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This paper presents the design of broadband miniaturized C-band stacked antenna and its analysis using TLM. The proposed antenna operates at C-band and acquires 45% bandwidth with a peak gain of 8 dBi. The generalized transmission-line model, developed earlier for the analysis of multilayered stacked antennas (without slots), has been implemented and modified for the analysis of the proposed antenna (having a slot in the driven patch). The slot coupling effect is incorporated in the modified TLM model for the circuit-level simulation and analysis of the designed antenna. Circuit simulation results agree with EM simulation and measured results. The proposed antenna occupies an overall volume of 52 × 50 × 4.5 mm3, while volume of the radiating elements is 13 × 19.89 × 4.5 mm3, which makes the design quite compact. The proposed stable antenna has unidirectional radiation patterns throughout the band of operation and is thus suitable for applications such as remote sensing, target detection, and imaging. [ABSTRACT FROM AUTHOR]

In this paper, transmission-line theory is applied to implement a physical model for compact one-turn inductors, which simultaneously incorporates the frequency-dependent effects introduced by the conductor skin effect and the loss originated by the coupling with the ground plane. For this purpose, S-parameter measurements are processed to extract the associated parameters, which exhibit scalability with the turn radius. This allows the model to be used for interpolation and extrapolation analyses. In this regard, the device performance is assessed for one-turn inductors in series connection, for different load impedances, and when the turn is narrowed. To validate the proposal, agreement between the model and the experimental transmission line RLGC parameters, the return loss, and the Q-factor is obtained up to 20 GHz.

One method for enhancing the electrochemical performance of a solid oxide fuel cell (SOFC) cathode at low temperatures is to mix two oxides with dissimilar structures to form a composite electrode. To understand the enhancement factor of the composite electrode consisting of an ionic conducting oxide, Ce 0.9 Gd 0.1 O 1.95 (GDC), and a mixed ionic and electronic conducting oxide, La 0.6 Sr 0.4 CoO 3- δ (LSC), electrochemical measurements were performed as a function of composition ratio, temperature (673–1073 K), and oxygen partial pressure (p (O 2), 1–10−4 bar). The area-specific conductivity (σ E) that was obtained from the impedance spectra was enhanced at low temperature (T < 873 K) in the high p (O 2) region (1–10−1 bar) for the samples that contained above 40 % of GDC. However, the enhancement was not significant at high temperatures (T > 873 K) under all measured p (O 2) conditions. Although some LSC particles were replaced by GDC, the enhancement of the chemical capacitance of the composite electrode was observed. This indicates that GDC particles function as ionic conducting pathways in the composite electrode. To understand the enhancement mechanism, the experimental data of σ E were compared with the calculated results using a one-dimensional transmission-line model (1-D TLM) considering only the contributions of surface resistivity and ionic resistivity. Results indicate that there is a discrepancy between the measured result of σ E and the calculated result. Several plausible reasons for the discrepancy were discussed, where the contribution of the triple phase boundary reaction resistivity could not be ignored in the calculation of σ E. • The enhancement of σ e in composite electrode was observed at low temperatures (T < 873 K). • The GDC particle functions as ionic conducting pathways in the composite electrode. • The enhancement factor was analyzed by a 1-dimensional transmission-line model. • The discrepancy between the measured and calculated data of σ e was discussed. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy (EIS) enables the examination of the electrochemical nature of electrodes and electrochemical cells by applying an alternating voltage (or current) and measuring the resulting current (or voltage). The resistance and capacitance components of the electrode can be evaluated by applying an AC voltage and changing the frequency. In particular, analysis using the equivalent circuit can determine important parameters related to the electrochemical reaction of the electrode, such as the charge transfer resistance, electric double-layer capacitance, and Warburg impedance. Moreover, the internal resistance of the cell can be divided into resistances caused by the positive electrode, negative electrode, and electrolyte. Because of these advantages, EIS is a powerful technique used for basic research, such as in identifying the rate-determining step of an electrochemical reaction, and also for applied research, such as characterizing electrochemical devices (e.g., batteries and capacitors). In this paper, the concept of impedance, which represents the relationship between the AC voltage and current, is first explained; then, the AC characteristics of various circuit elements used in equivalent circuits, which are essential for understanding EIS, are described. Finally, treatments of more complex circuits based on transmission-line models (TLMs), which are used to represent equivalent circuits of porous electrodes, are presented. Analyses based on TLMs are the foundation for understanding electrodes for practical applications because porous electrodes are usually used in electrochemical devices.

A broadband low-profile L-probe fed metasurface antenna is proposed by well exciting both transverse magnetic (TM) leaky wave and transverse electric (TE) surface wave resonances. The metasurface is composed of an array of rectangular metallic patch cells. An L-shaped probe positioned underneath the finite metasurface is utilized to excite a TM leaky wave resonance and a TE surface wave resonance simultaneously for broadband operation. The dispersion properties of the TM leaky wave and TE surface wave are used to analyze the dual resonance modes. The proposed L-probe fed metasurface antenna achieves a broad −10 dB impedance bandwidth of 34.5% with the peak gain of 10.3 dBi and the front-to-back ratio larger than 18 dB with a low profile of $0.06\lambda _{0}$ , where $\lambda _{0}$ is the free-space wavelength at the center operating frequency. [ABSTRACT FROM AUTHOR]

A varactor loaded pattern reconfigurable patch antenna with shorting pins is presented. Continuous beam reconfigurability and null scanning are realized by introducing two sets of shorting pins and only four varactors into a square patch antenna. For this antenna, the edge-shorting pins are placed along with the parallel edges of the square patch for different $E$ -fields. Another set of shorting pins are fixed symmetrically along the diagonal of the square patch for directivity and null depth enhancement. To achieve continuous pattern reconfiguration, varactors are connected with the edge-shorting pins to provide continuously tunable phase difference. The mechanism of the pattern reconfiguration and effects of the shorting pins are discussed based on a transmission-line model. The proposed antenna has a compact size of $0.4\,\,\lambda _{0} \times 0.4\,\,\lambda _{0} \times 0.06\,\,\lambda _{0}$. Both the simulated and measured results confirm that the proposed antenna has the capabilities of beam steering and null scanning. The measured main beam scans from −55°to −15.5°and 19° to 54°, with a gain reduction of 3.22 dB relative to maximum (7.55 dBi). Meanwhile, the coverage of radiation pattern null is from −74° to 62°. [ABSTRACT FROM AUTHOR]

• A new passivity enforcement approach with complete formulation. • Passivity enforcement in wideband line and cable models. • First demonstration of combined perturbation of residues. • Superior performance in passivity enforcement compared to existing approaches. • Formulation resulting in minimum perturbation. Passive component models are necessary to ensure numerical stability in the simulation of electromagnetic transients in power systems. However, it is challenging to represent transmission lines and cables with frequency-dependent wideband models that are accurate, efficient, and passive. This paper proposes a new method for the passivity enforcement of wideband line and cable models. The wideband models rely on pole-residue identification of characteristic admittance and propagation function in rational forms. In case the resulting models are not passive, the proposed method simultaneously applies perturbation to the residue matrices of characteristic admittance and propagation function. The set of equations related to passivity enforcement through the residues of propagation function in phase domain is complex and presented for the first time in this paper. The proposed approach minimizes the overall perturbation for maintaining passivity as opposed to the existing simplified approaches that rely on the perturbation of the residues of either characteristic admittance or diagonal elements of propagation function. The performance of the method is validated with application cases, and it is shown that it outperforms the existing methods that seek simplification in problem formulation. [ABSTRACT FROM AUTHOR]

This paper explores the characteristics of unidirectional carbon-fiber-reinforced-polymer (CFRP) laminas and their use in electromagnetic absorber design. Unidirectional CFRP composites have been used for decades in structural applications. The electromagnetic properties of unidirectional CFRP composites have been well documented in the open literature. Since many structural applications may also have specific electromagnetic compatibility requirements, it is logical to exploit the useful electromagnetic properties of unidirectional CFRP. Specifically, this paper investigates circuit-analog absorbers (CAAs) made from a unidirectional CFRP lamina, foam spacer, and a ground plane. The unique properties of the unidirectional CFRP sheet provide the necessary resistive and reactive properties for the development of a CAA. To investigate such a CAA, the electromagnetic properties of several off-the-shelf unidirectional CFRP laminas were measured from 4 to 18 GHz using a free-space measurement system. A surface-impedance representation of the unidirectional CFRP lamina was used to build rigorous transmission-line models that provide insights about the properties of the absorbing structure. Transmission line as well as full-wave models were compared to measured absorption performance of fabricated prototypes. Maximum absorption configurations were found to be highly dependent on incident polarization relative to fiber orientation. [ABSTRACT FROM AUTHOR]

The single- and dual-layer metasurfaces are proposed to miniaturize a low-profile wideband antenna. The single- and dual-layer metasurfaces consist of one and two square patch arrays, respectively, both supported by grounded dielectric substrate to form the waveguided metamaterials. After retrieving the effective refractive index along the propagation direction in the waveguided metamaterial, the effective propagation constant is subsequently derived to initially estimate the resonant frequencies of the dual-mode antenna. With the increased effective refractive index, both the proposed antennas realize the gain greater than 6.5 dBi over the bandwidth of ~30% with a reduced radiating aperture of 0.46λ0 ×0.46λ0 and a thickness of 0.06λ0 (λ0 is the free-space wavelength at 5.5 GHz). Moreover, the dual-layer metasurface provides more freedom to increase the effective refractive index with achievable gap widths compared with the single-layer metasurface. [ABSTRACT FROM PUBLISHER]

The ionic and electronic effective conductivities of an electrode mixture layers for all-solid-state lithium-ion batteries containing Li 2 S P 2 S 5 as a solid electrolyte were investigated by AC impedance measurements and analysis using a transmission-line model (TLM). Samples containing graphite (graphite electrodes) or LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM electrodes) as the active material were measured under a “substrate | sample | bulk electrolyte | sample | substrate” configuration (ion-electron connection) and a “substrate | sample | substrate” configuration (electron-electron connection). Theoretically, if the electronic resistance is negligibly small, which is the case with our graphite electrodes, measurement with the ion-electron connection should be effective for evaluating ionic conductivity. However, if the electronic resistance is comparable to the ionic resistance, which is the case with our NCM electrodes, the results with the ion-electron connection may contain some inherent inaccuracy. In this report, we theoretically and practically demonstrate the advantage of analyzing the results with the electron-electron connection, which gives both the ionic and electronic conductivities. The similarity of the behavior of ionic conductivity with the graphite and NCM electrodes confirms the reliability of this analysis. [ABSTRACT FROM AUTHOR]

A class of slow-wave substrate integrated waveguide (SIW) structures patterned with microstrip polyline is presented, theoretically studied, and experimentally validated, which demonstrates some interesting slow-wave propagation effects. The slow-wave SIW (SW-SIW) enables the size reduction of a physically large circuit without sacrificing its performance. A size reduction of 40% of the lateral dimension is achieved with reference to that of the conventional SIW counterpart at the same cutoff frequency. Meanwhile, the phase velocity of the waveguide is also reduced by 40%, resulting in a smaller longitudinal dimension for a given electrical length. Both lateral and longitudinal effects give rise to a total size reduction, largely extending the operation range of SIW structures in the low-frequency region, which has often been restrained by a physical dimension-related cutoff frequency. Also, a transmission line-based two-dimensional (2-D) equivalent-circuit model is proposed and deployed for the modeling and analysis of the slow-wave mechanism. The results from the equivalent-circuit model agrees very well with that from the full-wave simulations. Furthermore, a broadband microstrip to SW-SIW taper with good return loss is designed for measurement verification. Using the proposed SW-SIW structure, the size of conventional SIW-based microwave circuits such as power splitters, couplers, and filters can be further reduced in addition to the existing size-reduction techniques. [ABSTRACT FROM AUTHOR]

A metamaterial-based broadband low-profile grid-slotted patch antenna is presented. By slotting the radiating patch, a periodic array of series capacitor loaded metamaterial patch cells is formed, and excited through the coupling aperture in a ground plane right underneath and parallel to the slot at the center of the patch. By exciting two adjacent resonant modes simultaneously, broadband impedance matching and consistent radiation are achieved. The dispersion relation of the capacitor-loaded patch cell is applied in the mode analysis. The proposed grid-slotted patch antenna with a low profile of 0.06 \lambda0 (\lambda0 is the center operating wavelength in free space) achieves a measured bandwidth of 28% for the \vert\textS{11}\vert less than -10\;\textdB and maximum gain of 9.8 dBi. [ABSTRACT FROM PUBLISHER]

Mathematical solutions were obtained for the impedance of one-dimensional transmission-line (TML) models with all possible variations of the boundary conditions and connections to an external circuit. First, three types of connection (Z-type, T-type, and E-type) were considered. A more generalized connection that includes the characteristics of both Z-type and T-type (universal-type) was also considered. All four of the resulting general solutions were versatile, but quite complicated. Next, comprehensive variations of the general solutions depending on specific boundary conditions, which are generally simpler, were also considered. Finally, an equivalent transform from a three-terminal TML model to a simple Y-circuit was calculated. This enables calculation of the serial connection of multiple TML models with different parameters, which represents a multi-layered electrode. [ABSTRACT FROM AUTHOR]

This paper demonstrates the need for and provides an improved fitting of the line parameters when a wide range of frequencies with emphasis on the dc response is the objective. The improved fitting is based on a low-order fitting of a function error for each of the line parameters, that is, the characteristic admittance and propagation function, in the low-frequency range. The function error represents the difference between the analytical evaluation of the line parameters, that is, obtained from a frequency-dependent distributed parameters line model, and their initial rational approximation, for example, given by an electromagnetic transients software tool. The approximated function error, added to the initial rational approximation of the line parameters, provides the enhanced fitted line model. The enhanced fitting improves the dc response of the line and ensures numerical stability in time-domain simulations. This paper applies the proposed fitting approach to the universal line model for time-domain simulations. The simulation results by the enhanced fitting are validated by comparing the results with those obtained from a frequency-domain line model (FDLM). Two case studies are presented to illustrate the proposed fitting approach. [ABSTRACT FROM AUTHOR]

A metamaterial-based broadband low-profile mushroom antenna is presented. The proposed antenna is formed using an array of mushroom cells and a ground plane, and fed by a microstrip line through a slot cut onto the ground plane. With the feeding slot right underneath the center gap between the mushroom cells, the dual resonance modes are excited simultaneously for the radiation at boresight. A transmission-line model integrated with the dispersion relation of a composite right/left-handed mushroom structure is applied to analyze the modes. The proposed dielectric-filled (\varepsilonr=3.38) mushroom antenna with a low profile of 0.06\lambda0 (\lambda0 is the operating wavelength in free space) and a ground plane of 1.10\lambda0\times 1.10\lambda0 attains 25% measured bandwidth (\vert S11\vert<-10\ {\ {dB})} with 9.9-dBi average gain at 5-GHz band. Across the bandwidth, the antenna efficiency is greater than 76%, and cross-polarization levels are less than -20 dB. [ABSTRACT FROM PUBLISHER]

Abstract: Return-stroke peak current is one of the most important measures of lightning intensity needed in different areas of atmospheric electricity research. It can be estimated from the corresponding electric or magnetic radiation field peak. Electric fields of 89 strokes in lightning flashes triggered using the rocket-and-wire technique at Camp Blanding (CB), Florida, were recorded at the Lightning Observatory in Gainesville, about 45km from the lightning channel. Lightning return-stroke peak currents were estimated from the measured electric field peaks using the empirical formula of Rakov et al. (1992) and the field-to-current conversion equation based on the transmission line model (Uman and McLain, 1969). These estimates, along with peak currents reported by the U.S. National Lightning Detection Network (NLDN), were compared with the ground-truth data, currents directly measured at the lightning channel base. The empirical formula, based on data for 28 triggered-lightning strokes acquired at the Kennedy Space Center (KSC), tends to overestimate peak currents, whereas the NLDN-reported peak currents are on average underestimates. The field-to-current conversion equation based on the transmission line model gives the best match with directly measured peak currents for return-stroke speeds between c/2 and 2c/3 (1.5 and 2×108 m/s, respectively). Possible reasons for the discrepancy in the peak current estimates from the empirical formula and the ground-truth data include an error in the field calibration factor, difference in the typical return-stroke speeds at CB and at the KSC (considered here to be the most likely reason), and limited sample sizes, particularly for the KSC data. A new empirical formula, I =−0.66–0.028rE, based on data for 89 strokes in lightning flashes triggered at CB, is derived. [Copyright &y& Elsevier]

The universal line model is among the most accurate frequency-dependent transmission-line model available in Electromagnetic Transients Program-type simulation tools. One major drawback of this line model is that it sometimes gives unstable simulation results. The instability is related to the occurrence of close poles in the rational model of the propagation function which leads to large residue-pole ratios. In time-domain simulation, these large ratios give a magnification of the error associated with the interpolation of the reflected current wave which acts as the stimulus of the propagation function. An approach is described for avoiding the instability problem by introducing a two-segment interpolation scheme for the extraction of the current wave. The approach gives zero interpolation error when used together with the integration scheme known as recursive convolution and so error magnification becomes inconsequential. The new approach is demonstrated for pertinent examples, including one case with residue-pole ratios exceeding one million. [ABSTRACT FROM PUBLISHER]

Abstract: Electrodes designed for PCEC (Proton Conducting Electrolyzing Cell) should ensure both electron and proton conductions and also allowed the supply or the draining of gaseous phase such as steam, hydrogen and oxygen. Porous cermet electrodes fulfil these requirements: percolated metallic phase for electron conduction, ceramic for proton conduction, and pores for transport of reactant and products in gas phase. The electrochemical reactions will take place at boundaries of these three phases, commonly named triple points. Therefore, the cermet electrode has to possess a sufficient open porosity and the expanded metallic surface area exposed to pores as large as possible. In this work, the pore texture of cermet electrodes was characterized by means of Electrochemical Impedance Spectroscopy in aprotic liquid medium. The parameter regression calculation based on de Levie''s transmission-line model allowed us to determine the pore texture characterized by expanded surface area, number, mean radius of pores, and open porosity. [Copyright &y& Elsevier]

A theoretical treatment of distributed electro-thermally induced intermodulation distortion is developed for microstrip transmission lines. The growth of passive intermodulation distortion (PIM) along the length of a line is derived accounting for both loss and electrical dispersion. PIM dependencies on width, length, thickness, and substrate parameters are analyzed leading to design guidelines for low distortion lines. Single metal silver transmission lines are fabricated on sapphire and fused-quartz substrates to isolate the electro-thermal effect and validate the model. Electro-thermal PIM is measured in a two-tone test with tone separation ranging from 4 Hz to 10 kHz. [ABSTRACT FROM AUTHOR]

During a fault, protection relays of the faulty line as well as adjacent lines react and record measurement data. The records of an adjacent healthy line can be used for line parameter identification. The special feature of the proposed method is the consideration of unsymmetrical transmission lines and the application of a high-accuracy signal modeling technique. Derived from a \pi line model, an estimation equation for determining the different impedances is developed. This equation contains the signal models of measurements as well as their time derivatives, which can be estimated very precisely compared to the classical approach based on filtering. By means of a simple simulation model, the accuracy of the proposed algorithm is compared to an approach previously proposed which is based on deconvolution and filtering methods as well as on the representation of a transmission line using time-varying phasors. [ABSTRACT FROM AUTHOR]

Organic photovoltaic (OPV) cells provide an efficient alternative solution compared to traditional PV devices. Their conversion efficiency is directly dependent to the light intensity in the photoactive layer. The present work proposes a fast, accurate, and easy-to-implement transmission-line model, which evaluates the light intensity in any layer inside a multilayer OPV cell. In particular, a plane optical wave impinging normally on a planar multilayer OPV configuration is considered and next the optical field distribution is determined. Numerical results and optimization guidelines for a hybrid PV configuration are presented and discussed. [ABSTRACT FROM PUBLISHER]

The proliferation of power-electronic loads in the distribution system has raised concerns about their impact on the neutral-to-earth voltage [(NEV) or stray voltage]. It is desirable to analyze the effect of topology unbalance and harmonic distortion acting simultaneously to assess their influence on elevated NEV. A multiphase harmonic load-flow algorithm for radial distribution systems is presented for NEV analysis. A transmission-line model is developed that includes the neutral branch such that the NEV is available directly. Harmonic interaction is introduced by using a model for a single-phase rectifier. A well-documented IEEE radial feeder is used to demonstrate the algorithm. Results from several tests on different combinations of linear and nonlinear loads are presented and discussed. These tests show that triplen harmonics can have more effect on elevated NEV than unbalance acting alone. [ABSTRACT FROM AUTHOR]

Abstract: High central arterial blood pressure can be sustained by the capacity of living arteries to respond to hemodynamic stimuli by changing their structural and/or functional characteristics. These adaptations are considered to occur in a time-dependency, in which different patterns of vascular geometry are identified at all stages. This paper proposes a three-section transmission-line model of the brachial-radial arterial segment and a rational procedure to analyze its transfer function that can be used to interpret the longitudinal remodeling process of medium-sized arteries. The three sections of the model correspond to different arterial segments of the forearm. The model processed pressure signals collected noninvasively from normotensive and hypertensive volunteers at brachial and radial arteries. Aiming to explain possible hypertrophic inward remodeling, geometrical model parameters obtained from normotensive individuals were modified in order to generate high-pressure pulses observed in the hypertensive subjects. The resulting transfer functions for the hypertrophy adaptation exhibit properties related to the pathophysiology of the remodeling process, mainly the reduced amplification of the higher harmonics of the pulse waveform. The results suggest the model can be used to assess noninvasively the hypertension-induced adaptations related to geometrical characteristics of the medium-size arteries. [Copyright &y& Elsevier]

A simple explanation is provided for the advantages of magnetic materials in microstrip antenna miniaturization. The observations are derived from a standard transmission-line model, and the findings are qualitatively verified using numerical simulations. It is shown that the advantages of magnetic materials arise from the favorable antenna geometry and favorable feed technique. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3131–3134, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23931 [ABSTRACT FROM AUTHOR]

Inductor design is an important issue in millimeter-wave CMOS circuits. In these frequencies the required inductance is very small and hence special structure is required for inductors. The quality factor is the most important design parameter for these inductors, especially in CMOS process. To incorporate these inductors in circuit simulation, a simple lumped model is necessary. This work proposes a simple and accurate model, developed for design and optimization of such inductors. This model is based on quasi-transverse-electromagnetic-mode assumption. To increase the model accuracy we have separately modeled the short-end section of the inductor. Model parameters are calculated using reported analytic equations and some new empirical equations. Using this model we have designed and optimized a 250-pH inductor with different shield layers, for STMicroelectronics 90-nm digital CMOS process. The accuracy of the model parameters and the evaluation of the model has been carried out using 2-D and method-of-momentss electromagnetic solvers in Advanced Design System, with the substrate modeled using foundry design kit data. [ABSTRACT FROM AUTHOR]

The universal line model (ULM) is a frequency dependent transmission-line model based on the method of characteristics in the phase domain. Although the ULM is known to produce highly accurate models for both overhead lines and underground cables, situations have been encountered where the pole identification for the propagation function fails. In this paper, we overcome the problem by basing the pole identification on trace fitting rather than mode fitting. This is achieved by introducing delayed basis functions in the vector fitting algorithm, followed by time-delay refinement and model-order reduction. In situations where the modes can be fitted without difficulty, the existing approach using modes obtained by a frequency-dependent transformation matrix remains the most accurate. [ABSTRACT FROM AUTHOR]

Abstract: Time evolution of non-uniform voltage distribution on the powered electrode in a large-area very-high-frequency (VHF) capacitively coupled plasma processing system is studied based on a one-dimensional transmission-line model with an equivalent-circuit model of the plasma. With this model, time evolution of voltage and current distributions on the electrode is examined at its activation by the power supply with various frequencies, waveforms, and power-supply locations. It has been found, with the power supply of multiple frequencies, that effects of beat waves can significantly affect plasma uniformity especially if the difference in frequency is small. It has been also demonstrated that, with multiple power-supply locations combined with multiple frequencies, good voltage uniformity over the long electrode can be obtained. [Copyright &y& Elsevier]

This paper presents a quasi-TM approach for the fundamental mode of transmission lines with semiconductor substrates and nonperfect metallic conductors. The approach has allowed us to develop a transmission-line model by properly defining frequency-dependent parameters in terms of the quasi-static electric potential and the electric current density along the propagation direction in the line. The previous quasi-TM analysis avoids the involved numerical root finding process typical in full-wave analysis, and overcomes the limitations of the conventional quasi-TEM approach to account for the effects of the longitudinal currents present both in the lossy substrates and in the nonperfect conductors. The transmission-line parameters have been computed by a hybrid technique that combines the method of lines with the method of the moments (MoM). The total CPU effort has been considerably reduced thanks to the possibility of finding closed-form expressions for the reaction integrals appearing in the MoM. Comparisons with previous computed and measured results show the validity of the present model. [ABSTRACT FROM AUTHOR]

Herein, the well-known cable equation for non-myelinated axon model is extended analytically for myelinated axon formulation. The myelinated membrane conductivity is represented via the Fourier series expansion. The classical cable equation is thereby modified into a linear second order ordinary differential equation with periodic coefficients, known as Hill's equation. The general internal source response, expressed via repeated convolutions, uniformly converges provided that the entire periodic membrane is passive. The solution can be interpreted as an extended source response in an equivalent nonmyelinated axon (i.e., the response is governed by the classical cable equation). The extended source consists of the original source and a novel activation function, replacing the periodic membrane in the myelinated axon model. Hill's equation is explicitly integrated for the specific choice of piecewise constant membrane conductivity profile, thereby resulting in an explicit closed form expression for the transmembrane potential in terms of trigonometric functions. The Floquet's modes are recognized as the nerve fiber activation modes, which are conventionally associated with the nonlinear Hodgkin-Huxley formulation. They can also be incorporated in our linear model, provided that the periodic membrane point-wise passivity constraint is properly modified. Indeed, the modified condition, enforcing the periodic membrane passivity constraint on the average conductivity only leads, for the first time, to the inclusion of the nerve fiber activation modes in our novel model. The validity of the generalized transmission-line and cable equation models for a myelinated nerve fiber, is verified herein through a rigorous Green's function formulation and numerical simulations for transmembrane potential induced in three-dimensional myelinated cylindrical cell. It is shown that the dominant pole contribution of the exact modal expansion is the transmembrane potential solution of our generalized model. [ABSTRACT FROM AUTHOR]

In this paper, ring-resonator bandstop filters (BSFs) with three attenuation poles are designed and analyzed using a two-port ABCD matrix of the transmission-line model. The symmetrical geometry of the ring-type BSFs allows us to explain the resonance operation via even and odd modes. Moreover, perturbation elements are employed to control the attenuation poles and obtain good performances. In order to validate the analytic method, three different BSFs are built using the microstrip-ring resonator. The simulated and measured results are presented and compared with the theory over a wide frequency range. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 114–118, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20562 [ABSTRACT FROM AUTHOR]

Unlike the conventional magnetic-wall model, a simple transmission-line model unaffected by boundary conditions is used to calculate the frequency modes of ring resonators of any general shape such as annular, square, or meander. Moreover, it corrects an error in the literature concerning the frequency modes of the one-port ring resonator. Also, it can be used to describe the dual-mode behavior of the ring resonator, which the magnetic-wall model cannot address well, especially for a ring resonator with complicated boundary conditions. Experiments show good agreement with theory. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 209–213, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11017 [ABSTRACT FROM AUTHOR]

This paper proposes a new loop antenna for circular polarization with a single feed. It is an unloaded loop antenna with a peripheral length of one wavelength and uses a compound-wire loop in which adjacent wires have different cross-sectional structures. This antenna is considered as a transmission line above a ground plane and analyzed as an equivalent circuit in which the different cross-sections of the wires are represented by different characteristic impedances. Using the transmission-line model, the condition for circular polarization is derived in terms of the characteristic impedances and the antenna height. Then, as a simple example, a loop antenna with composite radius and a circular cross-section is designed, and the relations among the antenna height, radius ratio, and the input impedance are investigated. The results are discussed and compared to the results of numerical analysis by the method of moments. Then, providing a proof of the effectiveness of the proposed method, an experiment considering the feeding structure is also described; the results agree well with the theory. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(5): 42–50, 1999 [ABSTRACT FROM AUTHOR]

Dielectric connectors for multilayered hybrid integration technology are considered in this paper. The design of one of the connectors which works on the nonradiative dielectric (NRD) waveguide mode has been carried out using a transmission-line model. For this connector, since the slots for the microstrip NRD guide coupling lie directly above one another, considerable space is released compared to the traditional method of using an NRD guide. To further enhance the integration, a novel way of feeding the dielectric connector using a tail-ended tapered microstrip line has also been designed and tested. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 230–233, 1999. [ABSTRACT FROM AUTHOR]

A simple transmission-line model to design a broadband system consisting of a multilayered polarization rotator that rotates the polarization plane of a linearly polarized electromagnetic wave is presented. A simulation program that permits the design of the rotator parameters was implemented, and a prototype was designed, manufactured, and tested, Comparisons between the theoretical results and measurements are given, and a good correspondence is found. [ABSTRACT FROM AUTHOR]

Ensuring stability in transient simulations of power systems requires that intrinsically passive components of the network should be represented with passive models, including transmission lines and cables. Existing research on passivity enforcement of the wideband line or cable model is based on the perturbation of residues of the state-space model of the characteristic admittance, ignoring its poles and its constant term. This paper presents the advantages and limitations of including the poles and constant matrix of the characteristic admittance in the passivity enforcement method of wideband models. [ABSTRACT FROM AUTHOR]

A novel low-cost filter design for common-mode noise suppression in high-speed differential signals is proposed. It is realized by periodically etching the dumbbell-shape defected ground structure (DGS) to perturb the return current of the common- mode noise. A transmission-line model for the proposed structure is also developed with good agreement to the full-wave simulation and measurement result. It is found that over 20 dB suppression of common-mode noise can be achieved over a wide frequency range from 3.3 to 5.7 GHz with 3 cascaded DGS cells, while the differential signals still keep good signal integrity in eye-pattern observation. The common-mode current, which generally results in common-mode EMI, on the attached input/output cable is also proved to be efficiently suppressed (15 dB in average) within the stopband by the proposed filter. [ABSTRACT FROM PUBLISHER]

A new type of transmission-line model (TLM) as an equivalent circuit for the electrochemical impedance is developed to describe a porous electrode impregnated with an electrolyte solution. Two kinds of TLMs, i.e., one for diffusion-migration and the other for a porous electrode, are combined. To describe the double-layer capacitance strictly, the interfacial impedance is explicitly divided into the faradaic impedance and double-layer capacitance, and the latter is distributed into contributions of each ionic species. The obtained model describes diffusion, migration, and concentration changes of all ionic species within a porous electrode. In combination with a TLM for a bulk electrolyte solution, an equivalent circuit for a whole cell is also made. This should be a powerful tool for analyzing the impedances of devices with porous electrodes, such as batteries and electric double-layer capacitors, especially in the low-frequency region. Unlabelled Image • Equivalent circuits for electrochemical impedance of porous electrodes are proposed. • Two types of transmission-line model are combined. • Diffusion-migration of all ionic species impregnated in the electrode is described. • Contributions of all ionic species to the double-layer charging are described. [ABSTRACT FROM AUTHOR]

This article proposes an effective approach for designing a highly compact patch antenna for wireless applications at 2.4 GHz. Size reduction is realized here by adding a modified Minkowski fractal defected ground structure (M-MFDGS) under the center of the radiating patch. The antenna miniaturization procedure follows a sensitivity study for the selection of appropriate DGS shape. Incorporating this highly capacitive M-MFDGS, the resonant frequency of the patch is reduced from 4.16 GHz to 2.4 GHz without any alteration in the physical size of the microstrip patch. This enables a 71% reduction in the radiating patch compared to the conventional antenna at the same operating frequency. The variation in the antenna resonance characteristics is also validated by an equivalent transmission-line model. The fabricated antenna prototype with a very low patch size of 0.15 λ 0 × 0.13 λ 0 , has a 10-dB return loss bandwidth of 5.20%, a realized gain of 1.4 dBi, and radiation efficiency of 65% centered at 2.41 GHz. With this novel approach, the proposed miniaturized patch antenna is found to be a suitable candidate for portable wireless communications. [ABSTRACT FROM AUTHOR]

A novel compact structure with three controllable finite attenuation poles at stopband is presented. The new structure is composed of a pair of symmetrical parallel coupled-lines and a capacitive load. With this configuration, three finite attenuation poles are available, which can improve the stopband characteristics of low-pass filters (LPFs) or the upper stopband performances of band-pass filters. The research method is based on a transmission-line model for tuning the finite attenuation poles. In order to examine the feasibility of the proposed structure, a new type of LPF with broad stopband and sharp cutoff frequency response is designed, fabricated, and measured. The experimental results of the fabricated circuit agree well with the simulation and analytical ones [ABSTRACT FROM PUBLISHER]