Showing papers on "Equivalent circuit published in 2002"

Resonator-based analysis of the combination of mobile handset antenna and chassis

Abstract: The performance of the mobile phone handset antenna-chassis combination is analyzed based on an approximate decomposition of the waves on the structure into two resonant wavemodes: the antenna-element wavemode and the chassis wavemode. A double resonator equivalent circuit model is presented and used to estimate the impedance bandwidth and the respective distributions of radiation losses with typical parameter values at 900 and 1800 MHz. It is noticed that at 900 MHz, the radiation losses of the antenna element wavemode represent typically less than 10% of the total power. Thus, the antenna element works mainly as a matching element, which couples to the low-Q resonant wavemode of the chassis. At 1800 MHz, the contribution of the antenna element wavemode is larger. By enhancing the coupling and by tuning the chassis resonance, it is possible to obtain an impedance bandwidth of over 50% (6 dB return loss) at both at 900 and 1800 MHz. The results given by the equivalent circuit study are fully supported by those of three-dimensional phone-model simulations, including calculation of the SAR and efficiency values. In prototyping, the 6 dB bandwidth of 5.5% was obtained at 980 MHz with a nonradiating coupling element with a volume of 1.6 cm/sup 3/ on a 120 mm long chassis.

Deconvolution of electrochemical impedance spectra for the identification of electrode reaction mechanisms in solid oxide fuel cells

Abstract: The polarization processes occurring at the electrode–electrolyte interfaces of solid oxide fuel cells (SOFC) were investigated by electrochemical impedance spectra measured at single cells under realistic operating conditions. The approach presented is based on distributions of relaxation times which are the basic quantity of interest in electrochemical impedance data analysis. A deconvolution method was developed and implemented that yields these characteristic distribution patterns directly from the impedance spectra. In contrast to nonlinear least squares curve fit of equivalent circuit models, no a priori circuit choice has to be made. Even more importantly, the excellent resolving capacity allows the untangling of the impedance contributions of up to three physically distinct processes within one frequency decade. With the method, processes with the highest polarization losses can be identified and targeted to improve cell performance. Based on the distributions, a general strategy for the identification of the reaction mechanisms is given. The evaluation of the distributions in terms of peak parameters is illustrated by a physical model for oxygen reduction at the SOFC cathode–electrolyte interface. The method is expected to find many applications in electrochemistry beyond the field of solid oxide fuel cell development.

Deconvolution of electrochemical impedance spectra for the identification of electrode reaction mechanisms in solid oxide fuel cells

Abstract: The polarization processes occurring at the electrode-electrolyte interfaces of solid oxide fuel cells (SOFC) were investigated by electrochemical impedance spectra measured at single cells under realistic operating conditions. The approach presented is based on distributions of relaxation times which are the basic quantity of interest in electrochemical impedance data analysis. A deconvolution method was developed and implemented that yields these characteristic distribution patterns directly from the impedance spectra. In contrast to nonlinear least squares curve fit of equivalent circuit models, no a priori circuit choice has to be made. Even more importantly, the excellent resolving capacity allows the untangling of the impedance contributions of up to three physically distinct processes within one frequency decade. With the method, processes with the highest polarization losses can be identified and targeted to improve cell performance. Based on the distributions, a general strategy for the identification of the reaction mechanisms is given. The evaluation of the distributions in terms of peak parameters is illustrated by a physical model for oxygen reduction at the SOFC cathode-electrolyte interface. The method is expected to find many applications in electrochemistry beyond the field of solid oxide fuel cell development.

A design of the novel coupled-line bandpass filter using defected ground structure with wide stopband performance

Abstract: In this paper, a novel three-pole coupled-line bandpass filter with a microstrip configuration is presented. Presented bandpass filters use defected ground structure (DGS) sections to simultaneously realize a resonator and an inverter. The proposed coupled-line bandpass filter provides compact size with low insertion-loss characteristic. Furthermore, a DGS shape for a microstrip line is newly proposed. The proposed DGS unit structure has a resonance characteristic in some frequency band. The proposed coupled-line filter can provide attenuation poles for wide stopband characteristic due to resonance characteristic of DGS. The equivalent circuit for the proposed DGS unit section is described. The equivalent-circuit parameters for DGS are extracted by using a three-dimensional finite-element-method calculation and simple circuit analysis method. A design method for the proposed coupled-line filter is derived based on coupled-line filter theory and the equivalent circuit of the DGS. The experimental results show excellent agreements with theoretical simulation results.

Differentially driven symmetric microstrip inductors

Abstract: A differentially excited symmetric inductor that enhances inductor quality (Q) factor on silicon RFICs is presented. Compared with an equivalent single-ended configuration, experimental data demonstrate that the differential inductor offers a 50% greater Q factor and a broader range of operating frequencies. Predictions from full-wave simulations and a physics-based SPICE-compatible model are validated by experimental measurements on an inductor fabricated in a triple-level metal silicon technology. Application of the symmetric inductor to a cross-coupled oscillator improves output voltage swing and phase noise by 75% and 1.8 dB, respectively (for a given power consumption), while chip area is reduced by 35% compared to conventional inductor equivalents.

Frequency-independent equivalent circuit model for on-chip spiral inductors

Abstract: A wide-band, physical and scalable 2-/spl Pi/ equivalent circuit model for on-chip spiral inductors is developed. Using frequency-independent RLC elements, it accurately captures R(f) and L(f) characteristics beyond the self-resonant frequency. This new model is fully compatible with both AC and transient analysis. Verification with measurement data demonstrates excellent scalability for a wide range of inductor configurations.

Characterization of membrane electrode assemblies in polymer electrolyte fuel cells using a.c. impedance spectroscopy

Abstract: The most common methods used to characterize the electrochemical performance of fuel cells are to record current–voltage U(i) curves. However, separation of electrochemical and ohmic contributions to the U(i) characteristics requires additional experimental techniques. The application of electrochemical impedance spectra (EIS) is an approach to determine parameters which have proved to be indispensable for the development of fuel cell electrodes and membrane electrode assemblies (MEAs). This paper proves that it is possible to split the cell impedance into electrode impedances and electrolyte resistance by varying the operating conditions of the fuel cell (current load) and by simulation of the measured EIS with an equivalent circuit. Furthermore, integration in the current density domain of the individual impedance elements enables the calculation of the individual overpotentials in the fuel cell and the determination of the voltage loss fractions.

An MOS transistor model for RF IC design valid in all regions of operation

Abstract: This paper presents an overview of MOS transistor modeling for RF integrated circuit design. It starts with the description of a physical equivalent circuit that can easily be implemented as a SPICE subcircuit. The MOS transistor is divided into an intrinsic part, representing mainly the active part of the device, and an extrinsic part responsible for most of the parasitic elements. A complete charge-based model of the intrinsic part is presented. The main advantage of this new charge-based model is to provide a simple and coherent description of the DC, AC, nonquasi-static (NQS), and noise behavior of the intrinsic MOS that is valid in all regions of operation. It is based on the forward and reverse charges q/sub f/ and q/sub r/ defined as the mobile charge densities, evaluated at the source and at the drain. This intrinsic model also includes a new simplified NQS model that uses a bias and frequency normalization allowing one to describe the high-order frequency behavior with only two simple functions. The extrinsic model includes all the terminal access series resistances, and particularly the gate resistance, the overlap, and junction capacitances as well as a substrate network. The latter is required to account for the signal coupling occurring at RF from the drain to the source and the bulk, through the junction capacitances. The noise model is then presented, including the effect of the substrate resistances on the RF noise parameters. All the aspects of the model are validated for a 0.25-/spl mu/m CMOS process.

Comparative study of 3-D flux electrical machines with soft magnetic composite cores

Abstract: This paper compares two types of three-dimensional (3D) flux electrical machines with soft magnetic composite (SMC) cores, namely claw pole and transverse flux machines. 3D electromagnetic field analysis is conducted for the computation of some important parameters and optimization of the machine structures. An equivalent electric circuit is derived to calculate the machine performances. The analysis methods are validated by experimental results of a single phase claw pole permanent magnet machine with a SMC core. Useful conclusions are drawn from the evaluation and comparison of two machines with soft magnetic composite cores.

Dynamic Phasors in Modeling and Analysis of Unbalanced Polyphase Ac Machines

Abstract: The paper describes a novel approach to dynamical modeling of asymmetries in electric machines and polyphase systems (e.g., the ones caused by unbalanced supply waveforms). The proposed technique is a polyphase generalization of the dynamic phasor approach from power electronics and electric drives. The technique is applicable to nonlinear models, and offers distinct advantages in modeling, simulation, and control with respect to standard time-domain models. In a steady state, the dynamic phasors reduce to standard phasors from ac circuit theory. We performed experiments and simulations involving a three-phase induction motor and a three-phase synchronous permanent magnet motor, and we demonstrate that models based on dynamic phasors provide very accurate descriptions of observed transients. In a steady state, our approach yields improved equivalent circuits that contain coupling between the positive and negative sequence subcircuits.

A spiral-shaped defected ground structure for coplanar waveguide

Abstract: The authors present a spiral-shaped defected ground structure for coplanar waveguides (DGSCPW), which can be used as a kind of periodic structure for a planar transmission line. The proposed spiral-DGSCPW adopts spiral-shaped defects on both ground planes of CPW. Due to the spiral-shaped defects, the equivalent shunt inductance and slow-wave effects increase more rapidly than the standard CPW or CPW lines combined with the conventional PBG. The modeling and analysis to extract the equivalent circuit, increased slow-wave factor, and simulated and measured performances are presented.

Electrical properties of supported lipid bilayer membranes

Abstract: This paper describes a study of the electrical properties of supported lipid bilayer membranes on semiconductor and gold surfaces. The study is aimed to foster the understanding of supported membrane systems and to allow the rational design of biosensor assays for ion channel analysis. Impedance spectroscopy was applied for the electrical characterization of the supported membrane systems. A novel equivalent circuit model is introduced for the data evaluation, which accounts for the deviation of the impedance response of supported membranes from that of an ideal RC element. As a result of the improved accordance of model and data, the resistance and the capacity of supported membranes can be determined more accurately and independently from each other. Experimental results describe the phenomenology of the electrical properties of supported bilayers regarding variations in preparation, composition, and environmental conditions. We discuss the findings in terms of membrane−substrate interactions and models...

Prediction of IMD in LDMOS transistor amplifiers using a new large-signal model

Abstract: In this paper, the intermodulation distortion (IMD) behavior of LDMOS transistors is treated. First, an analysis is performed to explain measured IMD characteristics in different classes of operation. It is shown that the turn-on region plays an important role in explaining measured IMD behavior, which may also give a clue to the excellent linearity of LDMOS transistors. Thereafter, with this knowledge, a new empirical large-signal model with improved capability of predicting IMD in LDMOS amplifiers is presented. The model is verified against various measurements at low as well as high frequency in a class-AB power amplifier circuit.

Electrochemical and Thermal Characterization of Battery Modules Commensurate with Electric Vehicle Integration

Abstract: A relatively simple mathematical representation of a nickel metal hydride traction battery is developed and implemented. The approach is based in part on an equivalent circuit comprising a resistor element in series with a parallel resistor-capacitor combination. Additional features include self-discharge, current inefficiency, temperature and state-of-charge (SOC) dependencies, and mass-transport limitations. An energy balance is coupled to the electrochemical problem: the energy balance incorporates transient heat-transfer to the battery surroundings as well as reversible and irreversible heat generation. The high-frequency and pseudo-steady-state impedance exhibit an Arrhenius temperature dependence. All the model parameters arc constants or are described by continuous functions of temperature and SOC. Calculated results from the coupled electrochemical and thermal model are compared with charge and discharge experiments conducted over the time scales and current magnitudes of interest for electric-vehicle applications. The paper closes with a brief summary and a discussion of open questions.

An integrable electronic-controlled quadrature sinusoidal oscillator using CMOS operational transconductance amplifier

Abstract: This paper describes two approaches to implementing third-order oscillators. The first approach proposes a third-order oscillator using transconductors and capacitors. They are cascaded as two lossy and one lossless integrator circuit. This approach is a feedback from transconductance gain = 2. This first circuit is based on a basic transconductor with a simple configuration including 16 ransistors, four current sources and three capacitors. The second approach proposes a third-order oscillator using transconductors, capacitors and a transresistor circuit. These are cascaded as lossy integrator circuits and are fedback with voltage gain = 8. This voltage gain can be designed using a transconductor circuit and a transresistor circuit. This second circuit consists of 18 transistors, four current sources and three capacitors. Since both circuits use no resistors, they are suitable for further fabrication. These circuits use a ±3V power supply.

A simple and analytical parameter-extraction method of a microwave MOSFET

Abstract: A simple and accurate parameter-extraction method of a high-frequency small-signal MOSFET model including the substrate-related parameters and nonreciprocal capacitors is proposed. Direct extraction of each parameter using a linear regression approach is performed by Y-parameter analysis on the proposed equivalent circuit of the MOSFET for high-frequency operation. The extracted results are physically meaningful and good agreement has been obtained between the simulation results of the equivalent circuit and measured data without any optimization. Also, the extracted parameters, such as g/sub m/ and g/sub ds/, match very well with those obtained by DC measurement.

Class E with parallel circuit - a new challenge for high-efficiency RF and microwave power amplifiers

Abstract: In this paper, a new circuit configuration of switched-mode tuned Class E power amplifiers with load network consisting of a parallel capacitance, a parallel inductance and a series resonant circuit tuned on the fundamental is defined using a detailed analytical description with a complete set of the design equations. The ideal collector voltage and current waveforms demonstrate a possibility of 100-percent efficiency. The circuit schematic of a parallel-circuit Class E power amplifier can be realized with lumped or transmission-line elements. Two examples of high power LDMOSFET and low-voltage HBT power amplifiers, utilizing a parallel-circuit Class E circuit configuration, are presented.

Broadband and compact multi-pole microstrip bandpass filters using ground plane aperture technique

Abstract: A ground plane aperture technique is developed for effective enhancement of the capacitive coupling factor in a parallel-coupled microstrip line (PCML). By applying a so-called 'short-open calibration' (SOC) scheme in the fullwave method of moments (MoM) algorithm, this PCML with two external lines is characterised by an equivalent J-inverter network with its susceptance and two electrical line lengths. Extracted parameters indicate that the coupling factor appears to be frequency-dependent and its maximum value rises rapidly as the aperture is widened. With the introduction of a single microstrip line section between two identical PCMLs, a broadband and compact multi-pole microstrip bandpass filter is proposed for the first time, and its electrical behaviour is studied and optimised on the basis of its equivalent circuit network. The network-based optimised results are confirmed by an EM simulation of the entire filter layout, featuring ultra-broadband and four-pole bandpass behaviour. Further, a single capacitively loaded line section is utilised to formulate a multi-pole bandpass filter, and its electrical effects are also discussed for filter design. The predicted and measured results confirm attractive properties of the proposed multi-pole filter with BW=60%. |S/sub 11/|<-16 dB and 220% wide upper stop-band.

Statics and dynamics of fluorescent lamps operating at high frequency: modeling and simulation

Abstract: The static and dynamic response of a fluorescent lamp operating at high frequency was studied and modeled by a SPICE-compatible behavioral equivalent circuit. Good agreement was found between model simulations and experimental results. It was also found analytically that the proposed model predicts a zero at the right half-side of the complex plane as observed experimentally.

Wideband bandpass filter design with three-line microstrip structures

Abstract: A systematic procedure is described for designing wideband bandpass filters based on parallel coupled three-line microstrip structures. It starts with modal analysis of a three-line coupled microstrip circuit. A database of modal eigenvoltage coefficients and modal characteristic impedances for a specified value of substrate ɛr is established. The relation between the circuit parameters of a three-line coupling section and an admittance inverter circuit is derived, so that the filters can be synthesised by a standard procedure. As compared with traditional parallel coupled lines, the proposed three-line design has the following two important features for the design of wideband filters: the tight line spacings of end stages can be greatly relaxed; and the stopband rejections are improved. Four filters with fractional bandwidths from 40% to 70% are fabricated on substrates with low and high dielectric constants. Prediction and measurement results are in good agreement.

Simultaneous switching noise in on-chip CMOS power distribution networks

Abstract: Simultaneous switching noise (SSN) has become an important issue in the design of the internal on-chip power distribution networks in current very large scale integration/ultra large scale integration (VLSI/ULSI) circuits. An inductive model is used to characterize the power supply rails when a transient current is generated by simultaneously switching the on-chip registers and logic gates in a synchronous CMOS VLSI/ULSI circuit. An analytical expression characterizing the SSN voltage is presented here based on a lumped inductive-resistive-capacitive RLC model. The peak value of the SSN voltage based on this analytical expression is within 10% as compared to SPICE simulations. Design constraints at both the circuit and layout levels are also discussed based on minimizing the effects of the peak value of the SSN voltage.

Low frequency enhanced frequency selective surface technology and applications

Abstract: DC inductive FSS technology is a printed slow wave structure usable for reduced size resonators in antenna and filter applications of wireless applications. It is a dispersive surface defined in terms of its parallel LC equivalent circuit that enhances the inductance and capacitance of the equivalent circuit to obtain a pole frequency as low as 300 MHz. The effective sheet impedance model has a resonant pole whose free-space wavelength can be greater than 10 times the FSS period. A conductor-backed DCL FSS can create a DC inductive artificial magnetic conductor (DCL AMC), high-impedance surface with resonant frequencies as low as 2 GHz. Lorentz poles introduced into the DCL FSS create multi-resonant DCL AMCs. Antennas fabricated from DCL FSS materials include single-band elements such as a bent-wire monopole on the DCL AMC and multi-band (dual and triple) shorted patches, similar to PIFAs with the patch/lid being a DCL FSS.

Equivalent lumped elements G, L, C, and unloaded Q's of closed- and open-loop ring resonators

Abstract: A transmission-line model is used to extract the equivalent lumped-element circuits for the closed- and open-loop ring resonators. The unloaded Q values of the ring resonators can be calculated from the equivalent lumped elements G, L, and C. Four different configurations of microstrip ring resonators fabricated on low and high dielectric-constant substrates are used to investigate the lumped elements and unloaded Qs. The largest difference between the measured and calculated unloaded Q is 5.7%, which is due to measurement uncertainties and accuracies of the calculation. These simple expressions introduce an easy method for analyzing ring resonators in filters and provide, for the first time, a means of predicting their unloaded Q.

Design of defected ground structures for harmonic control of active microstrip antenna

Abstract: Photonic bandgap (PBG) structures are usually periodic structures in which propagation of a certain band of frequencies is prohibited. PBG structures for microwave frequencies are applied in planar circuits such as microstrip line and CPW (coplanar waveguide). In this case, they are more frequently termed defected ground structures (DGS). Most of the research performed on DGS has been based on the equivalent circuit consisting of lumped elements, L and C, extracted from EM simulations (see D. Ahn et al., IEEE MTT, vol.49, 2001). In addition, we also consider radiation effects by including resistance, R, in the equivalent circuit. The general 1D periodic structures with N unit cells are analyzed using an ABCD matrix formulation. The effects of the RLC elements of the unit cell, the spacing between the unit cells, and the cell number, N, are investigated in detail. For a design example, a simple 1D DGS with N=2 is designed for harmonic control through a modeling using transmission line theory. This 1D DGS with N=2 is much simpler than the one proposed by Y. Horii and M. Tsutsmi (see IEEE MGWL, vol.9, no.1. p.1895-8, 1999). The proposed approach enables us to design the required DGS quite easily and quickly.

Parametric macromodels of digital I/O ports

Abstract: Addresses the development of macromodels for input and output ports of a digital device. The proposed macromodels consist of parametric representations that can be obtained from port transient waveforms at the device ports via a well established procedure. The models are implementable as SPICE subcircuits and their accuracy and efficiency are verified by applying the approach to the characterization of transistor-level models of commercial devices.

An RF circuit model for carbon nanotubes

Abstract: We develop an rf circuit model for single walled carbon nanotubes for both dc and capacitively contacted geometries. By modeling the nanotube as a nano-transmission line with distributed kinetic and magnetic inductance as well as distributed quantum and electrostatic capacitance, we calculate the complex, frequency dependent impedance for a variety of measurement geometries. Exciting voltage waves on the nano-transmission line is equivalent to directly exciting the yet-to-be observed one dimensional plasmons, the low energy excitation of a Luttinger liquid.

Method and apparatus for improving digital circuit design

Abstract: A method and apparatus provide a digital circuit including dynamic logic that minimizes circuit-path delay, residue logic, and circuit area. The method and apparatus use a library of circuit cells to produce a digital circuit design using a mapping algorithm. The mapping algorithm firstly determines an arrangement of circuit cells to minimize the delay in the circuit design, secondly determines an arrangement of circuit cells to minimize the residue logic for the circuit design, thirdly determines an arrangement of circuit cells to minimize the circuit area for the circuit design, and then repeats the process for each node in the circuit until the best circuit design is produced in accordance with pre-determined criteria.

Characterization, Modeling, and Control of Ionic Polymer Transducers

Abstract: Ionic polymers are a recently discovered class of active materials that exhibit bidirectional electromechanical coupling. They are `soft' transducers that perform best when the mechanical deformation involves bending of the transducer. Ionic polymers are low voltage actuators { they only require inputs on the order of 1V and cannot tolerate voltages above approximately 10V. The mechanisms responsible for the electromechanical coupling are not yet fully understood, and reports of the capabilities and limitations of ionic polymer transducers vary widely. In addition, suitable engineering models have not been developed. This document presents a dynamic model for ionic polymer transducers that is based on a pair of symmetric, linearly coupled equations with frequency dependent coe±cients. The model is presented in the form of an equivalent circuit, employing an ideal transformer with a frequency dependent turns ratio to represent the electromechanical coupling. The circuit elements have clear physical interpretations, and expressions relating them to transducer dimensions and material properties are derived herein. The material parameters required for the model: modulus, density, electrical properties, and electromechanical coupling term are determined experimentally. The model is then validated by comparing simulated and experimental responses, and the agreement is good. Further validation is presented in the form of extensive experiments that con rm the predicted changes in transducer performance as transducer dimensions are varied. In addition, reciprocity between mechanical and electrical domains is demonstrated. This reciprocity is predicted by the model, and is a direct result of the symmetry in the equations on which the model is based. The capabilities of ionic polymer sensors and actuators, when used in the cantilevered bender con guration, are discussed and compared to piezoceramic and piezo polymer cantilevered benders. The energy density of all three actuators are within an order of magnitude of one another, with peak values of approximately 10 J/m3 and 4mJ/kg for ionic polymer actuators actuated with a 1.2V signal. Ionic polymer sensors compare favorably to piezoelectric sensors. Their charge sensitivity is approximately 3201C/m for a 0.2 x 5 x 17mm cantilevered bender, two orders of magnitude greater than a piezo polymer sensor with identical dimensions. This work is concluded with a demonstration of feedback control of a device powered by ionic polymer actuators. An ionic polymer sensor was used to provide the displacement feedback signal. This experiment is the rst demonstration of feedback control using an ionic polymer sensor. Compensator design was performed using the model developed in the rst chapter of this document, and experiments con rmed that implementation of the control scheme improved, in a narrow frequency range, the system's ability to track sinusoidal inputs. To my wife, Ann Marie

State of charge method and apparatus

Abstract: A method for determining state of charge (SOC) of a battery system based upon an equivalent circuit of the battery system. A potential and resistance of the equivalent circuit are computed. The method uses a least squares regression means, and includes: providing a plurality of data points as a starting point based upon determinations including measurement or prior computation, wherein the determinations include a determination of a voltage of the battery system; weighting the plurality of data points; and computing values of the resistance and potential based upon weighted data points using recursive formulas, wherein only a state at a previous time is reflected respectively.