Search Results (155)

With their superior switching speed, GaN high-electron-mobility transistors (HEMTs) enable high power density, reduce energy losses, and increase power efficiency in a wide range of applications, such as power electronics, due to their high breakdown voltage. GaN-HEMT devices are subject to long-term reliability due to the self-heating effect and lattice mismatch between the SiC substrate and the GaN. Depletion-mode GaN HEMTs are utilized for radio frequency applications, and this work investigates three wide-bandgap (WBG) GaN HEMT fixed-frequency oscillators with output buffers. The first GaN-on-SiC HEMT oscillator consists of an HEMT amplifier with an LC feedback network. With the supply voltage of 0.8 V, the single-ended GaN oscillator can generate a signal at 8.85 GHz, and it also supplies output power of 2.4 dBm with a buffer supply of 3.0 V. At 1 MHz frequency offset from the carrier, the phase noise is −124.8 dBc/Hz, and the figure of merit (FOM) of the oscillator is −199.8 dBc/Hz. After the previous study, the hot-carrier stressed RF performance of the GaN oscillator is studied, and the oscillator was subject to a drain supply of 8 V for a stressing step time equal to 30 min and measured at the supply voltage of 0.8 V after the step operation for performance benchmark. Stress study indicates the power oscillator with buffer is a good structure for a reliable structure by operating the oscillator core at low supply and the buffer at high supply. The second balanced oscillator can generate a differential signal. The feedback filter consists of a left-handed transmission-line LC network by cascading three unit cells. At a 1 MHz frequency offset from the carrier of 3.818 GHz, the phase noise is −131.73 dBc/Hz, and the FOM of the 2nd oscillator is −188.4 dBc/Hz. High supply voltage operation shows phase noise degradation. The third GaN cross-coupled VCO uses 8-shaped inductors. The VCO uses a pair of drain inductors to improve the Q-factor of the LC tank, and it uses 8-shaped inductors for magnetic coupling noise suppression. At the VCO-core supply of 1.3 V and high buffer supply, the FOM at 6.397 GHz is −190.09 dBc/Hz. This work enhances the design techniques for reliable GaN HEMT oscillators and knowledge to design high-performance circuits. Full article

Microwave energy is ideal for wearable devices due to its stable wireless power transfer capabilities. However, rigid receiving antennas in conventional RF energy harvesters compromise wearability. This study presents a wearable system using a flexible dual-band antenna (915 MHz/2.45 GHz) fabricated via conformal 3D printing on arm-mimicking curvatures, minimizing bending-induced performance loss. A hybrid microstrip–lumped element rectifier circuit enhances energy conversion efficiency. Tested with commercial 915 MHz transmitters and Wi-Fi routers, the system consistently delivers 3.27–3.31 V within an operational range, enabling continuous power supply for real-time physiological monitoring (e.g., pulse detection) and data transmission. This work demonstrates a practical solution for sustainable energy harvesting in flexible wearables. Full article

The advancement of Internet of Things (IoT) technology has enabled battery-powered devices to be deployed across a wide range of applications; however, it also introduces challenges such as high energy consumption and security vulnerabilities. To address these issues, adiabatic logic circuits offer a promising solution for achieving energy efficiency and enhancing the security of IoT devices. Adiabatic logic circuits are well suited for energy harvesting systems, especially in applications such as sensor nodes, RFID tags, and other IoT implementations. In these systems, the harvested bipolar sinusoidal RF power is directly used as the power supply for the adiabatic logic circuit. However, adiabatic circuits require a peak detector to provide bulk biasing for pMOS transistors. To meet this requirement, a diode-connected MOS transistor-based voltage doubler circuit is used to convert the sinusoidal input into a usable DC signal. In this paper, we propose a novel adiabatic logic design that maintains low power consumption while optimizing energy and current fluctuations across various input transitions. By ensuring uniform and complementary current flow in each transition within the logic circuit’s functional blocks, the design reduces energy variation and enhances resistance against power analysis attacks. Evaluation under different clock frequencies and load capacitances demonstrates that the proposed adiabatic logic circuit exhibits lower fluctuation and improved security, particularly at load capacitances of 50 fF and 100 fF. The results show that the proposed circuit achieves lower power dissipation compared to conventional designs. As an application example, we implemented an ultrasonic transmitter circuit within a LoRaWAN network at the end-node sensor level, which serves as both a communication protocol and system architecture for long-range communication systems. Full article

This paper presents a wideband low-power/low-voltage 60-GHz low-noise amplifier (LNA) in a 28-nm bulk CMOS technology. The LNA has been designed for high-speed millimeter-wave (mm-wave) communications. It consists of two pseudo-differential amplifying stages and a buffer stage included for 50-Ohm on-wafer measurements. Two integrated input/output baluns guarantee both simultaneous 50-ohm input–noise/output matching at input/output radio frequency (RF) pads. A power-efficient design strategy is adopted to make the LNA suitable for low-power applications, while minimizing the noise figure (NF). Thanks to the adopted design strategy, the post-layout simulation results show an excellent trade-off between power gain and 3-dB bandwidth (BW_3dB) with 13.5 dB and 7 GHz centered at 60 GHz, respectively. The proposed LNA consumes only 11.6 mA from a 0.9-V supply voltage with an NF of 8.4 dB at 60 GHz, including the input transformer loss. The input 1 dB compression point (IP_1dB) of −15 dBm at 60 GHz confirms the first-rate linearity of the proposed amplifier. Human body model (HBM) electrostatic discharge (ESD) protection is guaranteed up to 2 kV at the RF input/output pads thanks to the input/output integrated transformers. Full article

Forecasting future solar power plant production is essential to continue the development of photovoltaic energy and increase its share in the energy mix for a more sustainable future. Accurate solar radiation forecasting greatly improves the balance maintenance between energy supply and demand and grid management performance. This study assesses the influence of input selection on short-term global horizontal irradiance (GHI) forecasting across two contrasting Algerian climates: arid Ghardaïa and coastal Algiers. Eight feature selection methods (Pearson, Spearman, Mutual Information (MI), LASSO, SHAP (GB and RF), and RFE (GB and RF)) are evaluated using a Gradient Boosting model over horizons from one to six hours ahead. Input relevance depends on both the location and forecast horizon. At t+1, MI achieves the best results in Ghardaïa (nMAE = 6.44%), while LASSO performs best in Algiers (nMAE = 10.82%). At t+6, SHAP- and RFE-based methods yield the lowest errors in Ghardaïa (nMAE = 17.17%), and RFE-GB leads in Algiers (nMAE = 28.13%). Although performance gaps between methods remain moderate, relative improvements reach up to 30.28% in Ghardaïa and 12.86% in Algiers. These findings confirm that feature selection significantly enhances accuracy (especially at extended horizons) and suggest that simpler methods such as MI or LASSO can remain effective, depending on the climate context and forecast horizon. Full article

In the context of global e-commerce platform supply chains dominated by Alibaba and Amazon, power reconfiguration among tripartite stakeholders (platforms, manufacturers, and retailers) remains a critical yet underexplored issue in supply chain contract design. To analyze the strategic interactions between platforms, manufacturers, and retailers, as well as how platforms select the contract format within a tripartite supply chain, this study proposes a Stackelberg game-theoretic framework incorporating participation constraints to compare fixed-fee and revenue-sharing contracts. The results demonstrate that revenue-sharing contracts significantly enhance supply chain efficiency by aligning incentives across members, leading to improved pricing and sales outcomes. However, this coordination benefit comes with reduced platform dominance, as revenue-sharing inherently redistributes power toward upstream and downstream partners. The analysis reveals a nuanced contract selection framework: given the revenue sharing rate, as the additional value increases, the optimal contract shifts from the mode RR to the mode RF, and ultimately to the mode FF. Notably, manufacturers and retailers exhibit a consistent preference for revenue-sharing contracts due to their favorable profit alignment properties, regardless of the platform’s value proposition. These findings may contribute to platform operations theory by (1) proposing a dynamic participation framework for contract analysis, (2) exploring value-based thresholds for contract transitions, and (3) examining the power-balancing effects of alternative contract formats. This study offers actionable insights for platform operators seeking to balance control and cooperation in their supply chain relationships, while providing manufacturers and retailers with strategic guidance for contract negotiations in platform-mediated markets. These findings are especially relevant for large e-commerce platforms and their partners managing the complexities of contemporary digital supply chains. Full article

The Polish Free-Electron Laser (PolFEL), which is currently under construction in the National Centre for Nuclear Research in Świerk near Warsaw, will comprise an electron gun and from four to six cryomodules, each accommodating two nine-cell TESLA RF superconducting resonant cavities. To cool the superconducting resonant cavities, the cryomodules will be supplied with superfluid helium at a temperature of 2 K. Other requirements regarding the cooling power of PolFEL result from the need to cool the power couplers for the accelerating cryomodules (5 K) and thermal shields, which limit the heat inleaks due to radiation (40–80 K). The machine will utilize several thermodynamic states of helium, including two-phase superfluid helium, supercritical helium, and low-pressure helium vapours. Supercritical helium will be supplied from a cryoplant by a cryogenic distribution system (CDS)—transfer line and valve boxes—where it will be thermodynamically transformed into a superfluid state. This article presents the architecture of the CDS, discusses several design solutions that could have been decided on with the use of second law analysis, and presents the design methodology of the chosen CDS elements. Full article

This paper presents a highly linear two-stage InGaP/GaAs power amplifier integrated circuit (PAIC) using a dynamic predistorter for 5G small-cell applications. The proposed predistorter, based on a diode-connected transistor, utilizes a supply voltage to accurately control the linearization characteristics by adjusting its dc current. It is connected in parallel with an inter-stage of the two-stage PAIC through a series configuration of a resistor and an inductor, and features a shunt capacitor at the base of the transistor. These passive components have been optimized to enhance the linearization performance by managing the RF signal’s coupling to the diode. Using these optimized components, the AM−AM and AM−PM nonlinearities arising from the nonlinear resistance and capacitance in the diode can be effectively used to significantly flatten the AM−AM and AM−PM characteristics of the PAIC. The proposed predistorter was applied to the 2.6 GHz two-stage InGaP/GaAs HBT PAIC. The IC was tested using a 5 × 5 mm² module package based on a four-layer laminate. The load network was implemented off-chip on the laminate. By employing a continuous-wave (CW) signal, the AM−AM and AM−PM characteristics at 2.55–2.65 GHz were improved by approximately 0.05 dB and 3°, respectively. When utilizing the new radio (NR) signal, based on OFDM cyclic prefix (CP) with a signal bandwidth of 100 MHz and a peak-to-average power ratio (PAPR) of 9.7 dB, the power-added efficiency (PAE) reached at least 11.8%, and the average output power was no less than 24 dBm, achieving an adjacent channel leakage power ratio (ACLR) of −40.0 dBc. Full article

This paper proposes a hybrid energy-harvesting chip that utilizes both radio-frequency (RF) energy and solar energy for low-power applications and extended service life. The key contributions include a wide input power range, a compact chip area, and a high maximum power conversion efficiency (PCE). Solar energy is a clean and readily available source. The hybrid energy harvesting system has gained popularity by combining RF and solar energy to improve overall energy availability and efficiency. The proposed chip comprises a matching network, rectifier, charge pump, DC combiner, overvoltage protection circuit, and low-dropout voltage regulator (LDO). The matching network ensures maximum power delivery from the antenna to the rectifier. The rectifier circuit utilizes a cross-coupled differential drive rectifier to convert radio frequency energy into DC voltage, incorporating boosting functionality. In addition, a solar harvester is employed to provide an additional energy source to extend service time and stabilize the output by combining it with the radio-frequency source using a DC combiner. The overvoltage protection circuit safeguards against high voltage passing from the DC combiner to the LDO. Finally, the LDO facilitates the production of a stable output voltage. The entire circuit is simulated using the Taiwan Semiconductor Manufacturing Company 0.18 µm 1P6M complementary metal–oxide–semiconductor standard process developed by the Taiwan Semiconductor Research Institute. The simulation results indicated a rectifier conversion efficiency of approximately 41.6% for the proposed radio-frequency-energy-harvesting system. It can operate with power levels ranging from −1 to 20 dBm, and the rectifier circuit’s output voltage is within the range of 1.7–1.8 V. A 0.2 W monocrystalline silicon solar panel (70 × 30 mm²) was used to generate a supplied voltage of 1 V. The overvoltage protection circuit limited the output voltage to 3.6 V. Finally, the LDO yielded a stable output voltage of 3.3 V. Full article

This paper put forward a hybrid energy harvester for collecting RF and solar energy in quad-band (GSM-900/1800, ISM-2400 and WiMAX-3500). By introducing diverse parasitic structures, good impedance matching with unidirectional radiation is achieved in the multi-band. Below the solar antenna, a low-power rectifier circuit is employed to achieve broadband rectification. Under the input power of 0 dBm, and maximum RF-DC conversion efficiency of 56.94% is realized. Accordingly, the hybrid energy harvester collects RF and solar energy individually or simultaneously, and then converts it into DC for power supply. With a light intensity of 1500 lux, the solar cell obtains 1.732 mW, and the rectenna can harvest additional 0.37–0.405 mW power. The proposed RF–Solar energy harvester has the advantages of multi-frequency operation, high gain, and high energy harvesting conversion efficiency. Full article

This paper presents a three-channel galvanic isolation interface in GaN technology. Driver, diagnostic, and control channels have been implemented in a two-die integrated system to perform an isolation interface for a high-performance power switching system. Chip-to-chip communication has been used, which is based on planar micro-antennas with on–off keying modulated RF carriers. This approach provides a high isolation rating by properly setting the distance between chips. Various innovation aspects are adopted with respect to previously published works. They mainly involve the receiver robustness thanks to the switched-capacitor bias control, a bidirectional data channel implementation for power section diagnostic, and a duty cycle distortion compensation for accurate PWM signal. Driver and control channels use RF carriers of about 2 GHz and 0.9 GHz and achieve 2 MHz and 0.5 MHz measured pulse width modulation signals, respectively. The bidirectional channel adopts an RF carrier of about 400 MHz and exhibits a maximum measured data rate as high as 10 Mb/s. Thanks to the extensive use of switched-capacitor circuit solutions, well-controlled behavior is achieved against the large process tolerances and temperature drifts of the GaN technology. The isolation interface is supplied at 6 V and occupies a die area of 7.6 mm² for each chip. Full article

Radio-frequency (RF) microwave wireless power transfer (WPT) offers an efficient means of delivering energy to a wide array of devices over long distances. Previous RF WPT systems faced significant challenges, including complex hardware and control systems, software deficiencies, insufficient rectification power, lack of high-performance substrate materials, and electromagnetic radiation hazards. Addressing these issues, this paper proposes the world’s first watt-level RF WPT system capable of intelligent continuous tracking and occlusion judgment. Our 5.8 GHz band RF WPT system integrates several advanced technologies, such as millimeter-precision lidar, the multi-object image recognition algorithm, the accurate 6-bit continuous beamforming algorithm, a compact 16-channel 32 W high-power transmitting system, a pair of ultra-low axial ratio circularly polarized antenna arrays, ultra-low-loss high-strength ceramic substrates, and a 2.4 W high-power Schottky diode array rectifier achieving a rectification efficiency of $66.8\%$. Additionally, we construct a platform to demonstrate the application of the proposed RF WPT system in battery-free vehicles, achieving unprecedented ${360}^{\circ }$ uninterrupted power supply to the battery-free vehicle. In summary, this system represents the most functionally complete RF WPT system to date, serving as a milestone for several critical fields such as smart living, transportation electrification, and battery-less/free societies. Full article

This paper presents a low-power CMOS receiver with a complex continuous-time delta–sigma ADC designed for IoT applications in the 2.4 GHz band. The architecture employs a quadrature bandpass continuous-time delta–sigma ADC optimized for Bluetooth Low Energy (BLE) standards, achieving an ENOB of 10.9 bits while consuming only 0.81 mW from a 1.0 V supply. The receiver demonstrates impressive performance metrics, including a sensitivity of −95 dBm at a 10⁻³-bit error rate, an image rejection ratio of 54.2 dBc, and a spurious-free dynamic range of 79.8 dBc. Operating at a 1.5 MHz intermediate frequency with a 2 MHz bandwidth, the ADC achieves superior energy efficiency with a figure of merit (FOM_W) of 103.2 fJ/conv. Implemented in 28 nm CMOS technology, the complete receiver occupies 0.375 mm² for the RF front-end and 0.145 mm² for the ADC while consuming 4.08 mW total power, making it well suited for battery-powered IoT sensor nodes requiring both power efficiency and reliable wireless connectivity. Full article

Energy harvesting technology allows Internet of Things (IoT) devices to be powered continuously without needing battery charging or replacement. In addressing existing and emerging massive IoT energy supply challenges, this paper presents the design of multi-sourced multiple input and multiple output (MIMO) multiband hybrid wireless RF-perovskite photovoltaic energy harvesting subsystems for IoT application. The research findings evaluate the efficiency and power output of different RF configurations (1 to 16 antennas) within MIMO RF subsystems. A Delon quadruple rectifier in the RF energy harvesting system demonstrates a system-level power conversion efficiency of 51%. The research also explores the I-V and P-V characteristics of the adopted perovskite tandem cell. This results in an impressive array capable of producing 6.4 V and generating a maximum power of 650 mW. For the first time, the combined mathematical modelling of the system architecture is presented. The achieved efficiency of the combined system is 90% (for 8 MIMO) and 98% (for 16 MIMO) at 0 dBm input RF power. This novel study holds great promise for next-generation 5G/6G smart IoT passive electronics. Additionally, it establishes the hybrid RF-perovskite energy harvester as a promising, compact, and eco-friendly solution for efficiently powering IoT devices in smart cities. This work contributes to the development of sustainable, scalable, and smart energy solutions for IoT integration into smart city infrastructures. Full article

For RSSI measurement of RF systems, a wide band, large dynamic range (DR), parallel-summation logarithmic amplifier is presented in this paper. The circuit adopts an 8-stage DC-coupled cascaded limiting amplifier structure. The output voltage of the limiting amplifier is converted into current through a rectifier to realize parallel summation. In order to reduce offset, this paper introduces offset reduction circuits in the gain and output stage, respectively. In addition, a log slope adjuster is proposed, which can achieve log slope control of different frequency inputs. The post-simulation results show that at a power supply voltage of 5 V, the 3 dB gain bandwidth is 4.5 GHz, the dynamic range reaches 64 dB, and the log error is less than ±1 dB. The overall circuit consumes 21 mA of current. Full article