Lumped Elements Research Articles

Discharge Behaviour and Modelling of a 1.5T REBCO Magnet With Quench Tolerant Coils Impregnated with Conductive Epoxy.

We have designed and built a small, conduction cooled, 1.5 T high-temperature superconductor (HTS) magnet. The magnet coils have been wet-wound with a novel conductive epoxy resin system to achieve a derivative of the no-insulation coil winding method. The epoxy is filled with copper powder to reliably set the turn-to-turn contact resistivity and diamond powder to accurately space the coil turns apart, as well as match the filled epoxy thermal contraction rate to that of the HTS. The magnet is designed to act as a test bed to measure sudden discharge rates and hence validate models of coil behaviour using the filled epoxy system we have developed. A lumped-element electrical model was used to predict the coil contact resistivity needed to bring the magnetic field of the 1.5 T magnet down to a near-zero level within 0.5 s. The conductive epoxy blend was tuned to give a contact resistivity of 1 × 10-6 Ω m2, based on previous measurements of coil contact resistivity at 77 K. Once the magnet was wound and tested at 40 K, we found the magnet's sudden discharge time constant was 500 ms rather than 69 ms as was predicted from the 77 K measurements. The discrepancy was traced to the temperature dependence of the contact resistivity. With further testing of the individual coils this was accounted for and the model adjusted. The predicted discharge time was 2 s, in good agreement with the measured sudden discharge time of the magnet.

Design of Frequency Reconfigurable Patch Antenna for Sensing and Tracking Communications

This paper presents a front-end structure of a reconfigurable patch antenna for cognitive radio systems. The antenna structure consists of an Ultrawideband (UWB) sensing antenna and an array of frequency reconfigurable antennas incorporated on the same substrate. The UWB and reconfigurable antennas are fed by co-planar waveguides (CPW). The reconfigurability is achieved by rotating the series of patch antennas through a certain angle and the rotation is controlled by mechanical means using an Arduino microcontroller. The rotational reconfigurability has been preferred over MEMS switches, PIN diodes, and other lumped elements because the latter requires the need for bias lines. The entire structure is designed using High Frequency Structure Simulator (HFSS) software and the prototype is fabricated over FR-4 substrate having a thickness of 1.6mm and measurements are carried out. This antenna achieves a wideband frequency from 2 GHz to 12 GHz and distinct narrow band of frequencies by reconfigurability using single antenna consisting of different shapes spaced accurately to ensure isolation between adjacent frequency bands and each antenna element working for a bandwidth of 2 GHz for frequency from 2 GHz to 12 GHz upon a single substrate and the reconfigurable elements are controlled using a low cost Arduino microcontroller connected directly to the antenna which ensures accurate controlling of the rotation and fast switching between the antenna elements. The measured results agree with the simulated results and have less than 10 dB impedance bandwidth.

Computer aided design of ferrite lumped element circulators

The results of integrity of narrowband and wideband lumped element circulators design methodology to the computer aided design system of microwave devices AWR Microwave Office are presented in the article. The calculation method of narrow band circulators circuits which consist of serious and shunt tuning capacities is investigated. The simple and visual method of wideband ferrite isolators optimize design based on circulation impedance calculation is described here. The results of design of the ultra wideband circulator with shunt capacity, serious resonant matching circuit and serious resonant circuit between common terminal and ground are considered. The new theoretical results of calculation of two schematics of wideband high power circulators with serious tuning capacity are presented. The first schematic is formed with matching resonant network being connected in serious at each terminal. It is shown that double hump characteristic is realized. The second schematic is formed with serious resonant network connected between common terminal and the ground. It is shown that four-order Tchebycheff characteristic is realized.

Electrical modeling of cylindrical dielectric elastomer transducers

Dielectric elastomer transducers (DETs) are commonly modeled by lumped-element models (LEMs), however such models do not capture the cutoff behavior that manifests at relatively low frequencies due to the high resistivity of the stretchable electrodes. Moreover, the contribution of the electrodes into the lumped series resistance is not accurately known. The aim of this work is to define the accuracy and frequency limits of the LEM and to derive the exact values of its lumped components. This is achieved by developing a detailed three-dimensional distributed-element model (DEM) of the transducer structure. Based thereon, analytical expressions are developed for the LEM components and limits are explored. Through numerical evaluation of the DEM it is found that only two-third of the single-polarity electrode resistance contributes to the lumped series resistance, which is three times lower than predicted by existing models. Comparison between the LEM and DEM further shows that the LEM is adequate for frequencies significantly below the cutoff frequency. Thereafter, capacitance and resistance fall off as a result of signal propagation limitations. This has been experimentally verified. The developed DEM and established validity range of the simple LEM allows for more accurate sensors and better optimized transducers designs, with up to three times less electrode material.

ZnO/PDMS nanocomposite generator: Interphase influence in the nanocomposite electro-mechanical properties and output voltage

Nanocomposite generators convert mechanical energy into electrical energy and are attractive low-power solutions for self-powered sensors and wearables. Homogeneous dispersion, high concentration, and orientation of the embedded filler strategies have been assumed to maximize the voltage output in nanocomposite generators. This work contrast these assumptions by studying the dominance of the interphase in low filler concentrations (¡10%) and random dispersions in a ZnO/PDMS nanocomposite generator with high peak-to-peak voltage generation capabilities (≈150V). The interphase in the nanocomposite was studied by the analysis of the random dispersion of the nanocomposite through the estimation of the effective volume fraction (ϕagg) which allowed us to identify three levels of interaction: individual interphases, interacting interphases, and overlapping between NPs and interphases. The interacting interphase is responsible here for the high generated voltage. In addition, the impact of the interphase was studied by applying lumped element (LE) and interphasial power-law (IPL) models that capture the measured voltages and the electromechanical film properties. The obtained results justify that engineering of interphases could be a design strategy for high voltage generation.

Analysis of a 2D Periodic Array of Metal Cylinders with Lumped Elements in Passband

Eigenwaves of a homogeneous electromagnetic crystal (EMC) that represents a 2D array of metal cylinders with gaps containing lumped elements (LEs) forming a parallel LC circuit are studied. The array of cylinders with LEs is installed inside a planar waveguide (PW). Variations in the parameters of the EMC eigenwaves due to variations in the capacitance are analyzed. The problem of eigenwaves is solved with the aid of numerical electrodynamic simulation in the HFSS system using periodic boundary conditions. Dependences of the main technical parameters, in particular, passband on the geometrical parameters of the structure and circuit parameters are considered. It is shown that a decrease in the height of the PW filled with a dielectric material can be used to improve the EMC quality parameters. Excitation of a finite-width EMC layer is considered. It is shown that the main results obtained for the regime of eigenwaves are proven by the solution to the problem of the EMC excitation.

Miniature Electrodynamic Wireless Power Transmission Receiver Using a Micromachined Silicon Suspension

We present the design, modeling, fabrication, and experimental characterization of an electrodynamic wireless power transmission (EWPT) receiver for low-frequency (<; 1 kHz), near-field wireless power transmission. The device utilizes a bulk-micromachined silicon serpentine suspension, two NdFeB magnets and two precision-manufactured coils. The architecture of the transducer is designed to maximize the electrodynamic coupling coefficient while maintaining a low mechanical resonant frequency in order to maximize the power density for low-frequency wireless power transmission. An equivalent lumped-element circuit model is established to parameterize the system and to predict the output performance of the proposed system. A prototype device is fabricated, assembled and tested, and the results are compared with the model prediction. The 0.31 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> device generates 2.46 mW average power (7.9 mW·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> power density) at 4 cm distance from a transmitter coil operating at 821 Hz and safely within allowable human exposure limits. This data corresponds to a normalized power density of 21.9 mW·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ·mT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , which is 44% higher than similar reported devices. Based on these results, this device shows great suitability for wirelessly charging mobile, wearable and bio-implantable devices. [2020-0161]

2D modeling of the human ear using the equivalent mechanical impedance

Several mass–spring–damper models have been developed to study the response of the human body parts. In such models, the lumped elements represent the mass of different body parts, and stiffness and damping properties of various tissues. The aim of this research is to develop a 2D axisymmetric model to simulate the motion of the human tympanic membrane. In this contribution we develop our model using a Comsol Multiphysics software to construct a 2D axisymmetric objects, the acoustic structure interaction between the ear canal (field of propagation of the acoustic wave) and the structure of ear (skin, cartilage, bone, tympanic membrane) was solved using finite elements analysis (FEA). A number of studies have investigated the motion of the human tympanic membrane attached to the ossicular chain and the middle ear cavity. In our model, the tympanic annular is assumed to be fixed and the loading of what comes behind the tympanic membrane as the ossicular chain, while middle ear cavity and cochlea were replaced by the equivalent mechanical impedance of a spring mass damper system. The obtained results demonstrate that the maximum displacements of the umbo are obtained at the frequency range of 0.9–2.6 kHz, the sound pressure gain had the shape of peak with a maximum at 2–3 kHz frequency range. The umbo displacement depends on the damping coefficient d, and the sound pressure at the tympanic membrane was enhanced compared to that at the ear canal entrance.

Slow-Wave Microstrip Line Model for PCB and Metallic-Nanowire-Filled-Membrane Technologies

An electrical model composed of lumped elements is proposed for slow-wave microstrip lines that use grounded blind vias/nanowires to achieve the slow-wave effect. The main difference of this model, from the traditional RLGC model for transmission lines, is the modeling of the blind vias/nanowires that consider a mutual inductive coupling considered between sections of the model. Two transmission lines on two technologies are analyzed: printed circuit board (PCB) and metallic nanowire-filled membrane (MnM) substrate. The calculi for each component of the model are detailed. Electrical simulations are done, and a comparison between the measured and simulated data is shown. It is shown that the electrical model can predict the transmission lines' behavior, especially the dispersion on the results that happen in frequency.

A Simple Power Source Modeling and Experimental Investigation of a Spacecraft for EMC Applications

Simplified modeling of a spacecraft power system is proposed to predict the conducted electromagnetic compatibility (EMC) environment. A key element of the spacecraft conducted environment is the electrical power subsystem, which corresponds to the power source. Since the impedance of the power source has a significant effect on conducted interference, the assessment of power bus impedance is essential to control and manage spacecraft EMC. In the proposed model, all components inside the power system were modeled as simple equivalent circuits with lumped elements. The advantage is that it simplifies the complex power system so that its impedance can be quickly obtained at the early stage of spacecraft system design and development. The model is validated by comparing the calculated results with experimental data. The comparison results between simulation and experiment showed good agreements.

Simultaneous Decoherence and Mode Filtering in Quantum Channels: Theory and Experiment

Quantum networks require robust quantum channels for fast and reliable entanglement distribution over long distances. As quantum communication technology matures, it moves towards utilizing actual fibers and free-space optical channels; hence, there is a growing need for physical models describing decoherence. The primary challenge is to concisely account for numerous elements distributed along a lengthy optical path. We approach this by starting with an analytical model of a channel with just two lumped elements, one representing decoherence and the other representing mode filtering. Interestingly, we find that, while the order and relative orientation of the two elements produce a wealth of different biphoton states, the amount of entanglement in all those states is exactly the same. Then, we conduct experiments that implement this channel and verify our analytical findings. Finally, we expand our analysis to the most general fiber polarization channel, comprising a statistically significant number of arbitrarily oriented elements. We show that, over an ample range of parameters, our two-element analytical model is quite accurate in describing the fiber channel, which makes it an effective tool for gaining insights into channel decoherence.

A Global Model of the Collisional Plasma Boundary Sheath Using Step Model

Capacitively coupled plasmas (CCPs) are widely used for material processing, for example, for the manufacturing of semiconductors textile and modified surface. The ever-increasing requirements that companies face with respect to the quality, efficiency, and environmental friendliness of their manufacturing processes demand continuous progress. One simple and significant path to gain insight is the global model. Global models, which are, in engineering, called the lumped element model, allow for a complete and transparent mathematical analysis. Therefore, this work will study three models, the example of the exact model, and its verification using the step model to find the analytical relation between the sheath charge and the overall voltage drop across it. This formula is the missing factor in the global model that establishes the aim of the research. In addition, an effective lumped element model was studied, which allows describing the sheath dynamics in simple, though nonlinear engineering terms, such as resistance, capacitance, and inductance. The study achieves more detailed dynamics, such as the time-varying charge, voltage distribution, charge–voltage distribution $V_{\text {sh}}(Q)$ that controls the nonlinear sheath dynamics, current distributions, and the equation of the sheath distance for dc and ac sheaths. The results obtained at low computational complexity provide satisfactory calculations for nonlinear dynamics of collision sheath behavior.

Cryogenic microwave loss in epitaxial Al/GaAs/Al trilayers for superconducting circuits

Epitaxially grown superconductor/dielectric/superconductor trilayers have the potential to form high-performance superconducting quantum devices and may even allow scalable superconducting quantum computing with low-surface-area qubits such as the merged-element transmon. In this work, we measure the power-independent loss and two-level-state (TLS) loss of epitaxial, wafer-bonded, and substrate-removed Al/GaAs/Al trilayers by measuring lumped element superconducting microwave resonators at millikelvin temperatures and down to single-photon powers. The power-independent loss of the device is (4.8±0.1)×10−5, and the resonator-induced intrinsic TLS loss is (6.4±0.2)×10−5. Dielectric loss extraction is used to determine a lower bound of the intrinsic TLS loss of the trilayer of 7.2×10−5. The unusually high power-independent loss is attributed to GaAs’s intrinsic piezoelectricity.

Machine-learning engineering of quantum currents

The design, accurate preparation and manipulation of quantum states in quantum circuits are essential operational tasks at the heart of quantum technologies. Nowadays, circuits can be designed with physical parameters that can be controlled with unprecedented accuracy and flexibility. However, the generation of well-controlled current states is still a nagging bottleneck, especially when different circuit elements are integrated together. In this work, we show how machine learning can effectively address this challenge and outperform the current existing methods. To this end, we exploit deep reinforcement learning to prepare prescribed quantum current states in circuits composed of lumped elements. To highlight our method, we show how to engineer bosonic persistent currents as they are relevant in different quantum technologies as cold atoms and superconducting circuits. We demonstrate the use of deep reinforcement learning to re-discover established protocols, as well as solve configurations that are difficult to treat with other methods. With our approach, quantum current states characterised by a single winding number or entangled currents of multiple winding numbers can be prepared in a robust manner, superseding the existing protocols.

A computationally efficient hybrid 2D\u20133D subwoofer model

A subwoofer generates the lowest frequency range in loudspeaker systems. Subwoofers are used in audio systems for live concerts, movie theatres, home theatres, gaming consoles, cars, etc. During the last decades, numerical simulations have emerged as a cost- and time-efficient complement to traditional experiments in the design process of different products. The aim of this study is to reduce the computational time of simulating the average response for a given subwoofer design. To this end, we propose a hybrid 2D–3D model that reduces the computational time significantly compared to a full 3D model. The hybrid model describes the interaction between different subwoofer components as interacting modules whose acoustic properties can partly be pre-computed. This allows us to efficiently compute the performance of different subwoofer design layouts. The results of the hybrid model are validated against both a lumped element model and a full 3D model over a frequency band of interest. The hybrid model is found to be both accurate and computationally efficient.

Engineering the Threshold Switching Response of Nb2O5-Based Memristors by Ti Doping

Two terminal metal-oxide-metal devices based on niobium oxide thin films exhibit a wide range of non-linear electrical characteristics that have applications in hardware-based neuromorphic computing. In this study, we compare the threshold-switching and current-controlled negative differential resistance (NDR) characteristics of cross-point devices fabricated from undoped Nb2O5 and Ti-doped Nb2O5 and show that doping offers an effective means of engineering the device response for particular applications. In particular, doping is shown to improve the device reliability and to provide a means of tuning the threshold and hold voltages, the hysteresis window, and the magnitude of the negative differential resistance. Based on temperature-dependent current-voltage characteristics and lumped-element modelling, these effects are attributed to doping-induced reductions in the device resistance and its rate of change with temperature (i.e., the effective thermal activation energy for conduction). Significantly, these studies also show that a critical activation energy is required for devices to exhibit NDR, with doping providing an effective means of engineering the current-voltage characteristics. These results afford an improved understanding of the physical mechanisms responsible for threshold switching and provide new insights for designing devices for specific applications.

Compact Dual-band BPF Composed of &lt;i&gt;LC J&lt;/i&gt;-inverters Using Lumped Elements

Compact Dual-band BPF Composed of &lt;i&gt;LC J&lt;/i&gt;-inverters Using Lumped Elements

Method of determination of maximum possible operating frequency band of Y-circulators based on lumped elements

In the last 10–15 years, a significant development has been achieved in the design of Y-circulators on lumped elements based on the Y-junction of intertwined conductors placed between two magnetized ferrite disks, which are small even in the meter and decimeter wavelength ranges. Therefore, they are very attractive decoupling components for developers of electronic equipment, especially onboard. Increasing the operating frequency band of circulators of this type is an urgent task, the solution of which can expand the range of their application in promising radio-electronic equipment. Methods for solving this problem are based on the inclusion in the circulator circuit of the corresponding band-expanding matching circuits on the reactive elements. Matching circuits can be included both in each arm of the circulator, and between the common point of the intertwined conductors and the “body”. But it is important for developers of Y-circulators to know what maximum results can be achieved with the use of band-expanding circuits even before the start of development. The authors’ research, the results of which are presented in this article, is devoted to solving this problem. The studies have been carried out by a semi-empirical method based on the consideration of the eigenvalues of the impedance matrices of narrow-band and broadband Y-circulators constructed on their basis, including band-expanding circuits. Comparing the behavior of the eigenvalues of the impedance matrices in the frequency representation and in the φ-representation (φ – phase of the signal transmission coefficient from input to output) when using standard circulation conditions allowed us to obtain analytical relations for calculating the maximum possible operating frequency band and the maximum possible decoupling between the arms of the circulator, as well as to formulate a method for calculating the reactivities of matching circuits that should be included in the circulator circuit.

Lumped Mass Finite Element Method of the Nonlinear BBM Equation

In this paper, the full-discrete approximation scheme of the lumped mass nonconforming finite element method for BBM equation is discussed. Without the Riesz projection used in the traditional finite element analysis, the optimal error estimations are derived based on interpolation technique and special properties of element.

On the Modeling of Microstrip Lines Loaded With Dumbbell Defect-Ground-Structure (DB-DGS) and Folded DB-DGS Resonators

This paper presents a lumped-element equivalent circuit model of microstrip lines loaded with dumbbell defect-ground-structure (DB-DGS) resonators, etched in the ground plane. The model is valid for ordinary (i.e., unfolded) DB-DGSs, as well as for folded DB-DGSs with an arbitrary aperture angle and relative orientation between the line and the resonator. It is shown that in folded, or partially folded, DB-DGS resonators both magnetic and electric coupling between the line and the resonator should be considered, except for a particular DB-DGS orientation, namely, the one where the symmetry plane of the particle (a magnetic wall) is orthogonal to the line axis. In this case, the particle is exclusively excited by the electric field generated by the line. It is also shown that the circuit model of a microstrip line loaded with an unfolded DB-DGS resonator transversally oriented to the line can be derived from the general model by considering the effects of opening the particle, i.e., a reduction of the electric coupling. In the extreme situation where the DB-DGS is completely opened (unfolded), the electric coupling vanishes, and the particle is exclusively driven by the magnetic field generated by the line. This effect is taken into account in the model by considering that the capacitance between the line and the inner metallic region of the folded, or partially folded, DB-DGS depends on the aperture angle of the particle, and it is null when the particle is unfolded. The models are validated by parameter extraction and comparison of the circuit responses with the responses inferred by electromagnetic simulation and measurement.