Extended Transmission Line Research Articles

Extended Transmission Line Theory and its Application to the Broadband Modeling of Ferrite-Based RF Transformers

Extended Transmission Line Theory and its Application to the Broadband Modeling of Ferrite-Based RF Transformers

Transient induced voltages on aboveground pipelines parallel to overhead transmission lines

Lightning strikes to conductors of overhead lines may cause high transient induced voltages at neighbouring pipelines. Thus, the computation of these voltages is important for the safe and reliable pipeline operation. This work investigates the effects of line parameters and soil modelling on the transient voltages induced at an aboveground pipeline due to lightning strikes to a phase conductor of a nearby overhead transmission line. Three different earth formulations are evaluated: the Carson, Wise, and the method of moments with surface operator combined with the extended transmission line approaches. Computations are performed using both frequency- and time-domain models, as well as constant and frequency-dependent soil electrical properties. CIGRE lightning current waveforms are employed in simulations derived on the basis of the statistical distributions of their parameters for negative first return-strokes. Transient induced voltage waveforms differ among the evaluated lightning currents, with higher peak values for shorter and steeper current wavefronts. Conservative results are obtained for the constant soil properties and Carson’s earth formulations, which neglect, respectively, the dispersion of soil electrical properties and displacement current.

Analysis of Cross-Bonded Cables Using Accurate Model Parameters

This paper presents a thorough investigation of frequency and electromagnetic transient (EMT) responses of cross-bonded cables. The study adopts newly developed Line/ Cable Data (LCD) Module in an existing EMT-type simulation software. The input impedances evaluated by positive sequence and various mode energizations on a typical cross-bonded cable (CBC) in frequency domain are investigated.In addition to cross-bonded, the solid-bonded cable (SBC) and core-transposed cable (CTC) are analyzed for characteristics of input impedance. The mixed propagation modes of CBC and CTC are studied. The influence of bonding methods and cable models on transient voltages is investigated. The results simulated by the new LCD are compared with the Classical Parameter Calculation (CPC) method and validated by recently proposed extended transmission line (ETL) approach.

Assessment of Ground-Return Impedance and Admittance Equations for the Transient Analysis of Underground Cables Using a Full-Wave FDTD Method

In this paper, the validity of two extended transmission line approaches proposed for calculating the ground-return impedance and admittance of an underground insulated cable is evaluated taking as reference a full-wave approach based on the 3-D finite-difference time-domain (FDTD) method. The transient responses of an underground cable with realistic radius are calculated for a wide range of soil resistivities and cable lengths. It is shown that the extended transmission line approaches lead to transient waveforms in good agreement with the FDTD method even for relatively short cables and high soil resistivity. The limitations of a traditional formulation that neglects the influence of the ground-return admittance on the calculation of the cable parameters are also demonstrated. Overall, the results confirm the accuracy of the newly-proposed expressions for the calculation of underground cable parameters.

An efficient analytical based technique to numerical calculation of extended earth return impedance and admittance of overhead lines

This paper describes an efficient numerical integration technique for the extended overhead line earth return impedance and admittance formula. In-appropriate handling of the infinite integral in the formula can lead to erroneous calculated earth-return parameters at extreme frequencies, and a significant increase in computational effort. In this paper, an efficient technique based on an analytical approach is introduced to enforce proper discretization of the extended transmission line equations. Firstly, the line equations are analyzed, and a common cause of improper discretization is identified. Then the equations are further broken down numerically, based on which a procedure to suitably select a discretization interval and step is developed. Validation was conducted by calculating the earth return parameters of overhead-line cases using the proposed method and equal distance discretization. The proposed technique shows accurate results while using fewer discretization points than equal distance discretization.

Catalyst material comprising nanoparticles

This paper describes an efficient numerical integration technique for the extended overhead line earth return impedance and admittance formula. In-appropriate handling of the infinite integral in the formula can lead to erroneous calculated earth-return parameters at extreme frequencies, and a significant increase in computational effort. In this paper, an efficient technique based on an analytical approach is introduced to enforce proper discretization of the extended transmission line equations. Firstly, the line equations are analyzed, and a common cause of improper discretization is identified. Then the equations are further broken down numerically, based on which a procedure to suitably select a discretization interval and step is developed. Validation was conducted by calculating the earth return parameters of overhead-line cases using the proposed method and equal distance discretization. The proposed technique shows accurate results while using fewer discretization points than equal distance discretization.

Evaluation of external electromagnetic fields generated by a multi-phase underground cable based on transmission line approach

Recently developed extended transmission line (TL) approach and generalized formulas of external electromagnetic (EM) fields generated from a multiphase underground cable are reviewed and summarized in this paper. The lateral external EM field components of a three-phase underground cable with different arrangements are evaluated by classical and extended TL approaches. Two phase and single-phase energizations are applied to the cable. The characteristics of external EM fields at different field observation points are calculated.

Stenosis diagnosis based on peripheral arterial and artificial neural network

The current diagnosis methods of arterial stenosis need to rely on large-scale equipment, which cannot provide early warning for patients with arterial stenosis and make them miss the best treatment opportunity. Therefore, we present an algorithm for the diagnosis of arterial stenosis, which is based on neural network. The input of neural network is peripheral pulse wave signal, and the output is the degree and location of arterial stenosis. The acquisition of peripheral pulse wave signal is convenient, and patients can detect it at home. In this paper, we extend firstly the existing human arterial transmission line model to include cerebral vessels, so that we can study cerebral artery stenosis. Then, we use the extended transmission line model to verify the effect of arterial stenosis (including carotid stenosis, renal artery stenosis, middle cerebral artery stenosis) on peripheral pulse wave signal. Finally, a database of peripheral pulse wave was established to simulate the actual conditions of artery stenosis based on the transmission line model. In addition, a diagnosis model of artery stenosis was constructed by using artificial neural network (ANN). The diagnostic results showed that when the degree of stenosis varied from 10 to 90%, the diagnostic accuracy was 88.7%. For moderate (50%) and severe (90%) degrees of stenosis, the diagnostic accuracy was 90.5% and 98.7%, respectively. Moreover, when the degree of stenosis was greater than 50%, the diagnostic accuracy of narrow positioning is greater than 95%. In general, the proposed algorithm does not rely on large equipment and has high accuracy, which can provide patients with early warning of arterial stenosis.

An accurate analysis of lightning overvoltages in mixed overhead-cable lines

An accurate investigation of lightning overvoltages on a typical mixed overhead-cable line is performed. The recently developed extended transmission line (TL) approach, frequency-dependent (FD) soil model and FD grounding system modeling method are also reviewed. The wave propagation characteristics of an overhead and a cable in frequency domain are studied using classical and extended TL approaches. Moreover, transient simulations using Numerical Laplace Transform (NLT) are carried out with different FD soil parameters and FD grounding behavior, and the influences of FD characteristics on the transient cable sheath voltages are made clear.

Theoretical and NEC Calculations of Electromagnetic Fields Generated From a Multi-Phase Underground Cable

A generalized formulation of electromagnetic fields generated from a multi-phase underground cable is proposed based on a complete solution of Maxwell equations. The lateral electromagnetic field components, the shielding effect of cables and the phase currents at high frequencies of a three phase underground cable are evaluated by the newly derived formulas. The accuracies of the recently developed extended transmission line approach of underground cables are investigated based on the performance of electromagnetic field components. It is also shown that Numerical Electromagnetics Code verifies the results calculated from the new formulas presented in this article.

Effect of frequency-dependent soil parameters on wave propagation and transient behaviors of underground cables

This paper investigates the influence of frequency-dependent (FD) soil parameters in comparison to the constant soil (CS) parameters on wave propagations and transient characteristics of underground cables. Various FD soil models are summarized, and the calculated results of the FD soil parameters are compared with independent measured FD soil data. Longmire / Smith (LS) model is found to show the best agreement with the measured results. The frequency responses of wave propagations on underground cables are studied by the recently proposed extended transmission line (TL) approach together with the CS and the LS FD soil models. Calculated transient responses show more attenuation with a large soil resistivity at 100 Hz in comparison with those with a small soil resistivity at 100 Hz. Further, the transient voltage responses of a cross-bonded cable are compared with the transients solved by the Cable Constants and the existing FD soil routine in an EMT-type simulation tool, and a significant difference is observed.

Wideband Differential-Mode Bandpass Filters With Stopband and Common-Mode Suppression

This letter presents wideband differential-mode (DM) bandpass filters (BPFs) designed on a microstrip line for ultrawideband (UWB) applications. The proposed design is based on an optimized branch-line structure with extended transmission lines (TLs). An enhanced performance can be obtained using a very simple design approach. The introduced TLs can be used for improving the DM stopband response by introducing multiple transmission zeros (TZs) at the lower and upper stopband. The common-mode rejection level can also achieve around 40 dB within the band of interest. The proposed filters are fabricated for experimental verification. The predicted and measured results show a very good agreement.

Transient Responses of Overhead Cables Due to Mode Transition in High Frequencies

This paper investigates the effect of mode transition from low-frequency transverse electromagnetic (earth-return wave) to high-frequency Sommerfeld–Goubau (surface wave) propagation on switching surges in gas-insulated buses (overhead cables) by adopting complete formulas for earth-return impedance and admittance using the extended transmission line (TL) approach. The lower attenuation of the surface wave shows a significant difference in the propagation functions evaluated by the classical TL approach with Carson/;Pollaczeck's impedance and space admittance. The lower attenuation in the high-frequency region leads to a spike-like voltage at the wavefront of a step response in time domain, and results in switching surges with frequency components higher than 10 MHz. This phenomenon explains the reason why measured transient voltages and currents in gas-insulated substations show frequency components ranging from some MHz to about 100 MHz, and the transient voltages and currents are sustained for more than a few microseconds. This phenomenon cannot be reproduced by the classical TL approach. It is also verified in this paper by numerical Laplace transform and by electro-magnetic transients program simulations using the extended TL approach.

On the design of equal division single-band filtering dividers with an extended transmission line and resistor as isolation elements

This paper introduces a new scheme for effective output port isolation and return loss in RF-filtering divider design. The proposed design incorporates an extended transmission line and a conventional resistor as isolation elements. The technique has a simpler microstrip circuit implementation when it comes to the integration of a single-band band-pass filter with a Wilkinson power divider to achieve simultaneous filtering-dividing action. It is established that if a band-pass filter with a certain fractional-bandwidth is matched to 70.7 $\Omega $, a transmission line section and isolation resistor are sufficient for achieving reasonable output port return loss and isolation in the resulting filtering divider. In experimental validation, two single-band band-pass filters, namely a coupled-line filter and an open-loop coupled resonator triangular filter with center frequencies of 3 GHz and 1 GHz, respectively, effectively replace the conventional quarter-wavelength transformers for equal division of power. The proposed filtering divider structures were fabricated and a reasonable agreement was observed between respective simulated and measured S-parameter responses. The experimental results for a coupled-line filtering power divider and an open-loop triangular filtering power divider were as follows: 1 dB fractional-bandwidths of 15.3% and 12%, port isolations better than 31 dB and 20 dB, and good out-of-band performances up to 2.67f$_{0}$ and 2.85f$_{0}$, respectively.

Compact UWB Power Divider, Analysis and Design

In this paper, two ultra-wide band power dividers are introduced. Compact equal power divider is considered firstly where an extended transmission lines and double open stubs are used in order to increase the bandwidth. Secondly, an unequal UWB power divider is introduced where multi-stage impedance is used. The proposed power dividers are fabricated and measured. The overall sizes of the proposed power dividers are 11.37 × 17.87 mm2 for the equal one and 12.13 × 29.03 mm2 for the unequal power divider. The simulated results are compared with the measured results and good agreement is obtained.

A dual-mode reconfigurable patch antenna and an extended transmission line model

A reconfigurable patch antenna is proposed. The antenna design avoids any potentially interfering bias paths for switching; only an external bias-tee is required for biasing. An equivalent analytical model has been derived to describe the band shifting principle of the reconfigurable antenna. An example prototype resonating at two frequencies of 1712 MHz and 1793 MHz is demonstrated to prove the concept. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:57–61, 2016

An Impedance-Transforming Coupled-Line Wilkinson Power Divider with Port Isolations and Extensions

An impedance-transforming coupled-line Wilkinson power divider with port isolations and extensions is proposed in this article. It is composed of a coupled line section, an isolation resistor, and three extended transmission lines at each port for physical isolation and convenient installation. By substituting additional transmission lines for the three port extensions and introducing coupled lines, the power divider achieves suppressed insertion loss with enhanced physical output isolation. Closed-form design equations are successfully derived and verified. The excellent agreement between simulated and measured results shows that the proposed power divider can realize required functions with good matching, low insertion loss, fine isolation, and wide bandwidth.

Novel broadband conventional- and dual-composite right/left-handed (C/D-CRLH) metamaterials: properties, implementation and double-band coupler application

Broadband conventional- and dual-composite right/left-handed (C/D-CRLH) transmission line metamaterials are presented. The extended transmission line theory for these structures is developed and the fundamental C-CRLH and D-CRLH properties are described comparatively in terms of dispersion/attenuation diagrams and Bloch/characteristic impedances with subsequent transmission characteristics. A D-CRLHstructure, implemented in microstrip technology, is demonstrated experimentally for the first time and shown to have potential for unique applications. As an illustration of such applications, a novel double-band coupled-line coupler constituted of one C-CRLH and one D-CRLH transmission line is demonstrated and explained by generalized coupled-mode theory.

Transmission line description for doped conjugated polymers with polarons, bipolarons and counterions as charged species

Recently the electrochemical transmission line model has been extended by the author to account for traps (for polarons ( P) and counterions ( C)) and for the influence of a steady-state current leading to the occurrence of current generators in the transmission line. Now in the transmission line the occurrence of bipolarons ( BP) besides the Ps and the direct P– BP reaction are included. For the beginning the non-degenerate limit is considered. The mathematical description requires besides the Poisson equation and the continuity equations for Ps and Cs the rate equation for the P– BP reaction. The small signal ac analysis of the full system of equations leads to an extended transmission line model. It turns out that formally this reaction leads to similar elements as those describing trap recharging. Finally, for a more complicated transient behavior (including the formation of different complexes from Ps, BPs and Cs) the foundation for a mathematical description is given.

Extremely low resistivity erbium ohmic contacts to n-type silicon

Employing structures consisting of Pt, Si, and Er layers on Si, contacts to nSi with resistivities as low as 3.7×10−8 Ω cm2 were obtained and a low-leakage high-breakdown voltage Schottky diode on pSi was realized. Measured contact resistivities are lowest among the known contacts to nSi. Extended transmission line method measurements were made to determine contact resistivities for contacts to n-type silicon doped in the range 1018 –1020 cm−3 . The data are consistent with a barrier height of ∼0.37 eV. The metallurgy of the contacts was studied using transmission electron microscopy.