Showing papers on "Equivalent circuit published in 1999"

Treatment of the Impedance of Mixed Conductors Equivalent Circuit Model and Explicit Approximate Solutions

Abstract: The electrochemical impedance of a mixed conductor with two charge carriers sandwiched between two equal electrodes is modeled phenomenologically. A simple analytical approximation is found which applies in a very broad materials parameter window (arbitrary carrier mobilities and concentrations) as long as linear response is guaranteed and the sample thickness is great compared to the Debye length. The approximation is applicable to reversible, selectively blocking as well as to partially blocking electrodes. The validity of the approximation is justified by comparison with the exact solution of Nernst‐Planck‐Poisson set of equations as given, e.g., by Macdonald. The analytical approximation describes the typical Warburg response as well as the single‐carrier behavior as limiting cases. Finite interfacial resistances (not perfectly blocking or not perfectly reversible electrodes) lead to additional semicircles and/or to distorted Warburg responses. © 1999 The Electrochemical Society. All rights reserved.

General Equivalent Circuits for Faradaic Electrode Processes under Electrochemical Reaction Control

Abstract: Several different types of equivalent circuits for the faradaic electrode process involving n state variables besides electrode potential are established in terms of the corresponding faradaic admittance equation in the case of ignoring mass transport. These circuits can develop into general equivalent circuits by introducing negative resistive and inductive and capacitive elements, each of which can be used to analyze any electrochemical impedance spectroscopy of the faradaic electrode process under electrochemical reaction control. The correspondence between element values of the circuits and electrochemical parameters of the faradaic admittance equation has also been determined by comparing the admittance or impedance of the equivalent circuit and the faradaic admittance or impedance equation. The use of general equivalent circuits, together with the faradaic admittance equation, greatly simplifies the analysis of electrochemical impedance spectroscopy for the faradaic electrode processes. © 1999 The Electrochemical Society. All rights reserved.

Methods for linear systems of circuit delay differential equations of neutral type

Abstract: Delay differential equations (DDEs) occur in many different fields including circuit theory. Circuits which include delayed elements have become more important due to the increase in performance of VLSI systems. The two types of circuits which include elements with delay are transmission lines and partial element equivalent circuits. The solution of systems which include these circuit elements are performed with solvers similar to conventional ODE circuits simulators. Since DDE solvers are more fragile with respect to stability, we investigate the conditions for contractivity and determine sufficient conditions for the asymptotic stability of the zero solution by utilizing a suitable reformulation of the system.

Positive output Luo converters: voltage lift technique

Abstract: The voltage lift technique is a popular method that is widely applied in electronic circuit design. Because of the effect of parasitic elements, the output voltage and power transfer efficiency of DC-DC power converters are limited. The voltage lift technique opens a good way to improve circuit characteristics. After long-term research, this technique has been successfully applied for DC-DC power converters. Positive output Luo converters are a series of new DC-DC step-up (boost) converters, which were developed from prototypes using the voltage lift technique. These converters perform positive to positive DC-DC voltage increasing conversion with high power density, high efficiency and cheap topology in simple structure. They are different from other existing DC-DC step-up power converters and possess many advantages including a high output voltage with small ripples. Therefore, these converters will be widely used in computer peripheral equipment and industrial applications, especially for high output voltage projects.

Stray capacitances of single-layer solenoid air-core inductors

Abstract: This paper presents a method for predicting parasitic capacitances of solenoid HF inductors made of one layer of turns with circular cross sections, uniformly wound around a cylindrical nonconductive core. The method is based on an analytical approach to obtain the turn-to-turn and turn-to-shield capacitances of coils. The influence of the wire insulation is taken into account. An equivalent lumped parallel capacitance is derived. The method was tested by experimental measurements. The calculated and measured values were in good agreement in the considered cases. The derived expressions are useful for designing HF inductors and can also be adopted for modeling and simulation purposes.

Behaviour of grounding systems excited by high impulse currents: the model and its validation

Abstract: The behaviour of grounding systems excited by high impulse currents (such as lightning strokes or phase to ground faults) considerably differs from that at low-frequency and at low-current: inductive behaviour can become more and more important with respect to resistive behaviour and, in addition, these currents can generate soil breakdown (which makes the impulse response typically nonlinear). Many experimental tests confirm these aspects. In order to obtain a correct design of electrical systems, with respect to the protection of installations against anomalous events, it is fundamental to predict the impulse characteristics of grounding systems. An efficient solution to this problem may be obtained by a mathematical model based on a circuit approach. The development of this model (which is able to simulate complex grounding systems when nonlinear ionization phenomena take place) is described in this paper. The model has been validated by comparing the numerical results both with experimental tests and with the simulations executed by various approaches.

A circuit representation technique for automated circuit design

Abstract: We present a method of automatically generating circuit designs using evolutionary search and a set of circuit constructing primitives arranged in a linear sequence. This representation has the desirable property that virtually all sets of circuit-constructing primitives result in valid circuit graphs. While this representation excludes certain circuit topologies, it is capable of generating a rich set of them including many of the useful topologies seen in hand-designed circuits. Our system allows circuit size (number of devices), circuit topology, and device values to he evolved. Using a parallel genetic algorithm and circuit simulation software, we present experimental results as applied to three analog filter and two amplifier design tasks. In all tasks, our system is able to generate circuits that achieve the target specifications. Although the evolved circuits exist as software models, detailed examinations of each suggest that they are electrically well behaved and thus suitable for physical implementation. The modest computational requirements suggest that the ability to evolve complex analog circuit representations in software is becoming more approachable on a single engineering workstation.

Method and apparatus for determining battery properties from complex impedance/admittance

Abstract: A device includes a microprocessor or microcontroller and measures real and imaginary parts of complex immittance of a cell or battery at n discrete frequencies, where n is an integer number equal to or greater than 2. The device determines cell/battery properties by evaluating components of an equivalent circuit model comprising 2n frequency-independent elements. Equating real and imaginary parts of measured immittance to values appropriate to the model at the n measurement frequencies defines a system of 2n nonlinear equations. Introducing 2n intermediate variables permits solving these equations and leads to values for the 2n model elements. A table of element values contains virtually the same information as the spectrum of complex immittance over a wide frequency range but provides this information in a more concise form that is easier to store, analyze, and manipulate. Thus, the 2n element values may themselves comprise the desired result. If desired, however, a predetermined relationship between one or more of the elements and an additional electrical, chemical, or physical property of the cell/battery may be further invoked to determine the additional property.

AC impedance and state-of-charge analysis of a sealed lithium-ion rechargeable battery

Abstract: A 7.2V, 1.25 Ah sealed lithium-ion rechargeable battery has been studied for estimating its state-of-charge (SOC) by AC impedance. The dispersion of impedance data over the frequency range between 100 kHz and 25 mHz comprises an inductive part and two capacitive parts. As the inductive behaviour of the battery is attributed to the porous nature of the electrodes, only the capacitive components have been examined. The data obtained at several SOC values of the battery have been analyzed by a non-linear least-squares fitting procedure. The presence of two depressed semicircles in the capacitive region of the Nyquist plots necessitated the use of an electrical equivalent circuit containing constant phase elements instead of capacitances. The impedance parameters corresponding to the low-frequency semicircle have been found useful for predicting the SOC of the battery, mainly because the magnitude of these parameters and their variations are more significant than those of the high-frequency semicircle. The frequency maximum (f(max)) of the semicircle, the resistive component (Z') corresponding to f(max), the phase angle (phi) in the 5.0 Hz-0.1 Hz frequency range, the equivalent series resistance (R-s) and the equivalent series capacitance (C-s) have been identified as suitable parameters for predicting the SOC values of the lithium-ion battery.

Comparison of the Mason and KLM equivalent circuits for piezoelectric resonators in the thickness mode

Abstract: The parameters of the KLM and Mason's equivalent circuits in the thickness mode are presented to include dielectric, elastic and piezoelectric loss. The models are compared under various boundary conditions with and without acoustic layers to the analytical solutions of the wave equation. We show that in all cases equivalence is found between the analytical solution and the KLM and Mason's equivalent circuit models. It is noted that in order to maintain consistency with the linear equations of piezoelectricity and the wave equation care is required when applying complex coefficients to the models. The effect of the piezoelectric loss component on the power dissipated in the transducer is presented for loaded and unloaded transducers to determine the significance of the piezoelectric loss to transducer designers. The effect of the piezoelectric loss on the insertion loss was found to be small.

Crosstalk in VLSI interconnections

Abstract: We address the problem of crosstalk computation and reduction using circuit and layout techniques in this paper. We provide easily computable expressions for crosstalk amplitude and pulse width in resistive, capacitively coupled lines. The expressions hold for nets with arbitrary number of pins and of arbitrary topology under any specified input excitation. Experimental results show that the average error is about 10% and the maximum error is less than 20%. The expressions are used to motivate circuit techniques, such as transistor sizing, and layout techniques, such as wire ordering and wire width optimization to reduce crosstalk.

Accurate modeling and parameter extraction for MOS transistors valid up to 10 GHz

Abstract: Accurate modeling and efficient parameter extraction of the small signal equivalent circuit of submicrometer MOS transistors for high-frequency operation are presented The equivalent circuit is based on a quasi-static approximation which was found to be adequate in the gigahertz range if the extrinsic components are properly modeled It includes the complete intrinsic quasi-static MOS model, the series resistances of gate, source, and drain, and a substrate coupling network Direct extraction is performed by Y-parameter analysis on the equivalent circuit in the linear and saturation regions of operation The extracted results are physically meaningful and can be used to "de-embed" the extrinsic effects such as the substrate coupling within the device Good agreement has been obtained between the simulation results of the equivalent circuit and measured data up to 10 GHz

Frequency-dependent grounding system calculation by means of a conventional nodal analysis technique

Abstract: A new method to analyze the performance of grounding systems is presented. The model is based on electric circuit theory and is solved by applying a conventional nodal analysis technique. Although the problem is treated in the frequency domain, a transient response may be obtained by means of the Fourier transform. Comparison with other methods and practical applications are presented.

A monolithic transformer coupled 5-W silicon power amplifier with 59% PAE at 0.9 GHz

Abstract: This paper presents the circuit design and application of a monolithically integrated silicon radio-frequency power amplifier for 0.8-1 GHz. The chip is fabricated in a 25-GHz-f/sub T/ silicon bipolar production technology (Siemens B6HF). A maximum output power of 5 W and maximum efficiency of 59% is achieved. The chip is operating from 2.5 to 4.5 V. The linear gain is 36 dB. The balanced two-stage circuit design is based fundamentally on three on-chip transformers. The driver stage and the output stage are connected in common-emitter configuration. The input signal can be applied balanced or single-ended if one input terminal is grounded. One transformer at the input acts as balun as well as input matching network. Two transformers acts as interstage matching network.

An improved permeameter for thin film measurements up to 6 GHz

Abstract: We report a broad band technique allowing the measurement of the permeability of thin ferromagnetic films up to 6 GHz. The permeameter is based on a single coil technique. The input impedance of the loop is measured with and without the sample. The permeability is deduced from the impedance measurement using two approaches: the first one uses an equivalent electrical circuit model and the second a transmission line theory model. This leads to significant corrections compared to previous models. Calibration of the apparatus is presented using a known sample. Our two approaches are compared to the theoretical spectral permeability. The validity of the measurements is proven by showing a full spectral gyromagnetic response of a saturated magnetic sample at different fields.

An RC load model of parallel and series-parallel resonant DC-DC converters with capacitive output filter

Abstract: A novel analytical methodology is proposed and applied to investigate the steady-state processes in voltage-fed parallel and series-parallel resonant DC-DC power converters with a capacitive output filter. In this methodology, the rectifier, output capacitor and load are replaced by an equivalent circuit which includes a capacitor and resistor connected in parallel. Excellent agreement was obtained when comparing numerical values calculated by the proposed model to cycle-by-cycle SPICE simulation and to the numerical results of earlier studies.

Ultrahigh-speed traveling-wave electroabsorption modulator-design and analysis

Abstract: Theoretical analysis and numerical calculations are presented for ultrahigh-speed (>50 GHz) traveling-wave electroabsorption modulators (TW-EAM's), including effects of velocity mismatch, impedance mismatch, and microwave attenuation. A quasi-static equivalent circuit model is used to examine the TW-EAM microwave properties, including the effect of photocurrent. Due to the optical propagation loss of the waveguide, the TW-EAM waveguide length for maximum RF link gain is currently limited to 200-300 /spl mu/m. The discussion indicates that the carrier transit time in the intrinsic layer may not severely limit the TW-EAM bandwidth. Three TW-EAM design approaches are discussed: low-impedance matching; reducing the waveguide capacitance; and distributing the modulation region.

Modeling of a photonic bandgap and its application for the low-pass filter design

Abstract: A new photonic bandgap unit structure for microstrip line is proposed. The equivalent circuit for the proposed photonic bandgap unit structure is derived by means of three dimensional field analysis methods. The equivalent circuit parameters are extracted by using the circuit analysis method. By employing the extracted parameters, the wide-band harmonic rejection low-pass filter is designed. The experimental results show the excellent agreements with theoretical results.

Large signal frequency dispersion of AlGaN/GaN heterostructure field effect transistors

Abstract: Microwave AlGaN/GaN MODFET power devices have been analysed with respect to their frequency dispersion in terms of transconductance, gate capacitance and large signal output current swing. A electrical equivalent circuit model consistent with all experimental findings, based on the incorporation of a lossy dielectric layer, is presented. It may also enable an interpretation to be made of the RF power compression observed in these devices.

Semiconductor memory device having dynamic data amplifier circuit capable of reducing power dissipation

Abstract: In a semiconductor memory device including a pair of data input/output lines, a data amplifier circuit amplifies voltages at the data input/output lines, and a data maintaining circuit maintains output signals of the data amplifier circuit. A data determination circuit, generates a data determination signal after the data maintaining circuit manintains the output signals of the data amplifier circuit and transmits the data transmitting the data determination signal to the data amplifier circuit, thus suspending the operation of the data amplifier circuit.

Sensing circuit for a memory cell array

Abstract: The present invention addresses the foregoing need by providing a memory sensing circuit for accelerating a logic level transition of the complementary memory bit line of a complementary bit line pair having a full logic swing. The memory sensing circuit has a dual-rail circuit and at least one slew-rate acceleration circuit. The dual-rail circuit can be coupled across the complementary bit line pair for conditioning a signal undergoing a logical state transition placed on either of the bit lines. The at least one slew-rate acceleration circuit is coupled to the dual-rail circuit. The conditioned signal is input to the slew-rate acceleration circuit, said slew-rate acceleration circuit having an inverter circuit with an input terminal to receive the conditioned signal. A feed-back loop transistor, having a gate terminal coupled to an output terminal of the inverter circuit is responsive to an output signal placed on the output terminal such that the slew-rate of the conditioned signal is accelerated.

A new approach to vector control for a linear induction motor considering end effects

Abstract: An equivalent circuit model in the rotor flux oriented frame is developed for the vector control of a linear induction motor (LIM) by adding the so called "end effect" to the rotary induction motor (RIM) model. We describe the effects of the end effect by introducing speed dependent scale factors to the magnetizing inductance and series resistance in the d-axis equivalent circuit. Torque and flux equations are correspondingly modified. With the vector control scheme based on the proposed equivalent circuit, one can resolve the thrust attenuation problem in a high speed. We have demonstrated through experiments the improvements achieved by the proposed scheme.

Unified equivalent-circuit model of planar discontinuities suitable for field theory-based CAD and optimization of M(H)MIC's

Abstract: Unified dynamic equivalent-circuit model for characterizing planar unbounded discontinuities is reported for use in the field-theory-based computer-aided design and optimization of high-frequency integrated circuits and structures such as monolithic and hybrid microwave integrated circuits (M(H)MIC's). The proposal of the circuit model is stemmed from a new scheme called the short-open calibration (SOC) technique. This SOC technique is directly accommodated in a full-wave method-of-moments (MoM) algorithm. The developed MoM algorithm is applied to the modeling of unbounded planar discontinuities that can be segmented into two distinct sections: static model of feed lines and dynamic model of circuit discontinuity. In this paper, the MoM, is formulated in such a way that the port voltages and currents are explicitly represented through relevant network matrices. The SOC technique is used to remove or separate unwanted parasitics brought by the approximation of the impressed voltage source and also the problem of resulting consistency between the two-dimensional and three-dimensional simulations. Results for a class of planar circuit discontinuities are very well compared with measurements and also available publications. Generalized end-to-end coupling structure having offset and unequal input/output lines (to name a specific example) is studied to indicate the parametric and dispersion effects on its equivalent capacitance and radiation conductance. Advantageous features of the proposed unified circuit model suggests its practical usefulness and high accuracy in the design and optimization of a wide range of M(H)MIC's and planar antennas.

A joint field/circuit model of line-to-ring coupling structures and its application to the design of microstrip dual-mode filters and ring resonator circuits

Abstract: A joint field/circuit model is proposed in this paper to characterize a class of line-to-ring coupling structures for design and optimization of microstrip dual-mode filters and ring resonator circuits. The generic model is derived from field theory and presented in terms of circuit elements by applying a newly developed numerical deembedding technique called "short-open calibration" in a deterministic method-of-moments scheme. It provides a new design strategy for characterizing and optimizing electrical performance of the line-to-ring coupling structures. Such three-port topologies are explicitly formulated by using an equivalent network having circuit elements calculated by the proposed joint field/circuit model. Three microstrip tightly coupling geometries and their related ring resonators are studied with the extracted J-inverter susceptance parameters. Experiments are performed to validate the joint model and also show coupling characteristics of the three types of line-to-ring circuit for the design of ring resonators and dual-mode filters. With this new technique, an optimized microstrip dual-mode filter is successfully designed and the prediction agrees well with our measurements.

Method and apparatus for determining characteristic parameters of a charge storage device

Abstract: Provided with a method and an apparatus of determining characteristic parameters of a charge storage device based on wide frequency range of impedance measurement and a non-linear equivalent circuit model by which the parameters of the non-linear equivalent circuit model indicative of the characteristics of various charge storage devices such as primary battery, secondary battery, capacitor, supercapacitor and fuel cell, the method comprising the steps of: 1) measuring voltage and current characteristics in process of charging/discharging of charge storage device by applying a voltage/current at a predetermined discharge rate; 2) measuring impedance spectra at a predetermined range of frequency by measuring the current and voltage from both terminals of the charge storage device or from an electrical load directly connected to the charge storage device at a plurality of states of within the entire charge/discharge interval; and 3) obtaining the parameters of the non-linear equivalent circuit of the charge storage device from the charge or discharge characteristics measured in step (1) and the characteristic impedance spectrum in the predetermined range of frequency measured in step (2).

A Study of Depletion Layer Effects on Equivalent Circuit Parameters Using an Electrochemical Quartz Crystal Impedance System

Abstract: An electrochemical quartz crystal impedance system (EQCIS) was used to investigate depletion layer effects on equivalent circuit parameters of piezoelectric quartz crystal resonance in electrochemi

Full-wave modeling and automatic equivalent-circuit generation of millimeter-wave planar and multilayer structures

Abstract: A general method for the automated extraction of lumped-element equivalent circuits for linear passive reciprocal distributed microwave circuits from time-domain scattering signals is presented. The proposed method autonomously generates network topology as well as parameter values while preserving circuit properties like reciprocity and passivity. Modeling examples for a two- and three-port structure are given.

Five-legged wound-core transformer model: derivation, parameters, implementation and evaluation

Abstract: The ability to predict or confirm ferroresonance and to evaluate its severity depends primarily on the correctness of the transformer model used in the computer simulation. An equivalent circuit is developed here for the widely used three-phase grounded-wye to grounded-wye five-legged wound-core distribution transformer. Recently developed equivalent circuits are generally correct, but cannot faithfully reproduce all of the ferroresonant modes possible in this transformer. This new equivalent circuit is derived using duality transformations. Core saturation and losses and coil capacitances are included in the model. Model parameters are obtained via measurement, obviating the need for proprietary manufacturer design information. The model is implemented in EMTP. Simulation results are presented and compared to measurements. A technique for predicting ferroresonance on a system level, based on the use of bifurcation diagrams and Poincare sections, is developed and implemented using EMTP. The model performs quite well, even though coil capacitances are not entirely included in the model. One of the key advancements is the development of a bifurcation simulation method to predict ferroresonant behaviors for a large range of capacitance values.

Interface circuits for quartz-crystal-microbalance sensors

Abstract: The utilization of quartz-crystal-microbalance sensors in liquids yields new requirements to the applied interface circuits. In the present article, the fundamentals of the measuring principle and advantages and drawbacks of suitable interface circuits are discussed. Special requirements of oscillators as interface circuits are outlined. Possible solutions to those requirements are investigated and two recently developed oscillator circuits are presented.