High Frequency Operation Research Articles

Heat transfer enhancement on a concave surface using sweeping impinging jets: Comparison of vortex-based and conventional oscillators

While the impinging sweeping jet generated by a conventional fluidic oscillator has been extensively investigated for its remarkable convective heat transfer performance, the cooling performance of the recently designed vortex-based fluidic oscillator on impinged hot plates remains unexplored. This study numerically investigates the cooling performance of oscillatory jets generated by the vortex-based fluidic oscillator compared to the conventional fluidic oscillator and a steady non-oscillatory jet impinging on a hot concave surface. The Fluent 2023R2 software was employed for solving the unsteady Reynolds-averaged Navier–Stokes equations with the k–ω SST model through the finite volume method. Numerical simulations were conducted at various dimensionless nozzle-to-surface distances (X/D = 2, 4, and 6) and Reynolds numbers (20,000, 30,000, and 40,000). The performances of both oscillators were assessed through the time-averaged velocity, temperature, and Nusselt number. The results demonstrated that the vortex-based fluidic oscillator, as an innovative type of fluidic oscillator, outperformed conventional fluidic oscillators by enhancing heat transfer and reducing pressure drop, attributed to its smaller size and higher operational frequency. At X/D values of 2, 4, and 6, the mean Nusselt number for the vortex-based oscillator exhibited respective increases of 19 %, 23 %, and 16 % compared to the conventional oscillator. In addition, these values were respectively 38 %, 34 %, and 24 % higher than those for the steady non-oscillatory jet. Furthermore, the thermal enhancement factor of the vortex-based oscillator demonstrated increases of 20 %, 23 %, and 21 %, respectively, in comparison with the conventional oscillator. These findings suggest that the novel vortex-based fluidic oscillator holds significant promise for replacing conventional oscillators in industrial cooling applications.

Low-temperature curable permalloy-based soft magnetic composites for megahertz applications

This paper proposed low-temperature curable soft magnetic composites (SMCs) cores that consisted of permalloy powders and acrylic polymer (Trimethylpropane triacrylate, or TMPTA) for high-frequency applications. The effect of TMPTA content, compaction pressure and curing temperature on the magnetic properties of synthesized cores were investigated. The coated TMPTA insulating layer can effectively increase the electrical resistivity of the core and thereby improve the frequency characteristics. The magnetic performance of cores depends on the distribution and actual content of the TMPTA after pressing although the polymer content in the mixture is increased from 2 wt% to 6 wt%. As the compaction pressure increases from 100 MPa to 400 MPa, the relative permeability of the core increases but its imaginary part of the permeability has almost no change until 10 MHz. The increased curing temperature can increase the initial permeability of the cores but deteriorates the frequency stability and greatly increase the imaginary part of the permeability. It was noted that the core with 5 % TMPTA content, compacted at 400 MPa and cured at 200 °C has the best frequency stability, the lowest imaginary part of the permeability and acceptable real permeability over 30. It is beneficial for high frequency operation of power electronics.

Domain wall magnetic tunnel junction-based artificial synapses and neurons for all-spin neuromorphic hardware

We report a breakthrough in the hardware implementation of energy-efficient all-spin synapse and neuron devices for highly scalable integrated neuromorphic circuits. Our work demonstrates the successful execution of all-spin synapse and activation function generator using domain wall-magnetic tunnel junctions. By harnessing the synergistic effects of spin-orbit torque and interfacial Dzyaloshinskii-Moriya interaction in selectively etched spin-orbit coupling layers, we achieve a programmable multi-state synaptic device with high reliability. Our first-principles calculations confirm that the reduced atomic distance between 5d and 3d atoms enhances Dzyaloshinskii-Moriya interaction, leading to stable domain wall pinning. Our experimental results, supported by visualizing energy landscapes and theoretical simulations, validate the proposed mechanism. Furthermore, we demonstrate a spin-neuron with a sigmoidal activation function, enabling high operation frequency up to 20 MHz and low energy consumption of 508 fJ/operation. A neuron circuit design with a compact sigmoidal cell area and low power consumption is also presented, along with corroborated experimental implementation. Our findings highlight the great potential of domain wall-magnetic tunnel junctions in the development of all-spin neuromorphic computing hardware, offering exciting possibilities for energy-efficient and scalable neural network architectures.

RCVM‐ASS‐CICSKA‐PAPT‐VDF: VLSI design of high‐speed reconfigurable compressed Vedic PAPT‐VDF filter for ECG medical application

AbstractDuring signal acquisition, the signals are impacted by multiple noise sources that must be filtered before any analysis. However, many different filter implementations in VLSI are dispersed among many studies. This study aims to give readers a systematic approach to designing a Pipelined All‐Pass Transformation based Variable digital filter (PAPT‐VDF) to eliminate the high‐frequency noise from ECG data. The modified design emphasizes first‐ and second‐order responses to obtain high‐speed filter realization with high operating frequencies. The addition of adder and multiplier designs to the hardware architecture of a filter design improves performance. The fundamental blocks of the filter design are the adder and multiplier. The adder and multiplier are employed with an Adaptable stage size‐based concatenation, incremented carry‐skip adder (ASS‐CICSKA), and Improved reconfigurable compressed Vedic multiplier (IRCVM). Utilizing the adder design diminishes the delay with enhanced performance because receiving the carry from an incrementation block is not mandatory. In the multiplier design, the compressor and the reconfigurable approach are adapted with a data detector block to detect the redundant input and lower the logic gates' switching activity with less area overhead. The proposed filter design is implemented in vertex 7 FPGA family device, and the performance measures are analyzed regarding area utilization, delay, power, and frequency. Also, by using the denoised signal, the mean square error (MSE), and signal‐to‐noise ratio (SNR) are evaluated in the MATLAB platform.

Comparative study of a high‐speed permanent magnet motor when powered by different methods

AbstractThe authors present the multi‐physical field performances comparative research for a 30 kW, 30,000 r/min high‐speed permanent magnet motor (HSPMM) when the motor is powered by the sinusoidal pulse width modulation (SPWM) voltage inverter and sinusoidal voltage source, respectively. Firstly, electromagnetic performances including torque, voltage and current of the HSPMM with different driving methods are compared and analysed by the finite element method (FEM). Considering the effects of high operation frequency, power losses of the HSPMM with different driving methods under full‐load conditions are calculated and compared with the skin effect and the proximity effect considered for HSPMM winding copper loss estimation. Based on the above analysis, a prototype driven by the SPWM voltage inverter is manufactured, with its electromagnetic and thermal performances tested and verified. In addition, several influencing factors of the HSPMM rotor eddy current loss are studied, with their effects on the HSPMM under different driving methods further analysed and compared as well. A novel equivalent power supply method is proposed to effectively save the calculation time with a negligible error. Finally, in order to further improve the heat dissipation capacity of the HSPMM, a novel cooling method is intensively studied with its influencing factors further analysed. The cooling effect of the novel cooling method and the temperature of the motor components are verified and calculated by the computational fluid dynamics (CFD) method.

Influence of High-Frequency Operation on the Efficiency of a PMSM Drive with SiC-MOSFET Inverter

This paper investigates the effects of high-frequency switching and a high fundamental frequency on the parameters and efficiency of a high-speed permanent magnet synchronous machine (PMSM) drive. We discuss the design and modeling of the PMSM, taking into account these high-frequency effects. The impact of high frequencies is analyzed across three different inverters (IGBT, Fast IGBT, and SiC-MOSFET) and the motor, and we employ theoretical analysis, computer simulations, and experimental tests for validation. Our goal is to enhance our understanding of how these high-frequency factors affect the performance of the motor drive.

The preparation and performances of Co-Zn 18H hexagonal ferrite with an ultra-high magnetic resonance frequency and low-loss characteristics

Modern 5G communication technologies require evolution of antennas towards high frequency and miniaturization. The search for magneto-dielectric materials with simultaneous high permeability, matched dielectric constant, and low loss properties for sub-6 GHz band applications has received considerable attention from both academic and industrial circles. Due to the low magnetic resonance frequency and high magnetic loss, traditional spinel and hexagonal ferrites hardly meet these requirements. In this study, polycrystalline Co-Zn 18H ferrites (Ba5Co2-xZnxTi3Fe12O31) were synthesized by co-precipitation method with only one-step sintering process. The polycrystalline Co-Zn 18H hexagonal ferrite possesses an ultra-high natural resonance frequency (14.5 GHz) and low magnetic loss (tanδμ≤0⊡10), which provides a better performance factor (PF= 68.6 GHz) at a higher operating frequency (4.97 GHz) compared to traditional microwave ferrites. The miniaturization rate of the planar inverted F antenna (PIFA) with Co-Zn 18H ferrite working at 4.0 GHz reaches 13.3 %. These results demonstrate the high potential of Co-Zn 18H ferrites for high frequency and low loss applications.

Design and Fabrication of a Film Bulk Acoustic Wave Filter for 3.0 GHz-3.2 GHz S-Band.

Film bulk acoustic-wave resonators (FBARs) are widely utilized in the field of radio frequency (RF) filters due to their excellent performance, such as high operation frequency and high quality. In this paper, we present the design, fabrication, and characterization of an FBAR filter for the 3.0 GHz-3.2 GHz S-band. Using a scandium-doped aluminum nitride (Sc0.2Al0.8N) film, the filter is designed through a combined acoustic-electromagnetic simulation method, and the FBAR and filter are fabricated using an eight-step lithographic process. The measured FBAR presents an effective electromechanical coupling coefficient (keff2) value up to 13.3%, and the measured filter demonstrates a -3 dB bandwidth of 115 MHz (from 3.013 GHz to 3.128 GHz), a low insertion loss of -2.4 dB, and good out-of-band rejection of -30 dB. The measured 1 dB compression point of the fabricated filter is 30.5 dBm, and the first series resonator burns out first as the input power increases. This work paves the way for research on high-power RF filters in mobile communication.

An efficient position optimization method based on improved genetic algorithm and machine learning for sparse array

Sparse array antennas are significant in communication and radar systems due to the advantages of high resolution, low complexity, and immunity to interference. In this letter, a novel array synthesis method based on an improved genetic algorithm (IGA) is proposed to optimize the antenna position in the sparse array. Different from the traditional generic methods with high computational complexity, a method combined with Gaussian process regression (GPR) prediction is proposed to optimize the antenna position with low computational complexity. The proposed method can minimize the peak sidelobe level (PSLL) during the beam scanning procedures. Moreover, the minimum antenna spacing constraint is also considered to ensure a physically achievable solution. Simulation results show that the proposed method can achieve a lower PSLL with fewer iterations and provide a global optimization solution for large array synthesis compared with existing methods. Furthermore, a prototype of the sparse array principle optimized by IGA is designed. Measurement results indicate that the optimized sparse array has good synthesis performance in high frequency.

The effect of BaTiO3 on the magnetic behavior of MnZn ferrites at frequencies > 5 MHz

In this article an extensive study is presented on the effect of BaTiO3 on the high frequency performance of MnZn ferrite having a nominal composition Mn0.9Zn0.1Fe2.45O4. It is shown that BaTiO3 at an optimum concentration of 200 ppm wt. is a bulk dopant that dissolves in the spinel lattice leading to microstructures with smaller grain sizes, lower grain boundary resistivities and higher resonance frequencies. Despite an observed increase on the hysteresis losses, the main impact on the magnetic performance is the significant reduction of the high frequency resonance losses. In addition, no dependency has been observed on the particle size of BaTiO3 since nanoparticles produce the same effects as microparticles. Through exploitation of the beneficial effects of BaTiO3, MnZn ferrites with power losses of 195 kW m−3 (5 MHz, 10 mT, 100 °C) or 1125 kW m−3 (10 MHz, 10 mT 100 °C) and a relative initial permeability of 200 could be synthesized. These results belong to the best reported in literature and indicate that the application region of MnZn ferrites can be extended up to application frequencies traditionally dominated by other ferrite material families.

Rational Design of a Surface Acoustic Wave Device for Wearable Body Temperature Monitoring.

Continuous monitoring of vital signs based on advanced sensing technologies has attracted extensive attention due to the ravages of COVID-19. A maintenance-free and low-cost passive wireless sensing system based on surface acoustic wave (SAW) device can be used to continuously monitor temperature. However, the current SAW-based passive sensing system is mostly designed at a low frequency around 433 MHz, which leads to the relatively large size of SAW devices and antenna, hindering their application in wearable devices. In this paper, SAW devices with a resonant frequency distributed in the 870 MHz to 960 MHz range are rationally designed and fabricated. Based on the finite-element method (FEM) and coupling-of-modes (COM) model, the device parameters, including interdigital transducer (IDT) pairs, aperture size, and reflector pairs, are systematically optimized, and the theoretical and experimental results show high consistency. Finally, SAW temperature sensors with a quality factor greater than 2200 are obtained for real-time temperature monitoring ranging from 20 to 50 °C. Benefitting from the higher operating frequency, the size of the sensing system can be reduced for human body temperature monitoring, showing its potential to be used as a wearable monitoring device in the future.

Advances in High–Speed, High–Power Photodiodes: From Fundamentals to Applications

High–speed, high–power photodiodes play a key role in wireless communication systems for the generation of millimeter wave (MMW) and terahertz (THz) waves based on photonics–based techniques. Uni–traveling–photodiode (UTC–PD) is an excellent candidate, not only meeting the above–mentioned requirements of broadband (3 GHz~1 THz) and high–frequency operation, but also exhibiting the high output power over mW–level at the 300 GHz band. This paper reviews the fundamentals of high–speed, high–power photodiodes, mirror–reflected photodiodes, microstructure photodiodes, photodiode–integrated devices, the related equivalent circuits, and design considerations. Those characteristics of photodiodes and the related photonic–based devices are analyzed and reviewed with comparisons in detail, which provides a new path for these devices with applications in short–range wireless communications in 6G and beyond.

EXPERIMENTAL ANALYSIS OF POWER SEMICONDUCTOR ELEMENTS USED IN FLYBACK CONVERTERS

Switch-mode power supplies (SMPS) have become very popular lately due to their superior efficiency and compact dimensions as compared to conventional counterparts which contain low-frequency transformers. This efficiency and miniaturization are connected to several factors, including high operating frequencies typically in the kHz to MHz range, the utilization of ferromagnetic materials for inductive coupling, and the incorporation of active switching components to mitigate energy loss via the Joule-Lenz effect. Enhancing SMPS efficiency implies active circuit elements (diodes, transistors, etc.) sizing and arrangements. This paper presents a practical approach by addressing a series of experiments to analyze and compare the performance of different active components. It starts with the analysis of the PWM generator module from the primary and continues with the field-effect transistors and rectifier diodes in the secondary. The asynchronous flyback topology has been chosen to carry out the experiments. By using the same experimental platform, based on the obtained results, the analysis of behavioral differences between the different components has been performed.

Systolic Tensor Core for Arithmetics calculations

Today, it is the amount of data that defines the existence of mankind. Scientists respond to the large amount of required calculations by developing hardware in several directions. One of them is to increase the number of arithmetic elements. Another direction is to create new architectures that represent new algorithms for processing numerical data. We have chosen the second direction by developing a new systolic core architecture, which implies an improvement in efficiency, i.e. performing the same task with the same number of arithmetic elements but reducing the latency. Measurements are made in terms of computational capacity and the number of arithmetic elements involved in the operations. The results of the tests are compared with data from a number of selected articles. Today, we have achieved 3.2GFlops with only two modules. In the future, we plan to integrate up to four of our cores in a system with its own memory and management processor and at a higher operating frequency.

Male and female syringeal muscles exhibit superfast shortening velocities in zebra finches.

Vocalisations play a key role in the communication behaviour of many vertebrates. Vocal production requires extremely precise motor control, which is executed by superfast vocal muscles that can operate at cycle frequencies over 100 Hz and up to 250 Hz. The mechanical performance of these muscles has been quantified with isometric performance and the workloop technique, but owing to methodological limitations we lack a key muscle property characterising muscle performance, the force-velocity relationship. Here, we quantified the force-velocity relationship in zebra finch superfast syringeal muscles using the isovelocity technique and tested whether the maximal shortening velocity is different between males and females. We show that syringeal muscles exhibit high maximal shortening velocities of 25L0s-1 at 30°C. Using Q10-based extrapolation, we estimate they can reach 37-42L0s-1 on average at body temperature, exceeding other vocal and non-avian skeletal muscles. The increased speed does not adequately compensate for reduced force, which results in low power output. This further highlights the importance of high-frequency operation in these muscles. Furthermore, we show that isometric properties positively correlate with maximal shortening velocities. Although male and female muscles differ in isometric force development rates, maximal shortening velocity is not sex dependent. We also show that cyclical methods to measure force-length properties used in laryngeal studies give the same result as conventional stepwise methodologies, suggesting either approach is appropriate. We argue that vocal behaviour may be affected by the high thermal dependence of superfast vocal muscle performance.

Investigation of phonon lifetimes and magnon–phonon coupling in YIG/GGG hybrid magnonic systems in the diffraction limited regime

Quantum memories facilitate the storage and retrieval of quantum information for on-chip and long-distance quantum communications. Thus, they play a critical role in quantum information processing and have diverse applications ranging from aerospace to medical imaging fields. Bulk acoustic wave (BAW) phonons are attractive candidates for quantum memories because of their long lifetimes and high operating frequencies. In this study, we establish a modeling approach to design hybrid magnonic high-overtone bulk acoustic wave resonator (HBAR) structures for high-density, long-lasting quantum memories, and efficient quantum transduction devices. We illustrate the approach by investigating a hybrid magnonic system, consisting of a gadolinium iron garnet (GGG) thick film and a patterned yttrium iron garnet (YIG) thin film. The BAW phonons are excited in GGG thick film via coupling with magnons in the YIG thin film. We present theoretical and numerical analyses of the diffraction-limited BAW phonon lifetimes, modeshapes, and magnon–phonon coupling strengths in YIG/GGG planar and confocal HBAR (CHBAR) structures. We utilize Fourier beam propagation and Hankel transform eigenvalue problem methods and compare the two methods. We discuss strategies to improve the phonon lifetimes in the diffraction-limited regime, since increased lifetimes have direct implications on the storage times of quantum states for quantum memory applications. We find that ultra-high cooperativities and phonon lifetimes on the order of ∼105 and ∼10 milliseconds, respectively, could be achieved using a CHBAR structure with 10μm YIG lateral area. Additionally, high integration density of on-chip memory or transduction centers is naturally desired for high-density memory or transduction devices. The proposed CHBAR structure will offer more than 100-fold improvement of integration density relative to a recently demonstrated YIG/GGG device. Our results will have direct applicability for devices operating in the cryogenic or milliKelvin regimes. For example, our study will inform the design of HBAR devices that could couple with superconducting qubits for promising quantum information platforms.

Review Of Control Methods of Dual-Output Half-Bridge LLC Resonant Converter

Dual-output half-bridge LLC resonant converters are widely used in data centres, aerospace, portable electronic devices, new energy vehicles and other fields due to their superior performance of high frequency, high efficiency and high power density. This paper analyses the topology and operating principle of the dual output LLC resonant converter; introduces the traditional control methods and the new control methods in recent years. For each control method, its principle, characteristics, advantages and disadvantages are described. Finally, the future research direction and development trend of dual-output half-bridge LLC resonant converter are outlooked.

Thickness Effect of Copper Clips on Power Module Packaging Design

The superior switching performance of SiC MOSFETs compared to Si devices is limited by packaging-related issues. High electromagnetic parasitics which lead to high voltage overshoots, and higher power losses are the main challenges of high frequency operation. Hence, packaging design modification and optimisation are necessary to accommodate faster switching. Copper clips replacing the bonding wires show promising results in reducing stray inductances, while enhancing the current conduction and heat dissipation since the clip are in contact with a larger area of the semiconductor chip. Silver sintering instead of soldering further improves the electrothermal behaviour. This paper investigates numerically various thicknesses of the copper clips and their effect on double-sided silver sintering, half-bridge 1200V/400A SiC MOSFET power module. Moreover, the silver layer thickness is varied to reduce th maximum stresses on the chip - silver interface.

Time-dependent fatigue reliability analysis of heavy-haul railway steel bridges

Fatigue of heavy-haul railway bridges has been an ongoing concern due to the excessive stresses and frequent cyclic effects of freight trains. Current fracture-based fatigue research, which promotes fatigue reliability analysis caused by crack propagation, is challenged by the dilemma between the detailed modeling of cyclic stress and the reflection of temporal characteristics of loading conditions. In addition, due to the strong non-Gaussian nature of the fatigue limit state function and the computational inefficiency of integrating finite element analysis, current time-dependent reliability methods need to be further developed. To evaluate the fatigue reliability of heavy-haul railway steel bridges considering the temporal dependence of cyclic train loading, a time-dependent fatigue reliability methodology is developed in this study with two innovations. Firstly, a cyclic stress range model is proposed based on the load analysis at the bridge level, which can capture the time-dependent characteristics of the incurred stress range throughout service life. Then, an improved outcrossing rate method for strong non-Gaussian fatigue limit state functions is developed to reduce the computational costs associated with reliability analysis integrated with the finite element model. The developed time-dependent fatigue reliability methodology is then applied to a heavy-haul railway steel truss bridge located in Shandong, China, which proves its efficiency and accuracy in evaluating the time-dependent fatigue reliability of heavy-haul railway steel bridges. Furthermore, the developed methodology is able to provide insight into the balance between bridge fatigue damage and freight volume, and it is found that the combination of small train axle weight and high operation frequency is the optimal solution to achieve the fatigue reliability of the steel bridge while fulfilling the freight demand.

A light Darwin implementation of Maxwell’s equations to quantify resistive, inductive, and capacitive couplings in windings

High operating frequency is an enabler of high key performance indicators, such as increased power density, in electrical machines. The latter enhances the cross-coupling of resistive–inductive–capacitive phenomena in windings, which may lead to significant loss in performance and reliability. The full-wave Maxwell’s equations can be employed to characterize this coupling. To address the frequency instability that arises as a result, a simplification known as the Darwin formulation can be employed, where the wave propagation effects are neglected. Still, this modification is prone to ill-conditioned systems that necessitate intricate pre-conditioning and gauging steps. To overcome these limitations, a fast 2D formulation is derived, which preserves the current continuity conservation along the model depth. This implementation is validated experimentally on a laboratory-scale medium-frequency transformer. The computed impedances for the open- and short-circuit modes of the transformer are validated using measurements and compared with the multi-conductor transmission line model that is widely adopted for the analysis mentioned above. The developed formulation demonstrates a high accuracy and outstanding frequency stability in a wide frequency range, becoming an efficient and computationally light method to investigate the interconnected resistive, inductive, and capacitive effects in windings.