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Equivalent Circuit Model (equivalent + circuit_model)
Selected AbstractsRobust optimum design of SAW filters by the penalty function methodELECTRICAL ENGINEERING IN JAPAN, Issue 3 2007Kiyoharu Tagawa Abstract In order to increase the reliability of surface acoustic wave (SAW) filters, a robust optimum design technique is presented. The frequency response characteristics of SAW filters are governed primarily by their geometrical structures, that is, the configurations of the interdigital transducers (IDTs) and reflectors fabricated on piezoelectric substrates. To choose desirable structures of SAW filters through computer simulation, conventional design techniques utilize the equivalent circuit model of the IDT. However, they have rarely considered the accuracy of the underlying model, which may be degraded by the dispersion of the circuit parameters. In this paper, considering the errors of these parameters, the robust optimum design of SAW filters is formulated as a constrained optimization problem. Then, a penalty function method combined with an improved variable neighborhood search is proposed and applied to the problem. Computational experiments conducted on a practical design problem of a resonator type SAW filter demonstrate the usefulness of the proposed method. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(3): 45,54, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20469 [source] An investigation into the relationship between apical root Impedance and canal anatomyINTERNATIONAL ENDODONTIC JOURNAL, Issue 9 2008S. M. Ardeshna Aim, To investigate a possible relationship between apical root impedance and canal anatomy. Methodology, Twenty-three roots from human extracted teeth (mostly single rooted but also from molars) with different apical anatomy were selected. The apical anatomy was initially classified by staining the root tip to identify number of canal exits; after impedance measurements, the anatomy was confirmed by staining and clearing the dentine. The roots were divided into two groups; 12 had simple (S) anatomy (Vertucci type 1 with a single exit) and 11 had complex (C) anatomy (various Vertucci canal types with multiple exist). Impedance measurements were taken using a frequency response analyser at seven levels in the root (0.0, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mm short of the apical terminus) at 14 frequencies ranging from 1120 to 100 000 Hz. Care was taken to control the temperature and other variables that could confound measurement accuracy. The impedance characteristics of individual roots were compared with 37 equivalent circuits (based on a pool created from a previous study); the best fitting equivalent circuit was selected. The equivalent circuits were used as the single outcome measure describing the impedance characteristics and correlated with the canal anatomy (S/C). Generalized estimating equations were used to perform logistic regression to analyse the data. Results, Canal anatomy had a significant (P = 0.046) effect on the equivalent circuit model. One circuit (model 10) was found to be the commonest and occurred significantly more commonly in the simple canals. The odds of prevalence of circuit model 10 were 2.2 times (odds ratio 2.17, 95% confidence interval 1.01,4.63) higher in canals with simple anatomy compared with canals with complex anatomy. Conclusions, Canal anatomy had a significant effect on the equivalent circuit describing its impedance characteristics. It should be possible to use impedance spectroscopy to clinically predict and image apical canal complexities. [source] Accurate substrate modelling of RF CMOSINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 3 2006M. S. Alam Abstract The losses within the substrate of an RF IC can have significant effect on performance in a mixed signal application. In order to model substrate coupling accurately, it is represented by an RC network to account for both resistive and dielectric losses at high frequency (> 1 GHz). A small-signal equivalent circuit model of an RF IC inclusive of substrate parasitic effect is analysed in terms of its y -parameters and an extraction procedure for substrate parameters has been developed. By coupling the extracted substrate parameters along with extrinsic resistances associated with gate, source and drain, a standard BSIM3 model has been extended for RF applications. The new model exhibits a significant improvement in prediction of output reflection coefficient S22 in the frequency range from 1 to 10 GHz in device mode of operation and for a low noise amplifier (LNA) at 2.4 GHz. Copyright © 2006 John Wiley & Sons, Ltd. [source] On the transmission properties of left-handed microstrip lines implemented by complementary split rings resonatorsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 2 2006M. Gil Abstract In this paper, the transmission properties of left-handed microstrip lines implemented by etching complementary split rings resonators (CSRRs) and capacitive gaps in the ground plane and conductor strip, respectively, are investigated. To this end, we make use of the lumped element equivalent circuit model of the structure, from which an accurate analysis is carried out, and the influence of the main electrical parameters on the transmission properties is pointed out through electrical simulations. Aspects such as bandwidth and in-band ripple control are discussed in detail. The influence of the geometrical parameters is also discussed and interpreted to the light of the equivalent circuit model. From the results obtained, there are inferred design guidelines that are suitable for the design of metamaterial transmission lines subjected to specifications. Copyright © 2006 John Wiley & Sons, Ltd. [source] Analysis and modeling of microstrip-to-coplanar flip chip package interconnectsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2001Hussein H. M. Ghouz Abstract In this paper, the discontinuity of a flip chip transition between a microstrip line and a coplanar waveguide is investigated and modeled using the finite-difference time-domain method (FDTD) to predict the overall S -parameters of the package. Effects of the bump and via interconnects on the package performance are investigated and discussed. This includes the effects of different staggered transitions and ground connects on the package performance. A reduction of about 10 dB in the bump and via reflections can be achieved by staggering the signal (bump) and the ground connects (bump/via). A staggering distance of about twice the slot width gave minimum reflection over a wide band of frequencies. Moreover, the larger the relative distance between the ground and the center connects the less the reflection due to the discontinuity. Finally, the computed S -parameters of the flip chip package using the FDTD solution are used to develop an equivalent circuit model for the transition discontinuity over a wide frequency band. The equivalent circuit model of the microstrip to coplanar waveguide discontinuity includes more elements and is more complex than other types of transitions. A TEE or PI circuit model has been used to approximate the general circuit model of the discontinuity. Good agreement has been obtained between the S -parameters of the FDTD model and the equivalent circuit models over a wide frequency band. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 202,211, 2001. [source] Monomer concentration effect on electrochemically modified carbon fiber with poly[1-(4-methoxyphenyl)-1H -pyrrole] as microcapacitor electrodeADVANCES IN POLYMER TECHNOLOGY, Issue 2 2009A. Sezai Sarac Abstract In this study, films of poly[1-(4-methoxyphenyl)-1H -pyrrole] [poly(MPPy)] were electrochemically grown on carbon fiber microelectrodes (CFMEs) in 0.05 M of tetraethyl ammonium perchlorate,dichloromethane. The effect of different monomer concentrations (range = 1,10 mM) on electrochemical properties of resulting polymers was characterized by cyclic voltammetry, Fourier transform infrared reflectance-attenuated total reflection spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy. All modified CFMEs were found to have capacitance on the basis of Nyquist, Bode-magnitude, Bode-phase, and Admittance plots. An equivalent circuit model of (R(C(R(QR)))(CR)) gave the best fit for all monomer concentrations used. Furthermore, SEM and AFM results showed that poly(MPPy) was formed as a continuous and well-adhered film onto CFME. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:120,130, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20152 [source] Mathematical modeling of solid oxide fuel cells at high fuel utilization based on diffusion equivalent circuit modelAICHE JOURNAL, Issue 5 2010Cheng Bao Abstract Mass transfer and electrochemical phenomena in the membrane electrode assembly (MEA) are the core components for modeling of solid-oxide fuel cell (SOFC). The general MEA model is simply governed with the Stefan-Maxwell equation for multicomponent gas diffusion, Ohm's law for the charge transfer and the current-overpotential equation for the polarization calculation. However, it has obvious discrepancy at high-fuel utilization or high-current density. An advanced MEA model is introduced based on the diffusion equivalent circuit model. The main purpose is to correct the real-gas concentrations at the triple-phase boundary by assuming that the resistance of surface diffusion is in series with that of the gaseous bulk diffusion. Thus, it can obtain good prediction of cell performance in a wide range by avoiding the decrement of effective gas diffusivity via unreasonable increment of the electrode tortuosity in the general MEA model. The mathematical model has been validated in the cases of H2H2O, COCO2 and H2CO fuel system. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Effects of parasitic resonance on a vertical transition in multilayer printed circuit boardsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010Sung Tae Choi Abstract This article reports on parasitic resonance effects of a ground plane with/without a ground opening underneath a signal via with an open stub on the performance of a vertical transition in a multilayer printed circuit board. An equivalent circuit model that accounts for the parasitic resonance due to the open stub inductance and the parasitic capacitance is developed and verified with the measured and simulated results. The fabricated transition exhibits a return loss better than about 10 dB and an insertion loss less than 1.9 dB up to 21.5 GHz. A good agreement is observed between measured and simulated results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2098,2100, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25404 [source] Design of WiFi/WiMAX dual-band E-shaped patch antennas through cavity model approachMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2010Heng-Tung Hsu Abstract The design of dual-band, single patch microstrip antenna covering 2.4 and 3.5 GHz for WiFi and WiMAX applications based on E-shaped patch is presented. Although cavity model analysis is included in the design procedure, the slotted configuration is treated as the perturbed cavity to characterize the resonant frequencies of corresponding modes. Additionally, the feed point position is determined through the field distribution resulted from the modal analysis. A new equivalent circuit model based on the coupled resonators theory is proposed for analysis purposes. The relationship between cavity model analysis and antenna resonances is further evidenced by the surface current distributions on the conductors. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 471,474, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24954 [source] A miniature 5.2-GHz bandstop microstrip filter using multilayer-technique and coupled octagonal defected ground structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2009Ahmed Boutejdar Abstract In this article, we propose a new compact defected ground structure (DGS) bandstop filter with broad pass-band, low insertion loss in the stop-band, and sharp transition from pass- to stop-band. The bandstop filter structure is simple as it is composed of a pair of octagonal DGS slots and open stubs as a compensated microstrip capacitance. The filter is realized as a multiplayer structure with wide lossless stop-band. The behavior of the filter has been investigated using EM as well as lumped-element equivalent circuit model simulations. The design equations are derived using an equivalent circuit model of a parallel L,C resonator. The proposed filter has been optimized, fabricated, and measured. The agreement between the simulated and measured results confirms the effectiveness of the proposed concept. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2810,2813, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24770 [source] Dual-band-rejection filter based on split ring resonator (SRR) and complimentary SRRMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009Xin Hu Abstract A novel concept of a compact, low insertion-loss dual-band-rejection filter (DBRF) is proposed, and its equivalent circuit model is given. The filter consists of single split ring resonators (SRRs) on the top of the host microstrip line and Complimentary SRR etched on the back ground plane. The dimensions of the structure are as small as 1.4 cm × 2 cm, while high frequency selectivity is achieved at both band edges due to the presence of two transmission zeros. The filter has an insertion loss of better than 1 dB, a return loss of larger than 10 dB in the passband from 3.3 to 4.0 GHz, and two rejections of greater than 30 dB within 2.5,2.6 and 5.2,5.6 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2519,2522, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24596 [source] Composite right/left-handed transmission line based on Koch fractal shape slot in the ground and UWB filter applicationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009Jian An Abstract A novel composite right/left-handed transmission line is presented which is synthesized by etching Koch fractal shape slot in the ground plane and series capacitive gap in the conductor strip. Unlike the structures loaded with complementary split ring resonators, the proposed structure can operate at very wideband and is used to design an ultra-wideband (UWB) filter. The UWB filter is fabricated and tested. The relative bandwidth of the ,10 dB return loss is 128% and the insertion loss is larger than ,1.5 dB except at high frequencies. The equivalent circuit model of the proposed structure is presented and the electrical parameters are also extracted. The circuit model results are compared with the simulation and measurement results which verify that not only the extracted parameters are exact but also the equivalent circuit model is reasonable. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2160,2163, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24553 [source] Closed-form expression of asymmetric stripline open-end and its applications for analysis of LTCC components and circuitsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009Wanchun Tang Abstract In this article, we have obtained simple excess capacitance formula for asymmetric stripline open-end. The average error of the formula is less than 2%. On the basis of this formula and the field-based equivalent circuit model obtained by the authors before, a low-pass filter and an edge coupled stripline band-pass filter are analyzed by the field-based equivalent circuit together with the excess capacitance formula of this article. Compared with numerical results, the average errors of S parameters are less than 2%. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 406,408, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24072 [source] Analysis of V-slot loaded patch for wide-band operationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008J. A. Ansari Abstract In this article, analysis of V-slot loaded patch antenna is proposed using equivalent circuit model. Such antenna provides a wide bandwidth which depends inversely on the base width and slot thickness. The proposed results are compared with experimental and simulated results which are in good agreements. Radiation pattern of the proposed antenna is in good agreement with the simulated results. This validates the accuracy of the proposed model. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3069,3075, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23891 [source] Synthesis of ultrawideband bandpass filter by multisection of commensurate stepped-impedance resonatorsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2008Chun-Ping Chen Abstract A novel filter prototype composed of multisection of stepped impedance resonators (SIRs) is proposed to realize the ultra-wideband bandpass (UWB) filter. The relation between the modes number and stage number of resonators is first discussed, followed by the derivation of the corresponding Chebyshev filtering function. Furthermore, the equivalent circuit model of this new filter prototype is established based on the transmission-line theory for filter synthesis. As an example, a FCC UWB filter is synthesized with the proposed filter prototype to possess a passband from 3.1 to 10.6 GHz (fractional bandwidth is about 110%). The synthesized circuit model are further optimized by EM simulator, fabricated in microstrip line, and characterized by network analyzer. The good agreement between the measured and predicted frequency responses validates the effectiveness of newly proposed synthesis approach. In addition, the designed filter exhibits good characteristics of comparatively low insertion loss, quite sharp skirts, very flat group delay, and good stopband (especially in lower one) as well. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2635,2639, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23756 [source] An exact lumped-element equivalent circuit model for transmission-line transformers formed from coupled microstrip linesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2007John Post Abstract This paper introduces an exact lumped-element equivalent circuit model for Ruthroff transmission-line transformers (TLTs) constructed from coupled microstrip lines. Measured results are compared with model predictions from 0.01 GHz up to 16.7 GHz for the case of three spiral TLTs fabricated in a silicon multichip-module-deposited (MCM-D) process. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2983,2988, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22939 [source] Alternating-current conductance and capacitance of a diamond diode in the presence of deep-level impuritiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010Ana Rodrigues Abstract The alternating-current conductance and capacitance of a diamond film/aluminium diode was measured over the temperature range 230,330 K. Loss tangent curves for the frequency range 100 Hz,1 MHz exhibited three maxima. Doping of the CVD diamond was not uniform, indicating the presence of deep-level impurities. Results were analysed for the temperature range 230,270 K, at which it is possible to observe processes that are supposed to occur in grains and grain boundary regions of polycrystalline diamond. A loss tangent curve was simulated using an equivalent circuit model composed of resistances and capacitances corresponding to depletion regions and the bulk and of the electrical characteristics of the two phases of diamond. This model explicitly includes deep impurities. The curve-fitting parameters for the loss tangent plot demonstrate that at medium frequency (4 kHz, activation energy 0.2 eV) the bulk resistance is high (100 k,) and the maximum is related to the presence of microcrystals, which exhibit low conductivity. At high frequency (800 kHz, activation energy 0.5 eV) the bulk resistance is low (1 k,), suggesting that the maximum is associated with grain boundary regions. The low values of the relaxation times obtained (10,28 and 4×10,27 s) are justified. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Calculation of electric fields induced in the human knee by a coil applicatorBIOELECTROMAGNETICS, Issue 4 2001D.N. Buechler Abstract Calculations are presented of the induced electric fields and current densities in the cartilage of the knee produced by a coil applicator developed for applying pulsed magnetic fields to osteoarthritic knees. This applicator produces a sawtooth-like magnetic field waveform composed of a series of 260-,s pulses with a peak to peak magnitude of approximately 0.12,mT in the cartilage region. The simulations were performed using a recently developed 3 dimensional finite difference frequency domain technique for solving Maxwell's equations with an equivalent circuit model. The tissue model was obtained from the anatomically segmented human body model of Gandhi. The temporal peak electric field magnitude was found to be ,153,mV/m, averaged within the medial cartilage of the knee for the typical dB/dt excitation levels of this coil. The technique can be extended to analyze other excitation waveforms and applicator designs. Bioelectromagnetics 22:224,231, 2001. © 2001 Wiley-Liss, Inc. [source] | ||||||||||||||||