Modified Transmission Line Research Articles

Fabrication of Compact Superconducting Lowpass Filters for Ultrasensitive Detectors

Optimal performance of background limited thermal detectors requires adequate control over all relevant sources of incident electromagnetic radiation. In addition to the radiant power incident from the scene of interest, undesired or spurious power can potentially couple to the sensor via its bias and readout circuitry employed to operate the device. One means of limiting the contribution of this stray radiation is to filter or block leakage associated with electrical connections in the detector environment. Here we discuss a fabrication methodology for realizing compact planar filters embedded in the wall of the detector enclosure whose tailored response controls the propagation of light through the far infrared. This approach consists of fabricating an array of boxed-stripline transmission line blocking filters to control thermal radiation incident via this path. Topologically, each superconducting center conductor is encased by a silicon dioxide dielectric insulator and surrounded by a metallic shield to form a single mode transmission line structure. We report on achieved attenuation and return loss and find that it replicates simulated data to a high degree.

주기가 다른 격자들로 구성된 DFB 필터의 구현

The filtering characteristics of planar distributed feedback (DFB) waveguides composed by gratings with different period are solved using equivalent transmission-line network. To analyze explicitly its band-pass and resonance properties, a longitudinal modal transmission-line theory (L-MTLT) based on Floquet`s theorem and Babinet`s principle is newly developed. The numerical results reveal that this approach offers a simple and analytic algorithm to analyze the filtering characteristics of cascaded DFB structure with different period, and the bandwidth and side-lobe suppression of cascaded DFB filter are sensitively dependent on the variation of aspect ratio and the number of grating at each region.

Fast Distance Protection for Proximal Fault of EHV Transmission Line

As the full length is considered in the traditional EHV line protection, proximal circuit fault can’t be moved in an ideal short time. A fast distance protection algorithm for proximal fault of EHV transmission line is proposed in the paper. Based on differential equation model and power frequency variation principle, the method has fast response speed and small workload. And the protection for proximal fault of long distance EHV transmission lines can be correctly implemented in a very short time. The method is realized with a low pass prefilter and without digital filter. Finally, through the RTDS simulation platform, a variety of fault modes of 500kV transmission lines is realized, and the accuracy and rapidity of the algorithm is verified by the simulation result. DOI: http://dx.doi.org/10.11591/telkomnika.v11i2.1984

Silicon CMOS Ohmic Contact Technology for Contacting III-V Compound Materials

Silicon (Si)-encapsulated III-V compound (III-V) device layers enable Si-complementary metal-oxide semiconductor (CMOS) friendly ohmic contact formation to III-V compound devices, allowing for the ultimate seamless planar integration of III-V and Si CMOS devices in a common fabrication infrastructure. A method of making ohmic contacts to buried III-V films using silicide metallurgies has been established. NiSi/Si/III-V dual heterojunction contact structures are found to be optimal for integration. These structures allow contact resistivities to be controlled by Si/III-V interfaces and eliminate interactions between the buried III-V device and metal layers. Using a modified transmission line method (TLM) test structure fabricated using standard CMOS processing techniques, the specific contact resistivities of Si/GaAs and Si/InxGa1-xAs interfaces are extracted. The relationship between specific contact resistivity and heterojuntion barrier width is considered. Among the structures tested in this work, p-type Si/GaAs and n-type Si/InxGa1-xAs yielded the lowest contact resistivities. Using the p-type Si/GaAs interface, a GaAs/AlxGa1-xAs laser with NiSi top contact is demonstrated, confirming the feasibility of NiSi/Si/III-V contact structures for III-V devices.

THIN FILM THERMOELECTRIC CHARACTERIZATION TECHNIQUES

The key thin film thermoelectric characterization techniques are described. Due to the small dimensions, a careful examination of electrical and thermal paths in the device is necessary. We describe both in-plane and cross-plane measurement methodologies. Sample requirements for four-probe and van der Pauw methods for in-plane electrical conductivity measurement are discussed. The in-plane Seebeck coefficient is characterized under a temperature gradient which generates a voltage. Precise measurements of temperature and voltage at the same location in the sample are very important. For the cross-plane electrical conductivity, the modified transmission line method is evaluated. To eliminate parasitic contact and substrate resistances, several samples with varying thicknesses are required. Two approaches, a DC method and the 3ω method, are described in detail for the cross-plane Seebeck coefficient characterization. Next, we focus on the transient Harman method to directly measure the cross-plane thermoelectric figure of merit of a thin film. The device requirements for reducing parasitic heat losses and current nonuniformity are presented. Thermoreflectance imaging can be used together with transient Harman in order to extract electrical and thermal conductivities and the Seebeck coefficient simultaneously. Finally, Z-meters are described for directly determining the figure of merit and efficiency of a thermoelectric element or module under a large temperature gradient. Recent developments have significantly reduced thermal and electrical parasitics, as well as radiation heat loss in the system, enabling ZT measurement of legs as thin as one hundred microns.

Design of a Microstrip Antenna Based on the Magnetoelectric Composite Material

Based on the transmission line mode theory, designed one kind of small and dual band microstrip antenna on the magnetoelectric composite material. Then do the simulation by HFSS11.0 which based on the finite element method. The simulation results show that, when the return loss less than -10dB, antenna working in band 2360MHz~2500MHz and 3900MHz ~4200MHz, Compared with ordinary antenna, this antenna not only realizes the multi band, but also in the working frequency bandwidth compared to common antenna slightly raised, antenna size is reduced nearly 85%. Good impedance matching. This microstrip antenna has some value on the mobile device miniaturization for the miniaturization and dual band.

Impedance and power fluctuations in linear chains of coupled wave chaotic cavities

The flow of electromagnetic wave energy through a chain of coupled cavities is considered. The cavities are assumed to be of sufficiently irregular shape that their eigenmodes are described by random matrix theory. The cavities are coupled by electrically short single mode transmission lines. Approximate expressions for the power coupled into successive cavities are derived, and the predictions are compared with Monte Carlo simulations. The analytic formulas separate into a product of factors. Consequently, the distribution of power in the last cavity of a very long chain approaches lognormal. For lossless cavities, signatures of Anderson localization, similar to those of the conductances of quantum wires, are observed.

New Functions for Representing IEC 62305 Standard and Other Typical Lightning Stroke Currents

New functions for approximating various lightning currents, either measured, assumed or generalized in the standard IEC 62305, are presented in this paper. The channel-base current function and its parameters, as well as analytical expressions of this function derivatives, integrals, and integral transformations are given. Parameters of new functions for representing first stroke currents, subsequent stroke currents, and long stroke currents from the standard IEC 62305 are calculated, so as of two-rise front function typical for experimentally measured first negative stroke currents. Results for lightning electric and magnetic field at different distances from the channel-base obtained by using the proposed function and the Modified transmission line model with exponential decay with height are in good agreement with the results from literature, but any other lightning stroke model can be used as well.

The Mathematical Model of Power System with Static Var Compensator in Long Transmission Line

Problem statement: It is becoming increasingly important to fully utilize the existing transmission system assets due to environmental legislation, rights-of-way issues and costs of construction and deregulation policies that introduced in recent years. The Static Var Compensator (SVC) has been proposed for the better control power flow and dynamic performance. The exact long transmission line model consists of the resistance and reactance. Most of previous researches studies transient stability performance of the SVC in SMIB System with neglecting resistance of the line. Thus the fully capability of the SVC on transient stability improvement of power system may not be applied. The consideration of the resistance causes in the difficulty of deriving mathematical model. Approach: This study investigates the effect of the SVC on transient stability of the power system with consideration the exact long transmission line mode. The concept of two-port network is applied to simplify the mathematical model of the power system. The proposed method is tested on sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without resistance is obviously higher than that of with resistance whereas the second swing of the faulted system without resistance is slightly less than that of with resistance. The system with the SVC can improve transient stability of power system. Conclusion: It is found from this study that the SVC and resistance of the line can improve first swing of rotor angle. The resistance of the line provides the negative effect on second swing of rotor angle. The simulation results indicate that for practical long line, the resistance is very import parameters for evaluating transient stability of power system.

The Mathematical Model of Power System with Thyristor Controlled Series Capacitor in Long Transmission Line

Problem statement: It is becoming increasingly important to fully uti lize the existing transmission system assets due to environmental leg islation, rights-of-way issues and costs of construction and deregulation policies that introdu ced in recent years. The Thyristor Controlled Serie s Capacitor (TCSC) has been proposed for the better c ontrol power flow and dynamic performance. The exact long transmission line model consists of the resistance and reactance. Most of previous researches studies transient stability performance of the TCSC in SMIB System with neglecting the resistance of the line. Thus the fully capability o f the TCSC on transient stability improvement of power system may not be applied. The consideration of the resistance causes in the difficulty of deriving the mathematical model. Approach: This study investigates the effect of the TCSC on transient stability of the power system with consid eration the exact long transmission line mode. The concept of two-port network is applied to simplify the mathematical model of the power system. The proposed method is tested on sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without resistance is obviously higher than that of with resistance whereas the second swing of the faulted system without resistance is slightly less than tha t of with resistance. The system with a TCSC can impr ove transient stability of power system. Conclusion: It was found from this study that the TCSC and res istance of the line can improve first swing of rotor angle. However, the resistance of th e line provides the negative effect on second swing of rotor angle. The simulation results indicate tha t for practical long line, the resistance is very i mport parameters for evaluating transient stability of po wer system.

Instability control in microwave-frequency microplasma

Atmospheric argon microplasmas driven by 1.0 GHz power were studied by microwave circuit analyses and spatially-resolved optical diagnostics. These studies illuminate the mechanisms responsible for microplasma stability. A split-ring resonator (SRR) microplasma source is demonstrated to reflect excess microwave power, preventing the ionization overheating instability while limiting electron density to approximately 1 × 1014 cm−3 and OH rotational temperature to 760 K at 0.76 W. Providing the SRR microplasma with an electrical path to ground, however, allows the microplasma to transition from the SRR mode to the so-called transmission line mode (T-line). This transition is due to matching of the microplasma and transmission line impedances. The higher power T-line mode supports a more intense microplasma with electron density of 1 × 1015 cm−3 and OH rotational temperature of 1480 K with 15 W absorbed power. While the SRR mode is optimized for ignition and sustaining a stable nonequilibrium plasma, and T-line mode is better suited for driving a hot, high density microplasma. The estimated microwave discharge voltages were 15 V and 35 V in SRR mode and T-line mode, respectively, and the voltages are rather independent of input power. Microplasma stability is due to a combination of impedance mismatching and direct control of power, both inherent to microwave circuitry.

The Mathematical Model and Simulation of Thyristor Controlled Series Capacitor in Medium Transmission Line

Problem statement: It is becoming increasingly important to fully utilize the existing transmission system assets due to environmental legislation, rights-of-way issues, costs of construction and deregulation policies that introduced in recent years. The Thyristor Controlled Series Capacitor (TCSC) has been proposed for the better control power flow and dynamic performance. The exact medium transmission line model consists of the resistance and reactance. Most of previous researches studies transient stability performance of the TCSC in SMIB System with neglecting the resistance of the line. Thus the fully capability of the TCSC on transient stability improvement of power system may not be applied. The consideration of the resistance causes in the difficulty of deriving the mathematical model. Approach: This study investigates the effect of the TCSC on transient stability of the power system with consideration the exact medium transmission line mode. The concept of two-port network is applied to simplify the mathematical model of the power system. The proposed method is tested on sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without resistance is obviously higher than that of with resistance whereas the second swing of the faulted system without resistance is slightly less than that of with resistance. The system with a TCSC can improve transient stability of power system. Conclusion: It was found from this study that the TCSC and resistance of the line can improve first swing of rotor angle. However, the resistance of the line provides the negative effect on second swing of rotor angle. The simulation results indicate that for practical medium line, the resistance is very import parameters for evaluating transient stability of power system.

The Effect of the Static Var Compensator and R/X Ratio of Short Transmission Line on Transient Stability of Single Machine Infinite Bus System

Problem statement: It is becoming increasingly important to fully utilize the existing transmission system assets due to environmental legislation, rights-of-way issues and costs of construction and deregulation policies that introduced in recent years. The Static Var Compensator (SVC) has been proposed for the better control power flow and dynamic performance. The exact short transmission line model consists of the resistance and reactance. Most of previous researches studies transient stability performance of SVC in SMIB System with neglecting the resistance of the line. Thus the fully capability of the SVC on transient stability improvement of power system may not be applied. The consideration of the resistance causes in the difficulty of deriving the mathematical model. Approach: This study investigates the effect of the SVC on transient stability of the power system with consideration the exact short transmission line mode. The concept of two-port network is applied to simplify the mathematical model of the power system. The proposed method is tested on sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without resistance is obviously higher than that of with resistance whereas the second swing of the faulted system without resistance is slightly less than that of with resistance. The system with a SVC can improve transient stability of power system. Conclusion: It was found from this study that the SVC and resistance of the line can improve first swing of rotor angle. However, the resistance of the line provides the negative effect on second swing of rotor angle. The simulation results indicate that for practical short line, the resistance is very import parameters for evaluating transient stability of power system.

무선 전력 전송용 High-Q 스파이럴 영차 공진기

In this paper, various spiral zeroth-order resonators are proposed for wireless power transmission. Since a zerothorder resonance(ZOR) mode of meta-material transmission lines has the characteristic of an infinite wavelength, its frequency is independent of physical length. Also, to obtain high transmission efficiencies high-Q resonators and strong coupling coefficient between coupled resonators are required. Therefore, the resonators consist of spiral inductor and lumped capacitor to use the ZOR mode and they are optimized via parametric study and circuit analysis for a high-Q resonator design. The optimized resonators are simulated and compared with a conventional spiral resonator and one of them was fabricated and measured. The fabricated one has a dimension of () and the transmission efficiency of 80 % is measured at 13.56 MHz at transmitted distance of 40 cm.

Investigating the Critical Clearing Time of Power System with the Exact Medium Transmission Line Model

Problem statement: The exact medium transmission line model consists of the resistance, series reactance and shunt capacitance. Most of previous research studies show the critical clearing time of single machine infinite bus while neglecting the resistance and capacitance of the line. Approach: This study investigates the critical clearing time of power system with consideration the exact medium transmission line mode. The concept of two-port network is applied to simplify the mathematical model of the power system. The proposed method is tested on sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without resistance is obviously higher than that of with resistance whereas the second swing of the faulted system without resistance is slightly less than that of with resistance. Conclusion: It was found from this study that the resistance of the line provides the improvement of the first swing but not for the second swing. The simulation results indicate that for practical medium line, the resistance is very import parameters to determine the critical clearing time of the single machine infinite system whereas shunt capacitance doesn’t affect on the critical clearing time of the single machine infinite bus system.

The Effect of Thyristor Controlled Series Capacitor on Transient Stability of Single Machine Infinite Bus System with the Exact Short Transmission Line Model

Problem statement: It is becoming increasingly important to fully utilize the existing transmission system assets due to environmental legislation, rights-of-way issues, costs of construction and deregulation policies that were introduced in recent years. The Thyristor Controlled Series Capacitor (TCSC) has been proposed for better control power flow and dynamic performance. The exact short transmission line model consists of the resistance and reactance. Most of previous researches studies transient stability performance of TCSC in SMIB System while neglecting the resistance of the line. Thus the full capability of the TCSC on transient stability improvement of power system may not be applied. The consideration of the resistance causes difficulty of deriving the mathematical model. Approach: This study investigates the effect of the TCSC on transient stability of the power system with consideration the exact short transmission line mode. The concept of two-port network is applied to simplify the mathematical model of the power system. The proposed method is tested on sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without resistance is obviously higher than that of with resistance whereas the second swing of the faulted system without resistance is slightly less than that of with resistance. The system with a TCSC can improve transient stability of power system. Conclusion: It was found from this study that the TCSC and resistance of the line can improve first swing of rotor angle. However, the resistance of the line provides the negative effect on second swing of rotor angle. The simulation results indicate that for practical short line, the resistance is a very important parameter for evaluating transient stability of power system.

원형 수직 캐비티 표면 광방출 레이저의 모드특성

Abstract The resonance properties of circular vertical-cavity surface-emitting lasers (VCSELs) are studied by using a newly developed equivalent network approach. Optical parameters, such as the stop-band or the reflectivity of periodic Bragg mirrors and the resonance wavelength, are explored for the design of these structures. To evaluate the differential quantum efficiency and the threshold current density, a transverse resonance condition of circular modal transmission-line theory is also utilized. This approach dramatically reduces the computational time as well as gives an explicit insight to explore the optical characteristics of circular VCSELs. Key Words : Circular Modal Transmission Line Theory, Circular VCSELs, Bragg mirrors * 정회원, 한성대학교 정보통신공학과접수일자 2012.1.8, 수정완료 2012.2.8.게재확정일자 2012.2.10Received: 8 January 2012 / Revised: 8 February 2012 /Accepted: 10 February 2012 * Corresponding Author: kwangho@hansung.ac.krDept. of Information and Communication Engineering, Hansung University, Seoul, Korea

Researches on Reactive Compensation for Long-Distance and Highcapacity Hybrid Submarine Cable Lines

In order to balance reactive power, reduce line losses, prevent excessive power frequency and switching over-voltage and adjust and control the line voltage etc. The long-distance and high voltage transmission lines are needed reactive power compensation. High voltage overhead transmission lines and high voltage submarine cable (including mixed-submarine) transmission lines are different, for example, the capacitance in the submarine cable lines is larger than in the conventional overhead lines. Therefore, the reactive power compensation on the EHV transmission lines which contains submarine cable lines is focus on the compensation of submarine cable lines. The reactive power compensation in 500 kV AC submarine cable interconnection project for Hainan power grid and Guangdong power grid[1], which is the first 500 kV long-distance and high-capacity sea trails interconnection project in China and which is just completed soon, is researched by Electro-Magnetic Transient Program——PSCAD/EMTDC (Power System Computer Aided Design/ Electro Magnetic Transient in DC System in this paper). The simulation results verifies that the role of shunt reactor which could absorb charging power and suppress the power frequency overvoltage for the long-distance and high-capacity hybrid submarine cable lines. The conclusions can offer references to suppress power frequency overvoltage and the reactive power compensation in extra high voltage transmission lines which is the mixed mode of overhead transmission lines and submarine cables.

THIN FILM THERMOELECTRIC CHARACTERIZATION TECHNIQUES

The key thin film thermoelectric characterization techniques are described. Because of the small dimensions, a careful examination of electrical and thermal paths in the device is necessary. We describe both in-plane and cross-plane measurement methodologies. Sample requirements for four-probe and van der Pauw methods for in-plane electrical conductivity measurement are discussed. The in-plane Seebeck coefficient is characterized under a temperature gradient that generates a voltage. Precise measurements of temperature and voltage at the same location in the sample are very important. For the cross-plane electrical conductivity, the modified transmission line method is evaluated. To eliminate parasitic contact and substrate resistances, several samples with varying thicknesses are required. Two approaches, a DC method and the 3ω method, are described in detail for the cross-plane Seebeck coefficient characterization. Next, we focus on the transient Harman method to directly measure the cross-plane thermoelectric figure of merit of a thin film. The device requirements for reducing parasitic heat losses and current nonuniformity are presented. Thermoreflectance imaging can be used together with transient Harman in order to extract electrical and thermal conductivities and the Seebeck coefficient simultaneously. Finally, Z-meters are described for directly determining the figure of merit and efficiency of a thermoelectric element or module under a large temperature gradient. Recent developments have significantly reduced thermal and electrical parasitics, as well as radiation heat loss in the system, enabling ZT measurement of legs as thin as one hundred microns.

Light trapping in amorphous silicon solar cells with periodic grating structures

We report on the design of amorphous silicon solar cells with the periodic grating structures. It is a combination of an anti-reflection structure and the metallic reflection grating. Optical coupling and light trapping in thin-film solar cells are studied numerically using the Rigorous Coupled Wave Analysis enhanced by the Modal Transmission Line theory. The impact of the structure parameters of the gratings is investigated. The results revealed that within the incident angles of − 40 ° to + 40 ° the reflectivity of the cell with a period of 0.5 μm, a filling factor of 0.1 and a groove depth of 0.4 μm is 4%–22.7% in the wavelength range of 0.3–0.6 μm and 1%–20.8% in the wavelength range of 0.6–0.84 μm, the absorption enhancement of the a-Si layer is 0.4%–10.8% and 20%–385%, respectively.