Transmission Line Elements Research Articles

(Invited) Studying Ni-YSZ Fuel Electrode Microstructure and Characteristics Using Symmetric Cells

Electrode-supported solid oxide cell (SOC) performance, efficiency, and stability are largely dependent on their Ni-YSZ cermet electrodes and supports. The design variables for these Ni-YSZ layers include the Ni/YSZ ratio, pore former volume fraction/size, thicknesses, and the firing conditions that partly determine their microstructures. These parameters can be used to optimize the electrode by maximizing active triple phase boundary (TPB) density in the functional layer, maximizing gas transport through the support, achieving required conductivity, maintaining mechanical strength, and minimizing overall Ni content.This study aims to investigate how Ni-YSZ characteristics affect overall electrochemical performance and mechanical strength. In the initial studies, Ni-YSZ electrode-supported symmetric cells with a single uniform Ni-YSZ layer without pore former were studied to focus on functional layer properties. Cells with different Ni contents were compared. Cells were manufactured by laminating tape-cast layers and co-sintering at high temperatures, with a YSZ electrolyte thickness of ~ 10 μm and Ni-YSZ thickness of ~ 150 μm. Initial NiO weight percentages in the NiO-YSZ slurries were varied from 45 to 70% in different cells. Although NiO-YSZ layers with different compositions are expected to have different shrinkages, we found that by sintering the symmetric cells at 1300°C, all cell configurations were free of defects, curvature, or delamination.Flexural strengths of both the electrodes and symmetric cells were characterized at ambient temperature via three-point bending tests. The NiO-YSZ composite reduction to cermet Ni-YSZ decreases flexural strength. In addition, increases in Ni content decrease flexural strength. The flexural strength results will be compared with values expected based on classic laminate plate theory.Electrochemical impedance spectroscopy measurements were taken at open circuit voltage in 97% H2-3% H2O at 650°C, 700°C, 750°C, and 800°C. The impedance results fitted well using an equivalent circuit model that includes Ohmic, transmission line, and Warburg resistance elements. The Warburg resistance, which corresponds to gas diffusion processes, decreases significantly with increasing Ni content since most of the porosity results from the reduction of NiO to Ni. In these low steam conditions, the Warburg resistance element dominates overall impedance in 45 to 65 NiO weight percent electrodes. The 50-weight percent NiO electrode was found to minimize transmission line model resistance. The correlation between impedance results and the measured electrode microstructure (e.g., porosity, tortuosity, and active TPB density) will be discussed.

On the semi-infinite distributed resistor-constant phase element transmission line

Under a particular geometrical arrangements of impedances of the type resistors and capacitors for the modeling of a transmission line, the voltage and current along the line are known to follow the standard partial differential equation of diffusion. In this work we propose a generalization of this circuit network by considering the non-ideal fractional capacitive element, also known as constant phase element (CPE), as the energy storage component. The CPE’s impedance is given by Zc(s)=1/(Cαsα), where Cα>0 and 0<α⩽1, and offers an extra degree of freedom compared to the ideal capacitor of impedance Z=1/(Cs). This leads to an anomalous time-fractional diffusion equation that we solve considering the Caputo fractional derivative definition for the case of one-dimensional, semi-infinite propagation under a constant voltage excitation at x=0. The voltage and current responses are found analytically in terms of the Fox’s H-function. We discuss the implications of the dispersive nature of the CPE on the time-domain response along the transmission line system, as well as on the frequency-domain input impedance.

Symmetric CRLH-TL filter based dual band microstrip antenna design approach

This paper presents a novel filter-based analysis for the conventional rectangular patch antenna (RPA) using the Composite Right/Left-Handed Transmission Line (CRLH-TL) theory. We introduce two circuit models for RPA, described by lumped components and transmission line (TL) elements. An RPA is considered a Symmetric CRLH-TL (SCRLH-TL). We validated the analysis by comparing the circuit model and full-wave analysis simulation results. The TL circuit model error in the full-wave analysis was less than 5%. A dual-band Zeroth-Order Resonant (ZOR) antenna is designed and manufactured based on the introduced Lumped element circuit model, which exhibits filtering characteristics in both bands. We obtain the antenna circuit model by incorporating the RPA lump circuit model with LC resonators. We implemented the antenna structure by combining the RPA and complementary split-ring resonators (CSRR) modeled by the LC resonators. We initialized the antenna center frequency bands for WiMAX 2.45 GHz and 3.60 GHz. The CSRRs control the configuration of the center frequencies. The simulation and measured results are in good agreement. The proposed antenna dimensions are 0.66×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.66×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.012 λg\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda _g$$\\end{document} at 2.45 GHz (43.22×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}43.22×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document}0.81 mm3). The measured gains are 3.47 dB and 4.64 dB for 2.45 GHz and 3.60 GHz, respectively. Two radiation nulls were observed at 2.09 GHz and 2.98 GHz for the 2.45 GHz band and one radiation null at 3.45 GHz for the 3.60 GHz band. Also, the fractional bandwidth is 4.03% and 1.39%, respectively. The radiation pattern is nearly omnidirectional. The simulated efficiency is 90% for 2.45 GHz and 87% for 3.60 GHz frequency bands.

High Quality Factor Miniaturized CMOS Transmission Lines Using Cascaded T-Networks for 60 GHz Millimeter Wave Applications

This work presents an on-chip 60 GHz lumped element transmission line (TL) using cascaded T-networks with a high Quality factor. Each T-network consists of a series inductance with a shunt capacitance at its center. We have derived the design equations for this TL configuration and proved that a TL whose electrical length ≥ 60° achieves additional miniaturization when implemented with three or more cascaded T-networks. The inductance is implemented using a straight wire model with no ground below it, while the capacitance is implemented using a parallel plate model with a grounding pedestal. Both configurations guarantee maximum inductance per unit length and capacitance per unit area to further improve the miniaturization level. A quarter wavelength TL with three cascaded T-networks is fabricated as proof of concept. The measured and simulated results of the fabricated TL have good agreement, and the measured quality factor is 17 at 60 GHz.

Dual-band low-power RF-to-DC signal converter circuits for energy harvesting

This article presents dual-band low-power, high-sensitive radio-frequency (RF)-to-direct current (DC) signal converter circuits, operating at 2.45 and 5.5 GHz bands, for radio frequency energy harvesting applications. In particular, it focuses on the lumped element and microstrip transmission line model circuits. The lumped element RF-to-DC converter circuit is composed of a dual-band impedance matching circuit, voltage-doubler rectifier, and DC-pass filter with a resistive load of 5 kΩ. This converter circuit gives a DC output voltage of 48 mV at 2.45 GHz and 25 mV at 5.5 GHz on −25 dBm input power. Maximum conversion efficiency is 47% at the 2.45 GHz band and 27% at the 5.5 GHz band when the input power is set to −10 dBm. Circuit design steps, matching conditions, performance parameters, and so on, are presented using Advanced Design System simulation. To validate the concept of the lumped element model, a microstrip transmission line RF-to-DC converter model is simulated and fabricated. It also composes of a dual-band matching network, voltage-doubler, and DC-pass filter with a load resistance of 5 kΩ. At a low input power of −18 dBm, it gives an output voltage of 21 mV in measurement. An appropriate match between the simulation and measurement is noted.

Study of operation of a polymer insulator under uniform and non-uniform contamination

RELEVANCE. Suspended insulators, the technical condition of which largely determines the reliability of power supply to consumers of different categories, are one of the most damaged elements of overhead power transmission lines [1-2]. This is primarily due to the fact that during their operation, insulators are exposed to various climatic conditions that have a direct impact on their insulating properties. Moreover, precipitation, such as rain, fog or dew, has the greatest impact precisely in combination with various solid, liquid and gaseous particles deposited on the insulator surface from the air, and forming a layer of surface contamination. Wetting this layer increases the electrical conductivity of the entire overhead line insulation structure and reduces its insulating capacity. Study of influence of dampening of contaminated surface of suspended insulation on their discharge characteristics is an urgent scientific task. The solution of this task enables to develop the existing understanding of the mechanisms of formation and development of discharges on the contaminated and wetted surface of insulation and to formulate the appropriate diagnostic attributes applicable to control the condition of the overhead power line insulators. OBJECTIVE. To carry out laboratory research aimed at studying the behavior of suspended high-voltage polymer insulators of overhead power lines when they are moistened. To formulate appropriate diagnostic attributes applicable for control of condition of suspended insulators of overhead power lines during their operation. METHODS. At the solution of the posed problem experimental methods of research, consisting in simulation of work of the contaminated polymeric insulator in the atmosphere of a pure fog with application of the special experimental installation developed by the authors of this article were applied. RESULTS. As a result of laboratory research, by continuous registration of leakage current values, as well as signals coming from the remote sensor, characteristic features of contaminated insulator humidification were revealed, which can be used as diagnostic signs in the process of their operation.

A Novel Branch-Line Coupling Topology

This article presents a novel branch-line coupling topology, which offers superior performance to the conventional branch-line coupler. The structure of the proposed network is very simple; in fact, only one additional transmission line element is required to modify the ever-present branch-line coupler in such a way that the bandwidth is enhanced by roughly 25%. The proposed structure is analyzed using an even–odd analysis, and closed-form expressions for the dimensioning of the network parameters are given. The transmission-line impedances are equal or very close to the system’s impedance, and there is no need for very low or high transmission-line impedances.

Modern approaches of high-voltage transmission lines monitoring

Transmission lines require timely inspection and monitoring to prevent emergency situations during operation. System emergency situations as blackout are very undesirable, so they need their previous detection and prevention. Accordingly, this can be avoided by detailed monitoring the functioning of all elements of the power system. The directions of remote control for researching the operational state of electric power facilities through the use of special equipment, in particular aerial vehicles, have gained sufficient development. Possibilities of practical means of remote monitoring of power transmission lines are also considered. Due to their relatively inexpensive use and ease of operation, distant controlled aerial vehicles are an effective approach for surveying high-voltage power lines. A number of advantages of using distant controlled aerial vehicles are the extended functionality of monitoring quality provided by modern equipment. Functional analysis of modern on-board equipment indicates the possibility of detecting research objects on a real-time scale, due to the use of telemetry, satellite and combined television and thermal imaging systems, with the possibility of detailed observe. The most perspective is the use of combined heat-television systems, which allow improving the technical characteristics of the surveillance system significantly. This method provides monitoring of heat losses, detection of overheated elements of transmission lines and assessment of the performance of elements. Such technology ensures more safer and timely detection of malfunctions, threats to operation and carrying out work on their elimination. In addition, the fields of application of distant controlled aerial vehicles as surveys for the design of energy systems are increasing.

Precise Configuration of Transmission Line Class-E Power Amplifier Operating at GHz Frequency

Power amplifier (PA) is a core part of microwave power transmission (MPT) system. Featuring simple topology and theoretical 100% efficiency, class-E PA is widely discussed both in industry and academia. This article centers around the precise configuration of transmission line class-E PA operating at GHz frequency. Based on the conversion between lumped element topology and transmission line topology of class-E PA, the equal resistance surface-based configuration method is proposed. Specific configuration method for different types of matching network is analyzed according to the corresponding characteristics. Then, an L-type matching network-based class-E PA is designed in detail for the MPT system. Besides, extended application of the proposed method is discussed for different derivate topologies of class-E PA. Finally, a 2.5-GHz/10-W transmission line class-E PA is fabricated in the lab and the proposed configuration method is fully verified with experiments.

Complementary Metal Oxide Semiconductor Digitally Controlled Passive Phase Shifter Circuit for Bearing Angle Control in Multiple Antenna System

A Complementary Metal Oxide Semiconductor (CMOS) digitally controller passive phase shifter circuit for bearing angle control in multiple antenna systems with the changes of the frequency angle or phase shift by using the passive component is presented. The circuit has been designed by using TSMC 0.18 um CMOS technology on the Advanced Design System (ADS) software. This project aims to look for multiple phase transition angles on the same circuit by using the switch in order to get different shifter pattern selectors in series with a digital phase tuning phase adapted using digital capacitors and inductors loading a lumped element transmission line. The phase shifter has a range of 360° with 5.6° resolution at 8-11 GHz frequency band. These CMOS phase shifter characteristics are attractive for multiple antennae and commercial phased array communication systems where cost, size, weight, power and high linearity are required.

Full-Wave Methodology to Compute the Spontaneous Emission Rate of a Transmon Qubit

The spontaneous emission rate (SER) is an important figure of merit for any quantum bit (qubit), as it can play a significant role in the control and decoherence of the qubit. As a result, accurately characterizing the SER for practical devices is an important step in the design of quantum information processing devices. Here, we specifically focus on the experimentally popular platform of a transmon qubit, which is a kind of superconducting circuit qubit. Despite the importance of understanding the SER of these qubits, it is often determined using approximate circuit models or is inferred from measurements on a fabricated device. To improve the accuracy of predictions in the design process, it is better to use full-wave numerical methods that can make a minimal number of approximations in the description of practical systems. In this work, we show how this can be done with a recently developed field-based description of transmon qubits coupled to an electromagnetic environment. We validate our model by computing the SER for devices similar to those found in the literature that have been well-characterized experimentally. We further cross-validate our results by comparing them to simplified lumped element circuit and transmission line models as appropriate.

Modelling of overhead transmission lines with composite towers for 35-330 kV electric power networks

Based on the analysis of the technical condition of the equipment of the electric power networks of the UES of Ukraine, current challenges in the development of the energy sector and existing technologies for the transmission of electric energy, the expediency of using towers made of composite materials in the development, reconstruction and design of new overhead transmission lines for electric networks of different voltage classes is substantiated. The peculiarities of operation of towers made of composite materials in electric networks of many countries of the world are investigated, on the basis of which the prospects of using such towers for overhead transmission lines in Ukraine in the conditions of the introduced liberalised electricity market, as well as the requirements for the performance of electric power networks with the investigated towers made of composite materials are formulated. The article analyses the main characteristics and properties of composite materials that are most commonly used for the manufacture of towers in modern energy systems, as well as compares the physical and mechanical properties of towers made of different materials. The analysis of the obtained results confirms certain advantages of towers made of composite materials, which contribute to the widespread introduction of such towers in the Ukrainian energy system. To investigate the influence of the type of composite material and the design of the towers on the performance of electrical networks, a mechanical calculation of the towers was performed using the method of limit states. Using the obtained results, mathematical models of overhead transmission lines with composite towers for electric power networks with a voltage of 35-330 kV were developed, which take into account the technical characteristics of overhead transmission line elements and the operating conditions of electric power networks, and also allow forecasting quantitative indicators of further operation of the investigated electric power networks.

Equiripple design of low‐pass filter using stub‐loaded Z‐shaped coupled‐line section

Design procedure of a novel transmission line low-pass filter is presented. The filter has a flexible rejection response for a prescribed cut-off frequency and an in-band ripple factor. It is compact by using a Z-shaped coupled-line section, which is loaded with open-circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in-band specifications. The simulated results show that the circuit can generate low-pass responses with third-, fifth-, and seventh-order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut-off frequency of 0.5/0.3 GHz are fabricated using a three-/five-layer PCB process, which generate seventh-order low-pass filtering responses with good selectivity. The experimental results agree well with the predictions.

Novel modeling of ultrasonic wave propagation in ophthalmic tissue

Ultrasound has been widely used to diagnose a variety of anomalies present in ophthalmic tissue (detached retinas, tumors, cataracts, etc.), and to obtain a number of measurements in the eye like intraocular length, lens thickness, and so on. However, there has not been a clear understanding of how ultrasonic waves propagate and interact with the layers of the eye, and whether safety concerns are an issue. This presentation discusses two novel modeling techniques to complement these already existing tools to enhance ultrasonic evaluations of the eye by providing additional insight and a theoretical frame of reference. Axisymmetric finite element and PSpice transmission line models simulating a single-element transducer based on Redwood’s version of Mason’s equivalent circuit, a focusing lens, and a multi-layered medium that mimics propagation of ultrasound in the different layers of the eye are presented. Results are obtained for a normal eye and for one in the case of a retinal detachment. A-scans are also obtained in vitro using an extracted normal sheep’s eye for comparison. Both sets of results clearly show the transmission and reflection of the ultrasonic waves as they travel through the layers within the eye structure and confirm the validity of these modeling techniques.

The electromagnetic response of composition-regulated honeycomb structural materials used for broadband microwave absorption

The undesirable absorption bandwidth is the main limitation for the application of microwave absorbing materials. Noting that the design of structure and composition of absorbing coating allows it to obtain a satisfying absorption bandwidth and to avoid weight increasing, honeycomb and its sandwich structures coated by various absorbant have been developed and measured using an arch measurement system over 2−18 GHz. To further understand the absorption mechanisms of honeycomb structural materials, simulation based on finite element method and transmission line theory is performed to analyze the different responses to the applied microwave between honeycomb structural materials and uniform-medium slab materials. The proper composition design allows control over the microwave loss mechanisms, which optimize the coating to possess both of the dielectric and magnetic advantages. For the honeycomb structural materials, the magnetic resonation is found for the first time, which is resulting from the periodic honeycomb walls on both sides of the dielectric cavity (consisting of the aramid paper interlayer and vacuum hexagonal prisms). In addition, the conversion of structure from solid to honeycomb brings about changes in impedance, propagating path, effective wavelength, effective attenuation area, microwave phases, and inductive coupling effect, etc., which result in a better microwave absorbing performance. The honeycomb sandwich structure coated by CIP/CB/EP with the weight ratio of 4:0.03:1 shows the absorption bandwidth of ∼9.8 GHz for reflection loss (RL) lower than -10 dB which covers part of the S and C bands and almost the whole X and Ku bands.

Superconducting lines cable inputs. Thermal processes modelling

The article considers the thermal state in the basic elements of a cryogenic energy transfer line with high-temperature superconductors. The temperature fields distribution in the heat-stressed elements of the cryogenic energy transmission line with high-temperature superconductors depends on the methods of supplying the cryogenic coolant to cable cryostats and current leads. A large contribution to the total heat flux, especially in cable power lines of short length, falls at the current leads. Computations of complex real current lead structures consist in the joint solution of the hydrodynamics and heat transfer equations for the flux, and the energy equation for the wall. The article considers a three-dimensional non-stationary motion of weakly compressible media (gas and liquid) with a free surface in a semi-closed volume at Mach numbers up to 0.3. The mathematical model is based on the Navier-Stokes equations and total enthalpy. These equations are being solved in conjunction with the equation of state for gas or liquid, the equations for the low Reynolds k-ε turbulence model, and the three-dimensional energy equation for the wall. Recently, Flow Vision application package, or specially designed software are being used for complex three-dimensional thermal calculations.

Repair compositions for restoration of operated reinforced concrete structures

Power transmission lines (PTL) are strategic objects, the reliability of which depends on the life support of the country. Most of the currently operated power transmission lines were put into operation in the twentieth century, and by now there is a problem of assessing their technical condition, repairing them, if necessary, and maintaining them in a working condition. Defects that appear during the operation of reinforced concrete elements of power transmission lines have different localization and degree of manifestation, but typical is the destruction of the surface layer of concrete with exposure of rebar, more often at the base of the power transmission line. The aim of the work is to select the optimal composition of the repair mixture based on non-shrinking and expanding cements, ensuring reliable adhesion of the repair compounds to the concrete of the structure, which will restore the bearing and operational characteristics in the repaired reinforced concrete elements of the power transmission line at the design level.

EXPERIMENTAL INVESTIGATION OF SMOOTH MATCHING TRANSITIONS BASED ON MICROSTRIP TRANSMISSION LINE HETEROGENEOUS SECTIONS

An experimental investigation of smooth matching transitions based on inhomogeneous sections of a microstrip transmission line with different wave impedances profiles was carried out in the present work. Comparative tests of smooth matching transitions prototypes are presented in order to confirm the theoretical data obtained by the optimal parametric synthesis method. The possibility of using synthesized piecewise linear transition to ensure good coordination in a fairly wide frequency range has been proven. It has been shown that fabricated inhomogeneous microstrip waveguide transitions provide matching in the frequency range from 1.2 to 2.7 GHz. It has been proven that the use of two-stage transitions allows a 1.5-times increase in the frequency matching band. Locally-optimized matching transitions near the lower boundary of the operating frequency range can give a significant gain in comparison with matching transitions with an exponential wave impedance profile for the same electrical length. The developed matching transitions can be used in the design of filters, matching transformers and connecting elements of the microwave frequencies transmission line.

Optimal design of compact microwave fractional order differentiator

This paper presents a stable, accurate and wideband microwave fractional order differentiator (MFOD) based on infinite impulse response filter. The fractional order differentiator (FOD) design problem is formulated in the z-domain. This formulation alliances with the transmission line elements in cascading. Real coded genetic algorithm (RCGA), particle swarm optimization (PSO) and cuckoo search algorithm (CSA) are applied to determine the optimum values of the characteristic impedances of the transmission line elements. The performance measure criterion of CSA algorithm as compared with other nature inspired algorithms-based differentiator are carried by the magnitude response, absolute magnitude error, phase response, pole-zero response, percentage improvement graph and convergence rate. The simulation and statistical analysis clearly affirm that the proposed MFOD using CSA outperforms RCGA and PSO in all state-of-the-art. The absolute magnitude error for the designed fifth order is as low as 2.9022. The designed fractional order differentiator is implemented in the form of microstrip on RT/Duroid substrate with dielectric constant 2.2 and thickness 0.762 mm. that is eligible for wideband microwave differentiator. The proposed design is compact in size and has low absolute magnitude error over the entire bandwidth. The measured result agrees well with the simulated result in the frequency range 1–12.5 GHz in MATLAB and advanced design software (ADS) environment.

Compact Wideband Decoupling and Matching Network Design for Dual-Antenna Array

A novel wideband decoupling technique for multiple-input–multiple-output (MIMO) antenna arrays is proposed. Broadband isolation is achieved by creating controllable transmission zeros ( S 21 = 0) at two separated frequencies. The newly developed decoupling network is compact in size due to the elimination of multiple transmission line elements and the external matching circuit. Simulation and measurement results show that the proposed method can offer substantial enhancement in port isolation, pattern diversity (envelope correlation coefficient), and radiation efficiency over the designated frequency range.