Equivalent Transmission Line Research Articles

Simple algorithm for calculating the total electric field of high‐voltage direct current transmission lines

The basic equations of high-voltage direct current transmission lines’ ion current field are consisted of electric field Poisson equation, ion current density equation and the current continuity equation, hence, the key to calculating total electric field is to solve the non-linear differential equations, but the calculation process is very complicated. A simple algorithm is proposed to solve the problem in this study. First, the charge simulation method, an accurate numerical method, is employed to calculate the distribution of the electrical fields of a conductor. Then, the thought of emission charge is referred to calculate total electric field strength, this method does not need to adopt Deutsch hypothesis, and it avoids solving complex differential equations; hence, the calculation process can be greatly simplified. Finally, it is found that the calculated values agree satisfactorily with data measured on laboratory models and full-scale test lines.

Extraction of VLSI Multiconductor Transmission Line Parameters by Complementarity

Solving lossy multiconductor transmission line (MTL) equations is of fundamental importance for the design and signal integrity verification of interconnections in VLSI systems. It is well established that the critical issue is the efficient and accurate electrical characterization of the MTLs through the determination of their per-unit-length parameters. In this respect, the so-called complementarity has the potential to become a fast and accurate method for the extraction of these parameters. Besides the value of the parameters, in fact, complementarity provides rigorous error bounds for them. Despite this important feature, commercial software do not use complementarity yet, due to the fact that there are unsolved theoretical issues related to the nonstandard formulation based on the electric vector potential. Some attempts to fill this gap have been already reported. The aim of this paper is to fill this gap by introducing a general formulation based on the electric vector potential highlighting the advantages of complementarity with respect to the standard first- and second-order finite element formulations.

A Comprehensive Investigation of a Common-Mode Filter for Gigahertz Differential Signals Using Quarter-Wavelength Resonators

This paper presents a comprehensive investigation on an inexpensive and wideband common-mode noise suppression filter that uses a quarter-wavelength resonator. An equivalent transmission line model is also used to evaluate the effectiveness of the proposed structure in a common-mode filter (CMF). Moreover, more important parameters, such as coupling coefficients are presented to investigate the characteristics of CMF unit. The performance of CMF is then characterized using two coupling coefficients between two differential traces and between differential traces and a quarter-wavelength resonator. A simple design approach is also presented for a wideband CMF. Numerical results demonstrate that CMF with three different lengths of quarter-wavelength resonators have rejection bands of 3.94-8.74 GHz and 3.53-10.1 GHz at cutoff frequencies of -20 dB and -10 dB, respectively Time-domain common-mode noise is decreased by approximately 60%. Moreover, analyses of differential insertion loss and group delay indicate that the differential signals maintain sufficient signal integrity when the wideband CMF is used in single- and two-pair differential interconnects. Finally, CMF is validated by an eye diagram and by measurements of time/frequency-domain common-mode noise and I/O cable common-mode current.

Some limiting aspects of transmission line theory and possible improvements

Wiring still supports most of electric power fluxes as well as data transmission in various infrastructures and transport systems. Hopefully, transmission line theory is a very helpful approximation to estimate interference propagation among cable harnesses. This is definitely a useful tool for engineers, since it enables anticipating the probability of failure of equipment they are connected to. Everything has been written from the initial roots of transmission line derivation, dated from the ancient telegraphist's equations established by O. Heaviside back to...1880! until the last developments of sophisticated and off-the-shelf transmission line solvers for complex arrangements of cable networks. The fact is, that these tools are so familiar to many EMC engineers that it might come with some misunderstanding of some results. In this paper, we take a look at the root assumptions of this approximate theory and examine some of its potential weaknesses, through simple examples. Then, we investigate the question of the possible improvement of the classical transmission line theory (when and if required). In principle, this would require the derivation of some kind of generalized transmission line theory or even the examination of the super theory of transmission lines. We rather show that a much more simple modification of transmission line equations is possible for a better approximation of the experimental observations.

Experimental Investigation and Theoretical Analysis on Galloping of Iced Conductors

The aerodynamic forces of two typical iced conductor models are obtained by high frequency balance technique in wind tunnel test. The effects of wind directions and turbulence intensity on aerodynamic forces coefficients are discussed. An analytical expression for predicting the galloping instability trends in arbitrary directions is derived. An aerodynamic model considering the dynamic swing is developed according to the quasi-steady theory. Galerkins procedure is employed to discrete the governing equations of transmission line, which is modeled as a suspended homogeneous elastic cable having a small equilibrium curvature and neglecting the shear deformation. The forth order Runge-Kutta method are applied to obtained the approximate numerical results of iced transmission line galloping.

Analysis of the response to a lightning strike of a towers cascade equipped with its grounding systems

This paper presents an analysis of the response to a direct and indirect lightning strike of a transmission line towers cascade using a direct time domain approach based on the corresponding transmission lines equations and finite difference time domain (FDTD) method. The proposed work deals with a real case of towers being connected by ground wires and equipped with grounding systems with different topologies (vertical or horizontal conductor buried in the ground). In particular, this work realistically represents the tower geometry and accounts for the propagation phenomena along the tower and between the towers. The analysis carried out in time domain deals with rather complex electrical devices (towers, ground wires and grounding systems), but at the same time requires very low computational cost and also provides relatively simple implementation. Some illustrative computational examples related to some engineering applications are given in the paper.

Design of thin infrared quarter-wave and half-wave plates using antenna-array sheets

A thin quarter-wave plate and a half-wave plate are designed based on multiple antenna-array sheets (AAS). For transmission through cascaded antenna-array sheets, an equivalent transmission-line model is used. The interspacing dielectric is modeled as a transmission line with each AAS treated as a loaded shunt admittance. By utilizing this transmission-line model to treat the plates as a differential phase shifter between two orthogonal polarizations, a quarter-wave plate can be designed with two AAS and a half-wave plate can be designed with three AAS. Both wave plates can achieve high transmission with the desired 90° and 180° phase difference between two orthogonal polarizations.

Radiated Electromagnetic Immunity Analysis of Flex Cable with Ground Plane Using Transmission Line Equations

This paper presents the analysis of radiated immunity of flex cable with ground plane using transmission line equations. The conformal mapping transformation technique and the integral equations are employed to extract the equivalent RLCG parameters for canonical types and complicated types of structures, respectively. The external electromagnetic field sources are modeled as equivalent voltage and current sources in the transmission line equations. After the equivalent circuit is obtained, the induced voltage is computed via the SPICE solver. Validation with case studies shows that the approach is capable of efficiently modeling the radiated electromagnetic interference to evaluate the immunity level of devices under test.

Frequency-Dependent Transmission Line Fractional Model and its Solution Based on Skin Effect

Due to the continuous increasing of operating frequency in the power system and the transmission speed, under the high frequencies of the transmission line calculation and simulation process, it is necessary to consider the frequency-dependent properties. At present, the frequency-dependent transmission line modeling has a variety of methods, but in the modeling and calculation of frequency variable term, processing is relatively complicated. This article will introduce transmission line equation of fractional calculus, intuitive representation of frequency varying parameters, and by a time-domain fractional solution, simplify the operation, improve the computational efficiency. Application of this algorithm for fractional differential equations can be obtained the voltage and current responses at any point in the transmission line. Thesis also by comparison with actual example, confirmed the validity and feasibility of the algorithm. At the same time, proposed algorithm can be extended to the multiple conductor transmission lines of fractional order model, also has certain applicability.

Application of Metallic Strip Gratings for Enhancement of Electromagnetic Performance of A-sandwich Radome

Enhancement of the electromagnetic (EM) performance characteristics of A-sandwich radome wall over X-band using metallic strip gratings is presented in this work. Equivalent transmission line method in conjunction with equivalent circuit model (ECM) is used for modeling the A-sandwich radome panel with metallic strip gratings and the computation of radome performance parameters. Metallic strip grating embedded in the mid-plane of the core and those in the skin-core interface are the configurations considered in the present work. For a given thickness of metallic strip grating, its width and pitch are optimized at different angles of incidence such that the new radome wall configuration offers superior EM performance over the entire X-band as compared to the conventional A-sandwich wall. The EM analysis shows that the superior EM performance of A-sandwich with metallic strip gratings makes it suitable for the design of normal incidence and streamlined airborne radomes. Defence Science Journal, 2013, 63(5), pp.508 -514 , DOI:http://dx.doi.org/10.14429/dsj.63.2458

Measurements of Medium-Frequency Propagation Characteristics of a Transmission Line in an Underground Coal Mine

In underground coal mines, medium frequency (MF) communication systems couple their signals to metal infrastructures such as ac power cables and wire-based telephone lines, which guide the signals to propagate for a long distance. To better understand the propagation characteristics of MF signals, an easy-to-use measurement method was recently developed at the National Institute for Occupational Safety and Health. The method will be introduced along with an equivalent transmission line model for a long metallic infrastructure in underground coal mines. The model serves as the fundamental driver for the method development. Propagation measurements on a twisted pair of telephone lines in an underground mine were made using this method. The measurements confirmed the low MF signal attenuation rate and the dependence of the propagation characteristics of the line on the electrical properties of surrounding coal and rock as theoretical studies predicted.

Fractional Order Generalization of Anomalous Diffusion as a Multidimensional Extension of the Transmission Line Equation

In this paper, a new fractional order generalization of the diffusion equation is developed to describe the anisotropy of anomalous diffusion that is often observed in brain tissues using magnetic resonance imaging (MRI). The new model embeds three different fractional order exponents-corresponding to the principal directions of water diffusion-into the governing Bloch-Torrey equation. The model was used to analyze diffusion weighted MRI data acquired from a normal human brain using a 3T clinical MRI scanner. Analysis of the data revealed normal Gaussian diffusion in the cerebral spinal fluid (isotropic fractional order exponent of (0.90 ±0.1), and anomalous diffusion in both the white (0.67 ±0.1) and the gray (0.77 ±0.1) matter. In addition, we observed anisotropy in the fractional exponent values for white mater (0.59 ±0.1) along the fibers versus 0.68 ±0.1 across the fibers), but not for gray matter. This model introduces new parameters to describe the complexity of the tissue microenvironment that may be sensitive biomarkers of the structural changes arising in neural tissues with the onset of disease.

An Efficient Method Based on the Electromagnetic Time Reversal to Locate Faults in Power Networks

This paper presents a new method based on the electromagnetic time-reversal (EMTR) theory for locating faults in power networks. The applicability of the EMTR technique to locate faults is first discussed. Using the classical transmission-line equations in the frequency domain, analytical expressions are derived to infer the location of the fault. The accuracy of the proposed method is then discussed in relation to the number of observation points adopted to record the fault-originated electromagnetic transients. Then, this paper illustrates the extension of the proposed method to the time domain. The experimental validation of the proposed method is presented by making reference to a reduced-scale coaxial cable system where real faults are hardware-emulated. Finally, the application of the proposed EMTR-based fault-location method to Electromagnetic Transients Program-simulated cases is presented. The simulated test cases are: a mixed overhead/coaxial cable transmission system and the IEEE 34-bus distribution test feeder. Compared to other transient-based fault-location techniques, the proposed method presents a number of advantages, namely, its straightforward applicability to inhomogeneous media (mixed overhead and coaxial power cable lines), the use of a single observation (measurement) point, and robustness against fault type and fault impedance.

Macromodeling of Multilayered Power Distribution Networks Based on Multiconductor Transmission Line Approach

Typical modeling algorithms for multilayered irregular shaped power distribution networks are based on a finite difference solution of the Helmholtz equation. In this paper, the finite difference solution is demonstrated to be equivalent to a discretization of the Telegraphers partial differential equations for multiconductor transmission lines (MTL). With this concept, an efficient macromodeling algorithm for multilayered structures based on MTL theory is presented. The electromagnetic coupling between the plane layers due to wraparound currents is captured by the inductive and capacitive coupling between the multiconductor lines. A delay extraction-based macromodel is used to represent the MTL in SPICE that can better capture the distributed effects of the structure than existing lumped models. This approach is successfully implemented for multilayered structures with irregular geometries and is shown to be more accurate and efficient compared with existing SPICE lumped models.

Eigenmode on a Coaxial Resonator With Longitudinal Inner-Outer Corrugation

In this paper, eigenequations of TE and TM mode about coaxial resonator with longitudinal inner-outer corrugation are derived by the surface impedance theory and the first-order transmission line equations with mode coupling coefficients are obtained by means of the transmission line and coupling wave theory. According to these equations, the resonant frequency, diffractive quality factor Q, and field profile geometry of the eigenmode of the coaxial resonator can be calculated, and the effect of the inner (outer) slot depth and tooth width on the resonant frequency and Q factor can be discussed. Numerical results display as follows: 1) the resonator can effectively suppress the mode competition and 2) the inner slot depth and tooth width of the resonator does not almost affect the resonant frequency, and the outer slot depth and tooth of the resonator can affect the resonant frequency, whereas the Q factor is not affected by them.

Full-wave analysis of a compact bandpass meandering resonator filter using method of lines

Full-wave analysis based on the method of lines and the generalized transmission line equations is applied for the design of a small-size wide stopband bandpass filter. The analytical calculation in the direction of propagation and using nonequidistant discretization enables the analysis of the method of lines to be efficient for structures that can be divided into cascaded subsections along the propagation direction of the wave. The proposed filter consists of a pair of meandering uniform impedance resonators and feeding lines. Wide stopband and high selectivity as well as compact size of the filter are achieved due to the effect of multipath between the feeding points and the resonators that leads to suppression of the first and second harmonic of the filter. The modes distribution and the scattering parameters of the designed filter are computed and studied, leading to an achievement of a passband return loss greater than 18 dB and insertion loss about 1.7 dB. The designed filter is fabricated and tested, where good agreement is found between the numerical and experimental results.

Electromagnetic measurement while drilling technology based on the carrier communication principle

Abstract To improve data transfer rate and signal telemetry depth in electromagnetic measurement while drilling (EM-MWD), and to solve the problems of short life expectancy and poor reliability of drill pipes as well as serious electromagnetic scattering, this paper presents the measurement while drilling (MWD) method based on the carrier communication principle. Based on carrier technology, the electromagnetic wave signal was coupled with the drill pipe through the coupling transformer, where the drill pipe and formation can form the guiding wave system to achieve data transfer between the ground and the bottom. The transmission line equation is developed based on the analysis of the transmission characteristics of electromagnetic waves in strata and drill pipes, and the overall structure of the system is presented. The real transmitter and receiver are produced by using LM1893 as the carrier module. In addition, the system optimization is proposed. The electromagnetic waves loaded on the drill pipe using carrier technology can transmit drilling measurement parameters from the bottom to the surface in real time, and send setting parameters and commands from the surface to the bottom simultaneously through the drill pipe-formation channel, and thus achieve the implementation of bi-directional communication between the ground and the bottom.

Distance Protection for HVDC Transmission Lines Considering Frequency-Dependent Parameters

For distance protection, the measurement accuracy at the boundary of protective zone is the most important issue to distinguish internal faults from external faults correctly. Since the line parameters depend strongly on the frequencies, in order to obtain high accuracy, it should be considered during initial fault transients generally associated with plentiful harmonics. In this paper, a distance protection method considering a frequency-dependent parameters is introduced into HVDC transmission lines. According to transmission-line equations, the frequency-dependent parameter model is separated into two parts: 1) distributed parameter model and 2) a compensation matrix related to frequency-dependent parameters, and the latter is approximated in the time domain with finite impulse response filters. So the voltage and current at the setting point are calculated accurately using local sampling data, and the fault distance is obtained by solving differential equations. The proposed algorithm is able to enhance the calculation accuracy of fault distance greatly at the remote-end faults. Furthermore, it is performed in the time domain and, thus, a short data window is sufficient for it to achieve satisfactory accuracy. Simulation results show that this method is valid and is capable of detecting the faults occurring on the protected line quickly and accurately.

Application of TEM horn antenna in radiating NEMP simulator

In order to design a small radiating nuclear electromagnetic pulse simulator with fast rise time, we have investigated the application of TEM horn antenna in this kind of simulator. The TEM horn antenna is excitated by the integral double exponential pulse. Farfield response in time domain is analyzed based on the step response formula which is derived from the equivalent transmission line model of TEM horn antenna. Principle of antenna parameters selection is determined. The results of numerical calculation give a show of the radiation waveform and some problems. Then experiments are implemented and results are compared with the radiation waveforms generated by double exponential pulse excitation. It suggests that the TEM horn antenna can be used as radiating antenna in the NEMP simulator, which can radiate double-exponent-like pulse with the integral double exponential pulse as excitation. Meanwhile, impedance loading can improve farfield waveforms and enhance the low-frequency radiating ability of antenna.

주기가 다른 격자들로 구성된 DFB 필터의 구현

The filtering characteristics of planar distributed feedback (DFB) waveguides composed by gratings with different period are solved using equivalent transmission-line network. To analyze explicitly its band-pass and resonance properties, a longitudinal modal transmission-line theory (L-MTLT) based on Floquet`s theorem and Babinet`s principle is newly developed. The numerical results reveal that this approach offers a simple and analytic algorithm to analyze the filtering characteristics of cascaded DFB structure with different period, and the bandwidth and side-lobe suppression of cascaded DFB filter are sensitively dependent on the variation of aspect ratio and the number of grating at each region.