Search Results (224)

Vibration control is a critical aspect of engineering, particularly in structures and mechanical systems where excessive oscillations can lead to fatigue, noise, or failure. Vibration suppression is essential in aerospace, automotive, civil, and industrial applications to enhance performance and longevity of systems. Piezoelectric shunt circuits (PSCs) offer a passive or semi-active approach to damping vibrations by leveraging the electromechanical properties of piezoelectric materials. Traditional passive damping methods, such as viscoelastic materials, are effective but lack adaptability. Active control systems, while tunable, require external power and complex electronics, increasing cost and weight. Piezoelectric shunt circuits provide a middle ground, utilizing piezoelectric transducers bonded to a structure and connected to an electrical circuit to dissipate vibrational energy as heat or store it electrically. This review synthesizes the fundamental mechanisms, circuit designs, and practical applications of this technology. It also presents the modeling of lumped and distributed parameter systems coupled with PSCs. It complements the recent reviews and primarily focuses on the period from 2019 to date in addition to the earlier seminal works on the subject. It explores the principles, configurations, advantages, and limitations of piezoelectric shunt circuits for vibration control, alongside recent advancements and potential future developments. It sheds light on the research gaps in the literature that future work may tackle. Full article

This study introduces an electronically tunable resistorless mixed-mode universal filter and dual-mode quadrature oscillator configuration utilizing merely two voltage differencing gain amplifiers and two grounded capacitors. The suggested filter can perform all generic biquadratic filter functions in all four modes: voltage mode, trans-admittance mode, current mode, and trans-impedance mode, while utilizing the same design. The pole frequency and the quality factor can be tuned electronically and orthogonally by means of the transconductances of the voltage differencing gain amplifier. The dual-mode quadrature oscillator featuring both voltage and current outputs can also be obtained from the proposed filter core. It additionally provides separate electronic control of the oscillation condition and frequency. Several PSPICE simulations with the TSMC 0.18 μm CMOS model confirm the feasibility of the proposed configurations. Both proposed circuits were experimentally evaluated using commercially available integrated circuit LM13600s. Both simulation and experimental results have validated the performance of the design. Full article

Perovskite/organic tandem solar cells, as a next-generation high-efficiency photovoltaic technology, integrate the tunable bandgap characteristics of perovskite materials with the broad spectral absorption advantages of organic semiconductors, demonstrating remarkable potential to surpass the theoretical efficiency limits of single-junction cells, enhance device stability, and expand application scenarios. This architecture supports low-temperature solution processing and offers tunable bandgaps, lightweight flexibility, and ecofriendly advantages. This review systematically summarizes research progress in this field, with a primary focus on analyzing the working principles, performance optimization strategies, and key challenges of the technology. Firstly, the article discusses strategies such as defect passivation, crystallization control, and suppression of phase separation in wide-bandgap perovskite sub-cells, offering insights into mitigating open-circuit voltage losses. Secondly, for the narrow-bandgap organic sub-cells, this paper highlights the optimization strategies for both the active layer and interfacial layers, aiming to improve spectral utilization and enhance power conversion efficiency. Additionally, this paper emphasizes the optimization of optical transparency, electrical conductivity, and energy level alignment in the recombination layer, providing theoretical guidance for efficient current matching and carrier transport. Full article

This paper presents a fully integrated bandpass filter (BPF) with high tunability based on a novel differential active inductor (DAI), designed for sensor interface circuits operating in the ultra-high frequency (UHF) band. The design of the proposed DAI is based on a symmetrical configuration, utilizing a differential amplifier for the feedforward transconductance and a common-source (CS) transistor for the feedback transconductance. By integrating a cascode scheme with a feedback resistor, the quality factor of the active inductor is significantly improved, leading to enhanced mid-band gain for the bandpass filter. To facilitate independent tuning of the BPF‘s center frequency and mid-band gain, an active resistor adjustment and bias voltage control are employed, providing precise control over the filter’s operational parameters. Post-layout simulations and process corner results are conducted with 0.13 µm CMOS technology at 1.2 V supply voltage. The proposed second order BPF achieves a broad tuning range of 280 MHz to 2.426 GHz, with a passband gain between 8.9 dB and 16.54 dB. The design demonstrates a maximum noise figure of 16.54 dB at 280 MHz, an input-referred 1 dB compression point of −3.78 dBm, and a third-order input intercept point (IIP3) of −0.897 dBm. Additionally, the BPF occupies an active area of only 68.2×30 µm², including impedance-matching part, and consumes a DC power of 14–20 mW. The compact size and low power consumption of the design make it highly suitable for integration into modern wireless sensor interfaces where performance and area efficiency are critical. Full article

This paper presents a wide-tuning-range, low-power tunable active inductor (AI) designed and fabricated using 130 nm CMOS technology with six metal layers. To achieve high performance with a relatively small silicon area and low power consumption, the AI structure is carefully designed and optimized using a cascode stage, a feedback resistor, and multi-gate finger transistors. In the proposed circuit topology, inductance tuning is realized by adjusting both the bias current and the feedback resistor. The performance of the circuit is evaluated in terms of tuning range, quality factor, power consumption, and chip area. The functionality of the fabricated device is experimentally validated, and the fundamental characteristics of the active inductor are measured over a wide frequency range using a Cascade GSG probe, with results compared to simulations. Experimental measurements show that, under a 1 V supply, the AI achieves a self-resonant frequency (SRF) of 3.961 GHz and a quality factor (Q) exceeding 1586 at 2.383 GHz. The inductance is tunable between 6.7 nH and 84.4 nH, with a total power consumption of approximately 2 mW. The total active area, including pads, is 345 × 400 µm². Full article

The avalanche multiplication effect, capable of significantly amplifying weak optical or electrical signals, plays a pivotal role in enhancing the performance of electronic and optoelectronic devices. This effect has been widely employed in devices such as avalanche photodiodes, impact ionization avalanche transit time diode, and impact ionization field-effect transistors, enabling diverse applications in biomedical imaging, 3D LIDAR, high-frequency microwave circuits, and optical fiber communications. However, the evolving demands in these fields require avalanche devices with superior performance, including lower power consumption, reduced avalanche threshold energy, higher efficiency, and improved sensitivity. Over the years, significant efforts have been directed towards exploring novel device architectures and multiplication mechanisms. The emergence of two-dimensional (2D) materials, characterized by their exceptional light-matter interaction, tunable bandgaps, and ease of forming junctions, has opened up new avenues for developing high-performance avalanche devices. This review provides an overview of carrier multiplication mechanisms and key performance metrics for avalanche devices. We discuss several device structures leveraging the avalanche multiplication effect, along with their electrical and optoelectronic properties. Furthermore, we highlight representative applications of avalanche devices in logic circuits, optoelectronic components, and neuromorphic computing systems. By synthesizing the principles and applications of the avalanche multiplication effect, this review aims to offer insightful perspectives on future research directions for 2D material-based avalanche devices. Full article

Recent advancements in hybrid photonic integrated circuits (PICs) for wireless communications are reviewed, with a focus on innovations developed at Fraunhofer HHI. This work leverages hybrid integration technology, which combines indium phosphide (InP) active elements, silicon nitride (Si₃N₄) low-loss waveguides, and high-efficient thermal-optical tunable polymers with micro-optical functions to achieve fully integrated wireless transceivers. Key contributions include (1) On-chip optical injection locking for generating phase-locked optical beat notes at 45 GHz, enabled by cascaded InP phase modulators and hybrid InP/polymer tunable lasers with a 3.8 GHz locking range. (2) Waveguide-integrated THz emitters and receivers, featuring photoconductive antennas (PCAs) with a 22× improved photoresponse compared to top-illuminated designs, alongside scalable 1 × 4 PIN-PD and PCA arrays for enhanced power and directivity. (3) Beam steering at 300 GHz using a polymer-based optical phased array (OPA) integrated with an InP antenna array, achieving continuous steering across 20° and a 10.6 dB increase in output power. (4) Demonstration of fully integrated hybrid wireless transceiver PICs combining InP, Si₃N₄, and polymer material platforms, validated through key component characterization, on-chip optical frequency comb generation, and coherent beat note generation at 45 GHz. These advancements result in compact form factors, reduced power consumption, and enhanced scalability, positioning PICs as an enabling technology for future high-speed wireless networks. Full article

We propose a micro-electromechanical system (MEMS)-integrated Fabry–Pérot (F–P) microcavity designed for a tunable single-photon source based on a single semiconductor quantum dot (QD). Through theoretical simulations, our design achieved a Purcell factor of 23, a photon extraction efficiency exceeding 88%, and an optical cavity mode tuning range of more than 30 nm. Experimentally, we fabricated initial device prototypes using a micro-transfer printing process and demonstrated a tuning range exceeding 15 nm. The device exhibits high mechanical stability, full reversibility, and minimal hysteresis, ensuring reliable operation over multiple tuning cycles. Our findings highlight the potential of MEMS-integrated F–P microcavities for scalable, tunable single-photon sources. Furthermore, reaching a strong coupling regime could enable efficient single-photon routing, opening new possibilities for integrated quantum photonic circuits. Full article

Accurate parameter extraction for the Enz–Krummenacher–Vittoz (EKV) model is crucial for low-power integrated circuit design, especially in weak and moderate inversion regions. This work introduces a novel iterative subranging (ISR) technique for EKV model fitting, implemented in Python (version 3.10.12) using SciPy (version 1.10.1), NumPy (version 1.24.3), and Matplotlib (version 3.7.1). The core of the methodology is the Fitter class, which refines the threshold voltage ($V_{TH}$) by progressively narrowing the fitting range, controlled by the fit_range_parameter. This approach achieves a relative fitting error below 5% within a continuous interval of drain current, ensuring accurate parameter extraction in the region of interest while considering the full data range. Validation using SkyWater130 NMOS data demonstrated that the ISR method covers an inversion coefficient (IC) range from $1\times {10}^{-3}$ to nearly 50, showcasing its ability to accurately model device behavior across weak, moderate, and strong inversion. Compared to state-of-the-art EKV extraction methods, the ISR method exhibited at least a ×2 reduction in fitting error within the weak inversion region. More importantly, the ISR method is easily tunable by the designer in order to focus on specific current regions, where a greater accuracy is desired. This is a distinctive characteristic of the ISR method not present in any other extraction procedure. Moreover, the method demonstrated strong robustness against measurement noise, maintaining accuracy even with a 1 nA RMS noise level. This work provides a powerful and accessible tool for EKV model parameter extraction, enhancing reproducibility and accuracy in analog circuit design for low-power applications. Full article

In the context of increasing digitalization and the emergence of applications such as smart cities, embedded devices are becoming ever more pervasive, mobile, and ubiquitous. Due to increasing concerns around energy efficiency, gate density, and scalability in the semiconductor industry, there has been much interest recently in the fabrication of viable low-power energy-efficient devices. The Hetero-Dielectric Gate-All-Around (HD-GAA) MOSFET represents a cutting-edge transistor architecture designed for superior sustainability and energy efficiency, improving the overall efficiency of the system by reducing leakage and enhancing gate control; therefore, as part of the transition to a sustainable future, several semiconductor industries, including Intel, Samsung, Texas Instruments, and IBM, are using this technology. In this study, Hetero-Dielectric Single-Metal Gate-All-Around MOSFET (HD-SM-GAA MOSFET) devices and circuits were designed using Schottky source/drain contacts and tunable high-k dielectric Hf_xTi_1−xO₂ in the TCAD simulator using the following specifications: N-Channel HD-SM-GAA MOSFET (‘Device-I’) with a 5 nm radius and a 21 nm channel length alongside two P-Channel HD-SM-GAA MOSFETs (‘Device-II’ and ‘Device-III’) with radii of 5 nm and 8 nm, respectively, maintaining the same channel length. Thereafter, the inverters were implemented using these devices in the COGENDA TCAD simulator. The results demonstrated significant reductions in short-channel effects: subthreshold swing (SS) (‘Device-I’ = 61.5 mV/dec, ‘Device-II’ = 61.8 mV/dec) and drain-induced barrier lowering (DIBL) (‘Device-I’ = 8.2 mV/V, ‘Device-II’ = 8.0 mV/V) in comparison to the existing literature. Furthermore, the optimized inverters demonstrated significant improvements in noise margin values such as Noise Margin High (NM_H) and Noise Margin Low (NM_L), with Inverter-1 showing 38% and 44% enhancements and Inverter-2 showing 40% and 37% enhancements, respectively, compared to the existing literature. The results achieved illustrate the potential of using this technology (e.g., for power inverters) in embedded power control applications where energy efficiency and scalability are important, such as sustainable smart cities. Full article

Colloidal quantum dots (QDs) have emerged as promising materials for the development of infrared photodetectors owing to their tunable band gaps, cost-effective manufacturing, and ease of processing. This paper provides a comprehensive overview of the fundamental properties of quantum dots and the operating principles of various infrared detectors. We review the latest advancements in short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) detectors employing colloidal quantum dots. Despite their potential, these detectors face significant challenges compared to conventional infrared technologies. Current commercial applications are predominantly limited to the near-infrared and short-wave bands, with medium- and long-wave applications still under development. The focus has largely been on lead and mercury-based quantum dots, which pose environmental concerns, underscoring the need for high-performance, non-toxic materials. Looking forward, the development of large array and small pixel detectors and improving compatibility with readout circuits are critical for future progress. This paper discusses these hurdles and offers insight into potential strategies to overcome them, paving the way for next-generation infrared sensing technologies. Full article

This paper introduces a fully integrated memristive chaotic circuit, which is based on a voltage-controlled oscillator (VCO). The circuit employs a fully integrated architecture that offers reduced power consumption and a smaller footprint compared to the use of discrete components. Specifically, the VCO is utilized to generate the oscillatory signal, whereas the memristor emulator circuit serves as the nonlinear element. The memristor emulator circuit is constructed using a single operational transconductance amplifier (OTA), two transistors, and a grounded capacitor. This straightforward design contributes to diminished power usage within the chip’s area. The VCO incorporates a dual delay unit and implements current compensation to enhance the oscillation frequency and to broaden the VCO’s tunable range. Fabricated using the SMIC 180 nm CMOS process, this chaotic circuit occupies a mere 0.0072 mm² of chip area, demonstrating a design that is both efficient and compact. Simulation outcomes indicate that the proposed memristor emulator is capable of operating at a maximum frequency of 300 MHz. The memristive chaotic circuit is able to produce a chaotic oscillatory signal with an operational frequency ranging from 158 MHz to 286 MHz, powered by a supply of 0.9 V, and with a peak power consumption of 3.5553 mW. The Lyapunov exponent of the time series within the resultant chaotic signal spans from 0.2572 to 0.4341. Full article

Carbon-based nanomaterials with excellent electrical and optical properties are highly sought after for a plethora of hybrid applications, ranging from advanced sustainable energy storage devices to opto-electronic components. In this contribution, we examine in detail the dependence of electrical conductivity and the ultrafast optical nonlinearity of graphene oxide (GO) films on their degrees of reduction, as well as the link between the two properties. The GO films were first synthesized through the vacuum filtration method and then reduced partially and controllably by way of femtosecond laser direct writing with varying power doses. Subsequently, the four-point probe measurements of the reduced-GO (r-GO) films were demonstrated to exhibit superior resistivity and electrical conductivity compared with the pristine-GO counterpart. It was found that the conductivity of the film increases and then decreases with increasing ablation laser power (P), and GO was completely reduced at P = 100 mW, with a resistivity and electrical conductivity of 1.09 × 10⁻³ Ω·m and 9.19 × 10² S/m, respectively. GO was over-reduced at P = 120 mW, with its resistivity and electrical conductivity being 3.72 × 10⁻³ Ω·m and 2.69 × 10² S/m, respectively. We further tested the ultrafast optical nonlinearity (ONL) of the as-prepared pristine and reduced GO with the femtosecond Z-scan technique. The results show that the behavior of ONL is reversed whenever GO is reduced in a controlled manner. More interestingly, the higher the ablation laser power is, the stronger the optical nonlinearity of r-GO is. In particular, the nonlinear absorption and refraction coefficients of the r-GO films reach up to 3.26 × 10⁻⁸ m/W and −1.12 × 10⁻¹³ m²/W when P = 120 mW. The nonlinear absorption and refraction coefficients reach 1.9 × 10⁻⁸ m/W and −3 × 10⁻¹³ m²/W, respectively, for P = 70 mW. GO/r-GO thin films with tunable photovoltaic response properties have potential for a wide range of applications in microelectronic circuits, energy, and environmental sustainability. Full article

In this article, a series of novel conducting copolymers P(FuPy-co-EDOT) are prepared via cyclic voltammetry electropolymerization method by using N-furfuryl pyrrole (FuPy) and 3,4-ethylenedioxythiophene (EDOT) as comonomers. The molecular structure, surface morphology, electrochemical, and optical properties of the resulting copolymers are characterized in detail upon varying the feed ratios of FuPy/EDOT in the range of 1/1 to 1/9. The results demonstrate that the prepared P(FuPy-co-EDOT) copolymers with a higher proportion of EDOT units (FuPy/EDOT: 2/8~1/9) possess good redox activity, tunable optical absorption performances, and low band gaps (1.75~1.86 eV). Spectroelectrochemistry studies indicate that the resulting copolymers with increased EDOT units show strengthened electrochromic characteristics, exhibiting a red-to-green-to-blue multicolor reversible transition, especially for the P(FuPy₁-co-EDOT₉) copolymer films. They also show increased optical contrast (9~34%), fast response time (0.8~2.4 s), and good coloring efficiency (110~362 cm² C⁻¹). Additionally, the complementary bilayer P(FuPy-co-EDOT)/PEDOT electrochromic devices (ECDs) are also assembled and evaluated to hold excellent electrochromic switching performances with relatively high optical contrast (25%), rapid response time (0.9 s), and satisfactory coloring efficiency (416 cm² C⁻¹). Together with the superior open circuit memory and cycling stability, they can be used as a new type of electrochromic material and have considerable prospects as promising candidates for electrochromic devices. Full article

Integrated optical amplifiers are the building blocks of on-chip photonic systems, and they are often accompanied by a narrowband filter to limit noise. In this sense, a bandwidth-tunable optical amplifier with narrowband filtering function is crucial for on-chip optical circuits and radio frequency systems. The intrinsic loss and coupling coefficients between resonator and waveguide inherently limit the bandwidth. The parity-time symmetric coupled microresonators operating at exceptional points enable near zero bandwidth. In this study, we propose a parity-time symmetric coupled microresonators system operating near EPs to achieve a bandwidth of 46.4 MHz, significantly narrower than bandwidth of 600.0 MHz and 743.2 MHz achieved by two all-pass resonators with identical gain/loss coefficients. This system also functions as an optical bandwidth-tunable filter. The bandwidth tuning ranges from 175.7 MHz to 7.8 MHz as gain coefficient adjusts from 0.2 dB/cm to 0.4 dB/cm. Our scheme presents a unique method to obtain narrow bandwidth from two broadband resonators and serves as an optical bandwidth-tunable filter, thereby paving a new avenue for exploring non-Hermitian light manipulation in all-optical integrated devices. Full article