Literatura científica selecionada sobre o tema "Nonlinear chip impedance"

A method for label-free electrical impedance sensing of DNA is proposed, and experimentally demonstrated using a micro Electrical Impedance Spectroscopy (µ- EIS) device. The method features not only the detection of DNA without any labelling, but also the control of the conformation that would enhance the electrical impedance signal. In order to conduct semiautomated measurements controlled by an external PC, a microfluidic chip made of a silicone elastomer of polydimethylsiloxane (PDMS), a measurement chip embedded with micro-electrodes, and a micropump chip are fully integrated in the µ-EIS device. The µ-EIS device is capable of detecting DNA concentrations of a few nM in aqueous solution of a few pL in volume by virtue of the conformation-enhanced nonlinear impedance response. As a first demonstration of conformational-change-induced DNA analysis, the frequency and the electric field strength dependence of various lengths of DNA are evaluated.

Josephson parametric amplifiers are an important part of a modern superconducting quantum computing platform and squeezed quantum states generation devices. Traveling wave and impedance-matched parametric amplifiers provide broad bandwidth for high-fidelity single-shot readout of multiple qubit superconducting circuits. Here, we present a quantum-limited 3-wave-mixing parametric amplifier based on superconducting nonlinear asymmetric inductive elements (SNAILs), whose useful bandwidth is enhanced with an on-chip two-section impedance-matching circuit based on microstrip transmission lines. The amplifier dynamic range is increased using an array of 67 SNAILs with 268 Josephson junctions, forming a nonlinear quarter-wave resonator. Operating in a current-pumped mode, we experimentally demonstrate an average gain of 17 dB across 300 MHz bandwidth, along with an average saturation power of –100 dBm, which can go as high as −97 dBm with quantum-limited noise performance. Moreover, the amplifier can be fabricated using a simple technology with just one e-beam lithography step.

The development of portable electronic devices has greatly stimulated the need for miniaturized power sources. Planar supercapacitors are micro-scale electrochemical energy storage devices that can be integrated with other microelectronic devices on a chip. In this paper, we study the behavior of microsupercapacitors with in-plane interdigital electrodes of carbon nanotube array under sinusoidal excitation, step voltage input and sawlike voltage input. Considering the anomalous diffusion of ions in the array and interelectrode space, we propose a fractional-order equivalent circuit model that successfully describes the measured impedance spectra. We demonstrate that the response of the investigated micro-supercapacitors is linear and the system is time-invariant. The numerical inversion of the Laplace transforms for electric current response in an equivalent circuit with a given impedance leads to results consistent with potentiostatic measurements and cyclic voltammograms. The use of electrodes based on an ordered array of nanotubes reduces the role of nonlinear effects in the behavior of a supercapacitor. The effect of the disordering of nanotubes with increasing array height on supercapacitor impedance is considered in the framework of a distributed-order subdiffusion model.

The traditional method of calculating junction temperature does not consider the dependence of a material’s thermal conductivity on temperature, in which the thermal conductivity changes with temperature. However, with an increase in junction temperature, the temperature sensitivity (TS) will have a more significant impact on the actual temperature of chips. This study established an improved IGBT equivalent thermal impedance model that considers the nonlinear characteristics of the TS of chips and ceramic materials. The Fourier series analysis method was used to obtain the heat flux density curve, and then the heat diffusion angles of each layer were solved. Moreover, iterations were performed until the thermal conductivity and temperature of the chip and ceramic layers matched the nonlinear characteristics of the TS. When the power loss was less than 200 W, the maximum error of the junction temperature calculated by the proposed method considering TS was 3%, while the maximum error of the method without considering TS was 9.5%. Compared with the finite element simulation, the proposed method has a faster solving speed and high accuracy. The proposed method only requires the input material parameters, size parameters, and boundary conditions to solve the junction temperature, which has strong practicality and high accuracy.

In this paper, we investigate various graphene monolayer nanomesh structures (diodes) formed only by nanoholes, with a diameter of just 20 nm and etched from the graphene layer in different shapes (such as rhombus, bow tie, rectangle, trapezoid, and triangle), and their electrical properties targeting electromagnetic energy harvesting applications. In this respect, the main parameters characterizing any nonlinear device for energy harvesting are extracted from tens of measurements performed on a single chip containing the fabricated diodes. The best nano-perforated graphene structure is the triangle nanomesh structure, which exhibits remarkable performance in terms of its characteristic parameters, e.g., a 420 Ω differential resistance for optimal impedance matching to an antenna, a high responsivity greater than 103 V/W, and a low noise equivalent power of 847 pW/√Hz at 0 V.

With the continuous improvement of industrial production and manufacturing level, all kinds of equipment are developing in the direction of refinement and precision, especially the equipment manufacturing industry such as automobile manufacturing, equipment, integrated circuits, chip manufacturing, and other semiconductor industries. An intelligent virtual resistance control strategy based on machine research is proposed for rational power distribution and cycle suppression when multiple inverters are operated in parallel in low-voltage microgrids. Based on this, the control strategy of temporary power reduction of inverters is improved to improve the parallel inverter power distribution accuracy and ensure the reliable dynamic response of the constrained current in the circuit between parallel inverters. Finally, a multi-inverter parallel system model is established to verify the correctness and effectiveness of the proposed control strategy. The voltage waveform under nonlinear load conditions is improved and high-frequency harmonics are suppressed, which has obvious advantages compared with the general virtual impedance design method.

In this paper, some theoretical aspects and experimental results are discussed with the aim to provide supplementary dc energy to radio frequency identification (RFID) tags by exploiting the nonlinear nature of rectifier devices. Three nonlinear phenomena are treated: (i) the impedance power dependence, (ii) the harmonic production, and (iii) the dependence on the radio frequency waveform. The novelty of the work relies on proposing a double rectifier composite system in where the nonlinearity of each rectifier is exploited to enhance the global powering performance of the system. Using the passive RFID technology as a beacon for the implementation, the approach considers combining the internal rectifier circuit of a commercial RFID chip operating at 868 MHz with an external rectifier circuit operating at 2.17 GHz. The solution triggers in a composite system RFID tag-harvester integrated in a single-feed dual-band antenna. The experimental validation shows 5 dB of tag sensitivity enhancement when it is empowered by the external harvester. The enhanced sensitivity produces an increase in the theoretical reading range distance from 3.3 to 6.1 m.

The thermal management and channel temperature evaluation of GaN power amplifiers are indispensable issues in engineering field. The transient thermal characteristics of pulse operated AlGaN/GaN high electron mobility transistors (HEMT) used in high power amplifiers are systematically investigated by using three-dimensional simulation with the finite element method. To improve the calculation accuracy, the nonlinear thermal conductivities and near-junction region of GaN chip are considered and treated appropriately in our numerical analysis. The periodic transient pulses temperature and temperature distribution are analyzed to estimate thermal response when GaN amplifiers are operating in pulsed mode with kilowatt-level power, and the relationships between channel temperatures and pulse width, gate structures, and power density of GaN device are analyzed. Results indicate that the maximal channel temperature and thermal impedance of device are considerably influenced by pulse width and power density effects, but the changes of gate fingers and gate width have no effect on channel temperature when the total gate width and active area are kept constant. Finally, the transient thermal response of GaN amplifier is measured using IR thermal photogrammetry, and the correctness and validation of the simulation model is verified. The study of transient simulation is demonstrated necessary for optimal designs of pulse-operated AlGaN/GaN HEMTs.

Non-Von Neumann computing application constituted by artificial synapses based on electrochemical random-access memory (ECRAM) has aroused tremendous attention owing to its capability to perform parallel operations, thus reducing the cost of time and energy spent [1-3]. Existing ECRAM synapses comprise two-terminal memristors and three-terminal synaptic transistors (SynT). While low cost, scalability, and high density are the highlights for memristors, their nonlinear, asymmetric state modulation, high ON current withdrawal, and sneak path in crossbar array integration prevent them from becoming the ideal synaptic elements for artificial neural networks (ANN) [4]. SynT configuration, on the other hand, offers an additional electrolyte-gated control from which ion doping content can be monitored via redox reactions, thus decoupling write-read actions and improving the linearity of programming states [5-6]. Nevertheless, existing SynTs suffer from different integration issues stemming from liquid-based ionic conductors and manually exfoliated channels. Moreover, several kinds of SynTs possess highly conductive channels in the range of µS to mS, significantly scaling up the energy spent for analog states reading. Despite having numerous communications on the performance of different ECRAM, a comprehensive electrochemical view of ion intercalation into the active material, the main root of conductance modulation, is clearly missing. In this work, we present the elaboration procedure of an all-solid-state synaptic transistor composed of nanoscale electrolyte and channel layers. The devices have been elaborated on 8’’ Silicon wafers using microfabrication processes compatible with conventional semiconductor technology and CMOS back end of line (BEoL) integration. (Figure 1a) We demonstrate the excellent synaptic plasticity properties of short-term potentiation (STP) and long-term potentiation (LTP) of our SynT. We performed tests to study the correlation between linearity, asymmetry, and the number of analog states. By averaging the amount of injected ions per write operation, we estimated the energy consumed for switching among adjacent states of this device is 22.5 pJ, yielding area-normalized energy of 4 fJ/µm2. In addition, operating in the range of nS, our SynTs meet the critical criteria of low energy consumption for both write and read operations. Endurance was highlighted by cycling in ambient conditions with 100 states of potentiation and depression for over 1000 cycles with only a slight variation of Gmax/Gmin ratio of 6.2 % (Figure 1b, c). Approximately 95 % accuracy in MNIST pattern recognition test on ANN in the crossbar array configuration has been obtained by simulation with SynTs as synaptic elements reassured SynT is a promising candidate for future neuromorphic computing hardware. To shed light on the properties of intercalation phenomena of Li ions into the TiO2 layer, a further electrochemical study on a cell comprising Ti/TiO2/LiPON/Li corresponding to the SynT gate stack was performed. This understanding will help to elucidate the correlation with conductance modulation characteristics for a synaptic transistor. Multiple tests were carried out, including cyclic voltammetry (CV) with different scan rates, rate capability with Galvanostatic cycling with potential limit (GCPL), and electrochemical impedance spectroscopy (EIS) on different states of charge. A circuit model was introduced to fit the frequency response of the cell, and it explained well the behavior of charging capability at different OCV (Figure 1d). References [1] P. Narayanan et al., “Toward on-chip acceleration of the backpropagation algorithm using nonvolatile memory,” IBM J. Res. Dev., vol. 61, no. 4/5, p. 11:1-11:11, Jul. 2017, doi: 10.1147/JRD.2017.2716579. [2] J. Tang et al., “ECRAM as Scalable Synaptic Cell for High-Speed, Low-Power Neuromorphic Computing,” in 2018 IEEE International Electron Devices Meeting (IEDM), San Francisco, CA, Dec. 2018, p. 13.1.1-13.1.4. doi: 10.1109/IEDM.2018.8614551. [3] Y. Li et al., “In situ Parallel Training of Analog Neural Network Using Electrochemical Random-Access Memory,” Front. Neurosci., vol. 15, p. 636127, Apr. 2021, doi: 10.3389/fnins.2021.636127. [4] M. A. Zidan, H. A. H. Fahmy, M. M. Hussain, and K. N. Salama, “Memristor-based memory: The sneak paths problem and solutions,” Microelectron. J., vol. 44, no. 2, pp. 176–183, Feb. 2013, doi: 10.1016/j.mejo.2012.10.001. [5] Y. van de Burgt et al., “A non-volatile organic electrochemical device as a low-voltage artificial synapse for neuromorphic computing,” Nat. Mater., vol. 16, no. 4, pp. 414–418, Apr. 2017, doi: 10.1038/nmat4856. [6] E. J. Fuller et al., “Li-Ion Synaptic Transistor for Low Power Analog Computing,” Adv. Mater., vol. 29, no. 4, p. 1604310, Jan. 2017, doi: 10.1002/adma.201604310. Figure 1

AbstractLight travels in a zero-index medium without accumulating a spatial phase, resulting in perfect spatial coherence. Such coherence brings several potential applications, including arbitrarily shaped waveguides, phase-mismatch-free nonlinear propagation, large-area single-mode lasers, and extended superradiance. A promising platform to achieve these applications is an integrated Dirac-cone material that features an impedance-matched zero index. Although an integrated Dirac-cone material eliminates ohmic losses via its purely dielectric structure, it still entails out-of-plane radiation loss, limiting its applications to a small scale. We design an ultra-low-loss integrated Dirac cone material by achieving destructive interference above and below the material. The material consists of a square array of low-aspect-ratio silicon pillars embedded in silicon dioxide, featuring easy fabrication using a standard planar process. This design paves the way for leveraging the perfect spatial coherence of large-area zero-index materials in linear, nonlinear, and quantum optics.

Le contexte de cette thèse aborde les scénarios RFID UHF impliquant la mise en jeux d'un grand nombre de tags. Ces tags sont d'une part distribués de manière aléatoire et d'autre part concentrés dans un volume électriquement réduit. Dans cette situation, la proximité des éléments rayonnants entraîne un couplage électromagnétique important entre les antennes des tags, impactant le lien radio entre le lecteur et chaque tag. Par conséquent, on observe généralement une dégradation des indicateurs de performance clés du système, tels que la distance maximum de lecture ou le taux de lecture. Ce travail de recherche présente une analyse de performance d'un système RFID dans un contexte de forte densité de tags en incluant des aspects statistiques. À cette fin, un modèle est proposé pour les liaisons montante et descendante, incluant les effets de couplage entre les tags. Ce modèle est validé par des simulations et des mesures. Avant de se concentrer sur l'analyse complexe d'un ensemble de tags, une caractérisation complète d'un tag RF fabriqué au laboratoire est présentée. Ce tag RFID est composé d'une antenne gravée sur un substrat epoxy et utilise une puce Higgs-9. L'impédance de l'antenne est simulée et mesurée. L'impédance non linéaire de la puce est caractérisée par un impédancemètre. L'ensemble du tag est composé de l'antenne et de la puce et il est testé dans le cadre du protocole RFID. Compte tenu de la complexité du problème posé, l'ensemble des tags RFID est également modélisé par un ensemble de dipôles chargés afin de simplifier l'analyse electromagnétique. Ce modèle simplifié reste valide à condition qu'une corrélation élevée entre le comportement d'un ensemble de dipôle et celui des tags réels puisse être prouvée. La dégradation des performances due au couplage dans la liaison descendante est analysée en termes de surface équivalente radar différentielle ou SER différentielle, car elle est indicative de la discrimination possible des états de modulation présents sur le signal rétrodiffusé par le tag. La SER différentielle est calculée à l'aide des coefficients de réflexion estimés du tag environné. Les coefficients de réflexion du tag sont estimés pour deux niveaux de charge différents. La SER différentielle est également mesurée directement par le protocole RFID. Dans la dernière partie de ce travail de recherche nous prenons en compte l'impact des non-linéarités de l'impédance complexe de la puce en plus des effets du couplage dans la liason descendante. Sachant que l'impédance complexe de la puce est une fonction de la puissance au niveau de la puce, une procédure de mise en correspondance est présentée pour estimer précisement l'impédance complexe de la puce à partir d'une base de données issue de mesures. A partir du modèle de couplage il est possible d'estimer la puissance délivrée aux puces d'un ensemble de tags distribués aléatoirement incluant les phénomènes de non linéarités. Les déductions tirées de ce travail, combinées à des données statistiques pertinentes, pourraient être utilisées par les ingénieurs concepteurs RFID pour évaluer les performances d'un scénario RFID en prenant en compte le couplage mutuel et l'impédance non linéaire de la puce
The context of this thesis is primarily centered around UHF RFID scenarios which involve a large number of tags randomly distributed and confined in an electrically reduced volume. The proximity of the radiating elements would result in significant electromagnetic coupling between the tag antennas, impacting the communication link between the reader and the tags. Consequently, the key performance indicators of the system such as read-range and read-rate get degraded. This research work presents a performance analysis of such an RFID system by including statistical aspects. To this aim, a model for the forward and reverse links including coupling effects between the tags is presented, which is validated by electromagnetic simulations and measurements. Prior to delving into the analysis involving a set of tags, a comprehensive characterization of the home-made RFID tag integrated with a Higgs-9 chip which is used in the study is performed. The antenna impedance is simulated and measured, while the nonlinear chip impedance is characterized by an impedance analyzer. The whole tag composed of the home-made antenna and the chip is tested under the RFID protocols. Considering the complexity of the problem at hand, the set of RFID tags under study is also modeled by a set of loaded dipoles in order to simplify their electromagnetic model provided that a high correlation between their behaviour could be proved. At this stage, the monostatic RCS is studied with an objective of highlighting the degradation in the response of an isolated tag to that of the same tag while surrounded by other tags. The coupling effects on the impedance and the radiation pattern of a tag are thus included in this monostatic RCS response. Afterwards, the forward link is analyzed in terms of the power absorbed by the chip and the maximum read-range of an interrogated tag while being surrounded by neighboring loaded tags. Interestingly a clear correlation is observed between the power absorbed by the chip obtained by simulation and the maximum read-range which is obtained by simulation and measured under RFID protocol. Multiple random configurations of tags have been tested and as a result of this part, a circuit-level observable is correlated to a direct system-level observable. The performance degradation due to coupling in the reverse link is analyzed in terms of the differential RCS, as it is indicative of the modulation depth from the tag. The differential RCS is calculated using the estimated reflection coefficients of the surrounded tag for two different load levels and is also measured directly under RFID protocol. As the last part, this research work takes into account the impact of nonlinear evolution of the complex chip impedance, along with coupling effects in the reverse link. Knowing that the chip impedance is a function of the input power, a mapping procedure is presented for the chip impedance estimation. The coupling model provides the power delivered to the chip, which is then mapped to obtain the nonlinear chip impedance of each tag in a set of randomly distributed tags. The inferences drawn from this work when combined with relevant statistical data could be used by RFID design engineers to assess the performance of an RFID scenario while being exposed to both mutual coupling and nonlinearities

Abstract This paper presents a Nonlinear Electromechanical Impedance Spectroscopy (NEMIS) methodology for the comprehensive monitoring of carbon fiber reinforced composite (CFRC) laminates. This method can obtain structural impedance spectra and capture nonlinear ultrasonic features for damage detection, combining the merits of the conventional EMIS and the nonlinear ultrasonic techniques. A comparative illustration between the conventional EMIS and NEMIS is presented. Various damage types and damage mechanisms of CFRC laminates are reviewed. Numerical investigation on a reduced-order 1-D Contact Acoustic Nonlinearity (CAN) model are conducted to demonstrate the chirp-induced nonlinear features. Furthermore. a finite element (FE) model is established to verify the feasibility of the NEMIS for damage detection. The macro-scale damage types are modeled by the changes of material properties, while the incipient damage like delamination is simulated by setting the contact interfacing condition between the laminate debonding areas. Correspondingly, the chirp-based impedance spectra are employed to detect the macro-scale damage via the deviation of resonance peaks, while the nonlinear features, such as higher harmonics and wave modulation are utilized to monitor the delamination. Two damage indices are developed to quantify the severity of both the macro and incipient damage. This paper finishes with conclusion and suggestions for future work.