed. The considered models operate at low-, middle- and high-frequency signals, clearly demonstrating the main properties of memristors. Their appropriate operation in passive memory arrays is analyzed and established. The proposed models have a 26% enhanced accuracy in fitting experimental i-v relations. They ensure good memory and switching properties for memory arrays. This work could be a suitable step towards the design and manufacturing of ultra-high-density memristor-based integrated chips. Full article

This study presents the design, implementation, and validation of a thermoelectric energy harvesting system that exploits waste heat from an industrial electric motor to power an autonomous wireless sensor device. The proposed prototype integrates a single thermoelectric generator directly onto the motor housing and leverages the built-in cooling fan to maintain a stable thermal gradient of approximately 4–5 °C. Under real factory conditions, the system harvested 6.17 J of energy over 9612 s, sustaining continuous operation and 41 successful Long Range (LoRa) data transmissions with a positive energy balance. Compared with related works, the prototype achieved competitive or superior performance while operating at a lower motor rating of 0.25 kW, highlighting its efficiency relative to system scale. Key innovations include a hybrid DC/DC conversion chain bridging ultra-low input voltages to modern microcontrollers, and an adaptive transmission strategy that ensures predictable energy management and reliable wireless communication. These results demonstrate the feasibility of battery-free sensing in industrial environments and underline the potential of thermoelectric harvesting as a cost-effective, maintenance-free, and environmentally responsible solution for predictive maintenance and Industry 4.0 applications. Full article

To meet the high-sensitivity requirement of ultra-high-frequency (UHF) sensors for electromagnetic waves radiated by partial discharge (PD) in power equipment of substations, this paper proposes a Koch complementary fractal UHF antenna based on the artificial magnetic conductor (AMC) metasurface. First, based on the Iterated Function System (IFS), a finite element model of the UHF Koch fractal antenna is constructed via affine transformation. Then, leveraging the in-phase reflection characteristic of the metasurface, an AMC metasurface for gain enhancement of the Koch fractal antenna is designed, and a multi-dimensional parameter joint optimization method is adopted to obtain the optimal structural parameter set of the Koch fractal antenna loaded with the AMC metasurface. Finally, experimental tests and analyses are carried out on the Koch complementary fractal UHF antenna. The results show that the antenna loaded with the AMC metasurface achieves a better voltage standing wave ratio (VSWR) and improved gain in both low and high frequency bands: the average gain increases by 35.19% in the frequency range of 0.3 GHz to 1.5 GHz, and the peak gain reaches approximately 11.5 dB with an enhancement of 120%. Full article