Equivalent Circuit Simulation Research Articles

Electro-mechano-acoustical equivalent circuit model of z-structured piezoelectric transducer

To meet the demands of low frequency, small size, light weight and high power in the underwater application, a z-structured piezoelectric transducer (ZPT) is innovated, and its equivalent circuit representation is derived. In configuration, ZPT employs the bender beam to implement z-shaped structure for the compact design. In mechanics, ZPT utilizes the coupled longitudinal-bending vibration to produce a large output at a low frequency. In order to study the electro-mechano-acoustical behavior of ZPT, an equivalent circuit model is built based on the conception of analogy, and subsequently solved through the matrix-based methodology. The crux of this model lies in the derivation of the representation about the beam. The corresponding simulations indicate that the effect of the bender beam on ZPT is significant, and its connecting function and bending vibration makes it possible for ZPT to achieve the performance of compact structure and low frequency. The tests of the transducer prototype show that our ZPT has the size of Φ70 × 110 mm, the weight of ∼1.056 kg without housing and the transmitting voltage response (TVR) of 124.9 dB at the resonance frequency of 2.088 kHz. The experimental results show a good agreement with the equivalent circuit simulations of the ZPT. The benefits about low frequency, small size and light weight of the ZPT are attributed to its z-structured design and coupled longitudinal-bending vibration.

Predicting the Output Performance of Triboelectric Nanogenerators Using Highly Representative Data‐Based Neural Networks

Triboelectric nanogenerators (TENGs) are promising potential sustainable power sources for wireless sensing networks within the Internet of Things (IoT) realm. Developing an efficient TENG evaluation model, characterized by high speed, accuracy, and representativeness, facilitates its integration into practical applications, which is urgent and lack of investigation currently. Herein, an artificial intelligence (AI) based evaluation model is developed to predict the performance of freestanding rotational TENGs (FR‐TENGs) for demonstration. An accurate and representative train dataset is essential for development of AI‐based evaluation model, which has been generated using finite element analysis and equivalent circuit simulation alongside the non‐dominated sorting genetic algorithm II. Through comprehensive experiments and simulations, the accuracy of the model has been verified in predicting the power output performance of FR‐TENGs, which has 99.6% (three design parameters) and 99.2% (seven design parameters) maximum train set accuracy. More importantly, the predicted results from the AI‐based evaluation model have notably expanded the coverage of data and significantly expedited the generation time from days to seconds. Herein, the use of AI in assessing the performance of TENGs is enhanced. The TENG design process can be significantly simplified, while maintaining a high evaluation model accuracy, thus promising advancements of IoT applications in future.

Mechanical Characteristics and Corrosion Behavior of Two New Titanium Alloys

While Ti6Al4V is one of the most used titanium alloys in the biomaterials field, it is not without its challenges and limitations, among which very important is the modulus mismatch with the bone. This modulus mismatch can lead to stress shielding potentially leading to bone resorption and implant loosening. Researchers continue to explore alternative materials and modifications to address this challenge and improve the performance of biomaterials. Two new fabricated titanium alloys Ti-10Al and Ti-4Fe are analyzed in this paper from corrosion and elastic modulus points of view. Metallography, microhardness, open circuit potential, DC electrochemical linear polarization, and Electrochemical Impedance Spectroscopy were performed. It was found that the corrosion resistance measurement for the Ti4Fe alloy is two orders of magnitude lower than for the Ti10Al alloy as determined by the equivalent circuit simulation, which is also supported by the similar disparity in the corrosion rate values for the two alloys which was determined using the DC method. The modulus of elasticity values were fairly close, hovering about 35GPa, and were lower than those of many commercial alloys.

Detection of Rotor Field Winding, Damper Bar, and Eccentricity Faults in Salient Pole Synchronous Machines With the Pole Drop Test

The pole drop test is the most widely applied means of detecting shorted turns in the rotor field winding of salient pole wound field synchronous machines (WFSM). It is a simple off-line test that relies on detecting the asymmetry between the voltage drop in the windings of each pole with ac voltage applied to the field winding terminals. Although it can provide sensitive detection of shorted field turns, it is also influenced by asymmetries in the motor produced by defects or imperfections in the rotor poles or damper bars. In this work, the feasibility of using the pole drop test for detecting damper bar and eccentricity faults in addition to shorted field windings is investigated for the first time. The change in the impedance of each pole under the fault conditions is analyzed from the electrical equivalent circuit and finite element (FE) simulation. Based on the analysis, it is shown that the 3 faults can be detected and classified from the impedance or voltage distribution with the pole drop test. Experimental tests performed on 4 pole, 30 kVA and 6 pole, 5.5 kVA salient pole WFSMs confirm that the 3 faults can be identified as claimed.

Hole-Patterned Carbonyl Iron Powder/Epoxy Composite Low-Profile Electromagnetic Absorber Operating at Ka-Band

This research developed a mmWave electromagnetic (EM) absorber with a simply punched hole pattern, which was introduced on the flat CIP/epoxy composite to overcome the limitation of the magnetic materials. This absorber was designed on a carbonyl iron powder (CIP) and epoxy resin composite with Snoek's limit of about 26 GHz. First, the morphologies of the fabricated CIP/epoxy composite were characterized by scanning electron and atomic force microscopies. Subsequently, the constitutive parameters of the CIP/epoxy composite were measured in the frequency range of 26.5–50 GHz. These measured constitutive parameters of the CIP/epoxy composite material were iteratively revised by the curve-fitting technique to improve the measurement accuracy. An equivalent circuit model was utilized to determine the reflection coefficient of the hole-patterned CIP/epoxy composite mmWave EM absorber, taking into account its material parameters and dimensions. A comprehensive analysis was conducted to evaluate how the performance of the absorber is affected by the dimensions of its unit cell. This was achieved by utilizing both the equivalent circuit and full-wave FEM simulation. The absorption performance of the hole-patterned CIP/epoxy composite mmWave EM absorber is experimentally demonstrated at different angles and polarizations in 26.5–36.5 GHz.

A cell-electrode interface signal-to-noise ratio model for 3D micro-nano electrode.

3D Micro-nano electrodes (MNE) with the vertical nanopillar array distributed on the surface play an increasingly important role in neural science research. The geometric parameters of the nanopillar array and the cell adhesion state on the nanopillar array are the factors that may affect the MNE recording. However, the quantified relationship between these parameters and the signal-to-noise ratio (SNR) is still unclear. This paper establishes a cell-MNE interface SNR model and obtains the mathematical relationship between the above parameters and SNR. The equivalent electrical circuit and numerical simulation are used to study the sensing performance of the cell-electrode interface. The adhesion state of cells on MNE is quantified as engulfment percentage, and an equivalent cleft width is proposed to describe the signal loss caused by clefts between the cell membrane and the electrode surface. Whether the planar substrate is insulated or not, the SNR of MNE is greater than planar microelectrode (PME) only when the engulfment percentage is greater than a certain value. Under the premise of maximum engulfment percentage, the spacing and height of nanopillars should be minimized, and the radius of the nanopillar should be maximized for better signal quality. The model can clarify the mechanism of improving SNR by nanopillar arrays and provides the theoretical basis for the design of such nanopillar neural electrodes.

Experimental and Equivalent Circuit Analysis Approach to Estimate Contact Resistances on Different Sections in a D-Shaped NI HTS Coil

With well-known self-protecting behaviors of no-insulation (NI) high temperature superconductor (HTS) coils, their performance was verified by numerous high field magnets. As one of the initial investigations of the NI HTS technique being applied to toroidal field (TF) coils, an equivalent circuit analysis is carried out on a D-shaped NI HTS coil to predict its electromagnetic behaviors regarding the contact resistance, one of the most important parameters for NI HTS coils. A charging/discharging test is performed at 77 K to obtain the experimental data for contact resistance estimation. Using the measured voltage and the pressure dependency of surface contact resistivity, a combination of contact resistance is obtained through the modified lumped circuit and the partial element equivalent circuit simulation by which the shape-dependent contact resistance can be estimated. The results are expected to provide a source for careful management in the design stage to consider the uneven contact resistance and possible uneven electromagnetic behavior among different sections of the TF coil.

Study of black protective-decorative nanocomposite anodic coatings on the surface of AMg5 aluminum alloy

A widely used nanocomposite coating is a porous anodic alumina colored by particles of metals or their compounds deposited into the pores. The insertion of light-scattering nanosized particles into the pores changes the optical properties of the anodic oxide, whereas the immobilization of metal nanoparticles in pores ensures their corrosion resistance. We present the results of studying black protective and decorative coatings on the surface of AMg5 aluminum alloy. The surface morphology of the samples was analyzed using atomic force microscopy, and the electrophysical properties were monitored by electrochemical impedance spectroscopy (EIS). The growth kinetics of the anodic coating has been studied, and optimal conditions for the formation of a regularly porous oxide coating 10 – 12 μm thick with a regular pore diameter of 15 ± 5 nm on the alloy surface were determined. It is shown that subsequent electrochemical coloring for 15 min makes it possible to obtain a black color of the coatings due to the deposition of Cu and/or CuO nanoparticles into the pores. Simulation of electrical equivalent circuits makes it possible to separate and calculate the electrical parameters corresponding to different layers and elucidate their regular changes after coloring and hydrothermal treatment. The high corrosion resistance of electrochemically colored anodized alloy samples subjected to hydrothermal treatment has been revealed. The results obtained can be used in the application of protective and decorative anodic coatings for the manufacture, for example, of solar panels due to the high absorption and low reflectivity of black coatings.

Flexible microwave metasurface absorber with reconfigurable absorption intensity in ultra-wideband

This article proposes a flexible metasurface absorber (MA) with reconfigurable absorption intensity in an ultra-wideband spectrum. Due to the utilization of an ultrathin polyimide substrate, the MA is endowed with superior flexibility over previous rigid designs. The pattern of the MA consists of a fourfold symmetrical metal strip and four PIN diodes, which simultaneously activate multiple resonances to generate a wide operating band. By adjusting the voltage of the PIN diodes embedded in the strips, the MA can execute various stages of reconfigurable absorption intensity through varying states of ohmic loss. When the PIN diodes are off, MA is switched to a reflector. In addition, the results of the equivalent circuit simulation confirm the feasibility of the design. Finally, an MA sample is fabricated and measured, and good agreement is obtained between the measured and simulated results. The MA achieves a reconfigurable absorption intensity varies from −16.8 to 0 dB over an ultra-wide frequency range of 5.6–16.98 GHz, with relative bandwidth up to 100.8%. As expected, the designed MA features excellent characteristics both in plane and curved states.

Comparison the properties of carbon fiber-based Portland cement and alkali-activated fly ash/slag conductive cementitious composites

This study aims to investigate the essential differences of carbon fiber (CF) on the properties of Portland cement and alkali-activated fly ash/slag (AAFS) pastes. The workability, rheological performance, and electrical properties of CF-based AAFS were investigated and compared with CF-based cement paste. The electrical microstructure of CF composites was analyzed by electrical impedance spectroscopy (EIS). The simplified suspension model and the equivalent circuit model are proposed herein describing the carbon fiber based electrically conductive cementitious composites (ECCC). The results show that the flowability of the suspension (i.e. CF as solid phase, plain paste as fluid phase) depends on the fiber factor (F). When F is in the region (region II) between the critical (Fc) and dense F (Fd), satisfactory workability and electrical conductivity were simultaneously obtained from C-CF and AAFS-CF composite. AAFS system has the advantage of CF dispersion compare to cement due to the higher plastic viscosity and the softening effect of alkaline activator. The equivalent circuit simulation parameters show the bulk resistance of the of AAFS matrix is lower than that of cement matrix. The presence of mobile soluble ions in AAFS enhanced the conductivity of AAFS than cement. Therefore, AAFS-CF composite was considered as a promising material for ECCC.

Redoxless Electrochemical Capacitance Spectroscopy for Investigating Surfactant Adsorption on Screen-Printed Carbon Electrodes

Electrochemical impedance spectroscopy (EIS) is a sensitive analytical method for surface and bulk properties. Classical EIS and derived electrochemical capacitance spectroscopy (ECS) with a redox couple are label-free approaches for biosensor development, but doubts arise regarding interpretability when a redox couple is employed (redox EIS) due to interactions between electroactive probes and interfacial charges or forced potential. Here, we demonstrated redoxless ECS for directly determining surfactant adsorption on screen-printed carbon electrodes (SPCEs), validated through a simulation of equivalent circuits and the electrochemistry of electronic dummy cells. Redoxless ECS provides excellent capacitance plot loci for quantifying the interfacial permittivity of di-electric layers on electrode surfaces. Redoxless ECS was compared with redox EIS/ECS, revealing a favorable discrimination of interfacial capacitances under both low and high SDS coverage on SPCEs and demonstrating potential for probeless (reagentless) sensing. Furthermore, the proposed method was applied in an electrolyte without a redox couple and bare electrodes, obtaining a high performance for the adsorption of surfactants Tween-20, Triton-X100, sodium dodecyl sulfate, and tetrapropylammonium bromide. This approach offers a simple and straightforward means for a semi-quantitative evaluation of small molecule interactions with electrode surfaces. Our proposed approach may serve as a starting point for future probeless (reagentless) and label-free biosensors based on electrochemistry, eliminating disturbance with surface charge properties and minimizing forced potential bias by avoiding redox couples. An unambiguous and quantitative determination of physicochemical properties of biochemically recognizable layers will be relevant for biosensor development.

High-frequency inlaid cylindrical piezoelectric transducer for high-sensitivity acoustics

This work develops a high-frequency high-sensitivity inlaid cylindrical hydroacoustic transducer by enhancing the electromechanical coupling coefficient, amplifying stress, and adopting circumferential inlaid techniques. Equivalent circuit and finite element simulation methods were used to determine the optimum parameters of the unit, then the transducer was fabricated. Tests show that the resonant frequency of every array unit was 220 kHz. The maximum emission voltage response and reception sensitivity were respectively about 172 dB and −177 dB, with emission and reception bandwidths both about 40 kHz at 3 dB loss. The horizontal and vertical beamwidths were 15° and 4° for each unit respectively.

Accurate SiC MOSFET Chip Extraction Based on Parasitic Parameter Impact Compensation

With the growing use of SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> in power electronic equipment, it is meaningful to extract precise typical waveforms and characteristics for device manufacture, converter design, and operating evaluation. Many solutions have been proposed to improve measurement precision by equipment and essential techniques. However, the measured object should also be accurately identified as the existing measurement result consisting of the expected gate-source voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> ) and voltage drops on parasitic parameters between measuring points. This article, first, reveals the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> measurement deviation of TO-247-4 and TO-247-3 devices during the switching process and crosstalk, based on the equivalent circuit model and simulation waveforms. According to the clarification of the measured object, an improved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> extraction method is proposed to eliminate this deviation. Voltage drops on parasitic parameters are compensated, with the help of high-precision equipment and the proven parasitic parameter extraction technique. Experiments are constructed to verify the analysis of measurement deviation and the availability of the proposed method. Comparison between various operating conditions emphasizes its necessity, especially in high-capacity and low-driving-resistor applications, contributing to characterization, operating condition monitoring, protection design, and measurement understanding of wide band-gap devices.

A 2.5D low-profile wideband frequency selective structure with high-selectivity performance

In this paper, a low-profile high-selectivity 2.5D FSS based on the dislocation patch structure is proposed and discussed. The dislocation patch structure is used to construct the low-profile transmission line, and a second-order band- pass FSS with a controllable transmission zero is realized by introducing a series LC structure to the dislocation patch structure. The effects of the geometrical parameters on the frequency response of the proposed second-order bandpass FSS are analyzed based on the transmission matrix method and the equivalent circuit simulation. Then, two proposed second-order bandpass FSSs with different transmission zeros are combined and placed crossly to construct two propagation paths, and a high-selectivity third-order FSS is obtained. Finally, the prototype is fabricated and measured to prove the effectiveness of the proposed FSS. The measured results show that the proposed high-selectivity FSS has a wide working bandwidth, proper selective performance, and a thinner profile than other high-selectivity 2D/3D FSSs.

A droplet-based micropillar-enhanced acoustic wave (μPAW) device for viscosity measurement

Viscosity monitoring has recently received significant attention in various fields such as pharmacy, oil industry, food industry, and medical diagnostics. Given that the commercially available viscometers usually require a large sample volume to conduct accurate measurement, there is an urgent need to develop a viscometer that can consume the least sample while maintaining high accuracy. Despite of being simple, rapid, and cost-effective, quartz crystal microbalance (QCM) based viscometers are low in sensitivity and not able to measure viscosity directly. This work focuses on the development of a novel micropillar-enhanced QCM viscosity measurement device which relies on the coupled vibration between micropillars and quartz substrate (QCM-P) to achieve an ultra-sensitive viscosity measurement of a sample droplet. A hybrid model by integrating an equivalent circuit and numerical simulation approach was established to understand the working principle of the QCM-P device and evaluate the viscosity value. The experimental results and analysis demonstrate that the micropillar-enhanced acoustic wave (μPAW) devices such as QCM-P viscometer is a promising device for droplet-based viscosity measurement.

SPICE-Compatible Equivalent Circuit Models for Accurate Time-Domain Simulations of Passive Photonic Integrated Circuits

Passive photonic integrated circuits (PICs) can be easily characterized in the frequency-domain, but their accurate time-domain performance evaluation is a hurdle for system-level designers, especially when dealing with resonant circuits having highly dispersive behavior, such as ring resonators. In this paper, a new equivalent circuit modeling and simulation approach is proposed, based on the Complex Vector Fitting algorithm, able to perform accurate and robust time-domain simulations of passive PICs directly in standard SPICE simulators. The proposed modeling technique starts from scattering parameters of passive PICs, and is able to capture linear and high order dispersion, backscattering, and wavelength dependent effects. Considering the different nature of optical and electronic signals, a novel concept of equivalent voltage and current for optical waveguides is proposed to simplify the optical to electronic ports conversion and to make it possible to connect and terminate the equivalent circuit models as needed in SPICE simulators, natively supporting bidirectional signal propagation in a waveguide. This work provides a precise and reliable solution to evaluate time-domain characteristics of passive PICs and to access any internal nodes within a circuit, such as the signals inside a ring resonator. Three examples of time-domain simulations of passive PICs in commercial SPICE simulators are presented to demonstrate the flexibility and advantages of the proposed technique.

Design of compact-diode-SCR with low-trigger voltage for full-chip ESD protection

In this article, a compact-diode-silicon-controlled rectifier (CDSCR) for full-chip electrostatic discharge (ESD) protection is proposed and verified in 0.18 μm Silicon-on-Insulator (SOI) Bipolar-CMOS-DMOS (BCD) process. Intrinsic parasitic SCRs and diodes are employed as the main ESD paths, which greatly reduces area consumption. Besides, due to the RC- triggered circuit, low trigger voltage and short turn-on time are realized. With equivalent circuit and two-dimensional (2D) technology computer-aided design (TCAD) simulation, the operation principle and working mechanism are analyzed. In addition, transmission line pulse (TLP) and very fast TLP (VF-TLP) testing results show that the CDSCR could can endure human body model (HBM) pulse of 3420 V without latch-up issue and protect the chip effectively in charge device model (CDM) event. Furthermore, the proposed structure exhibits high current handing ability during ESD stress conditions and sufficiently low leakage current during normal circuit operating conditions. The CDSCR is conformed to provide full-chip ESD protection for 1.2 V application.

Integrated Inductor Model Verification for Microwave LC-filters in Si and SiGe Systems on a Chip

In this paper, the conductor model that can be used to design of various inductor layout configurations for any Si and SiGe technological processes is considered. The experimental prototypes of the test inductors were produced in the standard SiGe BiCMOS 130 nm process to verify the model. The chips measuring results showed that the characteristics of the prototypes taking into account the manufacturing tolerance are in the range of model simulated values. It has been found that the proposed model has a better convergence with the prototypes characteristics than 3D modeling. The equivalent circuit simulation speed can be orders of magnitude higher than the 3D simulation speed. The proposed model accuracy is achieved by taking into account the skin-effect and edge-effects in the dielectric and substrate. Using the skin-effect equivalent circuit the model can be run in Cadence Specter Simulator. It is necessary for the microwave LC-filters development.

Kinetic insights into LixNi0.67N (1.67 ≤ x ≤ 2.17), a quasi “zero-strain” negative electrode material for Li-ion battery

The kinetics of the electrochemical lithium intercalation in the nitridonickelate LixNi0.67N (1.67 ≤ x ≤ 2.17) is investigated by electrochemical impedance spectroscopy during a full reduction-oxidation cycle in a two-electrode cell. The layered structure of this anode material delivers a reversible and stable specific capacity of 200 mAh g−1 over 100 cycles at C/10 near 0.5 V vs Li+/Li. The equivalent electric circuit simulation allows a full assignment of the impedance spectra, with different contributions including the SEI layers on each electrode, charge transfer and Li diffusion. The calculated lithium diffusion coefficient value of approximately 5 × 10−9 cm 2 s−1 almost does not vary with the lithium content in LixNi0.67N (1.67 ≤ x ≤ 2.17). Conversely, the charge transfer resistance (Rct) is found to strongly depend on the depth of reduction to be maximum for the fully reduced electrode, with a totally reversible behavior during oxidation. The overall impedance of the cell remains stable upon long cycling, which indicates a good chemical stability of the SEI on LixNi0.67N as well as remarkable structural and chemical stability of the nitridonickelate upon cycles. The present kinetic findings shed light on the remarkable “zero-strain” behavior of this negative electrode material presenting numerous Li vacancies.

A Displacement Sensing Method Based on Permanent Magnet and Magnetic Flux Measurement.

This paper proposes a displacement sensing method based on magnetic flux measurement. A bridge-structured magnetic circuit, formed by permanent magnets and two ferromagnetic cores, is designed and discussed. The analyses of the equivalent magnetic circuit and three-dimensional finite element simulations showed that the magnetic flux density changes linearly with the reciprocal of the sum of a constant and the displacement. A prototype sensor of the bridge structure is developed that consists of four permanent magnets as excitation, a Hall sensor as reception, and two ferromagnetic cores as the connection. Experiments have validated the feasibility of this method. The measured results show a good linearity between the sensor’s output and the reciprocal of the sum of a constant and the displacement, with a correlation coefficient greater than 0.9995 across different measurement ranges. Additionally, the measured results significantly indicate that the proposed sensor is compatible with different ferromagnetic materials with a worst-case error of less than 5%. The proposed sensor has the advantages of low cost and good linearity; however, the test object is limited to ferromagnetic materials.