High Frequency Operation Research Articles

Small‐Signal Modelling of Bidirectional CLLC Converters for Onboard Charging Application in Electric Vehicles

ABSTRACTA two‐stage onboard battery charger with an CLLC resonant converter is a widely adopted configuration in the automotive industry. The ZVS and ZCS capability of the switching devices with high operating frequency of the CLLC converters encourages its application in various EV platforms to improve efficiency. In the literature, various authors proposed many methods to control the CLLC converters efficiently, but up to now, no simple and accurate small‐signal equivalent circuit modelling is available. As dynamic networks are load‐dependent, closed‐loop voltage and current controllers provide more stable operations in these converters. In this paper, a detailed mathematical modelling of the CLLC converters with time domain analysis has been presented. The proposed mathematical model accurately predicts the small‐signal behaviors seen in pulse‐frequency‐modulated (PFM) CLLC resonant converters whether the switching frequency is below, near to, or above the resonant frequency. Stable closed‐loop controllers for both current and voltage loops in battery charging applications are designed and detailed. A prototype hardware is been built and the experimental results with the load variations with the designed controllers are tested and the results are been discussed in the paper.

High-Rate Lithium-Ion Capacitor Diode Towards Multifrequency Ion/Electron-Coupling Logic Operations.

Ion/electron-coupling logic operation is recognized as the most promising approach to achieving in-depth brain-inspired computing, but the lack of high-performance ion/electron-coupling devices with high operating frequencies much restricts the fast development of this field. Accordingly, we herein report an orthorhombic niobium pentoxide (T-Nb2O5) based lithium-ion capacitor diode (CAPode) that possesses thoroughly improved performances to achieve multifrequency ion/electron-coupling logic operations. Specifically, benefiting from the unique crystal structure and fast ion-transport topology of T-Nb2O5, the constructed CAPode exhibits a high response frequency of up to 122 Hz, over three orders of magnitude higher than those of the state-of-the-art CAPodes. Meanwhile, the T-Nb2O5 based CAPode delivers a record-high rectification ratio of 108, a high specific capacity of 390 C g-1, a wide voltage window of -1.5-1.5 V, and a superior cycling stability over 2000 cycles. Combining these performance advantages, the T-Nb2O5 based CAPode is demonstrated to be fully competent in typical AND and OR logic gates over a wide frequency range of 1-100 Hz, validating great potential in the burgeoning field of multifrequency ion/electron-coupling logic operations.

High Impedance Microstrip Resonators and Transceiver Arrays for Ultrahigh Field 10.5T MR Imaging.

Multichannel transceiver coil arrays are needed to enable parallel imaging and B1 manipulation in ultrahigh field MR imaging and spectroscopy. However, the design of such transceiver coils and coil arrays often faces technical challenges in achieving the required high operating frequency at the ultrahigh fields and sufficient electromagnetic (EM) decoupling between resonant elements. In this work, we propose a high impedance microstrip transmission line resonator (HIMTL) technique that has unique high frequency capability and adequate EM decoupling without the use of dedicated decoupling circuits. To validate the proposed technique for the ultrahigh field 10.5T applications, a two-channel high impedance microstrip array with the element dimension of 8cm by 8cm was built and tuned to 447 MHz, Larmor frequency of proton at 10.5T, for signal excitation and reception. Bench tests and numerical simulations were performed to evaluate its feasibility and performance. The results show that the proposed high impedance microstrip technique can be a simple and robust way to design high frequency transceiver coils and coil arrays for ultrahigh field MR applications.

MODELING OF BANDPASS FILTERS WITH ATTENUATION POLES USING PARALLEL COUPLING CHANNELS

Background. Microwave filters are critical components in modern communication systems, playing a fundamental role in signal processing by allowing specific frequency bands to pass while attenuating unwanted frequencies. Over the years, significant advancements have been made in the design and development of various types of microwave filters, including directional, microstrip, and multi-resonator filters. These filters are widely used in radar, satellite communications, and wireless networks, where high performance and precise frequency control are essential. Objective. This paper is dedicated to reviewing various microwave filters that were constructed developed or analysed by the team, including directional filters, microstrip filters with attenuation poles, and multi-resonator filters. The studies focus on investigating their unique properties, such as the formation of attenuation poles, metamaterial characteristics, and the effects of resonator coupling on filter performance. New Python-based software realization for modelling different filters six resonators, four resonators, and two resonators were developed and frequently used. Methods. Electrodynamics simulations using software tools like CST Studio Suite, AWR Microwave Office, and LabVIEW, modelling filters using equivalent circuit models and bridge circuits. Use of microstrip lines, circular resonators, and dielectric resonators to construct and analyse different filter configurations. Analysis of energy propagation paths, resonator coupling, and transmission characteristics to optimize filter design. Results: Various structures were researched like Microwave Directional Filters, Microstrip Resonator Filters with 2, 4, 6 resonator, their structures and characteristics were analysed, New python-based software that allows modelling resonance curves using corresponding parameters for filters with 2, 4, 6 resonators. The parameters of the scattering matrix of a bridge quadrupole were expressed in an analytical form and were used for Python based program. Conclusions: the research presented across these publications contributes significantly to the development and understanding of advanced microwave filter designs. The article reveals various resonator-based filters, including directional, microstrip, and multi-resonator filters, these studies have highlighted key performance enhancements achievable through resonator coupling, metamaterial properties, and the introduction of attenuation poles. The use of advanced simulation tools, such as CST Studio Suite, AWR Microwave Office, and LabVIEW, allowed for accurate modelling and validation of theoretical designs. The introduction of Fano resonances and trapped modes in filters demonstrated improvements in selectivity and attenuation characteristics, which are critical for modern communication systems. Trapped modes manifest as attenuation poles, resulting from the interference of even and odd oscillations. This is evidenced by the presence of two independent energy pathways, along which these interfering oscillations propagate. With appropriate design parameters (such as resonator coupling coefficients and resonance frequencies), a complete energy exchange between resonators can occur at a certain frequency, in a direction perpendicular to the primary energy flow from input to output. The design and properties of directional filters based on circular resonators and dielectric resonators were described. These filters have "metamaterial" properties and are widely used in modern microwave technology. The characteristics of bandpass and rejector filters, as well as the characteristics of the filters formed by two microstrip resonators and resonators connected to each other, are given. It is important to emphasize the phenomena of "Fano resonances" observed in these filters, which arise as the interference of oscillations from individual resonators.

Mitigation of energy dissipation of graphene resonators by introduction of boron-nitride

Uncovering the material dissipation mechanisms of two-dimensional materials is essential for their implementation in advanced devices. While graphene resonators are highly attractive due to their high operational frequency and excellent durability, they dissipate a considerable amount of energy due to significant material dissipation associated with atomic friction manifested by the relative slipping of atomic layers. We mitigate the atomic friction by changing the atomic composition of the devices through the insertion of boron and nitride atoms that create polar interlayer bonds and, therefore, also reduce the energy dissipation. As a case study, we built boron carbonitride (BCN) foam cantilever devices and studied their frequency responses compared to those of their graphene counterparts. Indeed, we show that inserting boron and nitride atoms into the lattice improves the interlayer interactions and, thus, reduces the interlayer atomic friction. In addition, the air dissipation of BCN is also lower than that of graphene. Therefore, we pave the path for the development of BCN devices with tunable dissipation.

Response time of the type-II superlattice InAs/InAsSb mid-infrared interband cascade photodetector for HOT conditions

The article presents III-V InAs/InAsSb type-II superlattice (T2SL) mid-wave infrared (MWIR, 100 % cut-off wavelength, λcut-off ∼ 7.5 μm at 333 K) interband cascade photodetector (ICIP) developed to operate at temperatures > 300 K. That device solves the low quantum efficiency (QE) problem of the typical “thick absorber” photodetectors designed for high operating temperature (HOT, > 300 K) conditions. The 5-stage epilayer was grown by molecular beam epitaxy (MBE) on the lattice-mismatched GaAs substrates where absorbers are connected by the highly doped standard n+/p+ tunnel junctions. The developed and analyzed high-speed MWIR devices should be implemented in the emerging fields such as frequency comb spectroscopy (FCS), free space optical communication (FSO) and light detection and ranging (LIDAR). The majority of the MWIR ICIPs’ research have been focused on the QE increase and dark current suppressing to improve the detectivity (D*) while the high- frequency operation (HFO) is still not completely investigated. We report on the MWIR InAs/InAsSb T2SLs ICIP where tradeoff between response time and detectivity was obtained. The time constant being limited by the carriers’ transit time reaches ∼ 16 ns corresponding to 3-dB bandwidth, f3-dB ∼ 10 MHz (detectivity ∼ 2 × 108 cmHz1/2/W without immersion GaAs lens with ∼ 0.53 μm single absorber) for λcut-off ∼ 7.5 μm at 333 K and unbiased conditions. Under 1 V time constant reaches ∼ 2.4 ns (f3-dB ∼ 66 MHz).

Dynamic modelling and mechanical analysis of an inertial linear piezoelectric actuator with double stators

Abstract To achieve higher output performance in precision applications, and in order to gain deeper insight into operation principle, a dynamic model is established including the transmission relationship between the stators, the driving shaft, and the mover based on a slip-slip type inertial linear piezoelectric actuator with double stators. The influence of stator material and symmetry ratio of the excitation signal on the vibration characteristics of the stator and the output performance are investigated. This study reveals the relationship between these factors through a combination of simulations and experiments. Prototypes using several materials are machined and assembled, and the vibration characteristics and output performance are rigorously tested. The results obtained from the experimental measurements are consistent with the simulation results, confirming the validity and rationality of the dynamic model. The experimental results of the stator, as well as the actuator, are analyzed. It can be concluded that the actuator is able to output a larger effective displacement in one motion period with the increased symmetry ratio of the triangular wave signal, applied with a higher operating frequency, resulting in a higher output velocity of 42 mm/s and a larger load of 300 g with the steel stator, and a higher displacement resolution of 18 nm can be achieved using the AL alloy stator. This research not only provides an effective method for enhancing and selecting the desired output performance for the researched actuator but also can be extended to other slip-slip type inertial linear piezoelectric actuators.

What's the Status Quo of Performance and Durability for Low-Iridium Loadings with Commercial Catalysts in PEM Water Electrolysis?

Iridium scarcity and the associated challenges for the large-scale deployment of PEM water electrolyzer technology have been addressed in several studies. To meet the targets, several studies have shown that the iridium specific power density needs to be optimized to < 0.10 mgIr W-1.1,2 However, the current state of the art is fuzzy and it's unclear how far we need to go to achieve large-scale deployment of the PEM water electrolyzer. Therefore, we have analyzed four different commercially available catalysts to determine where the current limitations are in realizing large-scale deployment of PEM water electrolysis. Using a common N115 Nafion membrane, we compared the performance for loadings ranging from 0.1 mgIr cm-2 to 0.8 mgIr cm-2 using one catalyst from Alfa Aesar and Umicore together with two catalysts from Heraeus. Sheet resistance was investigated for all loadings and catalysts and correlated with corresponding high frequency resistance and performance. Durability was evaluated using a bottom-up approach, starting with the lowest loading and a total test time of 500 h. With the data presented, we shed light on the current state of the art for low iridium loading in PEM water electrolysis.Literature Minke, C., Suermann, M., Bensmann, B. & Hanke-Rauschenbach, R. Is iridium demand a potential bottleneck in the realization of large-scale PEM water electrolysis? Int. J. Hydrog. Energy 46, 23581–23590 (2021).Clapp, M., Zalitis, C. M. & Ryan, M. Perspectives on current and future iridium demand and iridium oxide catalysts for PEM water electrolysis. Catal. Today 420, 114140 (2023).

High Performance CMOS RF Switch Based on Highly Carbon Doped Raised Source/Drain Regions

The demand for high-performance Radio Frequency (RF) switches has rapidly increased in recent years due to the ever-growing demand for wireless communication. Complementary Metal Oxide Semiconductor (CMOS) RF switches are favored for their affordability, energy efficiency, and CMOS process compatibility. However, their performance is compromised by factors like insertion loss, isolation, linearity, and power handling. Enhancing CMOS RF switch performance is vital for advancing high-speed wireless communication and supporting emerging technologies like 5G, IoT, and smart homes [1]. The Figure of Merit (FoM) of a RF switch is a metric used to evaluate the overall performance, combining on-resistance (Ron) and off-capacitance (Coff), with lower values indicating better performance (fig 1). One of the methods used to reduce the Ron of switches is strain engineering of the channel. By growing a material with a different lattice constant than the silicon substrate, we can directly modify the strain of the channel, increase the mobility of the charge carriers (µ) and thus reduce Ron. The strain can be either compressive or tensile, depending on the material chosen. Materials investigated for strain engineering, include silicon-germanium (Si1-xGex), silicon-carbon (Si1-yCy), and silicon-nitride (SiN) [2].In this paper we will give new insights on a promising strain engineering method based on incorporation of 1% carbon on the Source/Drain regions, induced tensile strained Si channel (fig 2). The process involves Raised Source/Drain (RSD), where a layer of with a high concentration of substitutional carbon (Csub) is selectively grown on top of the silicon. This creates a tensile strained Si channel, improving the mobility of electron carriers and reducing Ron for N-type switch device [3,4]. We decided to selectively grow RSD, resulting in a theoretical 16% gain in current. The thickness of the layer was limited to 40 nm for 1 % Csub, to avoid its relaxation due to the critical thickness [5]. This approach was implemented in a 200 mm Reduced Pressure Chemical Vapor Deposition (RP-CVD) equipment from Applied Materials, using silane (SiH4) and methylsilane (MS) gases. The carbon concentration was determined by SIMS analysis for quantifying the total carbon concentration (Ctot) and XRD to measure the Csub within the layers.Growth parameters were carefully optimized to increase Csub. First, a compromise between the growth temperature and the growth rate was found around 600°C where 0.82% of Csub was reached (for 1.44% Ctot) while 0.58% of Csub was obtained at 625°C (for 1.26% Ctot). Further increase of Csub up to 1.22% were obtained thanks to the reduction of the H2 carrier gas/total pressure ratio, leading to a rise in the partial pressures of MS and SiH4 (fig 3). We indeed found that reducing the carrier gas debit and increasing the total pressure have a positive impact on the carbon concentration, thanks to the increased growth rate. However, two limitations were shown: (i) the growth rate should not be too fast to avoid the nucleation of extended defects preventing strain engineering; (ii) the thickness range should be reduced to not alter the uniformity of the grown layer (fig 4).Subsequent steps of the process will involve the RSD selective epitaxy of only on the S/D areas, thanks to the dielectric masking materials around the S/D with Cyclic Deposition Etch process (CDE). The final assessment of this based strain engineering process will be made through electrical and radio frequency characterizations of the CMOS RF SOI (Silicon on Insulator) switch devices.[1] STMicroelectronics RF-SOI[2] Maiti C K and Maiti T K 2012 Strain-Engineered MOSFETs (CRC press)[3] Ang K-W, Balasubramanian N, Samudra G S and Yeo Y-C 2007 Performance Enhancement in Uniaxial Strained Silicon-on-Insulator N-MOSFETs Featuring Silicon–Carbon Source/Drain Regions IEEE Trans. ELECTRON DEVICES 54[4] Bauer M, Machkaoutsan V, Zhang Y, Weeks D, Spear J, Thomas S G, Verheyen P, Kerner C, Clemente F, Bender H, Shamiryan D, Loo R, Hikavyy I, Hoffmann T, Absil P and Biesemans S 2008 SiCP Selective Epitaxial Growth in Recessed Source/Drain Regions yielding to Drive Current Enhancement in n-channel MOSFET ECS Trans. [5] Cherkashin N, Hÿtch M, Houdellier F, Hüe F, Paillard V, Claverie A, Gouyé A, Kermarrec O, Rouchon D, Burdin M and Holliger P 2018 On the influence of elastic strain on the accommodation of carbon atoms into substitutional sites in strained Si:C layers grown on Si substrates Appl Phys Lett Figure 1

An enhanced broadband piezoelectric energy harvester via elastic amplification structure for multidirectional vibration

Abstract Vibration energy harvesting using a piezoelectric mechanism has significant potential for powering wireless sensors. However, most current vibration energy harvesters face limitations such as bidirectionality, narrow bandwidth, and high operating frequencies. To address these issues, we propose an enhanced broadband piezoelectric energy harvester utilizing an elastic amplification structure for multidirectional vibration (EB-PVEH). By utilizing the multidirectional rotation capacity of the excitation block and the amplified foundation excitation provided by springs, the EB-PVEH effectively captures broadband vibrations in 2D space under low-frequency excitation. Additionally, its design features long-term durability, as the piezoelectric beams are smoothly excited by the pendulum-induced motion of the block without a tip mass. The practical feasibility and the impact of structural parameters on the output behavior of EB-PVEH were investigated through theoretical analysis and experimental testing. The results revealed that the introduction of springs dynamically amplified the harnessed electrical power output. Moreover, EB-PVEH could harvest the multidirectional vibration, and it exhibited different power-generating characteristics in various directions. Furthermore, the resonance frequency could be efficiently tuned by adjusting the flexible arm length and proof mass, with different optimal arm lengths identified for each vibration direction to maximize working bandwidth. The harvester achieved an optimal output power of 3.98 mW. Practical applications, such as charging a capacitor by driving an e-bike or a bike, demonstrate the potential of the proposed harvester to provide power for micro-electrical devices.

Enhanced breakdown strength and corona aging life in PI dielectric based on heterogeneous all-organic design

The high-speed train is developing towards higher speed and greater load capacity. As an important part of this, inverter-fed traction motors need higher power. As the turn-to-turn insulating material for inverter-fed traction motors, polyimide (PI) does not satisfy the requirements for breakdown strength and corona aging life with higher power. In this paper, the heterogeneous all-organic composite is designed with polyimide as matrix and acrylic elastomer (DE) as reinforcing material. When the load of DE is 0.5 wt%, the breakdown strength of the thermosetting DE/PI composites is up to 740 kV/mm, which is 60 % higher than PI (462 kV/mm) and the corona aging life is up to 70.4 h which is increased by about 340 % compared with PI (16 h). The synergy of free volume and trap makes comprehensive properties enhanced in the thermosetting DE/PI composite. This work provides a new design for turn-to-turn insulation with a high voltage level and a high operating frequency.

The Impact of Modulation Techniques on Brushless DC Motor Drive

ABSTRACTThree‐phase brushless DC (BLDC) motors are cost‐effective and are increasingly used in various speed control applications. The phase voltage, DC‐bus utilization, current ripple, and torque ripple are major performance parameters for a BLDC motor drive. Different pulse width modulation (PWM) methods will diversely influence these parameters. This paper presents the phase voltage, current ripple, and DC‐bus utilization analysis of BLDC motor drive for four PWM techniques and provides a comparative analysis. The current ripple of the BLDC drive is evaluated with low and high switching frequency operations. Phase voltage and DC‐bus utilization of a BLDC motor are evaluated using analytical methods and validated experimentally. The investigation provided in this work are significant for PWM selection and implementation for low and high switching frequency operations. Both low‐ and high‐frequency operations are performed by supplying the BLDC drive from a silicon carbide (SiC) based inverter. These PWM techniques are also compared, considering high and low‐speed applications. Experimental results of SiC inverter‐fed BLDC motor drive are provided to substantiate the proposed work.

Piezoelectric deicing system for aeronautics: Extensional mode actuator and power supply

AbstractRecent research shows a growing interest in low‐power avionic deicing systems, in particular, those based on piezoelectric actuators for their energy efficiency. The system generates micrometric vibrations in the structure to delaminate and break the ice with a low power requirement. However, designing the power supply and its control for driving piezoelectric actuators is challenging due to their distinctive capacitive behavior at most frequencies, especially in deicing applications requiring high operational frequency. This contribution addresses the two cross‐dependent parts of the deicing system, that is the piezoelectric actuator designed for breaking any kind of ice on a large area and its power supply made of a 1 kW/200 V/2 MHz auxiliary resonant commutated pole inverter (ARCPI). The choice of this converter is based on the specific constraints of the application, such as varying the operating frequency with the actuator working conditions, the long cables and necessary insulation between the actuator and its supply, the soft‐switching operation and reactive energy balancing for a good efficiency. Based on these criteria, the converter was developed and realized in the laboratory. Deicing tests confirmed effective operation with a power input density of 122 mW/cm2, using nine piezoelectric patches per dm2.

Investigation of Cavitation Phenomena in a “High-Power” Piezohydraulic Pump: A Computational Fluid Dynamics (CFD) Approach

Abstract Piezoelectric pumps, known as piezopumps, are highly versatile devices with applications in various fields due to their precise flow control, compact design, lack of magnetic interference, and low noise. These pumps are classified based on the number of pumping chambers, valve configuration, and driving power source mechanism. In fields requiring consistent flow rates and back pressures, particularly in fluid power applications, piezopumps employing a piezostack actuator as their power driving source are actively researched. This kind of piezopumps, also known as piezohydraulic pumps, operate using a piezostack actuator to drive a piston for fluid delivery, along with reed valves controlling fluid flow at the inlet and outlet of the pump chamber. The high operating frequency range of the piezostack actuator and reed valves, exceeding 1 kHz, allows piezohydraulic pumps to achieve significant flow rates despite the stack’s limited displacement. This enhances their performance without the need for increased size or power input. However, this also increases the risk of cavitation, which could lead to damage, reduced efficiency, and higher noise levels. Therefore, the purpose of this paper is to expand on previous research by using the CFD software Ansys Fluent to further investigate cavitation phenomena in a piezohydraulic pump developed at the University of Bath. In particular, the study focuses on simulating various oil flow scenarios through the pump with a fixed inlet pressure of 20 bar, while varying the opening of the inlet reed valve from the minimum (0.1 mm) to maximum (0.7 mm) value, as well as adjusting the pump chamber pressure.

Analysis of Machine Learning-Based NLOS Signal Identification Algorithm for UWB Indoor Localization Using CIR Waveform Features

Abstract. Ultra-wideband (UWB) technology stands out among numerous indoor positioning techniques due to its high operating frequency, low interception capability, resistance to multipath effects, and strong penetration. The UWB uses the time-of-arrival (TOA) to estimate the distance between the transmitter and receiver anchors in centimeter accuracy. However, in complex indoor positioning environments, obstacles such as walls, glass windows, metal plates, and wooden doors may block and reflect signals, inevitably causing non-line-of-sight (NLOS) errors that significantly affect positioning accuracy. The NLOS signal has lower signal energy due to the reflections. Thus, the channel impulse responses (CIR) from NLOS and LOS are different. To address the NLOS signal identification issue in UWB positioning, we utilize UWB CIR data collected from various positioning scenarios as the data source. CIR waveform input features are provided for the NLOS signal recognition model, and four machine learning models—Support Vector Machine (SVM), Multi-Layer Perceptron (MLP), K-Nearest Neighbors (KNN), and XGBoost—are trained and optimized for NLOS signal recognition. The aim of the study is to analyze the performance of different machine learning algorithms for NLOS signal recognition in UWB indoor localization using these features. Experimental results indicate that machine learning-based NLOS signal recognition algorithms can achieve an accuracy of approximately 77.46%, precision of 80.46%, and an F1 score of 0.81. Among the four models, the XGBoost model demonstrates generally better recognition performance.

The thermal performance model of a 105 mW@4.41 K 4He Joule-Thomson cryocooler designed for space applications

The 4He Joule-Thomson cryocooler (JTC) ensures the operation of space detectors working within the 4 K temperature range, such as the Block Impurity Band Infrared Detector (BIBID). In addition, the 4He JTC is one of the essential components of the 300 K to 50 mK space cryochain. It can precool sub-Kelvin refrigerators, such as the adiabatic demagnetization refrigerator (ADR) and the dilution refrigerator (DR). With the development of space science, the need for cooling power at the 4 K temperature range is growing. Thus, a thermal performance model of the 4He JTC precooled by a two-stage thermally coupled pulse tube cryocooler (PTC) is designed, manufactured, and tested with an eye toward space applications. A four-stage compression system with a high operating frequency and large pistons is designed and used to drive the JT cycle. This 4He JTC has a total mass of 55 kg and can provide a cooling capacity of 105 mW at 4.41 K with a total input electric power of 548 W.

Influence of Parasitic Elements on Flyback Converter at High Switching Frequency Operation: A Comprehensive Analysis

The presence of parasitic elements in the flyback converter amplifies the impact on the converter’s primary current quality, particularly when the converter's switching frequency exceeds its designated operational rate. In this paper, the parasitic and stray elements of the transformer have been comprehensively examined, modelled, and simulated to evaluate their influence on the converter, with specific emphasis on the primary current. The simulation was performed utilising MATLAB SIMULINK software, integrating the authentic critical characteristics of the components, and conducting tests at various switching frequencies. The simulation results indicate that the primary current exhibits pronounced resonance effects at higher switching frequencies. The experimental findings are presented to corroborate the theoretical analysis and simulations pertaining to the impact of parasitic elements on the transformer and its immediate environment.

Theoretical investigation of Rayleigh-type surface acoustic waves with high electromechanical coupling coefficient in c-axis-tilted ScAlN film/3C-SiC substrate structure

Surface acoustic wave (SAW) resonators are essential components of mobile communication technology. Advanced performance SAW resonators are needed to support beyond fifth-generation mobile communication technology, which aims to achieve unprecedentedly high data rates and low latency using wide frequency bands in the RF spectrum. This study theoretically investigates the propagation characteristics of a non-leaky Rayleigh-type SAW (RSAW) propagating in a c-axis-tilted ScAlN film/3C-SiC substrate structure. By appropriately selecting the c-axis tilt angle and the film thickness of the ScAlN film, a high electromechanical coupling coefficient (K2) value was obtained in the second-mode RSAW (Sezawa wave). The maximum K2 value for the Sezawa wave was 8.03%, with a phase velocity of 7456 m/s and a power flow angle of 0° under the structural conditions where the K2 value was maximized. These properties offer significant advantages for achieving wide frequency bands, high operating frequencies, and ease of design for SAW resonators. The structural conditions under which good propagation characteristics were obtained in the Sezawa waves were found to coincide with the conditions that maximize the electromechanical coupling coefficient of the quasi-longitudinal wave in the ScAlN film, and a significant increase in the shear vertical component of Sezawa wave particle displacement was observed. Additionally, ScAlN films with a 40% Sc concentration can be fabricated using sputtering and molecular beam epitaxy. Recent advancements have reported the production of high-quality 3C-SiC wafers and large 3C-SiC film/silicon wafers. Therefore, the c-axis-tilted ScAlN film/3C-SiC substrate structure shows great potential as a candidate for next-generation SAW resonators.

Generalized N-State Random Pulse Position Discontinuous PWM for High-Frequency Harmonics Reduction and Performance Improvement at High Modulation Ratios

Generalized <i>N</i>-State Random Pulse Position Discontinuous PWM for High-Frequency Harmonics Reduction and Performance Improvement at High Modulation Ratios

Multiswitch-Leg DAB Converter for Low $dv/dt$ at High Operating Frequency for MVDC Systems

Multiswitch-Leg DAB Converter for Low $dv/dt$ at High Operating Frequency for MVDC Systems