Nonuniform Lines Research Articles

THRU-Based Cascade De-embedding Technique for On-Wafer Characterization of RF CMOS Devices

In this paper, an accurate two-port cascade-based de-embedding technique is presented for characterization of RF devices. It uses two and four structures for device structure with symmetrical and asymmetrical layouts, respectively. Specifically, it outperforms the existing de-embedding techniques by showing distinct capability of accounting for both series contact resistance and distributed effects of interconnects. Furthermore, it is designed to overcome the deficiency of existing transmission line-based techniques in dealing with the interconnects of nonuniform line width. To avoid over de-embedding errors in lumped techniques, the deembedding is performed in unique steps with solely THRU structures for better prediction of test fixture parasitic. The proposed technique is verified on THRU line for a wide frequency range from 2 to 50 GHz. It demonstrates better performance over existing transmission line-based technique as evidenced by excellent agreement with electromagnetic simulation result of THRU line. This is further confirmed by validation result on deembedded gain and gate capacitance of 0.13-μm nMOS devices.

Efficient evaluation of thermodynamic properties of water and steam on p–h surface

An efficient algorithm for evaluating thermodynamic properties on p–h thermodynamic surface of water and steam is proposed based on bi-quadratic spline interpolation method. With focus on discontinuities of first- or second-order derivatives of thermodynamic property z(p,h) at the saturated p–h line, the p–h surface at 100kJ/kg≤h≤4180kJ/kg and 0.001MPa≤p≤100MPa was divided into single- and two-phase regions. The spline function zSPL(p,h) in two-phase regime was calculated using one-dimensional spline function hsatSPL(p) at the saturated p–h line and the corresponding spline function zSPL(p,h) in single-phase region. For zSPL(p,h) in the single-phase region, virtual two-phase region data evaluated through curve extension approach was adopted for increased accuracy of zSPL(p,h) near the saturated p–h line. Non-uniform grid lines and bisection algorithm were also introduced to reduce the memory loadings. Calculation results of TSPL(p,h), ρSPL(p,h) and sSPL(p,h) show with the spline functions developed in this paper were 2.47–94.1 times faster in computing speed and 1–4 orders of magnitude higher consistency with IAPWS-95 than IAPWS-IF97. We proposed that the currently developed spline algorithm and optimization algorithm are applicable to efficient evaluation of thermodynamic properties of water and steam on p–s, h–s or other state surfaces.

Lightning surge characteristics on inclined incoming line to substation based on reduced-scale model experiment

The lightning protection design of a substation is generally based on the surge overvoltage incoming to the substation, which is generated by the back-flashover across an insulator string of the transmission tower that is closest to the substation and struck by a lightning return stroke. In this case, surges propagate along non-horizontal or non-uniform lines such as the tower and the inclined lines incoming to the substation. Although the surge characteristics of a tower have been intensively studied as of today, those of inclined incoming lines to a substation have not yet been investigated. In this paper, experiments have been conducted using a reduced-scale model to clarify the surge characteristics of the conductor system that is composed of horizontal transmission line, two towers, inclined incoming line and a substation gantry. It turns out from the experiments that the potential (voltage) generated at the tower arm rises gradually, compared with the current injected in the tower top. Furthermore, it is found that the power line potential at the gantry is smaller than that that at the tower where the back-flashover occurs, while the opposite trend is obtained from a circuittheory- based simulation in which the inclined incoming line is represented by a horizontal line. The latter approximation has been usually employed in representing inclined incoming lines in lightning surge simulations using the Electromagnetic Transients Program (EMTP) or its alternatives. The fact that the power line potential at the gantry, evaluated by the present experiment, is smaller than the EMTPcomputed value would contribute to a more economical and rational design of a substation.

On the Transient Response and the Frequency Analysis of Transmission Line Towers

This paper proposes an approach to the study of the transient response and the frequency characteristics of power lines' towers, when subjected to lightening strikes. It starts with dividing the nonuniform line representing the tower into a number of sections. From the usually known dependence of the tower's characteristic impedance on the vertical coordinate and the application of a recursive circuit reduction technique, an s-domain expression for the tower input impedance can be obtained. This expression, followed by the numerical Laplace inversion, is utilized for the determination of the tower's transient response. The impedance expression can be also used to determine the tower's resonance frequencies. This was used to demonstrate some potentially critical situations in which the tower is hit by lightning strikes comprising multiple current pulses. The validity of the proposed technique is demonstrated by comparing the achieved results with those already available in the literature for the same case studies.

Investigation of Electromagnetic Field Coupling with Twisted Conducting Line by Expanded Chain Matrix

In the current paper, we propose a new modeling algorithm to analyze the coupling between an incident electromagnetic field (EMF) and a twisted conducting line, which is a kind of non-uniform line. Typically, analysis of external field coupling to a uniform transmission line (TL) is implemented by the Baum-Liu-Tesche (BLT) equation so that the induced load responses can be obtained. However, it is difficult to apply this method to the analysis of a twisted conducting line. To overcome this limitation, we used a chain matrix composed of ABCD parameters. The proposed algorithm expands the dimension of the previous chain matrix to consider the EMF coupling effectiveness of each twisted pair, which is then applied to multi-conductor transmission line (MTL) theory. In addition, we included a comparative study that involves the results of each method applied in the conventional BLT equation and new proposed algorithm in the uniform two-wire TL case to verify the proposed method.

AN UNCONDITIONAL STABLE 1D-FDTD METHOD FOR MODELING TRANSMISSION LINES BASED ON PRECISE SPLIT-STEP SCHEME

This paper presented a novel unconditional stable FDTD (US-FDTD) algorithm for solving the transient response of uniform or nonuniform multiconductor transmission line with arbitrary coupling status. Analytical proof of unconditional stability and detailed analysis of numerical dispersion are presented. The precise split-time-step scheme has been introduced to eliminate the restriction of the Courant- Friedrich-Levy (CFL) condition. Compared to the conventional US- FDTD methods, the proposed approach generally achieves lower phase velocity error for coarse temporal resolution. So larger time scales can be chosen for the transient simulation to achieve accurate results e-ciently. Several examples of coupled uniform and nonuniform lines are presented to demonstrate the accuracy, stability, and e-ciency of the proposed model.

Prediction of Electro-Thermal Responses of Non-Uniform Functionally Graded Metal Lines under a Direct Current Field

The electro-thermal response of thin, non-uniform functionally-graded metal lines subjected to a direct current flow is determined. The material properties associated with the problem are assumed to vary following a given functional relationship. The corresponding governing differential equations are derived in terms of variable electrical resistivity and thermal conductivity of the material. The solution of the boundary-value problem is then obtained numerically by using finite-difference technique. The electrical and thermal responses of a functionally graded metal line are presented in comparison with those of individual constituent metals. The results are claimed to be highly accurate and reliable, and are considered to be a valuable guide to thermal analysis of modern electronic devices.

Frequency domain modeling of nonuniform multiconductor lines excited by indirect lightning

This paper describes a methodology in the frequency domain for the modeling of a multiconductor transmission line excited by a lightning stroke hitting the nearby ground, considering also variations of the line parameters along its length (nonuniform line). Modeling of the line excited by an external field (also known as illuminated line) is based on Taylor’s formulation, while the incident electromagnetic field representing the nearby lightning stroke is computed following the expressions defined by Master and Uman. This formulation computes a nonuniform electromagnetic field dependent of the lightning’s point of impact with respect to the line. A nodal form is used to completely describe the field excited line, including the effect of the incident field by means of current sources connected at the line ends. From this description, nodal voltages are computed in the frequency domain, using the inverse numerical Laplace transform algorithm to obtain the corresponding time responses. As an initial verification of the method, a comparison with an experimental result previously published is provided. As a second application example, a test case is used to analyze the effect of the point of impact on the magnitude and waveshape of the transient overvoltages obtained, as well as the effect of line’s sagging between poles. Finally, it is demonstrated that the inclusion of lightning arresters can be considered in this frequency domain model by means of a combination of a piecewise linear approximation and the superposition principle.

New Pixel Circuit Design Employing an Additional Pixel Line Insertion in AMOLED Displays Composed by Excimer Laser-Crystallized TFTs

Active matrix organic light-emitting diode (AMOLED) displays are fabricated from polycrystalline silicon, which is formed in the single and double (overlap) scanned area during the excimer laser annealing (ELA) process. A redundant pixel line (RPL) design is proposed to remove the overlapping mura and, as a result, a 5-in AMOLED display is successfully fabricated without any non-uniform line image on the overlapping scanned area. This result indicates that the fabrication of a large-sized AMOLED panel is possible using ELA crystallization through an RPL design.

A lower bound for the length of nonuniform transmission line matching sections

A lower bound for the length of a nonuniform transmission line section needed to match a given load impedance to a given real input impedance is derived. The bound depends not only on the load and input impedances, but also on the maximum and minimum permissible values of characteristic impedance within the nonuniform line. Several specific cases are presented to illustrate the tightness of the bounds.

New S-Band Bandpass Filter (BPF) With Wideband Passband for Wireless Communication Systems

In this letter, a new wideband bandpass filter (BPF) using microstrip parallel-coupled line structure for s-band applications is proposed. The filter is constructed of two sections of three coupled lines separated by a nonuniform line resonator. In order to introduce one transmission zero at each edge of the desired passband, one of the outer coupled lines of each section is shorted to the ground. The nonuniform resonator is constructed by attaching pair of capacitive open-ended stubs at its central location. This resonator is implemented to increase the filter degree by moving the resonant mode inside the desired passband. The transmission zeros can be located at any desired frequency and the desired bandwidth can be obtained where the bandwidth is reversely proportional to the gap between the coupled lines. The filter is designed to have a wideband passband to cover the whole s-band frequency range. The design is successfully realized and verified by full-wave electromagnetic simulation and the experiment. Excellent agreement between the expected and measured results is obtained.

Spectral Models of Lossy Nonuniform Multiconductor Transmission Lines

This paper presents a new approach for modeling nonuniform lossy transmission lines. The proposed technique is based on the concept of Green's function of the differential problem represented by the Telegrapher's equations. The Green's function of nonuniform one-dimensional problems is expanded in terms of the eigenfunctions of the uniform problem, yielding a rational macromodel that has a simple representation in the time-domain. The use of global basis functions also addresses the problem of space dependence of the per-unit-length parameters, completely avoiding to resort to any discretization technique. Several examples of single and coupled nonuniform lines are presented and the accuracy of the method is verified by comparison with reference results.

Design and Analysis of Wideband Nonuniform Branch Line Coupler and Its Application in a Wideband Butler Matrix

This paper presents a novel wideband nonuniform branch line coupler. An exponential impedance taper is inserted, at the series arms of the branch line coupler, to enhance the bandwidth. The behavior of the nonuniform coupler was mathematically analyzed, and its design of scattering matrix was derived. For a return loss better than 10&#x2009;dB, it achieved 61.1&#x25; bandwidth centered at 9&#x2009;GHz. Measured coupling magnitudes and phase exhibit good dispersive characteristic. For the 1&#x2009;dB magnitude difference and phase error within <svg style="vertical-align:-0.17555pt;width:12.3875px;" id="M1" height="11.0375" version="1.1" viewBox="0 0 12.3875 11.0375" width="12.3875" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,11.0375)"> <g transform="translate(72,-63.17)"> <text transform="matrix(1,0,0,-1,-71.95,63.39)"> <tspan style="font-size: 12.50px; " x="0" y="0">3</tspan> </text> <text transform="matrix(1,0,0,-1,-65.7,68.56)"> <tspan style="font-size: 8.75px; " x="0" y="0">∘</tspan> </text> </g> </g> </svg>, it achieved 22.2&#x25; bandwidth centered at 9&#x2009;GHz. Furthermore, the novel branch line coupler was implemented for a wideband crossover. Crossover was constructed by cascading two wideband nonuniform branch line couplers. These components were employed to design a wideband Butler Matrix working at 9.4&#x2009;GHz. The measurement results show that the reflection coefficient between the output ports is better than 18&#x2009;dB across 8.0&#x2009;GHz&#x2013;9.6&#x2009;GHz, and the overall phase error is less than <svg style="vertical-align:-0.10031pt;width:12.3875px;" id="M2" height="10.7375" version="1.1" viewBox="0 0 12.3875 10.7375" width="12.3875" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,10.7375)"> <g transform="translate(72,-63.41)"> <text transform="matrix(1,0,0,-1,-71.95,63.56)"> <tspan style="font-size: 12.50px; " x="0" y="0">7</tspan> </text> <text transform="matrix(1,0,0,-1,-65.7,68.56)"> <tspan style="font-size: 8.75px; " x="0" y="0">∘</tspan> </text> </g> </g> </svg>.

Modeling piezoelectric parameters of bending mode transducers

The piezoelectric bender bar vibrator is commonly used for generating low frequency flexural plate mode vibrations. This study considers the excitation of “benders” using stripe-electroded piezoelectric elements of various electrode patterns and poling configurations using the k3'3 and k3'1, where the prime indicates field nonuniformity. A numerical analysis is used to calculate the nonuniform electric field lines and the corresponding coupling coefficients as well as other related electromechanical parameters by developing a Lagrangian description of the electromechanical body and using the energy method. The effective electromechanical coupling coefficients are calculated by taking into account the internal energies due to transverse, longitudinal, and shear vibrations in the bar. The contribution of the passive and the active capacitance is also explained and taken into account while calculating the electromechanical parameters.

Investigation on the hydrodynamics of slab x-ray laser plasma by nonuiform line focused laser irradiation

Based on the two-dimensional model, this paper compares the hydrodynamics of slab x-ray laser plasma produced by different nonuniform line focused irradiations. It finds that the average intensity and the duration of laser pulse and the overall shape of the intensity distribution in the focal line have different influences on the plasma. Calculations show that the evolution of temperature variation is more sensitive to the pulse duration and the electron density variation is more sensitive to the pulse intensity. Pulses with duration of 200 ps to 500 ps and with intensity of 0.2 TW/cm2 to 1.0 TW/cm2 are proved acceptable in slab x-ray lasers.

IMPEDANCE MEASUREMENTS OF NONUNIFORM TRANSMISSION LINES IN TIME DOMAIN USING AN IMPROVED RECURSIVE MULTIPLE REFLECTION COMPUTATION METHOD

In this paper, a recursive computation method is developed to derive the multiple re∞ections of nonuniform transmission lines. The true impedance proflles of the nonuniform transmission lines are then reconstructed with the help of this method. This method is more e-cient than other algorithm. To validate this method, two nonuniform microstrip lines are designed and measured using Agilent vector network analyzer E8363B from 10MHz to 20GHz with 10MHz interval. The re∞ection coe-cients of these nonuniform microstrip lines in time domain are attained from the scattering parameters using inverse Chirp-Z transform. The reconstructed characteristic impedance proflles of the nonuniform lines are compared with those reconstructed by Izydorczyk's algorithm. The agreements of the results illustrate the validity of the recursive multiple re∞ection computation method in this paper.

Transverse Standing Waves in a Nonuniform Line and their Empirical Verifications

We consider a one-dimensional elastic line with a linear varying density. Utilizing a Computer Algebra System (CAS), such as Mathematica symbolically we solve the equation describing progressive transverse waves yielding standing waves. For a set of suitable parameters the numeric mode of Mathematica displays and animates vibrating normal modes bringing the vibrations to life. We tailor a device that mimics the characteristics of the non-linearity; experimentally we explore its integrity.

Compact Modified Pentaband Meander-Line Antenna for Mobile Handsets Applications

A printed pentaband antenna for mobile handsets application is proposed in this letter. This antenna consists of a printed nonuniform meander line with perpendicular feed and open-stub structure, making it easy to operate in code-division multiple access (CDMA, 824-894 MHz), Global System for Mobile communications (GSM, 880-960 MHz), digital communication system (DCS, 1710-1880 MHz), personal communication system (PCS, 1850-1990 MHz), and wideband code division multiple access (WCDMA, 1920-2170 MHz). The experimental results of the constructed prototype are evidenced by mitigating the degradation of antenna bandwidth due to human head and hand effect, and the measurement results of specific absorption rate (SAR) are also presented.

Extra Losses in Imperfect Closed Grids

Extra Losses in Imperfect Closed GridsClosed grids consist of two-terminal power lines or/and of rings (loops). In non-uniform two-terminal lines, equalizing and circulating currents appear, in rings - circulating current. These currents cause extra power losses. Those losses are equal to the product of summary resistance and squared said extra currents and are independent of the direction of said currents. Equalizing current causes considerable losses by phase discrepancy of terminal voltages even when voltage magnitudes are equal. Equalizing current losses do not exceed 1/4 of load losses when terminal voltage difference is equal to maximum load voltage loss. The degree of non-uniformity of inhomogeneous rings can be estimated by inhomogeneous factor. The increased reliability and higher electricity quality in distribution grids can be attained by use of uniform or ameliorated ringed grids but the reservation can be implemented by controllable links between adjacent rings.

Design and Measurement of Nonuniform Ferrite Coupled Line Circulator

Nonuniform ferrite coupled line constructed by placing section of corrugated coupled lines on longitudinally magnetized ferrite substrates is investigated. Unlike the usual uniform ferrite coupled line, the proposed nonuniform ferrite coupled line is corrugated with different cosinusoidal contours on the coupling slots. Compared with a standard ferrite coupled line designed at 7.6 GHz, the nonuniform ferrite coupled line based on the same ferrite substrate and of the same dimension is found to operate at a higher frequency. The center frequency of operation is up shifted by about 1 GHz. It is also found that the nonuniform ferrite coupled line has a broader bandwidth. The proposed nonuniform ferrite coupled line operates at the center frequency of 8.6 GHz with a bandwidth of about 26.7%, while the standard uniform ferrite coupled line operates at 7.6 GHz with a bandwidth of 14.5%. Two 3-port circulators are built by adding simple T-junctions to the uniform and the nonuniform ferrite coupled lines respectively. The measurements confirm the up shift in center frequency and the broadening in operating bandwidth of the nonuniform ferrite coupled line circulator.