Electromagnetic Transmission Line Research Articles

Integrated numerical simulation of an electromagnetic transmission line galloping excitation test system

PurposeThis paper aims to establish the mathematical model and solve the complex calculation multi-field coupling problem for an electromagnetic overhead transmission line galloping excitation test system.Design/methodology/approachAn electromagnetic excitation test system is introduced. To calculate the vibration response of the transmission line, a transient coupled finite element model containing electromagnetic repulsive mechanism and transmission line system was established. Considering the advantages of Newmark-ß algorithm and fourth-order Runge–Kutta algorithm, the two algorithms are combined to solve the model. Compared with the simulation results of existing commercial finite element software, the accuracy of the calculation model of electromagnetic force and wire vibration response are verified.FindingsComparison results show that the proposed calculation model can accurately obtain the force of electromagnetic mechanism and the vibration response of the overhead power lines, and improve the calculation efficiency. The calculation results show that vibration under electromagnetic excitation presents a double half-wave mode, and the galloping amplitude varies according to the charging voltage.Originality/valueThis paper built the transient simulation model for a galloping test system. The Newmark-ß algorithm and the fourth-order Runge–Kutta algorithm are used to solve the model. The research results are of great significance for the actual galloping test system design.

In-depth study of the behaviour of the Rogowski coil for fast current pulses

New developments on Rogowski coil are presented due to the evolution of temporal shortening of the current pulses. Recently, to study biophysical stresses by electromagnetic pulses flat transmission lines are used. As a result, linear Rogowski coils for electrical current diagnostics have also been developed and applied. An electrostatic shield with a slim slit is used to protect the Rogowski coil. The presence of the slit is necessary to lead the input current around the coil. The response of the Rogowski coil on high frequency signals is influenced, not only by all inductances, the capacitance, the number of turns of the coil, the load resistance, but also by the small size of the slim slit operated on the metal shield. The new theory is able to justify the response of the device due to sub-ns pulses, ~100ps, on slit width. By the theory, the attenuation factor is dependent on the slit size. This behaviour was experimentally verified obtaining a value ranging from 15.6A/V to 24.7A/V. The longest measurable pulse was approximately 250ns. The device is very interesting owing to the radiation of the 5G communication mode.

Electromagnetic field and artificial intelligence based fault detection and classification system for the transmission lines in smart grid

ABSTRACT An electromagnetic field and artificial intelligence-based transmission line protection system for smart grid is proposed in this paper. Bayesian regularization neural network is used as an intelligence technique. Instead of conventional current transformers, the use of magnetic field sensors for monitoring the current in transmission lines is proposed. A mathematical model of the magnetic field due to the current in transmission line is developed by considering two positions of the magnetic field sensors. The developed model is simulated for extensive scenarios. Line to ground, line to line, double line to ground and three-phase faults are created. The fault current values are transformed into magnetic field values and given to the dyadic analysis filter bank for feature extraction process. The extracted features are given as an input to the neural network for the training. The Bayesian regularization algorithm is used as a training algorithm. The performance of the proposed system is compared with other algorithms. It shows that the proposed system with Bayesian regularization have 96.11% of accuracy with the combination of different faults. The results obtained show that the proposed system outperforms the existing approaches.

Dielectric properties and electromagnetic wave absorbing performance of granular polysilicon during 2450 MHz microwave smelting

The dielectric properties and electromagnetic wave absorbing performance of granular polysilicon have important influences on microwave smelting efficiency. In this study, the dielectric parameters (dielectric constant, dielectric loss factor and loss tangent) of granular polysilicon were measured from room temperature (25 °C) to 800 °C at 2450 MHz by using the cylindrical cavity perturbation method, and the reflection loss of granular polysilicon was calculated according to the theory of electromagnetic wave transmission line, and then the effects of temperature on microwave absorbing performance was analyzed. The results indicated that the dielectric constant and dielectric factor loss of granular polysilicon change little before 300 °C, but when the temperature is higher than 300 °C, the dielectric constant and dielectric loss factor increase gradually. The microwave absorbing performance of granular polysilicon fluctuates with the increase of granules thickness, there are multiple absorption peaks, and the position and intensity of absorption peaks change with the increasing temperature. This study provides theoretical guidance for the optimization of smelting process parameters of granular polysilicon and the design of microwave smelting equipment.

Novel planar quasi‐TEM transmission line with high isolation and its application to T‐junction power divider

In this study, a novel quasi-transverse electromagnetic (TEM) transmission line (TL) on a single-layer substrate is presented. The proposed structure comprises bilateral metalised vias and two longitudinal slots on the top and bottom plates, respectively. This two-conductor TL separated by the two slots allows the quasi-TEM mode and guarantees high isolation due to the vias which constrain the electromagnetic field. Additionally, the proposed structure provides a remarkable high range of the characteristic impedance, enabling a more flexible design. Furthermore, an empirical analytical formula is derived to calculate the characteristic impedance of the proposed TL adopting conformal mapping, and modified by a polynomial fraction. The transitions to the double-sided parallel-strip line and the microstrip line are proposed with which the propagation constant of this TL is extracted. The comparisons of the far-end couplings of several types of microwave TLs have been provided by the simulation and measurement to verify the isolation property of the proposed TL. Finally, the proposed TL is applied to the T-junction wideband power divider design to demonstrate its practicability. A prototype is fabricated and measured with a wide operating bandwidth from 6.8 to 17.6 GHz.

Electromagnetic wave absorbing performance of aspirin powder during 2450 MHz microwave drying

The absorbing performance of pharmaceutical powders has an important effect on the efficiency of microwave drying. In this study, in order to achieve optimal microwave absorption, the reflection loss (RL) of aspirin powder is calculated based on the theory of electromagnetic wave transmission line under different temperatures, moisture contents, microwave incident angles and polarization modes. In addition, the effect of the dielectric-assisted absorbing layer (SiC ceramics) on the microwave absorbing performance of aspirin powder (weak absorbing materials) with low moisture content is analyzed. The results show that the RL curve of aspirin powder fluctuates with increasing thickness; several absorption peaks appear, and the absorption peaks shift to smaller thicknesses as the temperature and moisture content increase. The RL of aspirin powder in the transverse electric polarization mode decreases monotonically as the incident angles increase. The effect of Brewster’s angle causes the RL of aspirin powder in the transverse magnetic polarization mode to first decrease and then increase with the increasing incident angle, and an absorption peak occurs. However, the RLs of both polarization modes are close to zero at 90°. The use of SiC ceramics as the susceptor can reduce the RL of the double-layer absorber and widen the aspirin powder thickness interval for an RL below −20 dB. This research can help to optimize the microwave drying process parameters of pharmaceutical powders and the design of microwave drying equipment.

Dielectric properties and electromagnetic wave transmission performance of polycrystalline mullite fiberboard at 2.45 GHz

Refractory lining is an indispensable part of high temperature microwave heating equipment, and its wave transmission performance exerts an important impact on the mode and efficiency of microwave heating, while the complex dielectric constant (dielectric constant and dielectric loss) of the material is the decisive factor in determining the wave transmission performance of the material. In this work, we measured the complex dielectric constant of polycrystalline mullite fiber board (PMF) in the temperature range of 25–1000 °C, and the effect of temperature on dielectric constant and dielectric loss was analyzed; The wave-transmission properties of the material were calculated according to the theory of electromagnetic wave transmission line, and the effects of temperature, material thickness, polarization modes of electromagnetic wave and incident angle on the wave transmission performance were analyzed. The results reveal that the dielectric constant of PMF does not change much with the increase of temperature, which is about 1.6; The dielectric loss does not change much within 200 °C, but when the temperature is higher than 200 °C, the change presents approximately exponential increase with the rise of temperature. The wave transmission performance fluctuates with the increase of the thickness, and there are maximum value and minimum value, and the overall wave transmission performance decreases with the increase of the material thickness. In a transverse electric (TE) field, the overall wave transmission performance decreases with the increase of the incident angle, and better wave transmission performance can be obtained by priority selection of vertical incidence of electromagnetic wave. In a transverse magnetic (TM) field, with the increase in the incident angle, the wave transmission performance firstly climbs up then declines, and there is an optimal incident angle where total transmission can occur. Finally, this work selected the thickness corresponding to different temperature as the preferred thickness. This work is of important theoretical significance for understanding the mechanism of the dynamic change of the wave transmission performance of the thermal insulation materials in microwave heating, and provides important practical guidance for the design and optimization of microwave heating equipment.

Investigation of electromagnetic wave transmission line 
 based on coupled dielectric resonators

An analogue of optical waveguide consisting of metallic nanoparticles chain was investigated using modified cylindrical dielectric resonators (DR) in the microwave range. The two lowest resonances of the DR correspond to the dipole and quadrupole modes of oscillations similar to plasma oscillations in spherical nanoparticles. It is shown that a waveguide consisting of seven resonators has high frequency selective properties and relatively low losses, if the resonances of quadrupole modes are used to form its bandwidth. The characteristics of the studied waveguide remain almost unchanged at its bending by 90. Cross-section of the main part of energy localization in waveguide is 5 times less than the length of the electromagnetic wave, which roughly corresponds to the optical waveguides based on plasmon oscillations in nanoparticles.

1-D Frequency-Diverse Single-Shot Guided-Wave Imaging Using Surface-Wave Goubau Line

This article presents a 1-D frequency-diverse guided-wave imaging technique based on a surface-wave Goubau line. It employs frequency diversity to capture spatial information of the scatterers with an almost real-time speed, which is much faster than mechanical scanning or electronic scanning approaches. The surface-wave Goubau line is used because it provides more independent measurement modes than conventional transverse electromagnetic (TEM) transmission lines. Compressed sensing algorithms are employed to recover the spatial distributions when some sparse metal scatterers are placed above the line. The proposed technique is validated by four numerical examples and two experimental validations, where both narrow scatterers and wide scatterers are considered. It shows that the proposed technique is able to reconstruct scatterer position within an error of 1 mm, about 1/30 space wavelength at the center frequency 10 GHz. It is also able to identify two close scatterers until their distance reduces to 1 mm. This guided-wave technique, although applicable to very near-field detection only, can find broad applications in localization, field measurement, and fault detection.

Radiation from free space TEM transmission lines

This work derives exact expressions for the radiation from two conductors non-isolated transverse electromagnetic (TEM) transmission lines of any small electric size cross-section in free space. The cases of infinite, semi infinite and finite transmission lines are covered and it is shown that while an infinite transmission line does not radiate, there is a smooth transition between the radiation from a finite to a semi-infinite transmission line. The present analysis is in the frequency domain and the authors consider transmission lines carrying any combination of forward and backward waves. The analytic results are validated by successful comparison with ANSYS commercial software simulation results, and successful comparisons with other published results.

LOSSY TRANSMISSION LINES TERMINATED BY PARALLEL CONNECTED RLC-ELEMENTS WITHOUT THE HEAVISIDE’S CONDITION

The paper deals with analysis of propagation of transverse electromagnetic waves along lossy transmission lines terminated by a circuit consisting of parallel connected RLCelements. Using the Kirchhoff’s laws we derive boundary conditions and formulate the mixed problem for hyperbolic system describing the lossy transmission line. Without the Heaviside's condition, we cannot guarantee the distortionless propagation of waves and hence we cannot apply the known methods. That is why we apply a different method and obtain conditions for existence-uniqueness of generalized solution. We change variables and formulate a mixed problem for the hyperbolic system with respect to the new variables. The nonlinear characteristics of the RLC-elements generate nonlinearity in the equations of neutral type on the boundary. We propose an operator presentation of the mixed problem for transmission line system and by means of fixed point technique we prove existence-uniqueness of a generalized solution.

LOSSY TRANSMISSION LINES TERMINATED BY PARALLEL CONNECTED RLC-ELEMENTS WITHOUT THE HEAVISIDE’S CONDITION

The paper deals with analysis of propagation of transverse electromagnetic waves along lossy transmission lines terminated by a circuit consisting of parallel connected RLCelements. Using the Kirchhoff’s laws we derive boundary conditions and formulate the mixed problem for hyperbolic system describing the lossy transmission line. Without the Heaviside's condition, we cannot guarantee the distortionless propagation of waves and hence we cannot apply the known methods. That is why we apply a different method and obtain conditions for existence-uniqueness of generalized solution. We change variables and formulate a mixed problem for the hyperbolic system with respect to the new variables. The nonlinear characteristics of the RLC-elements generate nonlinearity in the equations of neutral type on the boundary. We propose an operator presentation of the mixed problem for transmission line system and by means of fixed point technique we prove existence-uniqueness of a generalized solution.

Multi-functional RF coils for ultra-high field MRI based on 1D/2D electromagnetic metamaterials

Electromagnetic metamaterials have already proven very valuable for the enhancement and molding of RF magnetic fields within ultra-high field MRI scanners at 7T. We report on our development of coil elements based on composite right-/left-handed (CRLH) 1D electromagnetic (EM) metamaterial transmission lines (metalines) operating in the zeroth order resonance (ZOR) to foster uniform RF magnetic field distributions along the scanner axis. Tailored EM metalines supporting full-wave or quarter-wave resonances are used either as metamaterial ring antenna or as dual-band coil elements for simultaneous 1H/23Na imaging. The EM metalines are key to the MetaBore, which is a fully adaptive RF field control scheme based on a periodic axial arrangement of conformal metamaterial ring antennas in the framework of high-field traveling-wave MRI. With the 2D EM metamaterials (metasurfaces) we realized high-impedance surfaces (HIS) in order to enhance the uniformity and directivity of the RF magnetic field from e.g. overlaid (elongated) dipole elements towards the probe volume. The designs include simulation studies of the overall multichannel coil systems, which are carried out with our home-made, open source electromagnetic 3D EC-FDTD solver openEMS supporting conformal cylindrical inhomogeneous meshing. Experimental verifications of our coils have been carried out within 7T MRI scanners (Siemens Magnetom).

Microwave absorption properties of single- and double-layer coatings based on strontium hexaferrite and graphite nanocomposite

The microwave absorption properties of single- and double-layer doped strontium hexaferrite (SrCoZnFe16O27) and graphite nanocomposite were investigated. W-type SrCoZnFe16O27 nanoparticles was prepared via solid state reaction using high energy ball milling and sintered at different sintering temperatures. Microwave absorption properties of single- and double-layer structures of different thicknesses were investigated in the frequency range of 8–18 GHz using a network analyzer, and their behavior analyzed based on electromagnetic transmission line theory. The results show that double-layer absorbing material showed better microwave absorption properties than single-layer. Double-layer absorbing material which consisted of graphite as the matching layer and SrCoZnFe16O27 as the absorbing layer demonstrated higher reflection loss values of − 19.5 dB when both layers were 1 mm thick. The bandwidth corresponding to the reflection loss below − 10 dB (i.e. 90% absorption) was 3.8 GHz (11.0–14.8 GHz). The excellent microwave absorption properties of double-layer structures were influenced by good impedance match, multiple internal reflections and coupling interactions between the matching and absorbing layers.

Helping Students Learn About Electromagnetics [Book/Software Reviews

The reviewer of the book Conceptual Electromagnetics notes that the book describes the fundamental subject of electromagnetics, or field and wave theory, for an undergraduate college class using very advanced teaching and learning methods. It provides abundant opportunities for instructors to introduce innovative lectures, in-class and homework assignments, and tests (including those for online distance education and for students pursuing independent learning). An active teaching and learning methodology is built into this text by means of interactive in-class questions, explorations, and discussions. The book also includes peer instruction, allowing students to tutor one another. The learner-centered pedagogies and practices - and active teaching and learning, in particular - are very effective, motivational, and positively evaluated by students. There are many conceptual questions as well as multiple-choice ones that focus on core concepts of the material, requiring conceptual reasoning and understanding. This book is organized into 12 chapters on electrostatics fields, steady electric currents, magnetostatic fields, time-varying electromagnetic fields, uniform plan electromagnetic waves, transmission lines, waveguides and cavity resonators, and antennas and wireless communication systems. For many engineering students, the fields and waves, or electromagnetics, course is particularly challenging. But, with the author' advanced teaching and learning approach, this course can be pleasant and fun. His teaching technique should become the standard for all science and engineering courses.

Microwave absorption properties of double-layer absorbers based on spindle magnetite nanoparticles and flower-like copper sulfide microspheres

In this work, the spindle magnetite nanoparticles (SMNPs) and flower-like copper sulfide microspheres (FCSMSs) were synthesized via hydrothermal method. The structures, chemical composition and morphologies of samples were analyzed and characterized in detail. The microwave absorption properties of single-layer and double-layer absorbers were investigated based on the electromagnetic transmission line theory in the frequency range from 2 to 18 GHz. The results show that the double-layer absorbers consisting of FCSMSs as matching layer and SMNPs as absorbing layer display superior microwave absorbing performance compared to the single-layer ones due to the proper combination of magnetic loss of SMNPs and dielectric loss of FCSMSs, and the improved impedance matching characteristics. When the thicknesses of the absorbing layer and the matching layer are 1.6 and 0.4 mm, respectively, the minimum reflection loss reaches − 74.3 dB at 10.9 GHz, and the efficient absorption bandwidth is up to 5.34 GHz (8.46–13.8 GHz). The optimal SMNPs/FCSMSs double-layer absorbers can become a novel microwave absorption material with strong-absorption and broad-band.

Circuit Breaker Rate-of-Rise Recovery Voltage in Ultra-High Voltage Lines with Hybrid Reactive Power Compensation

With the development of ultra-high voltage (UHV) technology, hybrid reactive power compensation (HRPC) will be widely applied in the future. To study the mechanism by which HRPC influences the characteristics of circuit breakers in UHV transmission lines, this paper establishes an improved electromagnetic coupling transmission line model for out-of-phase and short-line faults. Based on the HRPC equivalent model, a simulation analysis was performed on the characteristics of the circuit breaker when a fault occurs. Using an equivalent lumped parameter circuit, the rate-of-rise of recovery voltage (RRRV) computational formula was deduced and computed. The RRRV variation in the circuit breakers in the system, with and without HRPC, was obtained. Given the circuit breaker interruption characteristics, the research results provide an analysis foundation and a theoretical basis for optimizing the HRPC parameters and selecting the arrangements of circuit breakers in an UHV transmission line.

Electromagnetic Transducer for In-Line Determination of Alcohol Content in Pisco

A specially designed electromagnetic transmission line is used as an in-line real-time transducer of alcohol content in pisco beverage production. During the distillation process, as the beverage is collected in a tank, it is homogenized, and a sample is continuously pumped into the coaxial line transducer. Pisco is a beverage with 53%–62% water, and 47%–38% alcohol, with 90% of the alcohol content being ethanol. The alcohol content of the flow is detected by measuring the electromagnetic attenuation of the TEM mode propagating inside the transmission line. The propagating mode frequency is selected in the 1–1.5 GHz range, enabling the measurement of alcohol concentration from 0% up to 100%, displaying an almost linear relationship between the alcohol concentration and power absorption in decibels.

Scanning microwave microscopy technique for nanoscale characterization of magnetic materials

In this work, microwave characterization of magnetic materials using the scanning microwave microscopy (SMM) technique is presented. The capabilities of the SMM are employed for analyzing and imaging local magnetic properties of the materials under test at the nanoscale. The analyses are performed by acquiring both amplitude and phase of the reflected microwave signal. The changes in the reflection coefficient S11 are related to the local properties of the material under investigation, and the changes in its magnetic properties have been studied as a function of an external DC magnetic bias. Yttrium iron garnet (YIG) films deposited by RF sputtering and grown by liquid phase epitaxial (LPE) on gadolinium gallium garnet (GGG) substrates and permalloy samples have been characterized. An equivalent electromagnetic transmission line model is discussed for the quantitative analysis of the local magnetic properties. We also observed the hysteretic behavior of the reflection coefficient S11 with an external bias field. The imaging and spectroscopy analysis on the experimental results are evidently indicating the possibilities of measuring local changes in the intrinsic magnetic properties on the surface of the material.

OPTIMAL NARROWBAND AND BROADBAND DATA COMMUNICATION TRANSMISSION IN LOW-VOLTAGE POWER LINE

We investigate the usage of low-voltage electrical power supply network as a communication channel for the provision of data communication services. This is done through simulations and measurements of the power line channel transfer function in the frequency band of 0-30 MHz. A Parallel Resonant Circuit (PRC) channel model is then proposed to model the power line network and results compared to a Series Resonant Circuit (SRC) model. The model is simulated and validation done through measurements on a test bed for a cascaded network with three T-node branches. Transverse Electromagnetic (TEM) transmission line resonant circuit theory is employed to calculate and optimize the obtained parameters of the model. From the results obtained, the simulated models and measurement results are confirmed to compare very well with each other, and thus the proposed PRC model is considered appropriate for the characterization and modelling of the power line network channel.