Unbalanced Transmission Line Research Articles

Generation of Artificial ULF/ELF Electromagnetic Emission in the Ionosphere by Horizontal Ground‐Based Current System

AbstractThe feasibility of the detection of electromagnetic response in the upper ionosphere to ground large‐scale ultra‐low‐frequency (ULF) and extremely‐low‐frequency (ELF) transmitters by low‐Earth‐orbit (LEO) satellites is considered. As an example of such transmitters, we consider the ZEVS 82 Hz transmitter, FENICS installation driven by 0.5–150 Hz generator, and industrial 50 Hz unbalanced power transmission lines. We numerically model the ULF/ELF wave energy leakage into the upper ionosphere from an oscillating grounded linear power line of a finite length suspended above a ground with a finite resistivity. The numerical scheme is based on the theoretical formalism developed to describe the excitation of an electromagnetic field by a horizontal grounded dipole. A realistic altitudinal profile of the plasma parameters has been reconstructed with the use of the IRI ionospheric model. For the ZEVS transmitter powered by 200 A current the modeled amplitudes of electromagnetic response can reach in the upper nightside ionosphere up to 60 µV/m and 6 pT. The assumption of an infinite source scale overestimates the ionospheric response by a factor of ∼7 as compared with realistic scale 60 km of the ZEVS transmitter. Unbalanced 50 Hz current of 10 A in large‐scale (>100 km) power transmission lines can produce the electric response in the upper ionosphere that is sufficient to be detected by electric sensors at LEO satellite. The stimulation of artificial Pc1 pulsations (0.5 Hz) with amplitudes ∼1 pT and ∼10 µV/m by large‐scale (>100 km) power lines is possible with driving current >100 A. The use of decommissioned power lines can be a cheap and efficient tool to stimulate Pc1 pulsations in the ionosphere.

Accurate Formulation of the Skin and Proximity Effects in High-Speed Cable System

An efficient transmission line model of high-speed cables is established, to predict its response at a high-frequency region (up to 20 GHz). Especially, an appropriate conformal mapping technique is applied to formulate the per-unit-length parameters of high-speed cables. Moreover, the skin and proximity effects of the conducting wires and the outer shield are derived in the closed form. As a result, the AC resistance/ inductance of all the conducting materials due to the skin and proximity effects are accurately incorporated for both layered and unlayered conductors. Furthermore, the mixed-mode S-parameters are precisely predicted for both balanced and unbalanced transmission line cables in the high-frequency region. In addition, the effects of the nonuniformities and cable geometry deformation on the mode conversions are also investigated. The proposed model is firstly validated with commercial software tools, COMSOL, FEKO, and HFSS; then, we further performed physical measurements to verify our new algorithm.

Analysis of balanced and unbalanced signal transmission lines and noise reduction technique for beam-current monitor in linear accelerators.

A signal transmission line and its characteristics were analyzed in detail for a beam-current monitor (CM) for long-pulsed electron beams. The monitor was based on a conventional current transformer, which comprised an induction coil wound around a ferrite core. The signal transmission and noise generation mechanism were analyzed by theoretical models based on balanced and unbalanced coaxial transmission circuits to effectively reduce noises superimposed on the beam-current signal waveform. The results of numerical analyses based on the theoretical models were in good agreement with those of an experiment for verification. It was found that the noise signals were generated by a high-power klystron operation and they were mode-transformed on the way to the transmission line. These results show that the locations of the grounded points in the transmission line were important. Based on a symmetrically configured three-line circuit theory, a new highly symmetrically configured coaxial transmission line is proposed to effectively suppress noises generated in CM. This report describes in detail the numerical and experimental analysis of a signal transmission line with coaxial cables for CM where the noise generation mechanism and its reduction technique are deeply involved.

Signal Balancing in Unbalanced Transmission Lines

Balanced lines operating as transmission line interconnects are subjected to differential-mode to common-mode conversion (and vice versa) in situations where symmetry imbalances (e.g., caused by line bends) are unavoidable. In this paper, a technique to compensate for such symmetry imbalances, providing pure differential-mode signals at the differential output port of the line, is presented. Such technique uses a rat-race balun (to generate the differential-mode signal) with the isolated port conveniently loaded, and it is based on the modification of the characteristic impedance of one of the unbalanced lines. A detailed analysis that justifies this compensation technique (valid for any arbitrary four-port network) and provides the design equations is presented. The approach is validated through simulation and experiment, by demonstrating that common-mode signals are not transmitted to the differential output port of a bended (i.e., unbalanced) line pair.

Performance improvement in long overhead lines associated to single-phase faults due to atmospheric discharges

In this research, a new analysis is proposed to detect the correct extinction of secondary arc in the re-closure protection, for long overhead lines in 220 kV. A new methodology for increasing the success rate of single-phase reclosing is proposed, with transient analysis (EMPT-ATP) have been done for over voltage detection in long overhead transmission lines, re-closure effect and probability, maneuver of line reactors, transient recovery voltages (TRV) caused by secondary arc phenomenon, unbalanced transmission lines and resonance. Finally, a case study is implemented with real fault conditions. Later, in the discussion section, the relation to the strength of the grounding system is analyzed and over voltage effects in the power system with the verification of the secondary arc extinction and the correct procedure of analysis.

Nanosecond Pulse Generator Based on an Unbalanced Blumlein-Type Multilayered Microstrip Transmission Line and Solid-State Switches

This paper combines an unbalanced Blumlein-type multilayered microstrip transmission line with solid-state switches to develop a high-voltage nanosecond pulse generator. This study was performed to emphasize the importance of a compact nanosecond pulse generator for biomedical applications. The unbalanced Blumlein-type transmission line reduces current flow through the solid-state switches. A multilayered microstrip transmission line is stacked onto the four-layered printed circuit board to minimize the system volume. Voltage wave propagation analysis is used to explain the principle of the system, which produced a rectangular pulse. The strategy to produce different pulse widths and the controlled timing of the related solid-state switches is interpreted according to this analysis, highlighting the approach needed to achieve a 50–100 ns pulsewidth. Also, the relevant principle of the variable load impedance of the unbalanced Blumlein-type multilayered microstrip transmission line system is also analyzed. To demonstrate the performance of the generator, a miniaturized system is established. Eventually, the nanosecond pulse generator produces a rectangular pulse on a resistor load of 50 $\Omega $ , with amplitude of 0–2 kV, pulsewidth of 50–100 ns, rise time of approximately 20 ns, and repetition frequency of 0 to several kilohertz. Also, when a 500 $\Omega $ resistor is used instead of a 50 $\Omega $ resistor, the output of the nanosecond pulse voltage is approximately two times that of the applied charging voltage.

New π –T generalised metamaterial negative refractive index transmission line for a compact coplanar waveguide triple band pass filter applications

This study presents, for the first time, a novel π − T generalised negative refractive index (NRI) transmission line (TL) configuration. It is innovated for increasing the possible passbands in designing microwave components. It is proved that the proposed transmission line can introduce up to seven passbands for completely unbalanced transmission line condition. The detailed mathematical analysis of that configuration based on the periodic network analysis and equivalent circuit model is introduced. As an application for the novel π − T generalised NRI TL configuration, a new compact triple band coplanar waveguide (CPW) metamaterial filter is introduced. The proposed triple bands CPW filter design steps are introduced and its performance is validated using equivalent circuit model simulation, electromagnetic full wave simulation and experimental measurements. Good agreements between the circuit modelling, electromagnetic full wave simulation and practical measurement results are achieved. All the results confirm that the proposed filter has triple passbands from 900 to 960 MHz, 1.4 to 1.48 GHz and 2.4 to 2.45 GHz. Moreover the filter size is compact whose length is only 12.1% λg at first passbands, 18.2 λg % at second passbands and 31.7 λg % at third passbands.

Study on Reactance Relays for Single Phase to Earth Fault on EHV Transmission Lines

Two questions about zero-sequence-reactance relay to overcome the disadvantages of high fault resistance for single phase to earth fault of high voltage transmission lines are discussed in this paper. The first question is about the phase difference between the measured zero-sequence current and voltage at fault position for un-balanced transmission lines. The second question is about the “in-phase” problem in reactance relays (or fault component reactance relays). This paper analyzes the two questions theoretically and the reactance relay is improved by a new discriminative principle. The capability against the fault resistance is largely enhanced by the improved schemes. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2835

Study on Voltage Unbalance Improvement Using SFCL in Power Feed Network With Electric Railway System

An electric railway system uses a single-phase source that is supplied through a Scott transformer from a three-phase transmission system. In addition, the electric railway system has rapidly changing load characteristics in time. An unbalance is generated owing to the rapidly changing large single-phase loads. Subsequently, the unbalanced load causes an unbalanced transmission line. A voltage unbalance in the source influences the power equipment by causing a reduction in the power generation capacity of the generator and a decrease in the output of the other facilities in the transmission line. In addition, many flexible ac transmission systems are applied to transmission lines to compensate for and control electric power. A voltage unbalance causes a control error in these systems. We propose the application of a superconducting fault current limiter to improve the voltage unbalance in a transmission system linked to a Scott transformer. In addition, we analyzed the effects of the proposed method using transient simulations.

Miniaturized Ring Coupler with Arbitrary Power Divisions Based on the Composite Right/Left-Handed Transmission Lines

A novel and miniaturized ring coupler capable of presenting arbitrary power divisions is proposed using the composite right/left-handed (CRLH) transmission lines. The unbalanced CRLH transmission lines that can be easily tailored to implement transmission lines of high or low Bloch impedance are applied to enhance the coupler's capability of arbitrary power divisions. To support our idea, a ring coupler that offers a 6 dB power division ratio and occupies only 44% of the conventional footprint was experimentally realized. Experimental results agree well with the simulation data. The proposed CRLH configuration demonstrates an alternative for implementing a compact ring coupler with arbitrary power division ratios.

ELECTROMAGNETIC RADIATION FROM UNBALANCED TRANSMISSION LINES

Abstract—A theory for the electromagnetic radiation from unbalanced transmission lines is developed. It is shown that radiation results from the convection current that develops in unbalanced transmission lines where the resistances of the lines are unequal. The process that leads to the generation of the nonlinear convection current in unbalanced transmission lines is explained. It is proved that the classical transmission line theory is not valid for unbalanced lines. The convection current and the radiation forces are included in the transmission line equations to develop a generalized model valid for all two-conductor transmission lines. The generalized model is validated via comparisons of its numerical solutions with laboratory measurements.

The Banyan Tree Antenna Array

A new wideband, wide-scan array is introduced, called the Banyan Tree Antenna (BTA) array, that employs modular, low-profile, low-cost elements fed directly from standard unbalanced RF interfaces. The elements consist of vertically-integrated, flared metallic fins over a ground plane that are excited by a vertical two conductor unbalanced transmission line. The antenna resembles the bunny-ear or balanced antipodal Vivaldi antenna (BAVA) designs, but most importantly uses metallic shorting posts between the fins and the ground plane that suppress a mid-band catastrophic common-mode resonance that occurs in 2D arrays of balanced radiators fed with unbalanced feeds. This work introduces simple circuit models that describe key performance attributes of the BTA array, leading to unique physical insights and design guidelines. Simulations of infinite single- and dual-polarized BTA arrays have achieved approximately two octaves of bandwidth for VSWR <; 2.2 at broadside and VSWR <; 2.8 at scans out to θ = 45°, while maintaining better than 14 dB polarization purity at θ = 45° in the D-plane.

Performance enhancement of microwave circuits using parallel-strip line

Nowadays, demands for compactness, light weight, and broadband have a great impact on design issues at both component and system levels in wireless communications. Multilayered structures fabricated with low-temperature co-fired ceramic (LTCC) technologies have been developed recently in response to these demands. With this trend, double-sided printed circuits using conventional fabrication techniques with lower cost have been receiving plenty of attention. The parallel-strip line, belongs to the family of balanced transmission lines. The conventional printed circuit board technology is able to realize it easily. It is a simple structure comprised of a piece of dielectric substrate sandwiched by two conducting traces. Signals flowing on the upper and lower conductors are always equal in magnitude and 180° out of phase; therefore, parallel-strip line has an inherent advantage of easy realization of a balanced configuration. Balanced or double balanced microwave circuits, such as amplifier, mixer, and antenna, are frequently employed in high-performance wireless communications systems, and they can be directly fed by parallel-strip lines. In contrast, microstrip line is an unbalanced transmission line; therefore, extra effort of designing balanced to unbalanced structures (balun) is required for using microstrip transmission lines.

Design and Analysis of a 3-Arm Spiral Antenna

A novel 3-arm spiral antenna structure is presented in this paper. This antenna similar to traditional two-arm or four-arm spiral antennas exhibits wideband radiation characteristic and circular polarization. Advantages offered by the new design are two fold. Unlike the traditional spiral antennas the three-arm spiral can be fed by an unbalanced transmission line, such as a coaxial line or coplanar waveguide, and therefore an external balun is not needed at the feed point. Also by proper choice of arms' dimensions the antenna can be directly matched to any practical transmission line characteristic impedance and therefore external matching networks are not required. This is accomplished by feeding the antenna at the outer radius by a coplanar waveguide (CPW) transmission line and tapering it towards the center. The antenna can also be fed from the center using a coaxial or CPW line perpendicular to the plane of the spiral antenna. A full-wave numerical simulation tool is used to optimize the geometry of the proposed 3-arm spiral to achieve a compact size, wide bandwidth operation, and low axial ratio. The antenna is also designed over a ground plane to achieve a unidirectional radiation and center loading is examined that improves the axial ratio. Simulated results like return loss, radiation pattern, gain, and axial ratio are compared with those obtained from measurements and good agreements are shown. Because of its unique feed structure and compact size, application of the proposed 3-arm spiral antenna for wideband array applications is demonstrated

Balance type pair transmission line for 60‐GHz band using multi‐layer substrate

AbstractFor a high‐density multilayer substrate ALIVH, balanced pair transmission lines on which 60‐GHz signals can be transmitted are proposed. First, it is shown that transmission of millimeter wave signals is difficult due to impedance mismatch of the vias in the conventional unbalanced transmission lines. Further, it is shown that transmission at up to 90 GHz is possible by a design such that the microstrip line on the surface, the strip line in the inner layer, and the vias connecting each layer have the same transmission line spacing and the same characteristic impedance. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(10): 1–8, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20249

A novel UWB feeding mechanism for the TEM horn antenna, reflector IRA, and the vivaldi antenna

This work proposes a method for feeding a balanced IRA with an unbalanced transmission line. This method is based on the current distribution on the surface of the antenna. The method of moments (MoM) simulations show that for the IRAs, there are some areas with low current density in comparison to the current density of the feeding points, almost over the entire frequency range. The coaxial cable is attached to the antenna's body all the way from the feeding point to an area of low current density, and extends out of the antenna structure at that point. This tremendously reduces the current density on the body of the coaxial cable. As a result, the current balance between two parts of the antenna is not disturbed. This method is applied to the TEM horn antenna, the reflector IRA, and the Vivaldi antenna. The TEM horn antenna was simulated using the HEMI software, and was fed by an unbalanced coaxial cable, both directly at the feeding point and using this method. This method was also applied to the reflector impulse-radiating antenna. Also, the Vivaldi antenna was fed both by considering the low-current density area and direct feeding. The E-plane far-field pattern of the new feeding method had good agreement with the result generated by the HEMI software for the balanced-fed antenna.

Optimum-shaped broadband balancing microstrip-couplerwithoutbridges or load but with even-mode suppression

A major problem in microwave technology is the connection of an unbalanced transmission line to a symmetrical (balanced) load, e.g., a dipole antenna. A broadband solution for this problem is presented in the shape of a simple and low-loss microstrip circuit without absorbing loads, shorts or expensive air-bridges, which offers more than one octave of bandwidth and good suppression of the even-mode.

The folded dipole: A self‐balancing antenna

AbstractThe folded dipole is known to have a fourfold increase in input impedance over that of a dipole. However, the half‐wavelength folded dipole also maintains a balanced radiation pattern when fed with an unbalanced transmission line. A numerical and experimental investigation of the folded dipole performance is reported in this paper. © 2001 John Wiley &amp; Sons, Inc. Microwave Opt Technol Lett 29: 155–160, 2001.

Estimation of lightning shielding failures and mid-span back-flashovers based on the performance of EHV double circuit transmission lines

In Japan, many unbalanced installation double-circuit EHV transmission lines were constructed to prevent simultaneous lightning faults on both the circuits. A one-line fault on the higher insulated circuit is either a shielding failure or a mid-span back-flashover. To discriminate shielding failures and mid-span back-flashovers among all the faults, the author analyzed the lightning performance of these unbalanced insulation lines. Both the unbalanced insulation lines and the balanced insulation lines are similar in the probability of causing a shielding failure and a midspan back-flashover, since both are the same in the configuration of shielding wires and phase conductors independent of the insulation mode. As a result of analysis, the author estimated that about 25/spl sim/40% of all the lightning faults on the double-circuit balanced insulation lines are shielding failures, and that few mid-span back-flashovers happen there.

Impedance and crosstalk of stripline and microstrip transmission lines

Signal conductors between two ground planes (i.e.. stripline transmission lines) and signal conductors above one ground plane (i.e., microstrip transmission line) serve as the means for propagating high-speed digital and analog signals on printed wiring boards (PWBs), and multichip modules (MCMs). For many important applications (e.g., wireless and other high speed technologies), the need for miniaturization requires that these high-speed electrical interconnections be provided on relatively dense PWBs and MCMs. This leads to design uncertainties concerning characteristic impedance and especially crosstalk. The purpose of this paper is to develop relatively simple formulas for computing the characteristic impedances and crosstalk of coupled stripline and microstrip transmission lines. Both unbalanced and balanced transmission lines are treated. The new formulas apply to both rectangular and circular conductors and are expressed in terms of the physical dimensions of the conductors and the effective dielectric constant of the medium. The formulas yield results which agree well with known results and experimental results.