Transmission Line Structure Research Articles

An Improved Method for Reconfiguring and Optimizing Electrical Active Distribution Network Using Evolutionary Particle Swarm Optimization

The presence of optimized distributed generation (DG) with suitable distribution network reconfiguration (DNR) in the electrical distribution network has an advantage for voltage support, power losses reduction, deferment of new transmission line and distribution structure and system stability improvement. However, installation of a DG unit at non-optimal size with non-optimal DNR may lead to higher power losses, power quality problem, voltage instability and incremental of operational cost. Thus, an appropriate DG and DNR planning are essential and are considered as an objective of this research. An effective heuristic optimization technique named as improved evolutionary particle swarm optimization (IEPSO) is proposed in this research. The objective function is formulated to minimize the total power losses (TPL) and to improve the voltage stability index (VSI). The voltage stability index is determined for three load demand levels namely light load, nominal load, and heavy load with proper optimal DNR and DG sizing. The performance of the proposed technique is compared with other optimization techniques, namely particle swarm optimization (PSO) and iteration particle swarm optimization (IPSO). Four case studies on IEEE 33-bus and IEEE 69-bus distribution systems have been conducted to validate the effectiveness of the proposed IEPSO. The optimization results show that, the best achievement is done by IEPSO technique with power losses reduction up to 79.26%, and 58.41% improvement in the voltage stability index. Moreover, IEPSO has the fastest computational time for all load conditions as compared to other algorithms.

Single-Switch-Based High-Power Bipolar Pulse Generator With Inverted U-Shaped Parallel-Plate Transmission Line

This paper presents a single spark-gap switch (SGS)-based high-power bipolar pulse generator (BPG) for many applications, such as high-power electromagnetic (HPEM) effect tests. Here, we propose an inverted U-shaped parallel transmission line structure to implement the single-SGS-based BPG. Unlike the previously reported BPGs based on synchronized operation of two SGSs, the proposed BPG does not require simultaneous or synchronized closure of the two switches. Detailed dimension parameters obtained by electromagnetic simulation. The proposed BPG was manufactured and tested for validation. The experimental results demonstrated that the BPG produced a bipolar pulse with a peak-to-peak amplitude of 44.9 kV and a pulsewidth of 2.27 ns, where the SGS was filled with nitrogen gas of 16 atm and the turn-ON voltage was 56 kV. For applications of HPEM effect tests, we discuss methodologies to control the amplitude and pulsewidth of generated bipolar pulses in the proposed BPG.

Modeling Strategies for Superconducting Microstrip Transmission Line Structures.

Strategies are explored to reduce the electromagnetic simulation time of electrically large superconducting transmission line structures while retaining model accuracy. The complex surface reactance of an infinite thin-film superconducting sheet is evaluated with the BCS (Bardeen-Cooper-Schrieffer) theory and used as an input to model the phase velocity and characteristic impedance of finite width transmission line structures. Commercially available electromagnetic simulation software are employed for the calculations and the results are compared with limiting analytic forms from the literature. The influences of line width, metallization thickness, and substrate height on microstrip transmission line propagation are considered in detail and a scaling approach is presented to compensate for the leading order effect in numerical simulations. These findings are particularly important near the energy gap of the superconductor due to the influence of the kinetic inductance on the transmission line dispersion.

Miniaturized fifth-order lowpass filters based on structure of artificial transmission line unit

ABSTRACTIn this article, several miniaturized microstrip fifth-order lowpass filters with structure of unit artificial transmission line are presented. Reactive elements including inductors and capacitors are constructed by microstrip structures directly by parameter extraction from electromagnetic simulation. A transmission zero in stopband can be achieved by inductors and capacitors (LC) series-resonant circuit composed by parallel-plated capacitors and connecting lines. Meanwhile, loading interdigital capacitors would bring in another transmission zero. In comparison, fifth-order Butterworth and Chebyshev lowpass filters with one and two transmission zeros are fabricated, respectively, to verify the extra transmission zero effect caused by LC shunt resonant-circuits with interdigital capacitors. The proposed lowpass filters are compact and their sizes occupies less than 40% of conventional microstrip lowpass filters. The simulated and measured results demonstrate good agreements between them, which verifies feasibility of the proposed designing method.

Dual-Band Leaky-Wave Antenna Based on Dual- Mode Composite Microstrip Line for Microwave and Millimeter-Wave Applications

A dual-mode composite microstrip line (DMC-MSL) is reported in this paper for the purpose of designing dual-band antennas and devices with a large frequency ratio. The metallic strip of the conventional MSL is replaced with a substrate integrated waveguide (SIW) arranged into a thin dielectric laminate, which leads to that two modes operating in different frequency bands, i.e., the quasi-TEM mode and the TE10-like mode, can propagate along the transmission line structure simultaneously. The DMC-MSL with a dual-layered planar configuration combines the merits of the MSL and the SIW. In addition, by adjusting the permittivity of the dielectric laminate used for realizing the thin SIW, the frequency ratio of the two operating modes can be varied flexibly. Based on the DMC-MSL structure, a novel dual-band leaky-wave antenna is presented. Periodic parasitic microstrip patches and the transverse slot array etched on the SIW are introduced in order to generate the required spatial harmonics. A feed structure that can excite the two operating modes of the DMC-MSL separately is designed as well. The fabricated prototype verifies that backward and forward frequency-scanning radiation beams are achieved within the low-frequency band from 5.75 to 8.5 GHz and the high-frequency band from 35 to 41.5 GHz, respectively. The proposed DMS-MSL structure and the leaky-wave antenna offer a new mean to implement antennas and devices for microwave and millimeter-wave dual-band applications.

Moving Reference Planes of Unit Cells of Reciprocal Lossy Periodic Transmission-Line Structures

An analysis of moving reference planes of unit cells of reciprocal lossy periodic transmission-line (TL) structures (RLSPTLSs) by using the equivalent bi- characteristic-impedance transmission line (BCITL) model is presented. Applying the BCITL theory, only the equivalent BCITL parameters (characteristic impedances for wave propagating in forward and reverse directions and associated complex propagation constant) are of interest. In the analysis, an arbitrary infinite RLSPTLS is firstly considered by shifting a reference position of unit cells along TLs. Then, a semi-infinite terminated RLSPTLS is subsequently investigated in term of associated load reflection coefficients. It is found that the equivalent BCITL characteristic impedances of the original and shifted unit cells, as well as the associated load reflection coefficients of both unit cells, are mathematically related by the bilinear transformation. However, the equivalent BCITL complex propagation constant remains unchanged. Numerical results are provided to show the validity of the proposed technique.

Critical load cases for lattice transmission line structures subjected to downbursts: Economic implications for design of transmission lines

An extensive research program was recently conducted at The University of Western Ontario, Canada to investigate the load profiles that can be used in the analysis and the design of transmission towers subjected to downbursts. This research was motivated by many transmission line failures that have occurred in different locations around the globe during downburst events. It was also triggered by the fact that the existing codes of practice and guidelines provide very limited information regarding the critical load profiles associated with downbursts, which act on the towers and conductors of a transmission line system. One of the challenges in predicting the critical forces acting on the towers and conductors is that they are not only dependent on the magnitude of the event but also on its size and location relative to the center of the tower. This complexity results from the localized nature of such events. In the current study, an extensive parametric study is conducted on a number of transmission line systems to evaluate their critical response to downburst loads. The study considers the variations in the downburst location, angle of attack, and size to determine the effect of changing these parameters on the response of the transmission line systems. Based on the results obtained from this parametric study, three critical load cases are identified. The studied towers are then used to assess the economic impact of applying those load cases, expressed by the increase in the weight of the tower.

DAC-Less and DSP-Free 112 Gb/s PAM-4 Transmitter Using Two Parallel Electroabsorption Modulators

Four-level pulse amplitude modulation (PAM-4) is widely regarded as the modulation format of choice for the next generation of 400 gigabit Ethernet short-reach optical transceiver. However, generating and receiving PAM-4 at line rates of 112 Gb/s has proven challenging, without relying on power-hungry tools as digital signal processing and digital-to-analog converters, as it requires linearity from the E/O-components in the link and/or predistortion techniques. Moving the binary to multilevel conversion to the optical domain would greatly relax these requirements. Electroabsorption-based transceivers would be ideally suited for this type of data center interconnects as they are capable of combining low-power and high bandwidth operation with a very compact layout, removing the need for large travelling wave structures and dedicated 50 Ω terminations. In this paper, we present a novel transmitter topology for generating PAM-4 using two binary-driven electroabsorption modulators in parallel. Using this approach, we achieve superior performance with respect to a single, but identical multilevel-driven EAM. Finally, we demonstrate the first silicon-based modulator capable of transmitting single-lane 112 Gb/s PAM-4 over 2 km of standard single-mode fiber without any electrical digital-to-analog converter, DSP, or long transmission line structures and terminations.

Analytic Modeling of Nonlinear Current Conduction in Access Regions of III-Nitride HEMTs

AbstractThe transconductance degradation caused by the non-linear resistance of access regions in III-nitride high electron-mobility transistors (HEMTs) is mainly responsible for limiting the RF linearity of the transistor. In this paper, we use Landauer’s transmission theory to develop an analytic electrothermal current-voltage (I-V) model of access regions in III-nitride HEMTs. With only 12 parameters, most of which have a physical origin and can be obtained through experimental calibration, the model is able to correctly predict the I-V behavior in access regions from the drift-diffusive to the quasi-ballistic transport regimes. Model accuracy is demonstrated by comparing the results against experimental and numerical hydrodynamic simulations of ungated transmission line structures with length scales ranging from few 10’s of nanometers to 10’s of micrometers.

Compact Single‐Layer Traveling‐Wave Antenna DesignUsing Metamaterial Transmission Lines

AbstractThis paper presents a single‐layer traveling‐wave antenna (TWA) that is based on composite right/left‐handed (CRLH)‐metamaterial (MTM) transmission line (TL) structure, which is implemented by using a combination of interdigital capacitors and dual‐spiral inductive slots. By embedding dual‐spiral inductive slots inside the CRLH MTM‐TL results in a compact TWA. Dimensions of the proposed CRLH MTM‐TL TWA is 21.5 × 30.0 mm2 or 0.372λ0 × 0.520λ0 at 5.2 GHz (center frequency). The fabricated TWA operates over 1.8–8.6 GHz with a fractional bandwidth greater than 120%, and it exhibits a peak gain and radiation efficiency of 4.2 dBi and 81%, respectively, at 5 GHz. By avoiding the use of lumped components, via‐holes or defected ground structures, the proposed TWA design is economic for mass production as well as easy to integrate with wireless communication systems.

4–20 GHz GaAs True-Time Delay Amplifier MMIC

A wideband amplifier with a fine control of the true-time delay (TTD) has been successfully implemented using a commercial 0.5-μm GaAs pHEMT monolithic microwave integrated circuit (MMIC) process. The proposed circuit effectively combines switching elements into an artificial transmission line structure in a distributed amplifier to achieve an adjustable TTD which enables time delay control with gain in a wider band than other GaAs-based TTD circuits. The TTD amplifier MMIC achieves a controllable delay of 9 ps, a gain of 9 to 2 dB, and a typical return loss of more than 10 dB from 4 to 20 GHz. The proposed TTD amplifier can be effectively integrated into a multifunction chip based on GaAs semiconductors for wideband active electronically scanned array or phased array systems.

Application of smart computing techniques in cost optimization of 1200 KV autotransformer

This paper aims to identify the scope for cost optimization in a 1200 kV autotransformer manufacturing through the use of smart computing techniques. A typical Ultra High Voltage (UHV) power transmission system consists of components like Autotransformers, Capacitive voltage transformer, Surge arrestors, Circuit breakers, Isolators, Bus post insulators and hardware of transmission line structure. Through various UHV projects running worldwide, technical feasibility of UHV system has already been proved but in view of cost optimization of overall system, research is going on. Autotransformer is a main component of UHVAC transmission system and needs to be critically investigated to find a room for most economic and commercial viable manufacturing. Use of Finite Element Method (FEM) based simulation has proved to be an effective tool for carrying out design of insulation system and other structural design prepared by Indian manufacturers. A questionnaire is developed for analyzing the scope for cost optimization of autotransformer on the basis of their complexity, design constraints, dielectric requirements, electrical stress, testing facility etc. The statistical analysis of data obtained, can be processed through statistical analysis software(s) available to identify the scope for cost optimization, efficiency improvement and cost saving in manufacturing.

Finite element modelling of pre-stressed concrete poles under downbursts and tornadoes

Among different types of electrical transmission line structures, pre-stressed concrete transmission poles have the advantages of low installation and maintenance cost, appropriate delivery time, and high corrosion resistivity. Typically, these concrete poles are designed to resist only synoptic wind loading as current codes do not consider high intensity wind events in the form of downbursts and tornadoes. To the best of the authors’ knowledge, this study is the first investigation to assess the behaviour of pre-stressed concrete poles under High intensity wind events. Due to the localized nature of those events, identifying the critical locations and parameters leading to peak forces on the poles is a challenging task. To overcome this challenge, a built in-house numerical model is developed incorporating the following: (1) a three-dimensional downburst and tornado wind field previously developed and validated using computational fluid dynamics simulations; (2) A computationally efficient analytical technique previously developed and validated to predict the non-linear behaviour of the conductors under non-uniform loads resulting from those events (3) a non-linear finite element model developed in the current study to simulate the structural behaviour of pre-stressed concrete poles considering material nonlinearity. The non-linear finite element model, is validated using experimental data available in the literature. Extensive parametric studies are conducted using the numerical model to determine the critical downburst and tornado configurations leading to peak overturning moment acting on a pole which is designed to remain un-cracked under synoptic wind load. Failure studies are then conducted to assess the downburst and tornado velocities that would lead to a full collapse of the pole.

Ku to V-band 4-bit MEMS phase shifter bank using high isolation SP4T switches and DMTL structures

This work presents a micro-electro-mechanical system (MEMS) based on a wide-band 4-bit phase shifter using two back-to-back single-pole-four-throw (SP4T) switches and four different distributed MEMS transmission line (DMTL) structures that are implemented on 635 µm alumina substrate using surface micromachining process. An SP4T switch is designed with a series-shunt configuration and it demonstrates an average return loss of >17 dB, an insertion loss of <1.97 dB and maximum isolation of >28 dB up to 60 GHz. A maximum area of the SP4T switch is ~0.76 mm2. Single-pole-single-throw and SP4T switches are capable of handling 1 W of radio frequency (RF) power up to >100 million cycles at 25° C; they can even sustained up to >70 million cycles with 1 W at 85 °C. The proposed wide-band phase shifter works at 17 GHz (Ku-band), 25 GHz (K-band), 35 GHz (Ka-band) and 60 GHz (V-band) frequencies. Finally,a 4-bit phase shifter demonstrates an average insertion loss of <6 dB, return loss of >10 dB and maximum phase error of ~3.8° at 60 GHz frequency over 500 MHz bandwidth. Total area of the fabricated device is ~11 mm2. In addition, the proposed device works well up to >107 cycles with 1 W of RF power. To the best of the author’s knowledge, this is the best reported wide-band MEMS 4-bit phase shifter in the literature that works with a constant resolution.

A mmWave Folded Substrate Integrated Waveguide in a 130-nm CMOS Process

A miniaturized millimeter-wave substrate integrated waveguide (SIW) in IBM 130-nm digital CMOS process is presented in this paper. The footprint of the interconnect is reduced compared with previous works using the folding technique. A current-loop transition structure is proposed in this paper that is built inside the SIW interconnect and excites its TE10 mode with minimal area overhead. A simulation-based comparison of T-FSIW and other planar transmission line structures reveals that the T-FSIW interconnect shows a much higher resonant quality factor. A prototype waveguide is designed and fabricated to operate with a cutoff frequency of 175 GHz. Furthermore, the current-loop excitation is optimized for the frequency range of 180–220 GHz. Simulation and experimental data are used to confirm the proposed interconnect approach.

A new hemostatic device utilizing a novel transmission structure for delivery of adrenaline and microwave energy at 5.8 GHz

A novel transmission line structure has been developed to facilitate the delivery of both adrenaline and microwave energy to achieve hemostasis. A proximal end impedance transformer and radiative tip have been designed and manufactured to provide good match between the novel hollow transmission line and the microwave source and tissue, respectively. Further consideration of the challenges and problems encountered along with evidence of successful microwave energy delivery at 5.8 GHz into porcine liver model providing a controlled and focused coagulation zone of approximately 5 mm.

Modeling of Metal-Fill Parasitic Capacitance and Application to On-Chip Slow-Wave Structures

Modern integrated circuit manufacturing processes generally require the insertion of a large amount of metal fill in layout regions of low metal density to reduce manufacturing defects. We present a general, process-independent, and scalable modeling technique for the computation of distributed capacitance of on-chip transmission lines in the presence of metal fill. The technique reduces the complex 3-D problem to a set of 2-D problems and solves using an effective length and an effective dielectric constant approach. We obtain speedups of about 12 fold for solving the set of 2-D reduced problems compared with a 3-D problem. We verify the accuracy of the technique by comparison with electromagnetic simulations in three process technologies and measurements in a 0.18-μm BiCMOS process. The maximum error in self-capacitance and mutual capacitance is <;6% and <;10%, respectively, over a wide range of processes and physical parameters. The rootmean-square error between measured and modeled capacitance is 9.5%. To further demonstrate the effectiveness of our modeling method, we apply it to various transmission-line structures in the presence of floating conductors.

Theoretical Analysis of Moving Reference Planes Associated with Unit Cells of Nonreciprocal Lossy Periodic Transmission-Line Structures

Theoretical Analysis of Moving Reference Planes Associated with Unit Cells of Nonreciprocal Lossy Periodic Transmission-Line Structures

An Application of Fractal-Based Lightning for SFR Calculation of High Voltage Substations

Objectives: To simulate the lightning more close to reality and investigate the performance of the lightning protection system of high voltage substation. Methods/Statistical Analysis: The method which is used for the system analysis is a new fractal-based model of simulated lightning by which the zigzag movement of lightning downward leader as well as branching nature is simulated. A new charge distribution is proposed for branched lightning channel. In addition, the branch fading during the lightning downward movement is also simulated in order to simulate the lightning more close to the reality. Findings: The results of the simulated lightning using the proposed method show that the proposed fractal method simulates the lightning close to the reality. The striking distances of a transmission line structure for different lightning return stroke currents are obtained by the proposed method and compared to those of Electrogeometric Model (EGM) and Leader Progression Model (LPM). The results show that how the proposed method obtains a wide range of possible results statistically. The lightning shielding system performance of a practical high voltage substation is investigated based on the proposed model in two different scenarios by which the effect of substation instruments on the lightning protection system is investigated. The results reveal that the presence of the substation instruments completely affects the shielding system performance. Using the propose method, the random behavior of the lightning is well modeled and the shielding failure of the protection system is investigated in a statistical manner. The obtained results are compared to those of EGM, and LPM. The results are discussed and superiority of the proposed simulated lightning model is concluded. Application/ Improvements: The proposed method simulates the different features of the lightning including 1- branching nature, 2- zigzag movement, 3- random behavior, 4- branch fading, 5- branched charge distribution.

Low-cost TO-CAN package combined with flexible and hard printed circuit boards for 25 - Gb / s optical subassembly modules

A low-cost transistor outline-CAN (TO-CAN) package, which is combined with flexible printed circuit board (PCB) and hard PCB, has been developed for a 25-Gb/s optical subassembly module. On the flexible PCB, the transmission line structure used top ground microstrip line, and the wider transmission bandwidth can be obtained. Using ground pads and ground notch technologies, the impedance of connection between flexible PCB and hard PCB was designed to match with the impedances of signal traces of the flexible and hard PCBs. In the TO-CAN package, a TO-46 header was used, and the header needs to closely connect with the flexible PCB. The bandwidth of TO-46 package combined with flexible and hard PCBs can achieve above 23 GHz. The clear 25-Gb/s transmission eye diagram was also measured, and the rise time, fall time, and Q-factor of the eye diagram are 13.78, 13.56 ps, and 8.76, respectively. The TO-46 package combined with flexible and hard PCBs has been verified to be suitable for application in 25-Gb/s optical subassembly modules.