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Showing papers on "Electrical impedance published in 2003"


Journal ArticleDOI
TL;DR: In this paper, the results obtained on the electrochemical behavior of electrochemical capacitors assembled in nonaqueous electrolyte are presented and the impedance of the supercapacitors is discussed in terms of complex capacitance and complex power.
Abstract: This paper presents the results obtained on the electrochemical behavior of electrochemical capacitors assembled in nonaqueous electrolyte. The first part is devoted to the electrochemical characterization of carbon-carbon 4 cm2 cells systems in terms of capacitance, resistance, and cyclability. The second part is focused on the electrochemical impedance spectroscopy study of the cells. Nyquist plots are presented and the impedance of the supercapacitors is discussed in terms of complex capacitance and complex power. This allows the determination of a relaxation time constant of the systems, and the real and the imaginary part of the complex power vs. the frequency plots give information on the supercapacitor cells frequency behavior. The complex impedance plots for both a supercapacitor and a tantalum dielectric capacitor cells are compared. © 2003 The Electrochemical Society. All rights reserved.

1,674 citations


Journal ArticleDOI
TL;DR: In this article, a periodic surface texture is used to alter the electromagnetic properties of a metal ground plane by covering the surface with varactor diodes, and a tunable impedance surface is built, in which an applied bias voltage controls the resonance frequency and the reflection phase.
Abstract: By covering a metal ground plane with a periodic surface texture, we can alter its electromagnetic properties. The impedance of this metasurface can be modeled as a parallel resonant circuit, with sheet inductance L, and sheet capacitance C. The reflection phase varies with frequency from +/spl pi/ to -/spl pi/, and crosses through 0 at the LC resonance frequency, where the surface behaves as an artificial magnetic conductor. By incorporating varactor diodes into the texture, we have built a tunable impedance surface, in which an applied bias voltage controls the resonance frequency, and the reflection phase. We can program the surface to create a tunable phase gradient, which can electronically steer a reflected beam over +/- 40/spl deg/ in two dimensions, for both polarizations. We have also found that this type of resonant surface texture can provide greater bandwidth than conventional reflectarray structures. This new electronically steerable reflector offers a low-cost alternative to a conventional phased array.

702 citations


Journal ArticleDOI
TL;DR: In this paper, a novel technique for suppressing power plane resonance at microwave and radio frequencies is presented, which consists of replacing one of the plates of a parallel power plane pair with a high impedance surface or electromagnetic band gap structure.
Abstract: A novel technique for suppressing power plane resonance at microwave and radio frequencies is presented. The new concept consists of replacing one of the plates of a parallel power plane pair with a high impedance surface or electromagnetic band gap structure. The combination of this technique with a wall of RC pairs extends the lower edge of the effective bandwidth to dc, and allows resonant mode suppression up to the upper edge of the band-gap. The frequency range for noise mitigation is controlled by the geometry of the HIGP structure.

249 citations


Journal ArticleDOI
TL;DR: In this article, structural mechanical impedance is extracted from the electro-mechanical admittance signatures of piezoelectric-ceramic (PZT) patches surface bonded to the structure using the EMI technique.
Abstract: Although structural mechanical impedance is a direct representation of the structural parameters, its measurement is difficult at high frequencies owing to practical considerations This paper presents a new method of damage diagnosis by means of changes in the structural mechanical impedance at high frequencies The mechanical impedance is extracted from the electro-mechanical admittance signatures of piezoelectric-ceramic (PZT) patches surface bonded to the structure using the electro-mechanical impedance (EMI) technique The main feature of the newly developed approach is that both the real as well as the imaginary component of the admittance signature is used in damage quantification A complex damage metric is proposed to quantify damage parametrically based on the extracted structural parameters, ie the equivalent single degree of freedom (SDOF) stiffness, the mass, and the damping associated with the drive point of the PZT patch The proposed scheme eliminates the need for any a priori information about the phenomenological nature of the structure or any ‘model’ of the structural system As proof of concept, the paper reports a damage diagnosis study conducted on a model reinforced concrete (RC) frame subjected to base vibrations on a shaking table The proposed methodology was found to perform better than the existing damage quantification approaches, ie the low-frequency vibration methods as well as the traditional raw-signature based damage quantification in the EMI technique Copyright © 2003 John Wiley & Sons, Ltd

208 citations


Journal ArticleDOI
TL;DR: In this article, the authors used impedance spectroscopy (IS) data from oxide-ion conducting La 0.80Sr0.20Ga0.83Mg0.17O2.82 ceramics over the range 182 to 280°C.
Abstract: Modelling of impedance spectroscopy (IS) data of electroceramics depends critically on the correct choice of equivalent electrical circuit so that the extracted parameters have physical significance. The strategy proposed to choose the correct circuit involves analysis of IS data in several of the four complex formalisms: impedance, electric modulus, admittance and permittivity together with consideration of the frequency and temperature dependence of data and the magnitude and temperature dependence of extracted resistance and capacitance values. This is demonstrated using IS data from oxide-ion conducting La0.80Sr0.20Ga0.83Mg0.17O2.82 ceramics over the range 182 to 280°C. Low temperature data are fitted first, to allow a full characterisation of the bulk response; some of the bulk parameters may then be fixed to enable fitting of the higher temperature data which increasingly feature lower frequency phenomena such as grain boundary impedances. The most appropriate circuit in this case is found to consist of a parallel combination of a resistor, capacitor and constant phase element (CPE) for the bulk response in series with a resistor and capacitor in parallel for a constriction resistance. The origin of the constriction resistance may be associated with the presence of plate-like LaSrGaO4 secondary phase within the grains and/or with the presence of pores at the grain boundaries. The importance of choosing (a) the correct equivalent circuit and (b) approximately correct input values for the various circuit parameters to be fitted and refined are demonstrated.

177 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a systematic approach to employ electrochemical impedance spectroscopy for determining model structure and parameters of a simulation model for a VRLA battery, focusing on the interpretation of the impedance data in terms of equivalent circuit models.

173 citations


Journal ArticleDOI
TL;DR: Experimental results demonstrate the feasibility of creating a high precision, multiple frequency, capacitance compensated current source for EIT applications.
Abstract: Questions regarding the feasibility of using electrical impedance tomography (EIT) to detect breast cancer may be answered by building a sufficiently precise multiple frequency EIT instrument. Current sources are desirable for this application, yet no current source designs have been reported that have the required precision at the multiple frequencies needed. We have designed an EIT current source using an enhanced Howland topology in parallel with a generalized impedance converter (GIC). This combination allows for nearly independent adjustment of output resistance and output capacitance, resulting in simulated output impedances in excess of 2 GΩ between 100 Hz and 1 MHz. In this paper, the theoretical operation of this current source is explained, and experimental results demonstrate the feasibility of creating a high precision, multiple frequency, capacitance compensated current source for EIT applications.

168 citations


Journal ArticleDOI
TL;DR: This study finds that the current densities and electric fields in the ECT case are stronger and deeper penetrating than the corresponding TMS quantities but both methods show biologically interesting current levels deep inside the brain.
Abstract: A comparative, computational study of the modeling of transcranial magnetic stimulation (TMS) and electroconvulsive therapy (ECT) is presented using a human head model. The magnetic fields from a typical TMS coil of figure-eight type is modeled using the Biot-Savart law. The TMS coil is placed in a position used clinically for treatment of depression. Induced current densities and electric field distributions are calculated in the model using the impedance method. The calculations are made using driving currents and wave forms typical in the clinical setting. The obtained results are compared and contrasted with the corresponding ECT results. In the ECT case, a uniform current density is injected on one side of the head and extracted from the equal area on the opposite side of the head. The area of the injected currents corresponds to the electrode placement used in the clinic. The currents and electric fields, thus, produced within the model are computed using the same three-dimensional impedance method as used for the TMS case. The ECT calculations are made using currents and wave forms typical in the clinic. The electrical tissue properties are obtained from a 4-Cole-Cole model. The numerical results obtained are shown on a two-dimensional cross section of the model. In this study, we find that the current densities and electric fields in the ECT case are stronger and deeper penetrating than the corresponding TMS quantities but both methods show biologically interesting current levels deep inside the brain.

157 citations


Patent
02 May 2003
TL;DR: In this paper, an internal impedance of a battery is automatically determined by operating a processor to analyze current flowing through the battery to determine if a transient condition due to change of current is occurring and determining when the transient condition has ended.
Abstract: An internal impedance of a battery ( 30 ) is automatically determined by operating a processor ( 13 ) to analyze current flowing through the battery to determine if a transient condition due to change of current is occurring and determining when the transient condition has ended. A voltage of the battery is measured while a steady current is being supplied by the battery. The present depth of discharge (DOD) of the battery is determined and a database is accessed to determine a corresponding value of open circuit voltage. The internal impedance is computed by dividing the difference between the measured voltage of the battery and the open circuit voltage at the present DOD by an average value of the steady current. A remaining run-time of the battery can be determined using a total zero-current capacity of the battery, integrating the current to determine a net transfer of charge from the battery, determining a value of total run-time that would be required to reduce the voltage of the battery to a predetermined lower limit, determining the duration of the integrating, and determining the remaining run-time by subtracting the duration of the integrating from the total run-time.

156 citations


Patent
Tommy D. Hollingsworth1
22 Oct 2003
TL;DR: In this article, an electric field proximity detection system was proposed for use as a touch sensitive keyboard or to be used in close proximity without direct contact, in which an AC signal is coupled to a single electrode functioning as an antenna radiating an electrical field through a high impedance circuit.
Abstract: The invention is related to an electric field proximity detection system suitable for use as a touch sensitive keyboard or to be used in close proximity without direct contact. In an embodiment of a circuit useful in the system, an AC signal is coupled to a single electrode functioning as an antenna radiating an electric field through a high impedance circuit. A conductive object in close proximity disturbs the field causing a voltage change across nodes of the high impedance circuit that is compared by a detector circuit that generates a DC output indicating an object is close to the electrode. In another embodiment, the circuit couples to an analog multiplexer to control a plurality of electrodes. In another embodiment, a row and column address scheme couples a plurality of electrodes and increases resolution without substantially increasing complexity. The circuits may be integrated in a semiconductor to reduce size and cost. The electric field proximity detection system extends to applications related to object detection such as remote sensing, motion detection and remote controls.

155 citations


Journal ArticleDOI
TL;DR: In this paper, the linearity of CMOS has been analyzed using the Taylor series and it has been shown that at a low frequency, the transconductance is a dominant nonlinear source for a low load impedance, but for a usual operation level impedance the output conductance is the dominant non-linear source.
Abstract: The linearity of CMOS has been analyzed using the Taylor series. Transconductance and output conductance are two dominant nonlinear sources of CMOS. At a low frequency, the transconductance is a dominant nonlinear source for a low load impedance, but for a usual operation level impedance the output conductance is a dominant nonlinear source. Capacitances and the substrate network do not generate any significant nonlinearity, but they suppress output-conductance nonlinearity at a high frequency because output impedance is reduced by the capacitive shunts, and output voltage swing is also reduced. Therefore, above 2-3 GHz, the transconductance becomes a dominant nonlinear source for a usual load impedance. If these capacitive elements are tuned out for a power match, the behavior becomes similar to the low-frequency case. As gate length is reduced, the transconductance becomes more linear, but the output conductance becomes more nonlinear. At a low frequency, CMOS linearity is degraded as the gate length becomes shorter, but at a higher frequency (above 2-3 GHz), linearity can be improved.

Patent
19 Nov 2003
TL;DR: A magnetic memory element switchable by current injection includes a plurality of magnetic layers, at least one of the magnetic layers having a perpendicular magnetic anisotropy component and including a current-switchable magnetic moment as discussed by the authors.
Abstract: A magnetic memory element switchable by current injection includes a plurality of magnetic layers, at least one of the plurality of magnetic layers having a perpendicular magnetic anisotropy component and including a current-switchable magnetic moment, and at least one barrier layer formed adjacent to the plurality of magnetic layers (e.g., between two of the magnetic layers). The memory element has the switching threshold current and device impedance suitable for integration with complementary metal oxide semiconductor (CMOS) integrated circuits.

Patent
21 Jan 2003
TL;DR: In this article, an amplitude modulation circuit provides modulated supply current (IPA) possibly in combination with modulated input voltage (VPA) to a radio frequency power amplifier (48) and includes a detection circuit (66) responsive to changes in the ratio of VPA to the AM modulation impedance.
Abstract: An amplitude modulation circuit provides modulated supply current (IPA) possibly in combination with modulated supply voltage (VPA) to a radio frequency power amplifier (48) and includes a detection circuit (66) responsive to changes in the ratio of that voltage (VPA) to the modulated supply current (IPA), described herin as its AM modulation impedance. Such impedance (resistance) changes commonly arise from changing coupling characteristics at the antenna assembly (54) driven by the power amplifier (48). A gain control circuit may be associated with the detection circuit (66), and made responsive thereto, thus allowing adjustment of modulation gain control responsive to changes in AM modulation impendance.

Journal ArticleDOI
TL;DR: In this article, the use of electrochemical impedance spectroscopy and current-interruption techniques with the scope of determining mass-transport limitations in PEFC gas-diffusion electrodes is investigated.
Abstract: The use of electrochemical impedance spectroscopy and current-interruption techniques with the scope of determining mass-transport limitations in PEFC gas-diffusion electrodes is investigated The porous electrode is assumed to be composed of spherical agglomerates consisting of a homogeneous mixture of the electrolyte and the electronic phase The model is applied to the O 2 reduction reaction in the cathode and includes Tafel kinetics for the O 2 reduction, Ohm's law for proton migration, Fick's law for O 2 diffusion, and capacitive current due to the contribution of the double layer A novel impedance is defined, enabling the results to be presented in a simpler manner than with the usual one It is shown how these transient techniques can be employed to qualitatively separate diffusion from migration effects The parameter groups that can be quantitatively determined from the processing of experimental data are presented The effect of O 2 pressure and electrode thickness on the predicted electrode response is also investigated

Journal ArticleDOI
L.F. Tiemeijer1, R.J. Havens1
TL;DR: In this article, a new de-embedding strategy using a physics-based lumped-element model for the test-structure parasitics calibrated on the frequency-dependent "open" and "short" dummy impedances is described, which reduces the experimental uncertainty on the deembedded figures of merit.
Abstract: The impedance errors remaining after conventional de-embedding for a high-speed transistor and a single-loop inductor test structure are investigated. A new de-embedding strategy using a physics-based lumped-element model for the test-structure parasitics calibrated on the frequency-dependent "open" and "short" dummy impedances is described, which reduces the experimental uncertainty on the de-embedded figures of merit. Using this new "calibrated lumped-element" de-embedding technique, we have been able to increase the "worst-case" values for the quality factor Q of a 0.6-nH 10-GHz single-loop inductor from 15 to 20 and for the f/sub max/ of a high-speed SiGe bipolar transistor from 80 to 110 GHz. The de-embedding technique presented here is of great importance to develop confidence in on-wafer S-parameter measurements taken at ever increasing microwave frequencies.

Journal ArticleDOI
TL;DR: In this paper, a dynamic model for the electromagnetic properties of such structures is developed, taking into account electromagnetic interactions between all patches in infinite arrays excited by normally incident plane waves, as well as higher-order Floquet modes between the array and the ground plane.
Abstract: New artificial reactive impedance surfaces have been recently suggested by Sievenpiper et al. for antenna and waveguide applications. In particular, high impedance values corresponding to a magnetic wall can be realized in dense arrays of conducting patches over a conducting plane. In this paper, a dynamic model for the electromagnetic properties of such structures is developed. The analytical model takes into account electromagnetic interactions between all patches in infinite arrays excited by normally incident plane waves, as well as higher-order Floquet modes between the array and the ground plane. The results are compared with the known experiments.

Journal ArticleDOI
TL;DR: In this article, a method for online adaptation of the shunting impedance of a piezoelectric transducer with an electrical impedance is presented. But the method is limited to a randomly excited beam.
Abstract: Piezoelectric shunt damping systems reduce structural vibration by shunting an attached piezoelectric transducer with an electrical impedance. Current impedance designs result in a coupled electrical resonance at the target modal frequencies. In practical situations, variation in structural load or environmental conditions can result in significant changes in the structural resonance frequencies. This variation can severely reduce shunt damping performance as the electrical impedance remains tuned to the nominal resonance frequencies. This paper introduces a method for online adaptation of the shunting impedance. A reconstructed estimate of the RMS strain is minimized by varying the component values of a synthetic shunt damping circuit. The techniques presented are applied in real time to tune the component values of a randomly excited beam.

Patent
30 Jan 2003
TL;DR: In this article, an impedance matching device is provided with an input detector for detecting RF voltage and current at the input terminal, and an output detector to detect RF voltage outputted from the output terminal.
Abstract: An impedance matching device is provided, for which the electric characteristics at an output terminal are accurately analyzed. The matching device is provided with an input detector for detecting RF voltage and current at the input terminal, and an output detector for detecting RF voltage outputted from the output terminal. The matching device also includes a controller for achieving impedance matching between a high frequency power source connected to the input terminal and a load connected to the output terminal. The impedance matching is performed by adjusting variable capacitors based on the detection data supplied from the input detector. When the impedance of the power source is matched to that of the load, the controller calculates the output impedance, RF voltage and RF current at the output terminal, based on the adjusted capacitances of the capacitors, a pre-obtained reactance-impedance data and the detection data supplied from the output detector.

Journal ArticleDOI
18 Apr 2003
TL;DR: In this paper, a millimetre wave uni-travelling-carrier photodiode with a monolithically integrated matching (impedance transform) circuit utilising a coplanar-waveguide short stub is presented.
Abstract: The design and characterisation of a millimetre wave uni-travelling-carrier photodiode with a monolithically integrated matching (impedance transform) circuit utilising a coplanar-waveguide short stub are presented. The device with the matching circuit shows about 50% higher efficiency at 100 GHz than the one without it. The frequency response was characterised through time-domain measurement by means of an electro-optic sampling technique. The 1 dB down bandwidth of the device is as wide as 40 GHz, and the frequency response characteristics are in good agreement with circuit model calculations. The maximum saturation output power is 20.8 mW at 100 GHz for a bias voltage of -3 V, which is the highest output power ever generated directly from a photodiode in the W-band.

Journal ArticleDOI
TL;DR: The problem of MR-EIT is treated as a hyperbolic system of first-order partial differential equations, and three numerical methods are proposed for its solution, and if some uniqueness conditions are satisfied, resistivity can be reconstructed apart from a multiplicative constant.
Abstract: Magnetic resonance-electrical impedance tomography (MR-EIT) was first proposed in 1992. Since then various reconstruction algorithms have been suggested and applied. These algorithms use peripheral voltage measurements and internal current density measurements in different combinations. In this study the problem of MR-EIT is treated as a hyperbolic system of first-order partial differential equations, and three numerical methods are proposed for its solution. This approach is not utilized in any of the algorithms proposed earlier. The numerical solution methods are integration along equipotential surfaces (method of characteristics), integration on a Cartesian grid, and inversion of a system matrix derived by a finite difference formulation. It is shown that if some uniqueness conditions are satisfied, then using at least two injected current patterns, resistivity can be reconstructed apart from a multiplicative constant. This constant can then be identified using a single voltage measurement. The methods proposed are direct, non-iterative, and valid and feasible for 3D reconstructions. They can also be used to easily obtain slice and field-of-view images from a 3D object. 2D simulations are made to illustrate the performance of the algorithms.

Journal ArticleDOI
TL;DR: In this paper, the electrical properties of polycrystalline Bi6Fe2Ti3O18 were investigated by impedance spectroscopy in the temperature range 30-550°C.
Abstract: The electrical properties of polycrystalline Bi6Fe2Ti3O18 are investigated by impedance spectroscopy in the temperature range 30–550°C. The imaginary part of impedance as a function of frequency shows Debye like relaxation. Impedance data are presented in the Nyquist plot which is used to identify an equivalent circuit and the fundamental circuit parameters are determined at different temperatures. The grain and grain-boundary contributions are estimated. The results of bulk a.c. conductivity as a function of temperature and frequency are presented. The activation energies for the a.c. conductivity are calculated. The polaron hopping frequencies are estimated from the a.c. conductivity data.

Journal ArticleDOI
TL;DR: In this paper, a series of experiments are performed to assess the validity of an equivalent circuit model of ionic polymer transducers, where the fundamental parameters of the model are the dielectric permittivity of the material, the viscoelastic modulus, and the effective strain coefficient of the transducers.
Abstract: A series of experiments are performed to assess the validity of an equivalent circuit model of ionic polymer transducers. The fundamental parameters of the model are the dielectric permittivity of the material, the viscoelastic modulus, and the effective strain coefficient of the transducer. The results demonstrate the validity of a simplifying assumption regarding the reflected impedance of the polymer. This allows us to use a simpler set of expressions to predict the time and frequency response of the polymer. The expressions for sensing and actuation are verified in a series of step response and frequency response tests of cantilevered transducers. The curvefit algorithm used for parameter identification works well but there is always a tradeoff in accuracy between the time domain and frequency domain measurements. This could imply the existence of an input-level dependence on the parameters. In spite of this level dependence, the linear model is able to predict the response of an input-output pair tha...

Journal ArticleDOI
Janko Jamnik1
TL;DR: In this paper, simple approximate circuits for polycrystals with grain boundaries that act as obstacles for ions, electrons or both are derived for analysis of impedance spectra obtained in studies of mixed conductive cathodes in Li-batteries.

Journal ArticleDOI
Seong-Hyun Lee1, Jeong-Guon Ih
TL;DR: The proposed empirical model of orifice impedance, with a very high correlation coefficient, is applied to the prediction of the transmission loss of concentric resonators, which have geometric configurations typical of acoustically short and long through-flow resonators.
Abstract: Although there are many analytical and empirical models for orifice impedance, the predicted acoustical performance when adopting any one of them sometimes shows a large discrepancy with the measured result in some cases. In order to obtain a new practical and precise empirical impedance model under grazing flow conditions, the acoustic impedance of circular orifices has been measured with a variation of the involved parameters under very carefully tested and controlled measurement conditions. The parameters involved in determining the acoustic impedance of an orifice are comprised of the orifice diameter, orifice thickness, perforation ratio, mean flow velocity, and frequency. The range of involved parameters is chosen to cover the practical data span of perforates in typical exhaust systems of internal combustion engines. The empirical impedance model is obtained by using nonlinear regression analysis of the various results of the parametric tests. The proposed empirical model of orifice impedance, with a very high correlation coefficient, is applied to the prediction of the transmission loss of concentric resonators, which have geometric configurations typical of acoustically short and long through-flow resonators. By comparing the measured and predicted results, in which the predictions are made by employing many previous orifice impedance models as well as the present model, it is confirmed that the proposed orifice impedance model yields the most accurate prediction among all other existing impedance models.

Patent
03 Nov 2003
TL;DR: In this paper, a wireless communication device is associated with an antenna system that has at least one conductive tab, including: a plurality of electrical components forming an impedance matching network, coupled to the conducting tab and wireless communication devices, that electrically interact with the dielectric material to maintain a substantial impedance match between the antenna system and the wireless communications device.
Abstract: An RFID tag or label includes a wireless communication system that is mounted in electrical proximity to the dielectric material. The wireless communication system includes a wireless communication device associated with an antenna system that has at least one conductive tab, including: a plurality of electrical components forming an impedance matching network, coupled to the conducting tab and wireless communication device, that electrically interact with the dielectric material to maintain a substantial impedance match between the antenna system and the wireless communication device; and/or a structural element forming a frequency selective by-pass trap circuit formed in the conducting tab, and electrically interacting with the dielectric material to maintain a substantial impedance match. The antenna system may be directly mounted on a dielectric substrate, which serves as the dielectric material, or alternatively may be mounted on a backing layer intermediate the dielectric substrate and the antenna system.

Proceedings ArticleDOI
01 Jan 2003
TL;DR: In this paper, an interactive high frequency structure simulator (HFSS) is used to model a PSS and various FSSs, and predicted and measured results for normal incidence are compared to results from the HFSS models.
Abstract: A PSS is a new type of microwave absorber that utilises the principle of phase modulation to produce a reflected field with a low time-averaged energy spectral density. It consists of one or more active layers whose impedance properties can be controlled electronically. The active layer of the PSS under consideration consists of a periodic grid of bow-tie dipole elements arranged in a rectangular grid. The control of its impedance is achieved by loading the centre of each dipole with a PIN diode. Traditionally, a TL model is used to model the PSS but this presents complications when trying to accurately model the periodicity and reactance of the active layer of the PSS, and when modelling finite structures. Ansoft HFSS (high frequency structure simulator) is an interactive software package for calculating the electromagnetic behaviour of a structure. HFSS uses the finite element method (FEM) to compute solutions. It allows for the computation of the basic electromagnetic field quantities, S-parameters, and resonance of a structure. This paper, describes how HFSS was used to model a PSS and various FSSs. Furthermore, predicted and measured results for normal incidence are compared to results from the HFSS models.

Patent
07 Oct 2003
TL;DR: In this paper, a method for measuring the volume, the composition and the movement of electroconductive body fluids, based on the electrical impedance of the body or a body segment, especially for performing electromechanocardiography (ELMEC) or impedance cardiography (IKG) measurements for determining hemodynamic parameters was proposed.
Abstract: The invention relates to a method for measuring the volume, the composition and the movement (HZV) of electroconductive body fluids, based on the electrical impedance of the body or a body segment, especially for performing electromechanocardiography (ELMEC) or impedance cardiography (IKG) measurements for determining hemodynamic parameters. According to said method, an alternating measuring current (52) of at least one frequency is introduced into the body (60, 70), and the impedance and temporal variations (AZ) thereof of essentially the same body segment through which the alternating measuring current flows are measured for at least two different measuring lengths (L, L2, L3, L4, L5), essentially in the longitudinal direction of the body.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a tapered slot antenna (TSA) profile and geometry, which is achieved through its modeling by a stepline terminated in free space intrinsic impedance, and the impedance matching of the TSA input impedance to the generator impedance is achieved by minimizing an error criterion constructed as the magnitude squared of the difference between the generator and input impedance over the desired bandwidth.
Abstract: The optimum design of the tapered slot antenna (TSA) profile and geometry is achieved through its modeling by a stepline terminated in free space intrinsic impedance. The impedance matching of the TSA input impedance (obtained by the transmission matrix properties) to the generator impedance is achieved by minimizing an error criterion constructed as the magnitude squared of the difference between the generator and input impedances over the desired bandwidth. The attenuation constant of the stepline is computed by the broadside radiation of TSA (which is an endfire antenna) and the longitudinal power flow. The spectral domain immitance approach is used to compute the broadside radiation, by first determining the electric field components in the slot by the Galerkin's method and then obtaining the equivalent magnetic surface current densities. The power flow in the endfire direction of TSA may be computed by the Poynting's vector in the substrate. The attenuation constant is calculated for various values of slot width. Finally, the minimization procedure gives the slotline widths and lengths.

Journal ArticleDOI
TL;DR: In this article, the electrical conductivity of this ceramic is studied by measuring impedance as a function of temperature (RT −575°C) and frequency (100 Hz −1 MHz).
Abstract: Sodium bismuth titanate (Na 1/2 Bi 1/2 )TiO 3 is strongly ferroelectric below 200 °C and antiferroelectric between 200 and 320 °C. The electrical conductivity of this ceramic is studied by measuring impedance as a function of temperature (RT–575 °C) and frequency (100 Hz–1 MHz). The complex impedance, electric modulus formalism and dielectric loss analysis are used to analyze the data. DC conductivity has been studied. The activation energies have been evaluated from the data. The dielectric constant of the sample has been calculated from the impedance data.

Journal ArticleDOI
TL;DR: In this article, a power-divider architecture whose characteristics are adjustable independently at two frequencies is presented. The circuits use a single semiloop stepped-impedance resonator filter coupled to the input and output lines.
Abstract: Presents a power-divider architecture whose characteristics are adjustable independently at two frequencies. The circuits uses a single semiloop stepped-impedance resonator filter coupled to the input and output lines. A specific methodology has been developed to design such a circuit.