Coupling Coefficient Research Articles

Design and Fabrication of Annular-Array Ultrasound Transducer Based (K, Na) NbO3 Lead-Free 1-3 Piezoelectric Composite.

This article reports the design, fabrication, and performance of an annular-array ultrasound transducer using (K, Na)NbO3 (KNN)-based lead-free 1-3 piezoelectric composite. The 1-3 piezoelectric composite based on lead-free 0.965(K0.45Na0.55)(Nb0.96Sb0.04)O3-0.035 Bi0.5Na0.5Zr0.85Hf0.15O3 (KNNS-BNZH) was first prepared with the dice-and-fill method. Different from previous reported studies, by patterning annular electrodes on this kind of 1-3 composite, a five-element annular-array transducer in diameter of 6 mm was designed and successfully fabricated and its working center frequency was increased from 5 MHz to around 15 MHz. Meanwhile, a -6 dB bandwidth of 50% was achieved for each annular-array element via a pulse-echo response measurement. Moreover, the obtained annular-array transducer exhibits low crosstalk (<-40 dB) and a high electromechanical coupling coefficient of around 0.7. The application of ultrasonic imaging was further demonstrated to show its excellent performance. Both theoretical analysis and experimental results show that the obtained annular-array transducer presented in this work has a competitive capability for ultrasonic application.

Neighbor event-triggered adaptive distributed control for multiagent systems with dead-zone inputs

&lt;abstract&gt;&lt;p&gt;The paper focused on the distributed tracking problem for a specific class of multi-agent systems, characterized by bandwidth constraint and dead zone actuators, where the bandwidth limitations exist in neighbor agents and the dead zone nonlinearity refers to a generalized mathematical model. Initially, a series of event-triggered mechanisms with relative thresholds were established for neighbor agents, ensuring that control signals were transmitted only when necessary. Next, the generalized dead zone models were decomposed into two parts: indefinite terms with control coefficients and disturbance-like terms, resulting in unpredictability and damaging effects. Subsequently, based on the backstepping procedure, final consensus controllers with multiple polynomial compensators were constructed. These controllers offset the coupling coefficients caused by event-triggered mechanisms and dead zone non-smooth. Stability analysis was given to substantiate the theoretical correctness of this method and support the claim of Zeno behavior avoidance. Finally, simulation studies were performed for the feasibility of our proposed methodology.&lt;/p&gt;&lt;/abstract&gt;

0.36BiScO3-0.64PbTiO3/Epoxy 1-3-2 High-Temperature Composite Ultrasonic Transducer for Non-destructive Testing Applications.

The development of high-temperature nondestructive testing (NDT) requires ultrasonic transducers with good temperature resistance and high sensitivity for improved detection efficiency. Piezoelectric composite can improve the performance of transducers because of its high electromechanical coupling coefficient and adjustable acoustic impedance. In this study, 1-3-2 composites and 1-3-2 high-temperature composite ultrasonic transducers (HTCUTs) based on 0.36BiScO3-0.64PbTiO3 (BSPT), which are preferred piezoelectric materials at 200°C-300°C, and high-temperature epoxy with a center frequency of 6 MHz were designed and fabricated. From 25°C to 250°C, 1-3-2 composites show a higher electromechanical coupling coefficient kt especially at high temperatures (~0.53 at 25°C, and ~0.64 at 250°C) than monolithic BSPT (~0.5). The signal of the pulse-echo response of 1-3-2 HTCUTs is distinguishable up to 250 °C and remains stable (Vpp~500 mV) below 150°C, exhibiting higher sensitivity (improved by 7 dB) than that of monolithic BSPT high-temperature ultrasonic transducers (HTUTs). Bandwidth has been greatly enhanced especially at high temperatures (~103250°C) compared with that of monolithic BSPT HTUTs(~30250°C). To verify the excellent performance, B-mode scanning imaging measurement of a stepped steel block and defect location detection of a steel block were performed, showing the potential for high-temperature NDT applications.

Energy efficiency and energy-saving evaluation methods for public building energy systems under the dual carbon background

The energy consumption characteristics and energy system structure of each type of building are different, so the evaluation methods and indicators need to be customized for different types of buildings, which increases the complexity of the evaluation. Therefore, a method for evaluating the energy efficiency and energy conservation of public building energy systems under the dual carbon background is proposed. Analyze the coupling coefficient data of energy quality, energy and flow, obtain the base of energy efficiency optimization coefficients, and use twin technology to establish a comprehensive energy efficiency model. Introduce matter element analysis and use matter element extension models to evaluate the energy efficiency and energy-saving effects of public building energy systems. The experimental test results show that the research method can accurately evaluate the energy consumption of public buildings and has an effective evaluation effect on different types of buildings.

Simulation of RFI Cancellation Using Subspace Projection Algorithm for PAF Receiver

The simulation of radio frequency interference (RFI) cancellation by applying a spatial filtering technique for phased array feed (PAF) is presented. In order to better reflect the characteristics of PAF, a new signal model is to add the coupling coefficient among elements of PAF to the conventional array signal model. Then the subspace projection (SP) algorithm is used to cancel RFI from the correlation matrix of the signal, and finally, the 2D power image is drawn. The power variation of signal-of-interest direction and RFI direction before and after using the SP algorithm is analyzed. The new signal model and simulation strategy can be used to test and verify the beamformer.

Radial sandwich radial-bending composite transducer designed based on acoustic black hole theory

A novel radial sandwich radial bending composite transducer is proposed based on the increasing amplitude of bending waves in the structure of an acoustic black hole (ABH). The transducer consists of a radial sandwich circular ring transducer and an outer acoustic black hole structure. The existence of ABH structure realizes the conversion between radial vibration and bending vibration of the transducer, and improves the acoustic radiation performance of the transducer. Based on the one-dimensional acoustic black hole bending vibration theory, the bending vibration equation of the annular ABH structure is given. An analytical model of ABH structure bending vibration is established by using the method of geometrical-acoustics, and the eigen frequency of its bending vibration is given. The relationship between the electromechanical conversion performance and the size of the transducer is discussed by using the finite element method, and the results show that when the eigen frequency of the bending vibration of the ABH structure is close to the resonant frequency of the transducer, the electromechanical coupling coefficient of the transducer reaches a maximum value. The radiation sound pressure field, radiation sound intensity, and radiation directionality of the transducer in the air are also analyzed by the finite element method. The results indicate that the presence of ABH structure can improve the electromechanical conversion performance of the bending vibration of the transducer, enhance the acoustic radiation performance of the transducer, make the transducer exhibit radiation directionality and the lower order of the bending vibration mode of the ABH structure, the stronger radiation directionality of the transducer towards the left side and the right side. Finally, we make a prototype transducer, in order to verify the accuracy of the simulation and theory. We carry out the experimental test of transducer electrical impedance and vibration mode. The measured results are in good agreement with the simulation results. The displacement distribution of the radiation surface of the transducer at resonance frequency is measured, which verifies the bending vibration modes of the ABH structure. This type of transducer is expected to be used as acoustic projector in the air or water.

Advanced technologies of FBAR for tuning effective electromechanical coupling coefficient

The film bulk acoustic wave resonator (FBAR) is one of the most popular devices in the radio frequency field. Numerous researchers are simultaneously working to develop an effective electromechanical coupling coefficient (keff2) tuning technology, aiming to meet the diverse bandwidth requirements of the 5 G era. Based on a traditional FBAR process, this work prepares several different devices and then analyzes the four factors that influence keff2 from the perspective of process, material, and design. The pillar structure achieves the largest keff2 tuning range of 2.84% (33 MHz). The composite piezoelectric film can tune the overall resonant frequency in a wide range, and its keff2 tuning range is 1.75% (12.5 MHz). The area effect tunes the fs in a small range, ultimately achieving a keff2 tuning range of 1.16% (11 MHz). Film stress regulation achieves keff2 tuning range of 2.73% (30 MHz), but it has the greatest difficulty. The integration of various keff2 tunable methods has important guiding significance for the design of FBAR filters in the future.

Characteristics of NaNbO3 templates and improvement of electrical properties of textured KNLNS-BNKT ceramics

In this study, plate-like perovskite NaNbO3 (NN) templates were formed from Bi2.5Na3.5Nb5O18 (BiNN5) precursors via a molten salt method. The structure and microstructure of BiNN5 precursors and NN templates were studied. As a result, the platelike BiNN5 precursor particles have a bismuth layer perovskite structure, which is the basis for forming the synthesized plate-like NN particles that have a high aspect ratio with a width of 2-7 μm, a length of 5-12 μm and a thickness of 0.5-1 μm. From NN templates, we fabricated textured lead-free 0.98(K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O3 − 0.02Bi0.5(Na0.4K0.1)TiO3 (KNLNS- BNKT) ceramic by the grain orientation technique. Experimental results show that the KNLNS-BNKT ceramics have a single-phase orthorhombic structure in which textured KNLNS-BNKT ceramics with 67% grain orientation. The electrical properties of the oriented ceramic are significantly improved compared to the non-oriented ceramic fabricated by the traditional method. Specifically, the electrical properties of the resulting KNLNS-BNKT oriented ceramics have a high dielectric constant (ε = 1323, an increase of 17%); large remnant polarization (Pr = 13.5 mC/cm2, an increase of 11.9%); high piezoelectric coefficient (d33 = 205 pC/N, an increase of 32%) and high electromechanical coupling coefficient (kp = 0.4, an increase of 11%).

Thermogravimetric experimental study on the co-combustion of coal gangue and polypropylene

To address the challenges posed by the challenging ignition, low volatile content, and high ash content of coal gangue (CG) during separate combustions, a proposed treatment involves mixing CG with polypropylene (PP), offering the potential for centralized treatment. Co-combustion experiments were carried out at varying ratios, and a corresponding model for co-combustion was established. The thermal impact of temperature variations during co-combustion is analyzed, and the kinetic characteristics of the co-combustion process are explored. The findings indicate that the volatile matter released by PP notably decreases the activation energy of the mixed fuel in the initial combustion stage. Co-combustion at different ratios enhances overall combustion, particularly when the PP content is 20 %. At this specific ratio, the temperature-averaged thermal relative coupling coefficients are 1.64 and 2.30 times greater than those at PP contents of 50 % and 80 %, respectively. These results hold significance for the comprehensive utilization of CG.

Magnetoelectric behaviour of Pb-free Na0.5Bi0.5TiO3-Ni0.5Co0.5Fe2O4 particulate novel ceramic composites

Magnetoelectric (ME) multiferroic composites are more promising candidates for low-power consumption devices, next-generation spintronic devices, and multistate memory devices since they exhibit significantly higher Magnetoelectric interaction over single-phase multiferroics. In this regard magnetic behaviour, dielectric, and magnetoelectric characteristics of a novel Pb-free (1-x) Na0.5Bi0.5TiO3-(x) Ni0.5Co0.5Fe2O4, (x = 0, 0.2, 0.4, 0.6, 0.8 & 1) particulate composites were explored. Solid-state synthesis was adopted to prepare the single-phase Na0.5Bi0.5TiO3 (NBT), Ni0.5Co0.5Fe2O4 (NCFO), and their composites. The presence of rhombohedral NBT and cubic inverse spinel NCFO in the composites were confirmed with X-ray diffraction (XRD) patterns. Microstrain (ε) induced in the prepared samples was estimated by using the Williamson-Hall (W-H) method. The piezoelectric NBT phase shows the tensile strain and the ferromagnetic NCFO shows the comprehensive strain. Among all the composites 0.8NBT-0.2NCFO shows a higher strain value of 0.012%, and the decrement in the strain values was observed upon increases in ferrite concentration. Backscattered scanning electron microscope (BS-SEM) images revealed the existence of highly dense uniformly distributed elements and Energy dispersive spectroscopy (EDS) confirmed the existing elements in the composites. UV–vis absorbance spectra disclosed a rise in energy gap values from 1.14 eV to 3.0 eV with increasing NBT percentage. Variations of dielectric permittivity and dielectric loss with respect to AC frequency were studied at room temperature (RT), and the 0.2NBT-0.8NCFO sample shows a high dielectric permittivity of 8500 at ∼100Hz. M − H (Magnetization-Magnetic field) hysteresis loops demonstrate the pure ferrite phase has a coercive field (Hc) = 578 Oe, remnant magnetization (Mr) = 21.43 emu/g and saturation magnetization (Ms) = 71.29 emu/g. The Ms and Mr values in the composites are enhanced with increasing ferrite percentage. Studies on ME behaviour of (1-x) NBT-(x) NCFO, (x = 0.2,0.4,0.6 & 0.8) show the coupling effect between both the phases at room temperature and the highest coupling coefficient value 3.16mV/Cm. Oe was observed for the 0.8NBT-0.2NCFO further the reasons and mechanisms are discussed.

Synchronisation of the ensemble of nonidentical FitzHugh–Nagumo oscillators with memristive couplings

The aim of the study is to investigate the features of synchronization in ensembles of nonidentical neuron-like FitzHugh–Nagumo oscillators interacting via memristor-based coupling. Methods. The collective dynamics in a ring of FitzHugh–Nagumo oscillators connected via memristive coupling was studied numerically and experimentally. The nonidentity of oscillators was achieved by detuning them by the threshold parameter responsible for the excitation of oscillator, or by detuning them by the parameter characterizing the ratio of time scales, the value of which determines the natural frequency of oscillator. We investigated the synchronization of memristively coupled FitzHugh–Nagumo oscillators as a function of the magnitude of the coupling coefficient, the initial conditions of all variables, and the number of oscillators in the ensemble. As a measure of synchronization, we used a coefficient characterizing the closeness of oscillator trajectories. Results. It is shown that with memristive coupling of FitzHugh–Nagumo oscillators, their synchronization depends not only on the magnitude of the coupling coefficient, but also on the initial states of both the oscillators themselves and the variables responsible for the memristive coupling. We compared the synchronization features of nonidentical FitzHugh–Nagumo oscillators with memristive and diffusive couplings. It is shown that, in contrast to the case of diffusive coupling of oscillators, in the case of meristive coupling, with increasing coupling strength of the oscillators, the destruction of the regime of completely synchronous in-phase oscillations can be observed, instead of which a regime of out-of-phase oscillations appears. Conclusion. The obtained results can be used when solving the problems of synchronization control in ensembles of neuronlike oscillators, in particular, for achieving or destroying the regime of in-phase synchronization of oscillations in an ensemble of coupled oscillators.

Establishment of magneto-electric response in GdFeO3 doped PbTiO3 solid solutions

This work promotes a thorough examination of the magnetic impact on the multiferroicity of the sample. The usual solid-state reaction method was used to synthesis Pb1-xGdxTi1-xFexO3 with x = 0.21, 0.22, and 0.23. XRD analysis showed a pure homogeneous single-phase compound with a tetragonal structure, indicating perfect diffusivity of Gd atoms into the PbTiO3 lattice. All of the samples show clear grain growth between 7.8 and 10.5 μm in the SEM images, proving that they were sintered at the correct temperature. Furthermore, ferroelectric transition temperature reduces from 388 K to below the ambient temperature range as the doping value of Gd grows. The room temperature P-E hysteresis loops indicated that the remnant polarization of the sample drops from 8.66 μC/cm2 to 2.065 μC/cm2 for x = 0.21 to 0.23 sample. Three distinct phenomena supported the ME coupling of all samples. The sample x = 0.21 exhibits the maximum magneto-dielectric response of 2.2 % at 1.2T having highest MDR coupling coefficient value of −1.41g2/emu2. Moreover, the sample x = 0.21 shows the highest shift in magnetization before and after electric poling of about 0.105 emu/g. As a result, the sample x = 0.21 emerges as a viable choice for application in a variety of multifunctional devices.

Quasi-Zero Stiffness Vibration Sensing and Energy Harvesting Integration Based on Buckled Piezoelectric Euler Beam.

This paper presents a novel quasi-zero stiffness vibration sensing and energy harvesting integration system for absolute displacement measurements based on a buckled piezoelectric Euler beam (BPEB) with quasi-zero stiffness (QZS) characteristics. On one hand, BPEB provides negative stiffness to the system, thus creating a vibration-free point within the system and transforming the absolute displacement measurement problem into a relative motion sensing problem. On the other hand, during the measurement process, the BPEB collects the vibration energy from the system, which can provide electrical energy for low-power relative motion sensing devices and remarkably suppress the frequency range of the jump phenomenon, thereby further expanding the frequency domain measurement range of the sensing system. The research results have shown that this system can measure the absolute motion signal of the tested object in low-frequency vibration with small excitation. By adjusting parameters such as the force-electric coupling coefficient and damping ratio, the measurement accuracy of the sensing system can be improved. Furthermore, the system can convert the mechanical energy of vibrations into electrical energy to power the surrounding low-power sensors or provide partial power. This could potentially achieve self-powering integrated quasi-zero stiffness vibration sensing, offering another approach and possibility for the automation development in wireless sensing systems and the Internet of Things field.

Wavelength-Stable Metal Grating Distributed Feedback Quantum Cascade Laser Emitting at λ ~ 7.2 μm

In this research, we demonstrate a wavelength-stable continuous wave (CW) distributed feedback (DFB) quantum cascade laser (QCL) emitting at 7.2 μm using a surface metal grating approach without epitaxial regrowth. The deep metal grating provides an appropriate DFB coupling coefficient and enhanced thermal extraction, resulting in improved lasing performance and the realization of impressive wavelength stability. Quantitatively, the temperature tuning coefficient of the single-mode emission is only 0.54 nm/°C from 20 °C to 70 °C, and the current tuning coefficient of the single-mode emission is 3.2 nm/A from 1.0 A to 1.6 A. A DFB-QCL with a 2 mm cavity length exhibits a low threshold current of 0.6 A and a power of 1.1 W with a slope efficiency of 1 W/A in the CW mode at 300 K. A single-mode operation with a side mode suppression ratio of 33 dB and a single-lobed far-field without beam steering is obtained in the working temperature range of 20–70 °C The improved wavelength stability using a deep surface metal grating approach promises simplified fabrication, which is meaningful for the commercial applications of QCLs.

Analysis of Different Piezoelectric Materials on the Film Bulk Acoustic Wave Resonator

The performance of film bulk acoustic wave resonators (FBAR) is greatly dependent on the choice of piezoelectric materials. Different piezoelectric materials have distinct properties that can impact the performance of FBAR. Hence, this work presents the analysis of three different piezoelectric materials which are aluminum nitride (AlN), scandium aluminum nitride (ScAlN) and zinc oxide (ZnO) on the performance of FBARs working at resonance frequencies of 6 GHz until 10 GHz. The one-dimensional (1-D) modelling is implemented to characterize the effects of these materials on the quality (Q) factor, electromechanical coupling coefficient (k2eff) and bandwidth (BW). It is determined that employing ScAlN in FBAR results in the highest Q factor, ranges from 628 to 1047 while maintaining a relatively compact area (25 µm × 25 µm) and thickness (430 nm to 720 nm). However, ScAlN yields the narrowest BW, measuring 0.11 GHz at 6 GHz, as opposed to AlN and ZnO, which exhibit broader bandwidths of 0.16 GHz and 0.23 GHz, respectively.

Progress in the Measurements of Coupled Transport Mechanisms in the Electrolyte of a PEM Based Thermogalvanic Cell

A promising measure to increase the efficiency of energy conversion is the use of low temperature waste heat being readily available in a vast amount. Thermogalvanic cells (TGC) offer the possibility of electrical energy harvesting from such thermal energy. An externally applied heat source leads to a temperature gradient across the electrolyte inducing a gradient in the chemical potential and a difference in the electrical potential between the electrodes. Due to the aim of approaching a homogeneous equilibrium different coupled molecular transport mechanisms are taking place in the electrolyte impacting the performance of the TGC. In contrast to the common approach of using classical transport correlations such as Fourier’s, Ohm’s or Fick’s law to describe these coupled processes this work applies the theory of non-equilibrium thermodynamics (NET). The method considers all interactions of the driving forces and resulting fluxes occurring in the electrolyte and clearly separates the transport phenomena into their origin. The knowledge of these relations, which can be described by characteristic phenomenological coefficients, gives a better understanding of the TGCs internal processes and the opportunity to determine the entropy production aligned with local heat sources inside its electrolyte. In this work a TGC based on a polymer electrolyte membrane with two gaseous hydrogen electrodes of different temperatures was investigated experimentally. Due to the need of water in the electrolyte to ensure ionic transport the TGC was fed with a humidified hydrogen gas. The experimental setup gives the opportunity of precisely adjusting the temperature and composition of the species at both electrodes thus control the gradients in temperature, concentration i.e. chemical potential and electric potential between the electrodes. By suppressing all but one driving force across the electrolyte and measuring the open circuit voltage (OCV) different coupling coefficients as well as the occurring fluxes in the electrolyte were determined for a wide variety of working conditions. By implementing the measured phenomenological coefficients in an earlier published model of the TGC considered in this work a significantly lower deviation of the modeled and measured OCV values compared to the approach of using classical transport coefficients can be determined. This indicates the importance of applying the NET when considering transport phenomena while different gradients being present. We also show that by an aligned combination of the gradients in temperature and chemical potential of the water their impacts on the electrical potential can sum up leading to a higher OCV or even cause a pole reversal due to contrary effects on the electrical potential difference. Figure 1

Multi-Material Radial Phononic Crystals to Improve the Quality Factor of Piezoelectric MEMS Resonators.

In this paper, a multi-material radial phononic crystal (M-RPC) structure is proposed to reduce the anchor-point loss of piezoelectric micro-electro-mechanical system (MEMS) resonators and improve their quality factor. Compared with single-material phononic crystal structures, an M-RPC structure can reduce the strength damage at the anchor point of a resonator due to the etching of the substrate. The dispersion curve and frequency transmission response of the M-RPC structure were calculated by applying the finite element method, and it was shown that the M-RPC structure was more likely to produce a band-gap range with strong attenuation compared with a single-material radial phononic crystal (S-RPC) structure. Then, the effects of different metal-silicon combinations on the band gap of the M-RPC structures were studied, and we found that the largest band-gap range was produced by a Pt and Si combination, and the range was 84.1-118.3 MHz. Finally, the M-RPC structure was applied to a piezoelectric MEMS resonator. The results showed that the anchor quality factor of the M-RPC resonator was increased by 33.5 times compared with a conventional resonator, and the insertion loss was reduced by 53.6%. In addition, the loaded and unloaded quality factors of the M-RPC resonator were improved by 75.7% and 235.0%, respectively, and at the same time, there was no effect on the electromechanical coupling coefficient.

Modeling the operation of an induction charger for mobile charging of electric vehicles

The speed of implementation of electric vehicles depends on the level of development of the charging infrastructure, which is subject to ever new requirements, including increasing ease of use and reducing charging time. A solution to the problem could be an introduction of wireless charging of electric vehicles (inductive charging device – WPT). However, in order to produce an effective WPT (without preliminary calculation and modeling the efficiency of the device may not reach 10 %), it is necessary to select the parameters of the coils and simulate the frequency characteristics of the voltage. For this purpose, as part of the implementation of the project to create a mobile charging installation for electric vehicles, the problem of modeling the operation of the WPT has been solved. In accordance with the technical specifications, a coil has been built in Excel, which was used as geometry in Comsol to evaluate the distribution of magnetic fields. To study the frequency characteristics, the CST Studio program has been used. Using these programs, we simulated various methods for implementing the WPT with obtaining frequency characteristics. It has been confirmed that the coupling coefficient increases with decreasing distance between parts of the WPT. Calculations of resonant circuits and the expected efficiency for both types of resonant circuits have been carried out, and it has been concluded that decreasing the distance leads to a decrease in the resonant frequency of the system of connected circuits. The developed model allows us to obtain the values of the circuit capacitances for the formation of resonance, move on to practical implementation and verify the resulting models.

Design of a bulk-lead zirconate titanate ultrasonic transducer array addressing specific excitation modes

Conventional ultrasonic transducer arrays generally use simultaneous or delayed excitation methods to generate various types of wave fronts in ultrasonic testing. Such array excitation modes are relatively simple and unable to maximize the functions of the array elements or element apertures. Accordingly, this study developed a novel excitation ultrasonic transducer array with flexible excitation aperture. A minimum row-column-addressing planar array structure for ultrasonic transducers based on bulk lead zirconate titanate (PZT) was designed for industrial ultrasonic testing. In addition, a transducer structure design scheme and truth table for array addressing with excitation logic were provided. By performing an acoustic field simulation, this study analyzed the relationship between the longitudinal amplitude and resonant frequency of the array elements and the impedance distribution. The transducer was fabricated and packaged using a circuit board and bulk PZT array elements. Testing revealed that the resonant frequency of the array was 1.07 MHz, the effective electromechanical coupling coefficient was 0.40, and the fractional bandwidth of the pulse echo response and spectrum was 38.46%. Using an aluminum block, performance in single-element, row-, column-, and full-array excitation was tested, and echo curves were obtained for multiple apertures. Using a single-circuit module, the transducer realized flexible gating and excitation of the array elements. The research provided a new method for industrial ultrasonic transducer array design.

Multifunctional coil technique for alignment-agnostic and Rx coil size-insensitive efficiency enhancement for wireless power transfer applications

This paper presents a multifunctional coil technique to enhance the transfer efficiency of an inductively-coupled wireless power transfer (WPT) system, regardless of the alignment condition and size ratio between the transmitter (Tx) and receiver (Rx) coils. The technique incorporates an auxiliary coil on the Tx side, where current is induced through coupling from the primary coil. Since the Tx coil consists of two coils, transmission to the Rx occurs through the coil with the higher coupling coefficient, determined by the misalignment state. Additionally, by controlling this current using a varactor placed on the auxiliary coil, an optimal magnetic flux is generated based on the alignment condition and/or the size of the Rx coil. In perfect alignment, the auxiliary coil focuses the flux from the Tx to the Rx coil, maximizing transfer efficiency. In misalignment scenarios, the current on the auxiliary coil is adjusted to shift the effective center of the Tx coil, achieving the strongest alignment of the magnetic flux traversing the Rx coil. This adjustment, which can be controlled adaptively based not only on the degree of misalignment but also on the size of the Rx coil, enables virtually null-free operation across varying misalignment conditions and for different Rx sizes. Furthermore, as this multifunctionality of the proposed system is achieved with a minimal number of additional components-just a single auxiliary coil and a single varactor-the impact on the overall quality factor (Q) of the system is minimized, contributing to the higher efficiency. In a size-symmetric system, where the Tx and Rx coils have the same size, the efficiency reaches 98.1% in perfect alignment and remains above 60% with up to 135% misalignment relative to the largest coil dimension. In a size-asymmetric system, with the Rx coil reduced to a quarter of the Tx coil, the efficiency is 96.1% in perfect alignment and remains above 60% up to 95% misalignment. Despite its enhanced practicality through a simple structure featuring only one auxiliary coil and an asymmetric configuration integrated solely on the Tx side, the proposed technique surpasses previous methods by delivering significantly superior performance. Moreover, it demonstrates unprecedented tolerance to both misalignment and smaller Rx coil sizes, which is frequently encountered in practical applications.