Transmission Line Transfer Research Articles

Capacitive Effect and Electromagnetic Coupling on Manganin Gauge Limiting the Bandwidth for Pressure Measurements under Shock Conditions.

In this study, we investigated the capacitive effect and the electromagnetic coupling on the measurement chain induced by impact experiments with a gas gun or powder gun. Reduced bandwidth and noise were noticed on experimental signals. Rogowski coil measurements were added on the cables to characterize the electromagnetic coupling. The perturbation currents on the cables were quantified depending on the configuration. The gauge, the transmission line and the conditioning system were modeled. The calculations reproduced the electrical wave arrival time, the transmission line transfer impedance and the conditioning system transfer impedance; and the bandwidth limitation has been displayed. A capacitive effect with the piezoresistive manganin gauge embedded into the sample was identified, depending on the experimental setup.

Temperature dependence of electrical characteristics of metal-carbon nanowall contacts

Electrical contacts to vertically-aligned nanographite structures, the so-called carbon nanowalls (CNWs), are studied in a temperature range of 25 °C to 300 °C using Ag, Au, and Mg as contact materials. The total resistance between a pair of metal electrodes on CNWs is regarded as the combination of serial resistances of CNWs and two metal-CNW contacts. The contact resistance and specific contact resistivity measured by the transmission line method and transfer line method, respectively, decrease with increasing temperature, with low thermal activation energies of the order of 10−2 eV. The contact resistance occupies a large portion of the total resistance between a pair of electrodes and dominates the current transport even at high temperatures, thus affecting electrical signal measurement in device applications profoundly. Little dependence of contact resistance upon work function of metal species is attributed to a semi-metallic feature of CNWs with a high degree of delocalization, overlap, and continuity of defect bands.

Electrical Characteristics of Metal Contacts to Carbon Nanowalls

The electrical characteristics of metal contacts to vertically-aligned nanographite structures, the so-called carbon nanowalls (CNWs), are examined using nickel as the electrode material. The total resistance between a pair of electrodes on CNWs is regarded as the sum of the serial resistance of CNWs and two metal-CNWs contacts to measure the contact resistance and specific contact resistivity by the transmission line method and transfer line method, respectively. The contact resistance and resistivity are around 2.8 Ω and 0.1 Ω cm2, respectively, at room temperature and decrease gently to 2.4 Ω and 0.06 Ω cm2, respectively, when the temperature is increased up to 300 °C. The apparent activation energy corresponding to the conduction barrier at the contact is in the range of 10−3 eV to 10−2 eV, which is comparable with that for the sheet resistance of CNWs. The contact resistance occupies a large portion of the total resistance between a pair of electrodes even at high temperatures, thus affecting electrical signal measurement in electronic and electrochemical device applications.

Real-Time Fault Location Using the Retardation Method

A new method for short-circuit fault location is proposed. The method is based on instantaneous signal measurement and its first and second derivatives, which are the novel elements of the current approach. The derivatives allow associating a precise time stamp to the occurrence of the fault. Due to retardation phenomena, the difference between the times in which a signal is registered in two detectors can be used to locate the fault. We offer several mathematical models to describe the fault. Although a description of faults in terms of a lumped circuit is useful for elucidating the methods for detecting the fault, this description will not suffice to describe the fault signal propagation; hence, a distributed models is needed, which is given in terms of the telegraph equations. Those equations were used to derive a transmission line transfer function, and an exact analytical description of the fault signal propagating in the transmission line was obtained. The analytical solution was verified both by numerical simulations and experimentally.

An efficient hybrid method for analyzing the coupling response of microstrip antenna system

This paper presents an efficient hybrid method consisting of Lorentz reciprocity theorem, finite-difference-time-domain (FDTD) method, thin wire model, transmission line (TL) equations and transfer impedance model, which can be utilized to analyze the system-level transient responses of the microstrip antenna system with antenna, metallic enclosures, braided shielded cable, and lumped element, when illuminated by an external electromagnetic pulse (EMP). In order to avoid over-fine mesh generation and repeated modeling of the antenna in multiple simulations, Lorentz reciprocity theorem is employed to extract an equivalent source model of antenna coupling, thereby improving the computational efficiency. Then, the transfer impedance model and thin wire model are incorporated into the FDTD-TL method efficiently to deal with the back-door coupling through the shielding layer of feeding coaxial cable. Finally, the hybrid FDTD method combined with the extracted equivalent source of antenna coupling is utilized to solve the coupling responses of the whole antenna system. The results of numerical simulation are verified by comparing with the simulation results of CST CS. Then, considering the influence of different incident conditions of external EMP, the characteristics of the coupling response of the system are analyzed. The obtained coupling response information demonstrate that the proposed method is available for further designing electromagnetic protection of the inner circuits of the microstrip antenna system against the impact of external EMP.

Internal and External Transmission Line Transfer Matrix and Near-Field Radiation of Braided Coaxial Cables

In this article, the coupling between the inner conductor and the shield of a coaxial cable is summarized with different coupling directions and shielding grounding conditions. An internal and external transmission line (IETL) transfer matrix is proposed to validate this coupling relationship. The induced voltage and current of the IETLs can be more intuitively represented by the IETL transfer matrix and the port voltage and current. By introducing the three-conductor system and the surface transfer impedance into the transmission line theory, the IETL transfer matrix representation of the transmission line equation with coupling components is obtained. Moreover, when analyzing the problems of coupling between field and transmission line, the coaxial cable can be equivalent to a bare wire by using IETL transfer matrix. According to this idea, an improved approximation method based on Hertzian dipole and a numerical method based on the finite element method algorithm are proposed to calculate the radiation of a coaxial cable and the crosstalk between a coaxial cable and a bare wire. Then, the results of the two methods are compared with the electromagnetic calculation software.

Design of a dual band-notched UWB antenna and improvement of the 5.5 GHz WLAN notched characteristic

ABSTRACTA novel dual band-notched ultra-wideband (UWB) planar antenna with improved characteristic in 5.5 GHz WLAN notched band is presented. Two kinds of L-shaped slots are inserted in the radiator in order to obtain the dual notched characteristics. A separated strip is added in the middle of the U-shaped radiator for further improving the performance. The antenna has a measured impedance bandwidth of 3.1–11.0 GHz with VSWR < 2, while it has dual notched bands of 3.4–4.0 GHz and 4.9–6.0 GHz. Besides, the equivalent circuit model, transmission line model and transfer function are also studied to investigate the band-notched performance of the proposed antenna.

Breakthrough in current-in-plane tunneling measurement precision by application of multi-variable fitting algorithm.

We present a breakthrough in micro-four-point probe (M4PP) metrology to substantially improve precision of transmission line (transfer length) type measurements by application of advanced electrode position correction. In particular, we demonstrate this methodology for the M4PP current-in-plane tunneling (CIPT) technique. The CIPT method has been a crucial tool in the development of magnetic tunnel junction (MTJ) stacks suitable for magnetic random-access memories for more than a decade. On two MTJ stacks, the measurement precision of resistance-area product and tunneling magnetoresistance was improved by up to a factor of 3.5 and the measurement reproducibility by up to a factor of 17, thanks to our improved position correction technique.

Research on Impedance Model of Intelligent Drill String Based on the Average Transformation Theory

Cable transmission has its intrinsic advantages and it is the development tendency of intelligent drilling among all kinds of signal transmission. According to the structure characteristics of the intelligent drill string, this paper analyzes the transmission line distribution parameters of intelligent drill string combined with average transmission theory; transfer matrixes of single drill pipe, drill pipe joint and that of cascaded transmission line between them are all calculated by the transmission line transfer function; impedance model of intelligent drill string communication channel model are built according to that transfer matrix based on the two-port network, then this model is simulated by experiment and the result is analyzed; curve of error rate is got and the influence of different signal-noise ratio, different transmission rate and different transmission distance on signal transmission performance are analyzed. This model simplifies the calculation, and the frequency characteristics and attenuation characteristics of transmission line are obtained under the analog signal and the digital signal, then the average transmission signal characteristics of intelligent drill string is analyzed by intuitive squiggle. Maybe this paper could provide some theoretical guidance for intelligent drill string.

Improvement of integrated transmission line transfer index for power system voltage stability

Abstract With the increased loading of transmission lines, the voltage stability problem has become a critical issue for most power system planners and operators. Some important studies related to the voltage stability indices used in the electric power systems are first sorted. Then, a new approach for voltage stability is developed to find the weak lines in this paper. The new method is based on the practical line ABCD parameters, the power factor of receiving end, and the power angle between the sending end and the receiving end. This concept of integrated transmission line transfer index (ITLTI) is derived for a radial transmission system and later applied to a large system. However, ITILI index has a more integrated content and should be a better solution for on line voltage stability evaluation. The new ITLTI index and other existing techniques are demonstrated and compared with numerical studies by IEEE 14-bus test system, using gradually increase reactive load.

Multistage Transmission Expansion Planning Considering Fixed Series Compensation Allocation

This paper proposes a mathematical model for multistage transmission expansion planning (TEP) considering fixed series compensation (FSC) allocation and N-1 security constraints for both transmission lines and FSCs. FSCs can increase the transmission lines transfer capacity, but the importance of using them in TEP is to dispatch the power more efficiently, resulting in a different topology with less investment cost compared with planning without FSCs. This problem is modeled as a linear mixed binary programming problem and is solved by a commercial branch-and-cut solver to obtain the optimum solution. FSC is modeled as a fixed impedance located in the transmission lines in discrete steps and with an investment cost based on the prices of reinforcement lines. The results obtained using two known test systems show the economic benefits of using FSC in multistage TEP problems.

A Novel Metamaterial FSS-based Structure for WidebandRadome Applications

A novel metamaterial based FSS (frequency selective surfaces) structure is presented in this paper for wideband airborne radome applications. The proposed metamaterial-FSS structure consists of three layers, where a DPS (double positive sign) layer is sandwiched between a MNG (μ-negative) and ENG (e-negative) layer, exhibits very good bandpass characteristics inside the operational band along with excellent roll-off characteristics outside the band. The EM performance analysis of the proposed structure has been carried out using transmission line transfer matrix (TLTM) method, which shows excellent bandpass characteristics over wide frequency range. The transmission efficiency is over 95% both at normal incidence and at high incidence angles of 30°, and 60°. The frequency range extends from S- to X-band (2.5-9.9 GHz). In view of streamlined airborne radome applications, the reflection properties and insertion phase delay (IPD) are also determined at high incident angles.

Low Frequency Oscillations Damping by UPFC with a Multi Stage Fuzzy and Supplementary Controllers

Low frequency electromechanical oscillations are inevitable characteristics of power system which affect the transmission line transfer capability and the system stability. In this work, a new POD controller with DC-voltage regulator based on genetic algorithm is proposed for the UPFC for damping low frequency oscillations. The construction and implementation of this controller is fairly easy, which can be useful in real world power system. The effectiveness of the proposed controller has been tested on a SMIB power system in comparison with conventional UPFC controllers, GAMSF DC-voltage regulator and PSOMSF DC-voltage regulator under different operating conditions.

FEM-BASED METHOD FOR THE SIMULATION OF DIELECTRIC WAVEGUIDE GRATING BIOSENSORS

Label-free optical biosensors are important tools to study the kinetics, interaction and presence of (bio) chemical compounds in various flelds such as biotechnology, pharma, diagnostics as well as environmental and food quality monitoring. Systems based on planar optical waveguides with input/output grating couplers are of interest as they ofier multiple tuning parameters for the chip design and their high sensitivity. In the present paper, an algorithm based on the Finite-Elements Method (FEM) is proposed for flnding the chip response and optimizing the sensitivity of the sensor system. Total fleld and scattered fleld coupled with the Transmission Line Transfer Matrix Method (TLTMM) are compared for the FEM. Unlike some widely used approximations, the impact of the grating depth, shape, duty cycle as well as losses and surface roughness are taken into account. Another advantage of the presented method is the possibility to implement a large part of the algorithm with commercially available FEM solver. Several practical situations are treated proving the validity of the approach against the Local Interference Method (LIME). The waveguide losses appear to be a decisive parameter for the chip design.

TRANSMISSION LINE MODELING AND NUMERICAL SIMULASION FOR THE ANALYSIS AND OPTIMUM DESIGN OF METAMATERIAL MULTILAYER STRUCTURES

The transmission line transfer matrix method (TLTMM) is proposed for the analysis of planar multilayer metamaterial (MTM) structures, where a transmission line model is developed by the transfer matrix method. This novel method may consider any oblique incident plane wave at any angle of incidence, any linear polarization (TE or TM with respect to the incidence plane), circular and elliptical polarizations, any frequency range (microwave or optical frequencies), any number of layers, any combination of common materials (DPS) and MTMs (such as DNG, ENG, MNG), any layer thickness, consideration of any dispersion relations for e and μ, etc. A unified formulation is presented for both TE and TM polarizations, which lead to the evaluation of the fields and powers inside the layers and half spaces. The objective of the paper is to analyze and design several diverse problems of multilayered structures by TLTMM and a matrix method. The results of computations by TLTMM are agreed with the literature where possible and with the matrix method.

A switched high-Tc superconductor microstrip resonator using a MEM switch

We have used a high performance (less than 0.05 dB insertion loss, greater than 30 dB isolation) high-Tc superconductor based micro electromechanical (MEM) switch to insert a shunt microstrip resonator into a microstrip transmission line thus forming a ‘T’-resonator structure. This allows the insertion of a series of notches and peaks (depending on termination of the shunt line and the harmonic in use) into the transmission line's transfer function thus forming a rudimentary switched filter. The ‘T’-resonator is designed for a resonant frequency of 3.5 GHz and is implemented using high-Tc YBa2Cu3O7, BaTiO3 is used as a dielectric patch underneath a suspended gold membrane. The design, fabrication, testing and most recent results are presented in this paper.

Al/Ni And Al/Ti Ohmic Contact To P-type SiC Diffused Layer

ABSTRACTOhmic contacts to p-type SiC were fabricated by depositing Al/Ni and Al/Ti followed by high temperature annealing. A p-type layer was fabricated by Al or B diffusion from vapor phase into both p-type and n-type substrates. The thickness of the diffused layer was about 0.1–0.2 μm with surface carrier concentration of about 1.0×1019cm−3. Metal contacts to a p-type substrate with a background doping concentration of 1.2×1018cm−3, without a diffusion layer, were also formed. The values of specific contact resistance obtained by Circular Transmission Line Method (CTLM) and Transfer Length Method (TLM) for the n-type substrate, and by Cox &amp; Strack method for p-type substrate, respectively, varied from 1.3×10−4Ωcm2 to 8.8×10−3 Ωcm2. The results indicate that the specific contact resistance could be significantly reduced by creating a highly doped diffused surface layer.

Active transmission lines driving-point and transfer immittance parameters

In this paper, the driving-point and transfer immittance parameters and gain functions of uniform active transmission lines are derived and examined. The poles and zeros of these functions are identified and used to determine the sinusoidal steady-state characteristics of rcg active lines. Various approximations are introduced to interpret the results.