Search Results (808)

In this paper, we present a study on the automated design optimization of a wideband low-noise amplifier (LNA) operating in Ku-band (12 to 18 GHz) using proximal policy optimization (PPO), one of the widely applied reinforcement learning (RL) algorithms for engineering problems. As a target microwave active circuit, we select a two-stage LNA architecture, where transmission lines (TLs) are dominantly used for impedance matching and gain/noise optimization. For simplicity, all widths of TLs were fixed so that the characteristic impedance is 50 Ω, with lengths of TLs being set as design parameters. In addition, dimension variables of capacitors were treated as design parameters and, in total, we optimized 29 parameters. For target specifications, we set both $S_{11}$ and $S_{22}$ to be below −10 dB over the 12–18 GHz band and the noise figure (NF) to be below 2 dB. A total of 20,140 simulations were performed for training and the overall process took about 24 h. The results show that both the reward and the loss converged appropriately, achieving the target specifications successfully. For the final results, we performed up to 25 predictions, and the prediction process was terminated early if a solution meeting all target specifications was found within the given number of attempts. The device model used was a commercial 150 nm GaN high-electron-mobility transistor (HEMT) process technology. Full article

This paper presents a nanowatt-scale operational transconductance amplifier (OTA) and an electronically tunable third-order low-pass filter (LPF) designed for energy-constrained biomedical signal conditioning. The circuits are implemented in a 65 nm CMOS process and verified through comprehensive schematic-level simulations. Biased in the deep subthreshold region at 1 nA, the OTA achieves a 50 dB low-frequency gain, a 225 Hz unity-gain bandwidth at 10 pF load capacitance and an input-referred noise floor of 1.55 μV/√Hz, with a total power consumption of only 1.75 nW. The integrated third-order LPF provides a wide tuning range (37–668 Hz) via bias current modulation, exhibiting excellent linearity with a THD of 0.059% and a 65.3 dB dynamic range. Monte Carlo and PVT corner analyses demonstrate the design’s theoretical robustness against process variations and environmental fluctuations. ECG signal simulations validate the circuit’s effectiveness in suppressing high-frequency artifacts while preserving morphological integrity, providing a proof-of-concept for ultra-low-power wearable healthcare architectures. Full article

All-optical logic gates have emerged as a critical technology for enabling broadband, low-loss, and high-speed communication systems, addressing the inherent bandwidth limitations of electronic counterparts. Here, we propose a Y-shaped structure leveraging unidirectional modes in the terahertz regime, which enables the realization of multifunctional all-optical logic gates within the lower- and upper-frequency bandwidth regions, including, but not limited to, AND, OR, NOT, and XNOR gates. Numerical simulations and theoretical analyses confirm that the proposed logic gates exhibit robust one-way propagation characteristics, with electromagnetic signals demonstrating complete immunity to backscattering even in the presence of structural defects. Furthermore, nonlocal effects are found to have a negligible impact on the operational bandwidths of our design. Building upon this Y-shaped configuration, we further develop an all-optical digital logic system (AODLS) capable of supporting bifrequency multi-input and multi-output logic operations. When lower- and upper-frequency signals are injected into separate input ports, their corresponding output signals remain fully independent, eliminating cross-talk and enabling true parallel computation. This dual-band parallel processing capability represents a significant advance over conventional single-band all-optical logic systems, opening new avenues for high-throughput all-optical computing and integrated photonic circuits. Full article

The increasing penetration of renewable energy has led to the large-scale integration of power electronic devices into the power grid. In weakly connected grids, such devices are connected to the grid via voltage source converters (VSCs) using grid-forming (GFM) control strategies. Ideally, the point of common coupling (PCC) with the grid is treated as a purely inductive circuit. However, in weak grids, the resistance-to-inductance ratio (R/X) cannot be ignored, which leads to the power coupling problem between active power (P) and reactive power (Q). This phenomenon impedes the precise control of P and Q, potentially resulting in steady-state power deviations and even system instability. Traditional power-decoupling methods based on virtual inductance (VI) have inherent limitations and fail to achieve complete decoupling between P and Q. To address this issue, this paper first analyzes the influencing factors of power coupling through an established power coupling model. Comparisons between the output voltage and the degree of power coupling demonstrate that power decoupling can be achieved by compensating the output voltage. Consequently, an improved power-decoupling strategy based on apparent power feedforward (APPFF) is proposed. The proposed APPFF method realizes complete P-Q decoupling, with a steady-state reactive power error of less than 1% of the rated value. Compared with the PI-decoupling method, the reactive power overshoot is reduced by about 24%, and no additional active power overshoot is introduced. Compared with the conventional virtual inductance method that only reduces coupling by up to 35%, APPFF eliminates the power coupling fundamentally while retaining the reactive power–voltage droop characteristics and fast dynamic response. By directly compensating the reference voltage to the ideal value using apparent power as the feedforward variable, the proposed method is essentially different from the existing voltage/angle compensation schemes. The feasibility and effectiveness of the proposed decoupling method are verified under various working conditions, such as different R/X ratios, line resistances and power references, through both Simulink simulations and experimental results. Full article

Integrated Gate-Commutated Thyristor (IGCT) serves as the core power electronic device in high-voltage and high-power renewable energy conversion systems. Aiming at the problems of slow convergence, easy to fall into local optima, and difficulty in balancing multi-objective performance in traditional IGCT gate drive design under power fluctuation conditions, this paper proposes an IGCT gate drive optimization method based on the Improved Grey Wolf Optimization (IGWO) algorithm. A multi-objective optimization model is established with switching loss reduction, voltage overshoot suppression, current oscillation attenuation and driving capability guarantee as objectives and gate resistance and driving voltage as optimization variables. The traditional grey wolf algorithm is improved by adaptive weight adjustment and dynamic search step strategies to balance global exploration and local exploitation. Simulation and experimental results show that, compared with the traditional Grey Wolf Algorithm (GWO) and Particle Swarm Optimization (PSO), the convergence speed of IGWO is increased by 40.4% and 51.0%, and the optimization accuracy is improved by 12.7% and 18.1%, respectively. Compared with the conventional empirical design, the optimized drive circuit reduces the switching loss by 31.8%, suppresses the voltage overshoot by 33.7%, decreases the current oscillation by 38.6%, and shortens the driving rise time by 39.3%. The proposed method realizes the automatic and precise tuning of IGCT gate drive parameters, effectively improves the switching performance and operation stability of IGCT under renewable energy fluctuation conditions, and provides a practical intelligent optimization scheme for the high-performance gate drive design of high-power IGCT devices. Full article

Surface Acoustic Wave (SAW) technology, long central to analog signal processing and RF filtering, is undergoing a major renewal. Driven by advances that decouple SAWs from traditional piezoelectric materials and fixed-function devices, the field is gaining unprecedented control over acoustic, optical, and electronic interactions at the micro and nanoscale. This review synthesizes these developments across four fronts: new physical mechanisms for SAW manipulation, emerging material platforms, ranging from thin films to 2D systems, along with reconfigurable device architectures and circuits, and the expanding landscape of applications they enable. Optical methods are reshaping how SAWs are generated and controlled, bypassing the limits of conventional electromechanical coupling. Coherent optical excitation of high-Q SAW cavities via Brillouin-like optomechanical interactions now grants access to modes in non-piezoelectric substrates such as diamond and silicon, while on-chip SAW excitation in photonic waveguides through backward stimulated Brillouin scattering opens new integrated sensing routes. In parallel, magneto-acoustic experiments have revealed nonreciprocal SAW diffraction from resonant scattering in magnetoelastic gratings. On the device side, ZnO thin-film transistors integrated on LiNbO₃ exploit acoustoelectric coupling to realize voltage-tunable phase shifters; UHF Z-shaped delay lines achieve high sensitivity in a compact footprint; and parametric synthesis of wideband, multi-stage lattice filters targets 5G-class performance. Atomistic simulations show that SAW propagation in 2D MXene films can be engineered via surface terminations, while aerosol jet printing and SAW-assisted particle patterning provide agile, cleanroom-light fabrication of microfluidic and magnetic components. These advances enable applications ranging from hybrid quantum systems and quantum links to lab-on-a-chip particle control, SBS-based and UHF sensing, reconfigurable RF front-ends, and soft robotic actuators based on patterned magnetic composites. At the same time, optical techniques offer non-contact probes of dissipation, and MXenes and other emerging materials open new regimes of acoustic control. Conclusively, they are transforming SAW technology into a versatile, programmable platform for mediating complex interactions in next-generation electronic, photonic, and quantum systems. Full article

Semiconductor miniaturization demands stricter material uniformity. Core-shell nanofibers, promising for semiconductor packaging and flexible circuits, face application limits due to traditional coaxial electrospinning’s electric field instability—causing poor fiber diameter uniformity and challenges with high-viscosity and low-conductivity solutions. To address this, airflow-assisted coaxial electrospinning leveraged airflow-electric field synergy to enhance fiber stretching. COMSOL Multiphysics 6.4 simulated the influence of different inner diameters of the air flow nozzles on the air flow field, while the response surface method optimized parameters. At 10 kPa air pressure, 16.71 kV voltage, and a gas nozzle inner diameter of 3.42 mm, nanofibers showed regular morphology with a diameter coefficient of variation as low as 9.2%. This study enables stable preparation of highly uniform core-shell nanofibers, providing key process support for their large-scale semiconductor application and advancing flexible electronics and photodetection. Full article

Fully maintenance-free smart collars for range cattle, sheep and deer must survive years of uncontrolled grazing under highly variable shade and motion conditions. This paper presents an ultra-low-power buck converter governed by a fast integral terminal sliding mode controller (FITSMC) with a fixed-time observer. A new reaching law retains the initial sliding manifold and a negative-power term maintains the constant switching gain to preserve robustness near the surface while attenuating chattering without widening the bandwidth. The fixed-time observer estimates the irradiance and load changes and provides a feed-forward correction, tightening the output regulation regardless of initial conditions. Load step tests with moderate resistance swings showed the proposed method recovers noticeably faster and exhibits slightly lower overshoot than a recent method based on a two-phase power reaching law, while visible inductor current spikes are also suppressed. Simulations under daily grazing profiles confirmed tight output regulation adequate for microwatt data logging and periodic long-range (LoRa) bursts. The sleep mode quiescent current remained in the 9 microamps range, eliminating the need for manual recharge across multi-season field deployments. By integrating robust power electronics with collar-grade solar harvesting, the circuit offers a truly maintenance-free energy path for untethered livestock wearables and supports sustainable precision agriculture. Full article

A compact dual-polarized beam-steerable patch antennas with filtering characteristics is proposed in this paper. By digging two orthogonal coupling slots on the ground plate, dual polarization is achieved while ensuring the isolation between the ports. By constructing properly arranged parallel microstrip resonators and open-circuited stubs, the effect of suppressing a broad stopband is produced. The beam steering characteristic is accomplished through the integration of a driven patch antenna with two dual-element metallic walls, each incorporating PIN diodes for electronic tuning. A prototype antenna has been fabricated to substantiate the efficacy of the proposed methodology. The simulated and measured results agree well, demonstrating good performance in terms of impedance bandwidth, stopband suppression, isolation and beam-steering capability. Under six radiation states, the proposed antenna operates from 2.3 GHz to 2.5 GHz with isolation exceeding 20 dB. Additionally, the antenna gain remains below −10 dBi over the 2.6 GHz to 10 GHz band, achieving out-of-band suppression greater than 15.8 dB within the wide stopband. When port 1 is excited, the antenna generates three distinct radiation patterns, enabling beam scanning at 0° and ±30° in the yoz plane. Similarly, exciting port 2 yields three radiation patterns, allowing beam scanning at 0° and ±30° in the xoz plane. This work presents the first integration of dual-polarized, beam-steering, and filtering characteristics into a single compact antenna. Full article

The global rise in electronic waste (e-waste), especially in semiconductor components such as circuit boards and microchips, underscores a critical need for improved recycling technology. Current industrial sorters often miss small, high-value components. This leads to the loss of precious metals and inefficient recycling processes. This paper introduces an automated detection framework for detecting semiconductor components in e-waste. It assesses ensemble learning methods that leverage the strengths of multiple YOLO (You Only Look Once) object detection models, including YOLOv5, YOLOv8, YOLOv9, YOLOv10, YOLOv11, and YOLOv12. Three ensemble fusion strategies are systematically compared: standard Non-Maximum Suppression (NMS), voting-based strategies (Affirmative, Consensus, Unanimous), and Weighted Box Fusion (WBF) with both static and dynamic weight optimization. Our simulations demonstrate that using multiple models together is far more effective than a single model for the following reasons. 1. Higher Accuracy: The best configuration, Top-4 Consensus Voting ensemble strategy, achieved an mAP@0.5 of 59.63%, a 10.3% improvement over the best individual model (YOLOv8s, 54.04%); 2. Greater Reliability: It significantly reduced “false negatives” (missed detections), even in cluttered or crowded e-waste scenarios; 3. Enhanced Detection: While the individual YOLOv8 model is fast (taking only 62.6 ms), supporting real-time detection, the best ensemble configuration (Consensus Top-4) takes 384.9 ms, creating a trade-off between detection accuracy and speed; 4. Well-Balanced Performance: Some fusion strategies showed slight trade-offs in mAP for certain parts, but collectively achieved a 7% rise in F1-score, indicating a better balance between precision and recall. This research marks significant progress in smart recycling. Improved component identification allows for more efficient recovery of high-purity materials. This promotes a circular economy by ensuring that rare and strategic materials in electronics are reused instead of discarded. Full article

This study focuses on the zonotope-based set-membership estimation issue for switched Takagi–Sugeno (T-S) fuzzy systems with application to tunnel diode circuits. Given the practical importance of tunnel diodes in radio-frequency, microwave, and high-speed electronic systems, we first model the tunnel diode circuit as a switched T-S fuzzy system to characterize its inherent dynamics. To address the state estimation issue, we propose a zonotopic set-membership estimation framework for the system under mode-dependent average dwell-time (MDADT) switching, which enables tighter state bounding while ensuring $H_{\infty }$ robustness. A mode-dependent observer is designed to attenuate the effects of external disturbances and measurement noise, and the stability of the estimation error system is analyzed based on an appropriate Lyapunov function. Numerical simulations are conducted and the corresponding results show that the estimated boundary can accurately encompass the true state of the system, and the volume of the estimated set is reduced by approximately 28.99% compared with the interval observer method, thus demonstrating the effectiveness and potential of the proposed approach. Full article

Proton exchange membrane fuel cells (PEMFCs) play a key role in hydrogen-based energy systems; however, accurate and practical modelling remains challenging due to system nonlinearities, parameter variability, and degradation effects. This paper presents a low-complexity parameter estimation methodology for a simplified PEMFC equivalent circuit model using current-switching techniques. The approach enables direct extraction of key parameters, including internal resistance and capacitance, from transient voltage responses without requiring complex optimization or large datasets. Experimental validation was conducted using 100 W and 1 kW PEMFC systems under current loading and interruption conditions. The results demonstrate good agreement between measured and simulated voltage responses, with a maximum error below 10% and typical error levels in the range of ~1.4–3%. Compared to conventional mechanistic and data-driven models, the proposed method significantly reduces computational complexity and measurement requirements while maintaining high predictive accuracy. Moreover, the combination of the simplified equivalent circuit model with current-switching-based parameter estimation offers an effective and practical tool for electrical engineers, enabling real-time monitoring, control-oriented modelling, and seamless integration with power electronic systems. The proposed approach is particularly suitable for applications in DC microgrids and digital twin-based monitoring of hydrogen energy systems. Full article

Phase-change materials (PCMs) are capable of storing or releasing a substantial amount of thermal energy within a small volume through the latent heat of fusion during phase transitions of melting and solidification, i.e., from solid to liquid or vice versa, in a near isothermal process. However, commonly used organic PCMs, such as paraffin wax, exhibit very low thermal conductivity, contributing to an adverse increase in overall thermal resistance and, thus, a slow thermal response. This limitation often becomes a bottleneck for the system from a thermal performance standpoint. To mitigate this issue, the present work explores the fabrication of heat sinks incorporating nano-structured graphitic foams, including carbon foam (CF) and expanded graphite (EG), as well as micro-structured metal foams such as open-cell copper foam (OCCF), all impregnated with a paraffin-based PCM with a melting temperature near 37 °C. This study focuses on applying passive thermal management strategies to design efficient heat sinks capable of maintaining the temperatures of battery modules and electronic circuits within an acceptable thermal safety threshold for small satellites and spacecrafts, exemplified by the OPTIMUS and Pumpkin battery modules designed for CubeSats with a nominal cross-sectional area of almost 4″ × 4″. Temperature responses and average overall thermal resistances for fabricated heat sinks are accordingly assessed and compared in a vacuum chamber to simulate space conditions. Furthermore, the impact of operating pressure on the thermal performances of various heat sinks will be investigated by executing the same tests in both atmospheric and vacuum conditions. The findings demonstrate a superior thermal performance of composite heat sinks integrating carbon foam and copper foam into the paraffin PCM compared to the baseline PCM heat sink under both vacuum and atmospheric operating pressure conditions. 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

A conventional resonant-inductive wireless charging system includes a power factor corrector (PFC) to maintain a high input power factor (PF) and low distortion of the input current (THDI). Although a conventional low-power wireless charging system with a PFC has relatively simple power electronic circuitry, its control stage is comparatively complex and expensive. This complexity arises because it relies on multiple feedback loops, as well as a radio communication link with complex communication protocols. As a result, the design complexity and development time are relatively high, and a highly qualified engineer with strong programming and communication expertise is needed. Some state-of-the-art solutions have eliminated the wireless communication link at the cost of increased size of the receiving side. To overcome these drawbacks, this paper proposes a simpler control and communication method that combines output voltage and current limiting with a low-latency wireless communication link transmitting 1-bit logic signals. This approach improves the cost-effectiveness of the control circuit, reduces system complexity, and keeps the receiving side compact, while maintaining performance comparable to conventional and state-of-the-art solutions. The proposed method is validated through simulations and experiments using a 60 W prototype. Results show that the power-factor-corrected wireless charging system with the proposed control and communication scheme achieves a THDI of 4.3%, a power factor of 0.99, high charging voltage accuracy (±0.5%), and satisfactory current accuracy (±9%). Full article