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The group of matrices P 1 of Pauli is a finite 2-group of order 16 and plays a fundamental role in quantum information theory, since it is related to the quantum information on the 1-qubit. Here we show that both P 1 and the Pauli 2-group P 2 of order 64 on 2-qubits, other than in quantum computing, can also appear in dynamical systems which are described by non-self-adjoint Hamiltonians. This will allow us to represent P 1 and P 2 in terms of pseudofermionic operators. [ABSTRACT FROM AUTHOR]

Abstract The auto‐passing neutral section (ANS), applied in the traction substation or section post (SP), is one of the effective methods to improve the continuity of power supply, and the electromagnetic transient is the key issue impacting its application value. An equivalent switching circuit is established to reveal the causes of the electromagnetic transient. The suppression methods for reducing transient overvoltage and inrush current are proposed, adopting an improved RLC filter to suppress the transient overvoltage with low active power loss, and a switching strategy to minimize magnetic flux variation. The correctness of the proposed methods has been confirmed by simulation and experimental results, which can improve the transient performance and increase the practicality of the ANS.

Improving tactile sensation by vibrating insoles was recommended to prevent foot ulcers in diabetic peripheral neuropathy (DPN). Lack of an insole design for diabetics was a challenge. Clinical trials on applying vibrating insoles with noise and stochastic resonance (SR) stimulating tactile were also required. In this study, vibrating foot orthoses (VFO) with a total contact design based on orthotics were proposed to provide proper insoles for diabetes. This study aimed to determine if VFO were beneficial at enhancing tactile in DPN. VFO were developed in combination with individual’s custom-made foot orthoses and stimulation signals—integrating random 0–100 Hz square wave pulse signals with pseudorandom white noise by a SR approach. Sixty patients with mild-to-severe DPN were randomized to conduct crossover experiments: using and without VFO for 60 minutes stimulation at 90% of individuals’ vibration perception threshold (VPT) level. VPT values when using VFO at the 1st and 5th metatarsophalangeal joints of the left foot decreased by 9.35% (${P} \lt $.001); 9.04% (${P} \lt $.001), and of the right foot decreased by 7.63% (${P} \lt $.001); 7.24% (${P}~\lt $.001), respectively. Without VFO, there was no significant difference. Subgroups of mild and moderate DPN tended to benefit greatly from utilizing VFO. VFO can improve tactile in DPN. VFO may contribute to restoring/prolonging tactile and protective sensations, also decreasing peripheral nervous system deterioration. VFO might be useful for neurorehabilitation, and help prevent foot ulcers and disabilities. [ABSTRACT FROM AUTHOR]

Interventional magnetic resonance imaging (MRI) could allow for diagnosis and immediate treatment of ischemic stroke; however, such endovascular catheter-based procedures under MRI guidance are inherently difficult. One major challenge is tracking the tip of the catheter, as standard fabrication methods for building inductively coupled coil markers are rigid and bulky. Here, we report a new approach that uses aerosol jet deposition to three-dimensional (3-D) print an inductively coupled RF coil marker on a polymer catheter. Our approach enables lightweight conforming markers on polymer catheters and these low-profile markers allow the catheter to be more safely navigated in small caliber vessels. Prototype markers with an inductor with the geometry of a double helix are incorporated on catheters for in vitro studies, and we show that these markers exhibit good signal amplification. We report temperature measurements and, finally, demonstrate feasibility in a preliminary in vivo experiment. We provide material properties and electromagnetic simulation performance analysis. This paper presents fully aerosol jet-deposited and functional wireless resonant markers on polymer catheters for use in 3T clinical scanners.

All-photonic response in Silicon (Si) nanoparticles is dominated by magnetic resonance, leading to enhance light concentration for energy harvesting and magnetic imaging applications. The resonance phenomena occur when the natural frequency of the system matches external excitation and is well-explained by linear circuit analysis. In this paper, we propose a spherical wave impedance approach by employing the basic concept of impedance known at microwave frequencies, where it is defined as the ratio of the electric and magnetic fields to derive necessary magnetic resonance conditions. The model is used to derive various cross-section efficiencies, with results showing close agreement with the Mie solution. The proposed model is simple and compact and defines the resonance phenomena in Si nanoparticles using lumped circuit components, which is necessary for the large-scale all-photonic application of magnetic resonance using dielectric nanoparticles. [ABSTRACT FROM AUTHOR]

This article presents a novel low-cost, single-switch, high-step-upresonant dc–dc converter with high reliability. The proposed converter topology comprises a low count of components and a simple structure and achieves the low ripple input current characteristic. The inductors in the resonant network participate in the resonant process rather than creating voltage spikes across the switch and likely reverse recovery problems. The circuit operates in the soft-switching condition (ZVS–ZCS conditions in the turn-off and turn-on transitions), leading to a significant reduction of the switching losses. Moreover, employing film capacitors instead of electrolytic capacitors reduces the size of the circuit and improves reliability. The operational principle and comprehensive steady-state analysis in the continuous conduction mode are discussed in detail, alongside the design considerations of the proposed converter. The validity of the theoretical equations is investigated via experiments, achieving maximum efficiency of 97.69% for a converter designed at the input of 24.5 V, the negative output of 200 V, and the maximum powerof 200 W. [ABSTRACT FROM AUTHOR]

Most existing capacitive power transfer (CPT) circuits are developed from basic series–series CPT compensation, which have a common drawback of unavoidable reactive power circulating from the primary side of the capacitive coupler to its secondary side, causing reactive power loss, weakening power transfer capability, and aggravating electric field emission. To solve these concerns, this letter proposed a parallel–parallel (PP) compensation-based CPT system with double-side series–parallel (SP) inductive power transfer (IPT) links. The PP CPT compensation aims at zero reactive power circulating while the SP IPT links achieve high-power transfer capability. A 2.5-MHz prototype is implemented, and experiments validate the zero reactive power circulating property with 3.55 kW output power at a 94.2% dc–dc efficiency, and the peak efficiency achieves 94.6% at 1.62 kW output power. This letter is accompanied by slides as multimedia material demonstrating the motivations, contributions, and advantages over existing state-of-the-art CPT designs. [ABSTRACT FROM AUTHOR]

LLC resonant converter is widely used due to its soft switching, high power density, and high efficiency. To incorporate the merits of the LLC resonant tank into a three-phase single-stage ac/dc converter, this article proposes a three-phase single-stage ac/dc converter based on Swiss rectifier and three-level LLC topology. It takes advantage of the high-efficiency Swiss rectifier to convert three-phase ac voltages into three variable dc voltages and interface a three-level LLC resonant circuit. With help of the LLC resonant tank, all the high-frequency three-level switches achieve soft switching. To both regulate the output voltage and achieve three-phase power factor correction, the frequency modulation in combination with the duty cycle control strategy is employed by splitting the resonant current into three parts and then forming three phase sinusoidal currents. The proposed converter's detailed operation principles, steady-state characteristics, and design considerations are given. Finally, a 10 kW experimental prototype with three-phase 220 Vac inputs and 500 Vdc output is built to verify the effectiveness and feasibility of the proposed topology and its control strategy. [ABSTRACT FROM AUTHOR]

The stepwise common-mode (CM) voltage at the output of inverters causes electromagnetic interference (EMI) and damage to motor bearings. This article proposed a new output active CM filter (ACF) to compensate for the steep rising/falling edges of CM voltage for EMI reduction and bearing protection. An input ACF is also necessary to attenuate the CM noise injected into the grid. Hence, a holistic assessment of input and output ACFs for inverter-fed motor drive systems has been demonstrated. The motor drive system satisfies the CM EMI standard with this new active CM filtering architecture. Ferrite materials and winding configurations of the CM transformer used in the output ACF have been investigated. Moreover, the relationship between the input and output ACFs has been discussed. This article aims to provide new perspectives and implementation guidelines for the ACFs in motor drive systems. [ABSTRACT FROM AUTHOR]

Bipolar dc distribution systems face imbalances in voltages when unbalanced loads are connected at the outputs. To address imbalances in bipolar voltage levels, dedicated voltage balancers are required. However, they add extra active and/or passive components; including, magnetics, capacitors, etc. This increases the cost, reduces the conversion efficiency, and power density of dual-output converters. Therefore, to tackle the imbalances in output voltages without adding any extra active and/or passive components, this article presents coupled inductor (CI) based voltage balancing in dual-output CLL resonant converter. The main features of the proposed method are as follows: since CI is the result of already present resonant inductors of CLL tank circuit, therefore, it does not require extra magnetic components to balance the output voltages; with no additional components, it does not increase the magnetic volume, component count, cost, and complexity of the converter; due to the direct coupling, a half of circuit inductances are integrated to achieve the respective resonant inductance of the tank circuit; and it can also avoid complex control schemes applied to voltage balancing. Besides, with the proposed CI, the CLL converter maintains all of its good features including; zero-voltage and zero-current-switching (ZVZCS). The detailed analysis of the proposed CI with different load conditions is discussed. Moreover, LLC or Type-12 resonant tank circuit is presented to validate ZVZCS operation in the reverse power flow condition. To verify the effectiveness of the proposed CI based voltage balancing, a 3.6-kW hardware prototype has been built and tested. [ABSTRACT FROM AUTHOR]

This letter reports characterization of the novel nanocrystalline flake ribbon (NFR) soft magnetic material. The comparative analysis among the ferrite N87, N27, and the NFR is presented at different temperature, frequency, and peak magnetic flux density, respectively. Experimental results prove that the NFR has lower loss density, higher magnetic flux density saturation, and better temperature stability from 85 to 300 kHz. A LCL resonant tank based circuit is employed for large signal characterization. The mass-based stacking factor of the NFR core is adopted to describe the core structure. This letter suggests that the NFR is a good alternative to the ferrite for high power magnetic cores due to its superior performance and flexibility structures. [ABSTRACT FROM AUTHOR]

This brief focuses on the asynchronous bumpless transfer finite-time $H_{\infty }$ control problem for a class of Markovian jump systems (MJSs). The hidden Markov principle is introduced to represent the asynchronous jumping phenomenon between the MJSs and the designed bumpless transfer finite-time $H_{\infty }$ controller. The asynchronous jumping transient behavior of MJSs is described by using a bumpless transfer constraint index. First, an asynchronous bumpless transfer constraint is proposed to limit the control bumps caused by asynchronous jumping. Then, an asynchronous bumpless transfer finite-time $H_{\infty }$ controller is constructed, and sufficient conditions are given to ensure the finite-time $H_{\infty }$ performance for MJSs under the proposed asynchronous bumpless transfer method. Finally, an RLC circuit model is provided as an application example to show the effectiveness of the proposed control method. [ABSTRACT FROM AUTHOR]

High-voltage/high-power capacitor chargers are primarily interested in many industrial applications. Resonant converters have been a proper choice in such applications because of their advantages. However, the performance of the resonant converter is highly affected by the parasitic elements of the high-voltage/high-power transformer. Also, a short-circuit condition is a frequent event in high-voltage applications, so that the resonant converter should be robust against the short-circuit condition. This article presents a novel LCCL resonant converter with current-source characteristics used as a high-voltage capacitor charger. The proposed resonant converter eliminates the undesirable effect of the stray capacitance in high-voltage devices and is robust against the short-circuit condition inherently. It also provides a semitrapezoidal resonant current wave, which produces a lower crest factor. Furthermore, a frequency-sweep operation is applied, which has advantages in reducing the resonant current's peak value and the resonant network's size. Simulation results show a satisfactory performance of the proposed resonant converter. Moreover, experimental results confirm the effectiveness of the proposed resonant converter in the application of capacitor charging. [ABSTRACT FROM AUTHOR]

This article presents the analysis of a converter based on an LLC resonant output inverter and its optimal design used in induction heating applications. The new optimal design method improves several operating parameters that leads to an optimization of the dimensioning of the components of the converter. Additionally, this converter achieves an output power factor that can be considered optimal since it allows to minimize the reactive power of the resonant circuit components and reduces the rms values of the output current of the inverter and the current of its switching devices in relation to that found in traditional designs. A complete study of the circuit based on classic models is carried out to introduce simple rules for the design of this type of inverter for induction heating applications and to control its output power based on a phase shift (PS) system. Since the inverter is made with silicon carbide MOSFET transistors, an efficiency greater than 99% is reached. The experimental results were obtained from the test of a 12 kW 20 kHz converter for induction heating application. [ABSTRACT FROM AUTHOR]

Contribution: Two general rules for calculating, in the time domain, step discontinuities of voltages and currents in electric circuits, combining physical principles and basic mathematical treatment. The two general rules, resulting from a formal method of analysis, provide a straightforward way to update the states of a circuit, immediately after the occurrence of switching or impulsive excitation. Among its advantages, they can be used to simplify the numerical simulation of elaborate circuit topologies by avoiding approximate models of impulsive sources or switches. Background: In most engineering undergraduate textbooks, the effects of switching and impulsive sources on higher order electric circuits are usually studied for the particular case of linear time-invariant (LTI) circuits in the Laplace transform domain. This approach, however, can be time consuming and demands little reasoning on the physical principles of circuit operation. Moreover, it is not adequate for linear time-variant or nonlinear circuits. Intended Outcomes: Step discontinuities in electric circuits, caused by switching or impulsive sources, are identified and calculated through the method, allowing complete responses to be obtained afterward. Not only can the method be extended to linear time-variant and nonlinear circuits but it also has interesting consequences in numerical simulation of circuits. Application Design: An application exercise and a set of conceptual questions on the subject were proposed to electrical engineering students. Findings: The analysis of the educational experiment indicates that applying the method presented herein improves the students’ ability to obtain initial conditions of circuits, being a more straightforward and effective approach than using Laplace transform techniques. [ABSTRACT FROM AUTHOR]

This article presents a commutated-inductor–capacitor (commutated- $LC$) or switched- $LC$ circuit that acts as a radio frequency (RF) delay line. Thanks to its linear-periodically time-varying (LPTV) operation and fully passive implementation, it concurrently achieves long maximum delays, fine delay tuning steps, and wide instantaneous bandwidths while being low loss and highly linear. Unlike existing LPTV switched-capacitor broadband delays, the introduction of inductors in the proposed commutated- $LC$ delay circuit provides a new degree of freedom, allowing it to operate at a much higher RF with a wider instantaneous bandwidth. A proof-of-concept prototype in a 65-nm CMOS process demonstrates a measured 1.3-GHz 3-dB bandwidth around a 4.3-GHz RF, i.e., a 30% fractional bandwidth, when clocked at 250 MHz. The measured maximum delay is 1.4 ns with a 23-dB loss and noise figure; this loss or noise is orders of magnitude lower compared with fully passive linear-time-invariant RF delay lines operating at a similar frequency with the same delay. The measured IIP3 is +16 dBm. [ABSTRACT FROM AUTHOR]

The radome absorber, always be defined as rasorber, is investigated based on the SiO $_{2{\text{f}}}$ /SiO $_{2}$ fiber-reinforced ceramic matrix composite (CMC) for high-strength environment. The prominent advantage of using CMC as the substrate is that it can significantly improve the power capacity and environmental tolerance of the rasorber. The surface roughness and the dielectric stability are considered key factors in the electromagnetic-material codesign. Silica sol is used to densify the surface of fiber CMC for screen printing, and the process is characterized by scanning electron microscopy. The passband can be controlled by integrating p-i-n diodes on the screen-printed silver paste. The equivalent ground condition for the bandpass reflector is theoretically analyzed, and ideal integration of absorbing and transmitting functions is achieved. Afterward, a CMC-based rasorber is manufactured. A dual-polarized transmission window at 1.6 GHz can be triggered, while a low radar cross section (RCS) band is designed from 2.7 to 4 GHz. Transmission and RCS characteristics of the CMC rasorber under 25–700 $^{\circ }$ C environment are both analyzed. The tensile, compressive, and flexural strength of the proposed CMC rasorber are tested, and the electromagnetic properties are verified using compact antenna test range. [ABSTRACT FROM AUTHOR]

The transcutaneous energy transmission system (TETS) has been studied for wireless power supply in ventricular assist devices embedded in the body. To be approved as a medical device, it is necessary to measure the high-frequency patient leakage current (Ip) and to suppress it to a safety limit below 10 mA. However, it is difficult to suppress because the terminal voltage and the frequency of the transmitting coil are extremely high (500 V and 400 kHz). In this study, we propose an original measurement method for Ip in TETS and measure the Ip. Furthermore, the suppression method of Ip is investigated using a high-frequency isolation transformer (HFIT) and an insulation sheet for transmitting coils. Consequently, an Ip of 17.14 mA is obtained when the HFIT without countermeasures and an insulation silicone sheet is used (Type A), whereas an Ip of 7.68 mA is obtained when using two series-connected HFITs and an expanded polystyrene sheet with a thickness of 3.58 mm (Type B). Thus, it is possible to drastically suppress Ip below 10 mA. Additionally, we define the combined capacitance CCom based on the series connection of the capacitance of the insulation transformer Cp and that of the insulation sheet Cc and calculate the theoretical Ip. The theoretical Ip decreases from 20.8 mA for Type A to 5.6 mA for type B. The calculation results of Ip are mostly in agreement with the measurement results, indicating that a reduction in CCom is important for suppressing Ip of the TETS. [ABSTRACT FROM AUTHOR]

In this article, a high-frequency (HF) six-port delta- and star-connected three-phase induction motor model is proposed. The model consists of multistage RLC circuits, which include the mutual inductances between the phases. The three-phase HF motor model is derived from common-mode (CM) and differential-mode (DM) equivalent circuits, which are extracted from CM and DM measurements on the motor. A methodology is developed to consider the nonlinear DM inductance effect in the low-frequency (LF) range. The per-phase circuit is symmetric concerning the begin and end points. This symmetry allows us to connect a star configuration into a delta configuration by simply changing the phase connections of the proposed three-phase circuit without recalculating the parameters and vice versa. The three-phase motor model is eventually combined with external circuitry and simulated by a standard circuit solver. The proposed model allows impedance predictions with good accuracy up to 100 MHz. The method is verified with two induction machines, which have 3- and 11-kW rated powers. The proposed HF six-port three-phase motor model can be used for decoupled CM and DM noise predictions as well as for six-port mixed-mode noise prediction. [ABSTRACT FROM AUTHOR]

A high selectivity frequency selective rasorber (FSR) with an ultraminiaturized unit based on 2.5 dimensional (2.5-D) parallel resonator (PR), exhibiting low insertion loss passband between two absorption bands, is investigated. The lossy unit is realized by inserting a 2.5-D strip-type PR structure into the center of each side of the metal square ring and loaded with resistors connected at the four corners. The novel 2.5-D PR consists of interdigitated capacitors and strip metal wire connecting the other side of the lossy layer obtained by using metallized vias. The 2.5-D PR can effectively alleviate the congestion of the single-sided structures and achieve a high degree of miniaturization by means of tortuous extension inductance structure; as an additional feature, the values of L and C can be independently adjusted to determine the passband frequency allowing to provide additional degree of freedom to the design. An equivalent circuit model is proposed to analyze its operating principle. The dimensions of the miniaturized unit are 0.13λf × 0.13λf × 0.16λf (being λf the free space wavelength at the passband). A transmission window with low insertion loss of 0.125 dB is obtained at 4.65 GHz under normal incidence. The fractional bandwidth for −10 dB reflection is about 96%. The miniaturized FSR satisfies the characteristic of polarization insensitivity (TE and TM) and angular insensitivity (up to 45°). A prototype of miniaturized FSR has been manufactured and measured, showing a reasonable agreement with simulations. [ABSTRACT FROM AUTHOR]

This paper presents a passive lumped model for DC cables and overhead lines, taking into account the frequency dependency of the per-unit-length parameters due to the skin and proximity effects. In comparison to distributed parameter line models, such as the Frequency-Dependent Phase model of PSCAD, the proposed model does not require line propagation delay extraction and does not impose any restrictions on the simulation timestep. As a result, for electrically short lines, the introduced model is more computationally efficient than distributed parameter models as it enables simulation using larger timesteps. The performance of the proposed model is evaluated in comparison with the PI model and the Frequency-Dependent Phase model through time-domain simulations of a DC microgrid and a radial DC distribution feeder. The studies performed in PSCAD focus on fault-induced transients. The results indicate that for electrically short lines the developed model is significantly more accurate compared to the PI model and provides similar accuracy with more computational efficiency compared to the Frequency-Dependent Phase model. [ABSTRACT FROM AUTHOR]

The MHz series resonant converter (SRC) dc transformer (dcX) is attractive for its good soft-switching characteristics, which is suitable for high efficiency high power density applications. For a 380–12 V dcX, it has been proved that using series-connected low voltage devices with low NFoM can reduce the conduction loss of the switches [Wu and Shi (2020)]. However, its large driving loss at megahertz frequency becomes a concern, which restricts the further improvement of the efficiency. Furthermore, numerous drivers are required for the series-connected devices and the power density is deteriorated. To reduce the driving loss and improve the power density, a low-profile multioutput resonant drive transformer is applied to the SRC dcX in this article. However, without a well-designed drive speed, the dead time provided will be inappropriate, leading to increased losses or even loss of ZVS in SRC. By properly designing the parameters of the drive circuit, ZVS can be both achieved for the SRC and the drive circuit, diving loss and footprint are reduced significantly and symmetry drive voltages can be achieved. A 380–12V/170A 1 MHz dcX prototype with the reduced power magnetics and the proposed resonant drive transformer is built up, which achieves 98.4% peak efficiency and 1.3 kW/in3 power density. [ABSTRACT FROM AUTHOR]

The limitation in enhancing the absorption bandwidth of a microwave absorber with a thin thickness in the ultrahigh-frequency (UHF) band has become an important challenge in the electromagnetic scattering field. Therefore, in this study, a new design concept of a single-layer impedance-well (IW) passive absorber is put forward for the first time, which exhibits enhanced absorption bandwidth and effectively approaches the Rozanov thickness limit for passive absorbers. The design concept proposed in this study is explained by using the transmission line theory and circuit analysis. Furthermore, the input impedance and electric field distribution of the IW absorber are systematically analyzed to demonstrate the existence of the IW effect and the predicted functionalities of the IW absorber. The simulated and measured results reveal that the designed absorber with the IW effect can obtain an absorption band over 0.45–2.34 GHz range with a bandwidth ratio (BWR) of 5.2 (135.5%) at a minimum reflectivity reduction of −10 dB under normal incidence. In addition, the thickness is reduced to $0.069 \lambda _{{\mathrm {L}}}$ , which $\lambda _{{\mathrm {L}}}$ is the wavelength at the lowest operating frequency. [ABSTRACT FROM AUTHOR]

Tendon and ligament injuries are common complications in orthopedic and sports medicine. Tears to tendons and ligaments, many of which are treated surgically via suturing, require postoperative physical therapy to restore tissue structure and function. However, to effectively treat these injuries, the duration and intensity of rehabilitation need to be regulated to prevent tissue reinjury while promoting regeneration. Currently, physical therapy procedures following tendon and ligament repair rely on qualitative factors such as tissue swelling or patient pain tolerance, which can prevent optimal healing outcomes due to the patient and medical caregiver variability. Therefore, the goal of this project is to develop and characterize a sensing platform for detecting tension magnitude in sutures for rehabilitation applications. Specifically, a wireless suture pledget sensor was engineered to provide quantitative biofeedback during physical therapy by monitoring tension in sutures after soft tissue repair. To measure suture loading, an electrical resonance biosensor was integrated into the design of commercially available suture pledgets. This innovative approach had many advantages over previous suture monitoring systems including remote operation and passive function. In this work, a prototype suture pledget sensor was fabricated for proof-of-concept functionality studies. Loading experiments showed that the sensor could reliably detect suture loading forces ranging from 2 to 12 N, while signal transmission distance through tissue mimics was tested up to 16 mm. Overall, this device could be used to develop evidence-based physical therapy guidelines to accelerate rehabilitation and improve healing outcomes for patients with tendon and ligament injuries. [ABSTRACT FROM AUTHOR]

A novel single-stage ac/dc isolated onboard charger with modular stacked switches structure utilizing interleaved control is proposed in this article for high-voltage (HV) battery systems in electric vehicles (EVs). In the proposed converter, modular interleaved bridgeless ac/dc boost converters are integrated with modular CLL resonant circuits through sharing the two legs of stacked switches. With this configuration, the voltage stress across each switch is reduced to half of the dc-link voltage, which makes the circuit applicable for HV battery system (such as 800 V) in EVs. In the proposed design, the integrated interleaved boost circuit modules allow low input current ripple to be achieved. Two step-up resonant circuit modules are then connected to the two interleaved legs with their outputs connected in series at the input of a current-fed high-frequency rectifier. Soft-switching commutation is achieved for all switches and diodes in the proposed converter. The descriptions of the proposed converter and its operating principles will be discussed in this article. A silicon-carbide-based hardware prototype with a rated power of 2.4 kW, 90–135 Vac/800 Vdc system has been tested in the laboratory. Results confirmed that a power factor of 0.97 and a peak efficiency of 97.9% were achieved. [ABSTRACT FROM AUTHOR]

In many technical applications at low frequency, wave propagation effects can be neglected, and Darwin models promise to accurately describe the electromagnetic fields because they include resistive, inductive, and capacitive terms. In a former work, we developed an efficient, frequency stable method to solve the full Maxwell model, i.e., without neglecting any effect. This method employs the electro-quasistatic gauge, which allows to cleanly separate the calculation of capacitive effects in a first step, from the calculation of inductive effects in a consecutive second step. The Darwin model in frequency domain and electro-quasistatic gauge can easily be derived from this method by neglecting just one term, namely the induced displacement current. Here, we compare this Darwin model with the full Maxwell model, e.g., for the example of an $RLC$ -series circuit. We found that this Darwin model cannot describe the interaction between $L$ and $C$ in the $RLC$ -circuit. [ABSTRACT FROM AUTHOR]

High voltage direct current (HVDC) systems have been increasingly employed to provide a connection amongst various energy sources, especially renewable energies. In order to switch the load current in these systems, the passive resonance breaker (PRB) is employed as a transfer switch. The interruption capability of the PRBs is highly dependent on the dynamic behavior of the arc in this system. Accordingly, this article presents a black-box high-degree of freedom arc-model based on Schwarz and the genetic algorithm as a heuristic optimization to follow the characteristics of the static and quasi-static arc regarding the oscillation frequency of the interruption current. The model has been verified by the published experiments. Subsequently, the PRB operation has been quantified based on the state-space approach along with an accurate dynamic arc model to follow in a wide frequency range of the arc current. The results are indicated that the amplification coefficient alone is insufficient to determine the interruption capability of these protection tools. Therefore, this article attempts to quantitatively determine the interruption capability curve by introducing criteria, such as ΔtPZ (peak to zero time-interval), diarc/dtCZ- and duarc/dtCZ+ to obtain the origins of the interruption failure probabilities and dimensioning of the PRBs with respect to the interruption limits for gas blast CBs. [ABSTRACT FROM AUTHOR]

This article studies and summarizes the operating characteristics of a ${G}$ -band folded waveguide traveling wave tube (TWT) amplifier enhanced by the $\pi $ -mode extended interaction cavities. Compared with conventional ${G}$ -band TWTs, the proposed amplifier can at once obtain a higher gain in a shorter interaction circuit length and ensure a proper operating bandwidth. The key of the design is introducing the $\pi $ -mode multigap resonant cavity with alternating wide and narrow slots, which will improve the working performance of the whole device by shortening the length of the interaction circuit, enhancing its interaction effect, and improving its gain of unit length. In this design, the operation bandwidth is expanded by stagger tuning technique. In addition, the influence of cavity loss is examined so that the optimal performance is achieved. The PIC simulation results show that when the operating voltage is 21 kV and the operating current 80 mA, the maximum average output power of the designed TWT amplifier is 65.78 W at 217.4 GHz, which is corresponding to the maximum gain and efficiency of 37.38 dB and 3.9%, respectively. The gain per unit length is 12.64 dB/cm and the 3-dB bandwidth is 3.5 GHz. [ABSTRACT FROM AUTHOR]

Traditional multichannel wireless power transfer (WPT) systems suffer from the complex system structure and cross-interference among receivers. To solve such problems, this article presents the design and control methods of a decoupled multichannel WPT system based on multilevel inverters. A single-phase multilevel inverter is utilized to drive the transmitter circuit with a voltage waveform consisting of multiple components. Particularly, these components are independent in the frequency spectrum, and their amplitudes can be controlled independently. Moreover, primary compensation is used to offer multiple frequencies for the primary circuit. Additional damping filters are used in the secondary circuits to reduce the cross-interference between the receivers. In addition, the features of the system topology are analyzed, and an exact parameter design method is presented. Furthermore, combined with the neutral point voltage balance strategy, a simple vector-based control method is proposed to regulate the transmitted power in each power channel. As a result, the power can be transferred to loads through the designed power channels simultaneously without mutual interference. Finally, both simulation and experiment of a 1-kW experimental prototype with SIC-MOSFET are given to verify the feasibility of the proposed multichannel WPT system and the control strategy. [ABSTRACT FROM AUTHOR]

In order to solve the problem of high voltage spikes on the secondary side of the high-frequency transformer when the three-phase high-frequency isolated matrix inverter (HFIMI) operates under the conventional modulation strategies, a new modulation strategy is proposed without introducing an auxiliary circuit. In the proposed scheme, the H-bridge inverter adopts phase-shift control. The matrix converter (MC) adopts the voltage-type de- and recoupling idea, and the decoupled positive and negative group inverters are, respectively, applied with a modified Space vector pulse width modulation (SVPWM) strategy to operate synchronously with the H-bridge inverter. When the H-bridge inverter is in dead-zone mode, the switching tubes of MC are all turned on to provide continuous flow paths for leakage inductance and output filter inductance current and suppress high voltage spikes. The operating mode of the three-phase HFIMI under the proposed modulation strategy is analyzed in detail, the realization conditions for soft switching are designed, and the soft-switching ranges are also discussed. The feasibility and validity of the voltage spike suppression strategy are verified by building a 3-kW principle prototype. The experimental results show that the voltage spikes are effectively suppressed, all switches achieve zero-voltage soft-switching, and the peak efficiency of the three-phase HFIMI can reach 95.2%. [ABSTRACT FROM AUTHOR]

In the analysis of most circuit analog (CA) absorbers, it is only the absorption performance under normal incidence that is taken seriously, leading to a much worse absorption with the increase of incident angle, especially when it is larger than 30°. In this communication, a novel absorber, which consists of a conductive square-loop (SL) array embedded with lumped resistors and a well-designed wide-angle impedance matching (WAIM) layer, is proposed. Equivalent circuit (EC) and strict formula derivations are introduced to present a great insight into the deterioration of absorption performance under oblique incidence and the effect of WAIM layer. An absorber sample is further fabricated and measured for verification. It is shown through measurement that the structure has a fractional bandwidth of 137.1% for at least 10 dB reflection reduction under normal incidence. When the incidence angle is increased to 45°, the overlapped bandwidth for both transverse electrical (TE) and transverse magnetic (TM) polarizations is still measured to be 110.5%. [ABSTRACT FROM AUTHOR]

An extremely high scanning-rate beam-steering antenna based on coupled resonators is proposed in this communication. Coupling resonators in a controlled manner provides a sharp phase variation across a narrow frequency band, which contributes to the extremely high scanning rate. To steer the beam across broadside, alternating +90° and −90° impedance inverters are employed in the topology. Such a coupled-resonator array antenna is modeled and analyzed by coupling matrix technique, which was conventionally used in filter design. To illustrate the proposed technique, two examples with 50 and 100 MHz bandwidths are designed. Experimental validation is also provided for the 50 MHz bandwidth example, which demonstrates that the proposed antenna reaches a high relative scanning rate of $52.8^{\circ }/\%BW$ with efficiency of 75%. [ABSTRACT FROM AUTHOR]

This article proposes the high-frequency link three-phase integrated-optimized power electronic transformer (PET) for electric vehicle (EV) charging infrastructure in the distribution network. The structural elements and configuration of PET significantly affect its design and performance. However, the different topologies of PET available in the literature did not consider the influence of the circuit’s structural elements with their parasitic components. Consequently, it violates the value of control variables which fails to accomplish essential control characteristics required for EV charging infrastructure in the smart distribution network. Therefore, in this article, detailed modeling and analysis of the proposed PET are carried out at each stage by incorporating its structural effect to analyze the circuit behavior during different operating conditions. As a result, it provides the design and operating constraints for the proposed PET, employed in the design procedure and control algorithm. Furthermore, the dual-degree control (DDC) method is proposed to utilize the structural framework and dual control variables of the proposed PET to meet out significant aspects of EV charging infrastructure in the distribution network such as wide range of voltage regulation, active control over the power flow, and soft-switching operation. Finally, a 4-kW prototype of the proposed PET is built up, which has a bidirectional power flow feature and isolated dc dual-port output terminals. Hardware testing and experimental results verify the effectiveness of the proposed PET based on the DDC method. [ABSTRACT FROM AUTHOR]

DC short-circuit current calculation is necessary to design and protect modular multilevel converter-based (MMC-based) multiterminal dc (MTDC) grids. In this article, a general and analytical short-circuit current calculation method is proposed for bipolar MTDC grids. For pole-to-pole (P2P) faults, the superposed fault equivalent network of the MTDC grid is first developed in the frequency-domain. Then, a decoupling method based on the network inductance ratio is proposed, which simplifies the high-order network into the superposition of several independent two-order RLC circuits. As a result, the short-circuit current can be expressed as the sum of the currents of these RLC circuits. For pole-to-ground (P2G) faults, the phase-domain dc line impedance considering the coupling effects is determined based on its modal-domain parameters, so that the P2G fault current can be calculated using the method of the P2P fault. The proposed method’s effectiveness is verified through simulations and experiments, and the calculation error is classified and analyzed. Compared with the existing methods, the proposed method is more accessible, more accurate, and available for hand-solution. [ABSTRACT FROM AUTHOR]

Fishtail divertor (FTD), a new divertor concept, is a significant research object of Experimental Advanced Superconducting Tokamak (EAST) tokamak divertor system. In order to meet the requirement of sinusoidal current precision and variable frequency, the combination of inductance and capacitance (LC) series resonance theory and high-frequency pulsewidth modulation (PWM) technology is put forward. A sine wave power supply with multifrequency points (1–3800 Hz) and current up to 8000 A is developed. The FTD power supply (PS) adopts dc switching power technology, sinusoidal PWM (SPWM) technology, and LC series resonance theory. The operating points of output current include 10–20 Hz at 8000 A, 30–110 Hz at 5000 A, and 1300–3800 Hz at 2400 A. The electromagnetic environment in the device is complex and arguable. The output current accuracy can reach 5% by the current feedback and frequency feedback control strategy. The test results demonstrate that the FTD PS can meet the system requirements, and it has strong reference significance, which can provide reference for the design of other divertor PS. [ABSTRACT FROM AUTHOR]

In this article, a compact distributed septuple-band negative group delay circuit (NGDC) is proposed and analyzed. It is mainly composed of a high–low–high step-impedance microstrip line with an E-shaped groove and two T-shaped open stubs. This NGDC was first simulated and then fabricated by using a conventional printed circuit board (PCB) process with the substrate of RO4350. To investigate the operational mechanism of the NGDC, an equivalent circuit, consisting of nine transmission lines, four series–parallel LC resonant circuits, and two T-type series LC resonant circuits, has been developed and analyzed. It is found that the theoretical group delay characteristic calculated from the equivalent circuit agrees well both with the simulated data by using ADS as well as HFSS and with the experimental results. The measured seven NGD resonant frequencies occur at 2.03, 2.84, 8.14, 8.74, 13.0, 16.02, and 18.46 GHz, and the corresponding NGD values read −3.65, −3.04, −1.73, −3.23, −1.16, −1.20, and −1.47 ns. The dimensions of the presented passive NGDC are only 25 mm $\times22$ mm without using any lumped components. [ABSTRACT FROM AUTHOR]

In this article, we present a novel dual-band bandstop filtering cable by surrounding inner wire with asymmetric bridge-connected spiral-shaped defected structure on outer conductor. The simulation results demonstrate that the proposed dual-band bandstop filtering cable can be modeled by two parallel RLC resonance circuits in cascade and the performance can be easily adjusted by changing the structural parameters. The well-designed dual-band bandstop filtering cable can be fabricated by core wire surrounding with polytetrafluoroethylene (PTFE) dielectric layer and polyimide defected conductor layer with asymmetric bridge-connected spiral-shaped defected structures. The proposed filtering cable with ten asymmetric bridge-connected spiral-shaped defected resonators on defected conductor layer has a compact size of diameter 1.66 mm and length 200 mm, and its insertion loss in experimental results is greater than 20 dB at 0.88 and 1.3 GHz. Compared with the traditional microstrip bandstop filter, the proposed dual-band bandstop filtering cable can achieve better stopband and passband performance within more compact size. In essence, it is a cable replacement technology, which can improve electromagnetic compatibility (EMC) performance at system level and equipment level, and has the potential to be widely used in wireless system. [ABSTRACT FROM AUTHOR]

In this article, a modified LLC resonant converter with LC antiresonant circuit in parallel branch is proposed. The proposed converter is derived by placing LC antiresonant circuit on parallel branch. In comparison with LLC resonant converter, the equivalent inductance of parallel branch of the proposed converter decreases along with switching frequency within regulating frequency range. This advantageous property contributes for that the turn-off current and circulating conduction loss in the primary side can be reduced at unity voltage conversion ratio due to large impedance of LC antiresonant circuit. Moreover, by optimizing resonant parameters design of parallel branch based on time-domain analysis, the magnetizing current is in close proximity to a sine wave and the conduction loss in the secondary side will be reduced, especially in the light load. A higher voltage conversion ratio can be achieved at low switching frequency due to decreased impedance in parallel branch. In addition, a design flowchart and a design practical case are given to help to implement an efficiency optimization algorithm to decide five resonant design parameters. Finally, a 2 kW 250 V—400 V-input and 48 V-output prototype is built, and the main experimental results are provided to verify the feasibility of the proposed converter and compare with LLC resonant converter. Comparative state-plane trajectories are depicted to compare their characteristics and to verify the model-domain analysis. [ABSTRACT FROM AUTHOR]

This article presents a detailed circuit analysis of energy selective surface (ESS), which adaptively protects electronic equipment from high-power microwaves (HPMs) thanks to its self-actuated response and nonlinear transmission feature. With the help of the equivalent circuit model (ECM), four types of ESS schemes are individuated and two of them are analyzed in detail to explore the influence of ECM parameters on the performance of ESS. Then, a high-performance ESS is designed through the proposed method. The proposed structure is realized by metal periodic structures loaded with diodes and lumped capacitors. A prototype is fabricated and measured. The results of simulations and experiments agree well, showing that the proposed ESS provides more than 30 dB shielding for high-power signals and an insertion loss lower than 1 dB for low-power signals. The excellent nonlinear transmission characteristic makes the proposed ESS practical for HPM protection. [ABSTRACT FROM AUTHOR]

This paper presents a new sensing method based on passive generalized Parity-Time (GPT)-symmetry with enhanced sensitivity compared with the traditional method in the microwave frequency range. GPT-symmetry circuit that is the basis of the sensing method is derived, facilitating the establishment of a sensor. The perturbation of equivalent lumped elements including R, L and C to reflection coefficients of the circuit is investigated, showing better sensitivity of the resonant frequency shift, and in particular, reflection magnitude change to the perturbation than the conventional method. In addition, the operating frequency in this method can be tuned by the coupling coefficient. An experiment of noncontact measuring concentrations of glucose water is implemented to verify the method, showing the sensitivity in terms of the resonant frequency and reflection magnitude change is 12 MHz/[g/dl] and 20 dB/[g/dl] respectively which have a good consistency with the simulation. Noteworthily, weak coupling needed in this sensor indicates that we can easily carry out long-distance noncontact measurement with the high sensitivity. [ABSTRACT FROM AUTHOR]

This brief presents a model of chaotic oscillator based on leaky integrate-and-fire (LIF) neuron with a switching element, which has an S-shaped current-voltage characteristic (S-IVC), and with nonlinear firing rate coding by control resistor. The circuit contains variable resistance feedback of LIF neuron, which includes a second order filter and two gain modules. Simulation results show that active RC-circuit can be used as a feedback filter and a bipolar transistor can be used as a control resistor. A mathematical model of the chaotic oscillator has been built. The transition to the dynamic chaos occurs according to the scenario of a period-doubling bifurcation cascades. The circuit provides theoretical perspectives for the creating devices of neuromorphic computing based on chaotic dynamics. [ABSTRACT FROM AUTHOR]

Defected Ground Structure (DGS) based on-chip bandstop filter (BSF) design is proposed for millimeter-wave applications. In the proposed structure, a capacitively loaded T-shape resonator is embedded in the original DGS resonator, which forms two high quality (${Q}$ -) factor small loop resonators. Moreover, this structure, in combination with the feedline and series capacitor, independently realizes the position of two transmission poles: one at each side of the parallel resonance without increasing the layout size. The proposed BSF presents a sharp scattering (S-) parameter response due to the appearance of two transmission poles. As a result, the loaded ${Q}$ -factor and negative group delay of the BSF are improved. The prototype of the proposed BSF is fabricated in 0.18- $\mu \text{m}$ Complementary Metal-Oxide-Semiconductor (CMOS) process and measured. The measurement result shows a return loss of 1.78 dB at 53.2 GHz center stopband frequency with the negative group delay of 161 pS. The measurement results also agree well with the electromagnetic simulation results. Without pads, the active area of the prototyped BSF is only 0.024 mm2. [ABSTRACT FROM AUTHOR]

This article proposes a two-mode active balancing circuit for series-connected cell strings. The proposed balancing circuit has two operation modes: any cell to any cell (AC2AC) and direct cell to cell (DC2C) modes. In AC2AC mode, the balancing circuit can be equivalent to an improved switched-capacitor (SC) balancing circuit, and the energy is transferred among all imbalanced cells, implementing the higher balancing speed when the voltage gap between cells and the number of imbalanced cells are large. In DC2C mode, the proposed balancing circuit can be equivalent to a balancing circuit based on three-resonant-state LC unit, and the energy is transferred from the highest voltage cell to the lowest voltage one, achieving the higher balancing efficiency and speed as well as accuracy when the voltage gap between cells is small. The operation state, balancing power, and balancing efficiency of each mode are analyzed in detail. The control strategy and design considerations of the balancing circuit are introduced to obtain the optimal balancing performance. Experimental results are provided to verify the validity of the proposed balancing circuit. The results show that the proposed balancing circuit achieves high balancing accuracy and efficiency as well as balancing speed. [ABSTRACT FROM AUTHOR]

Enhanced active resonant (EAR) dc circuit breakers (DCCBs) are a novel type of DCCB that use a discharge closing switch as interruption medium. A technical limitation of discharge closing switches is the minimum voltage across the main gap required for successful triggering. A novel commutation process creating the minimum voltage internally is proposed, which allows to simplify the EAR DCCB configuration and to reduce its component count. In the prototype, the discharge closing switch is implemented with a TVG. Experiments show that the TVG can be triggered reliably down to a voltage of 50  $\mathrm{V}$ and that the discharge in the TVG is highly oscillatory at low current. The originally proposed EAR DCCB configuration has to be tuned such that the commutation to the TVG succeeds at low current. Conversely, the novel commutation process decouples the minimum voltage from the current level by adjusting the triggering delay. This allows reliable commutation irrespective of the operating conditions. It is shown that the novel commutation process does not adversely affect dc interruption. Proactive commutation operation and auto-reclosing strategies are demonstrated. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive study on the occurrence mechanism, instability analysis, and suppression methods of self-sustained turn-off oscillation, which occurs on cascode gallium nitride high electron mobility transistors (cascode GaN HEMTs). In the beginning, the oscillation waveforms are analyzed, which indicate that the occurrence of the oscillation is determined by test circuit instability. Based on the double pulse test, the impact of the load current $I_L$ , dc bus voltage $V_{\text{DC}}$ and gate resistance $R_{G}$ on the self-sustained oscillation is identified. To investigate the instability of the resonant circuit, a small-signal ac model of the resonant circuit is derived. Based on the model, the influences of various parameters on the self-sustained oscillation are analyzed. The analyses reveal the possible methods which can suppress the oscillation. The effectiveness of the proposed methods is validated by the experimental data and simulation results in the end. [ABSTRACT FROM AUTHOR]

This letter proposes a CMOS divide-by-16 injection-locked frequency divider (ILFD) with a divide-by-4 ring-oscillator frequency divider (FD) stacked on a capacitive cross-coupled LC divide-by-4 ILFD. The divide-by-16 ILFD in the Taiwan Semiconductor Manufacturing Company, Limited (TSMC) $0.18~\mu \text{m}$ 1P6M CMOS process has a locking range from 10.76 to 12.6 GHz at the power consumption of 12.5 mW and an external injected signal power $P_{\mathrm {inj}}$ of 0 dBm. The varactor-less divide-by-16 ILFD uses the ring-oscillator FD with wide locking range to track the input frequency from the LC ILFD output, and occupies an area of $1.2\times1.198$ mm2. [ABSTRACT FROM AUTHOR]

A new low-pass prototype, i.e., cascade hybrid triplet (CHT), is proposed in this article. This triplet, as a synthesis building block, offers two arbitrary-placed transmission zeros (TZs) to suppress the target frequency area or produce a complex TZ pair to flatten the group delay. The CHT can be used to accurately synthesize and design three types of real circuit configurations, i.e., double-dangled extracted-pole section (DDEPS), coupled-resonator-dangled extracted-pole section (CDEPS), and frequency-dependent triplet (FDT) with the asymmetric response. We present the detailed synthesis and the related design method for three types of circuits, while a series of typical examples is synthesized and designed to demonstrate the proposed approach. Finally, four planar four-TZ filters with asymmetric responses based on the proposed approach are designed and fabricated to exhibit the high-order filter application. A good agreement between the synthesis and experimental results is obtained. [ABSTRACT FROM AUTHOR]

In this article, for the first time, a power delivery network (PDN) noise absorber is applied to the power system and verified based on a power trace system. Among all the existing absorptive circuits, a low-pass reflectionless circuit is chosen as our PDN noise absorber due to its broadband characteristic. Since the speed of the signal becomes higher and higher nowadays, a millimeter distance of a power trace with the traditional reflective PDN noise suppression devices, such as decoupling capacitors (de-caps), may provide serious standing wave on it and seriously affect the system. The proposed PDN noise absorber, on the other hand, can absorb the PDN noises so that the standing wave on the power trace can be prevented. This makes power trace systems more stable and avoids significant power noises at some locations. A prototype using a PDN noise absorber was fabricated. The power integrity performance of this prototype was compared with two other cases, power trace only and power trace with a de-cap. Compared with the de-cap case at the designed frequency 750 MHz, a PDN noise absorber can reduce 40% maximum voltage ripple. On the other hand, noise coupling between the digital and radio frequency circuits has also been demonstrated and compared for those three different PDNs. It shows a 3.7-dB decrease in gain fluctuation for the PDN with power noise absorber compared with the de-cap case. According to these results, no matter from power integrity or noise coupling suppression viewpoint, PDN noise absorber can be a good candidate to make the power system more stable. [ABSTRACT FROM AUTHOR]

LLC half-bridge converters have been extensively studied in low power industrial applications. However, the phase shift angle between the voltage and current of the LLC resonant network makes the converter have power circulation, that is, backflow power. The increase of the backflow power will increase the converter conduction loss, which restricts the improvement of the converter efficiency. The existing literature often improves the backflow power from the control aspect, which greatly increases the control complexity. To solve this problem, this article proposes an LLC half-bridge resonant converter analysis method that takes the backflow power into account. Based on the analysis of operating mode and ac equivalent model of the converter, backflow power is indirectly characterized by the phase-shift angle of the resonant network voltage and current. Based on this, this article analyzes the internal relationship between resonant parameters and backflow power to reduce backflow power by optimizing resonant parameters. Under the setting operating conditions, converter can achieve zero voltage switching (ZVS) switching, voltage gain conditions, and minimum backflow power. Compared with the existing methods, the proposed optimization method avoids additional auxiliary circuits and control complexity, improves the stability of the circuit. Experimental results verify the accuracy and feasibility of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This article proposes a contactless power transfer for rail-guided vehicles with power equalization and efficiency improvement considerations. This study is motivated since the rail-guided vehicles may encounter the power imbalance and low efficiency during the power transfer under a multireceiver environment. Therefore, the article is devoted to designing an approach of evenly dispatching power among receivers as well as developing a tracking compensation technique to search the maximum power-transmitting efficiency under different number of receiving modules. Through this proposed method, the constant power output, power equalization, and efficiency improvement are all achieved. Circuit derivation, frequency response, and resonance features are all made. A hardware circuit is also realized with different tests carried out under various scenarios. The maximum efficiency of this system is recorded to be 90.3%, supporting the practicality of the method. Experimental outcome gained from this study is beneficial for on-rail charging applications. [ABSTRACT FROM AUTHOR]