Capacitive Coupling

We present transport measurements on a lateral double dot produced by combining local anodic oxidation and electron beam lithography. We investigate the tunability of our device and demonstrate, that we can switch between capacitive and tunnel coupling. In the regime of capacitive coupling we observe the phenomenon of spin blockade in a magnetic field and analyze the influence of capacitive interdot coupling on this effect.

Aiming to introduce new directions to improve the performance of narrow-band power line communication (PLC) systems in low-voltage electric power grids, this study presents an active-based capacitive PLC coupling circuit for duplex communication. Simulations show that transmission and reflection parameters achieved good results while the Op-Amp provided a desired signal gain in the pass-band.

Universidade Federal do Rio de Janeiro, UFRJ DEDICAT ÓRIA À minha família e aos meus amigos. AGRADECIMENTOS À minha esposa Tereza e aos meus filhos Vinícius e Vitor pela paciência, incentivos e minhas ausências. À minha família, especialmente minha mãe, Maria Lúcia, e aos meus irmãos Cláudia, Carlos Augusto, Alexandre e Leonardo, por todo apoio, suporte, motivação e confiança depositada em mim. Ao meu orientador, Professor Moisés Vidal Ribeiro, pelos ensinamentos, incentivos e disposição durante todo o decorrer deste trabalho.

This paper introduces an analog notch filtering-based coupling circuit for receivers in ultra-narrowband and narrowband power line communication systems, which are connected to low-voltage electric power grids. It is composed of a twin-T notch analog filter, which is responsible for imposing a significant attenuation on the main frequency (i.e., f 0 ∈ {50, 60} Hz) in cascade with an elliptic low-pass analog filter, designed with a 3 dB cut-off frequency of f c f 0 . For f 0 = 60 Hz and f c = 2 MHz, the prototype of the analog notch filtering-based coupling circuit attains attenuation values of 22 dB and less than 2 dB at the main frequency and in the rest of the frequency bandwidth, respectively, when practical scenarios are considered. Lastly, it shows that the analog notch filteringbased coupling circuit is more effective than a typical capacitive coupling circuit when frequencies lower than 3 kHz are considered for data communication and sensing purposes.

Atualmente, ha um grande interesse no desenvolvimento de transceptores PLC (power line communication) para a transmissao banda larga e banda estreita de dados visando, sobretudo, aplicacoes smart grids e de acesso banda larga. Para o avanco da tecnologia PLC, ha grande demanda pela introducao de acopladores com caracteristicas e desempenhos que viabilizem a conexao dos tranceptores PLC `as redes de energia eletrica, com o minimo de distorcao possivel. Neste contexto, a presente contribuicao versa sobre o estudo, a investigacao, especificacao, projeto e analise de acopladores capacitados para transceptores PLC SISO (single input single output) banda larga e banda estreita. Para tanto, sao introduzidos acopladores PLC nas seguintes faixas de frequencias: de 9 kHz `a 2 MHz, de 1,7 MHz `a 100 MHz e de 1,7 MHz `a 150 MHz. As analises dos projetos e dos prototipos dos acopladores, concebidos para operar nas referidas bandas, mostram as dificuldades encontradas para garantir que as especifica...

Scaling the minimum feature size of VLSI circuits to sub-quarter micron and the clock frequency to 2GHz has caused the crosstalk noise to become a serious problem, degrading the performance and reliability of high speed integrated circuits. This paper presents an efficient method for computing the capacitive crosstalk in sub-quarter micron VLSI circuits. In particular, we provide closed-form expressions for the peak amplitude, the pulse width, and the time-domain waveform of the crosstalk noise. Experiments show that our analytical predictions are at least two times better than the previous models in terms of the prediction accuracy. More precisely, experimental results show that the maximum error of our predictions is less than 10% while the average error is only 4%. Finally, based on the proposed analytical models, we discuss the effects of transistor sizing and buffering on crosstalk noise reduction in VLSI circuits.

Requirements for patient safety and a high interference rejection ratio in medical equipment create a demand for effective isolation devices. A system scale approach that uses capacitive coupling for power and signal isolation is presented. In addition, we describe the development of an instrumentation system prototype that applies microwaves for power exchange and bidirectional data transfer across the isolation barrier. The system consists of an isolated transducer unit, a central unit, and a single coaxial cable between the units. The isolation capacitance is as low as 1.6 pF, inclusive of the digital data transfer and power exchange up to 600 mW of isolated direct current (dc) power. The system is suitable for line-powered biopotential measurements and it is shown that reducing the isolation capacitance from 180 to 1.6 pF improves the power line rejection by 30 dB in a typical electrocardiogram (ECG) measurement setup.

This paper presents the design of a broadband planar inverted-F antenna whose geometry splits the top (radiating plate), short, ground, and capacitive feed plates into two parts. The proposed geometry together with the capacitive-feed technique make it possible to achieve both measured-pattern and impedance bandwidths of about 52.44% (1.66 GHz-2.84 GHz) and 8% (3.36 GHz-3.64 GHz) for VSWR ≤ 2.0. These values are larger than the bandwidth obtained using a traditional wire-fed PIFA or other capacitive feeding techniques. A constructed prototype is enough to simultaneously cover various frequency bands, namely DCS 1800, DCS 1900, UMTS, Wi-Fi, 2.4GHz, WiMAX (2.3-2.5 GHz; 3.4-3.5 GHz), and Bluetooth. Radiation patterns are reasonably omni-directional throughout the whole operating bandwidth.

An architecture of a quadruplet for the realization of inductive waveguide filters, in which the bypass coupling of the two central cavities is inductive, instead of the more classical capacitive solution, is proposed. This arrangement is quite handy because it makes easier the realization of very weak couplings, as those required in such schemes, without the need of expensive solutions. At the same time, one capacitive coupling is used to couple two electrically adjacent cavities of the quadruplet, possibly the more external ones, so that the coupling is large enough to be effectively implemented.

This study describes geometric characteristics of a nonvolatile memory (NVM) device with a designed chromium (Cr) nanocrystal (NC) floating gate. By using a block copolymer (BCP) nanotemplate as a mask layer, cone-shaped NCs and disc-shaped NCs were formed. It was found that the NVM device using the cone-shaped NC had a better program efficiency than that of the device using the disc-shaped one. This trend was verified by a theoretical model, which considered an effect of the capacitive-coupling ratio between a control gate and a NC floating gate. Index Terms -Nonvolatile memories (NVM), nanocrystal (NC), geometric effect, block copolymer (BCP) nanotemplate, modeling, capacitive-coupling ratio.

Surface acoustic delay lines patterned on lithium tantalate piezoelectric substrate propagating a guided shear wave is demonstrated for direct detection chemical sensing in aqueous solutions with no need for additional microfluidic handling. The high dielectric permittivity substrate prevents excessive losses from capacitive coupling with water when dipping the whole chip, including interdigitated electrodes, in water, while the shear wave only couples with the first few hundred nanometers of the adsorbed layer. A measurement of non-specific protein detection demonstrates the principle.

This paper reviews the techniques for optimization switching frequency used in Wireless power transfer (WPT). WPT is one of the most useful ways to transfer power. Based on distances power transfer, the WPT system can be divided into three categories, namely, near, medium, and far fields. Inductive coupling and capacitive coupling contactless techniques are used in the near-field WPT. Magnetic resonant coupling technique is used in the medium-field WPT. Electromagnetic radiation is used in the far-field WPT. From the comparison in this paper, a model and design algorithm to optimize switching frequency for energy encryption of medium field wireless power transfer system are purposed. The maximum value of the performance are suitable to compute the optimal circuit parameter by algorithm itself.

We describe measurements of plasma properties of pulsed, low pressure, capacitively coupled discharges operated in argon. The research aims to determine the effect of modulating the radiofrequency power during the discharge part of the pulse cycle. Measurements of local electron density and optical emission were made in capacitively-coupled rf discharges generated in a Gaseous Electronics Conference (GEC) reference reactor. Gas pressure was in the range 7-70 Pa, rf power in the range 1-100 W and pulse durations in the range of 10 µs-100 ms. The results indicate that the ignition and afterglow decay processes in pulsed discharges can be controlled by modulating the shape of applied radiofrequency pulse.

This paper outlines the state of the art in the field of AC interference assessment on buried metallic pipelines. In particular, the attention is on pipelines that are located close to high voltage transmission-lines. Due to both the complexity and hazard of AC interference caused by overhead power-lines on metallic buried pipelines, there is an industrial need for reliable simulation software able to provide capabilities for predicting and possibly mitigating coupled voltages on these structures. This electromagnetic interference is present during both normal operating conditions and faults, and it generally consists of an inductive, a conductive, and a capacitive contribution. In particular, the focus of this paper is on the inductive coupling mechanism, but the other two are still discussed. Furthermore, the main risks for equipment and personnel are highlighted, in order to clarify the pivotal importance of performing an accurate analysis of these effects. The two main methods that were used over the course of the years to investigate this topic are described, starting from the circuital analysis. Afterwards, the main physical assumptions are discussed and the field theory is introduced, reporting the main pros and cons compared to the previous approach.

Instruments for large 10 meter class telescopes increasingly require high sensitivity large format focal planes. The high spatial resolution achieved with adaptive optics combined with multiple integral field units feeding high resolution spectrographs are driving the pixel performance and require large detector formats. In the infrared spectral range the array formats have arrived at 2Kx2K pixels with both LPE and MBE grown HgCdTe on CdZnTe substrates. In the optical, fully depleted Si-PIN diodes of the same format are used. The light sensitive diode arrays are hybridized to CMOS FET switched multiplexers such as the Hawaii-2RG array, which has recently been installed in one of the infrared instruments of the Very Large telescope VLT. Basic performance characteristics of the Hawaii-2RG arrays will be discussed such as the noise performance when a special technique of using reference pixels is employed. Larger focal planes are realized as mosaics of 2Kx2K arrays. In order to increase the format of single arrays to 4Kx4K and larger, the limited substrate sizes makes it necessary to reduce the pixel size. However, with smaller pixels the coupling between pixels becomes a limiting factor for the detector point spread function. Fundamental calibration issues relevant to photon transfer techniques of modern CMOS active pixel sensors with special regard to the influence of inter-pixel coupling capacitances will be analyzed in detail. A novel technique will be presented to directly measure the point spread function generated by the capacitive coupling between adjacent pixels.

In this paper we propose a dynamic noise model to verify functional failures due to crosstalk in high-speed circuits. Conventional DC noise analysis produces pessimistic results because it ignores the fact that a gate acts as a low-pass filter. In contrast, the dynamic noise model considers the temporal property of a noise waveform and analyzes its effect on functionality. In this model, both capacitive and inductive coupling are considered as the dominant source of noise in high-speed deep-submicron circuits. It is observed that in the case of the local interconnects (where wire lengths are short), the effect of inductive coupling is small; however, for long interconnects this effect may be considerable. Based on this noise model, we have developed an algorithm to verify high-speed circuits for functional failures due to crosstalk. Design of a 4-bit precharge-evaluate full adder circuit is verified, and many nodes which are susceptible to crosstalk noise are identified. It is observed and further verified by SPICE simulation that dynamic noise analysis is more realistic for verifying functional failures due to crosstalk than DC noise analysis.

A study of the impedance and noise of an integrated poly-silicon resistor with distributed capacitive coupling to bulk is presented. The system is analyzed by using a closed-form calculus which produces non approximated results. In particular, deviations from ideal conditions are shown when that kind of resistor is used as a continuous-discharge feedback device for charge-sensitive preamplifiers. The effect of using a feedback resistor with capacitive coupling to bulk is an evident deformation of the shape of the signals. An innovative technique is presented, which allows overcoming the problem of the distortions in the CSP output signals. Several n-wells are placed under the resistor and driven with an auxiliary low-impedance divider which minimizes the voltage variations on the plates of the parasitic capacitors. In this way the pulses provided by the charge-sensitive preamplifiers show again a clean R-C exponential-decay shape and are so optimized for signal shaping and adequate for high-resolution spectroscopy.

constructed a tissue model out of fresh round steak to simulate the uterus, contiguous posterior vaginal wall, and introitus. 1 He used a Storz 50 series (Karl Storz GmbH & Co., Tuttlingen, Germany) resectoscope to simulate the clinical procedure of hysteroscopic endometrial ablation using variable sizes of rollerballs and variable waveforms and power outputs. The model was not perfused with an irrigant solution. Based on the above model, Dr. Munro was able to cause visible blanching (burns) to the surrogate cervical, vaginal, and perineal tissue. He concluded: "The incidence of vaginal and perineal burns associated with unipolar radiofrequency (RF) resectoscopes can likely be minimized by careful attention to technique." Dr. Munro's conclusion implies that all such burns are due to bad technique used by the surgeon. Using a bad technique, of course, implies breach of the standard of care and negligence on the part of the surgeon. However, when one reads the Results section of Dr. Munro's experiment, the above conclusion cannot be supported. To the contrary, the surgical technique is totally absolved. Specifically, Dr. Munro describes 3 prerequisites for vaginal burns to occur. These are: (1) a proximal electrode insulation defect; (2) cervical overdilation; and (3) less than 2 cm of the external sheath of the resectoscope in the cervical canal. Furthermore, Dr. Munro noted that "there was greater risk with larger electrode insulation defects, and there was a greater degree of coupling and injury with high-voltage outputs." It is generally accepted that injuries occur due to 1 or a combination of 3 things: (1) bad technique; (2) faulty technology; and (3) an accident not attributable to either one. Dr. Munro concluded that genital tract burns occur due to a bad technique when his findings clearly indicate that they are due to faulty technology.

This study describes the design and performance of a discrete ultra wideband GaN HEMT distributed power amplifier (DPA) with over 5 W (37 dBm) output power and a PAE exceeding 27% in the 0.02-3 GHz frequency range. The implemented DPA design is comprised of three discrete GaN HEMT devices. Its performance was enhanced using tapered drain lines and non-uniform gate capacitive coupling. The design methodology is based on both small and large signal analysis using harmonic balance technique, and their associated predicted and experimental results are discussed here in detail.

Rapid, efficient and robust methods for sampling and extracting genuine nerve agents sarin, soman and VX were developed for analyzing these compounds on various solid matrices, such as concrete, tile, soil and vegetation. A portable capillary electrophoretic (CE) system with contactless conductometric detection was used for the in situ analysis of the extracted samples. A 7.5 mM MES/HIS-based separation electrolyte accomplished the analysis of target analytes in less than 5 min. The overall duration of the process including instrument start-up, sample extraction and analysis was less than 10 min, which is the fastest screening of nerve agents achieved with liquid phase separation methods to date. The procedure can easily be performed by a person in a protective suit and is therefore suitable for real-life applications. The CE results were validated by an independent GC-MS method and a satisfactory correlation was obtained. The use of a proper sampling strategy with two internal standards and "smart" data-processing software can overcome the low reproducibility of CE. This has a significant impact on the potential acceptance of portable CE instrumentation for the detection and analysis of genuine chemical warfare agents (CWA).

We study the influence of a tunable dissipative environment on the dynamics of Josephson junction arrays near the superconductor-insulator transition. The experimental realization of the environment is a two dimensional electron gas coupled capacitively to the array. This setup allows for the well-controlled tuning of the dissipation by changing the resistance of the two dimensional electron gas. The capacitive coupling cuts off the dissipation at low frequencies. We determine the phase diagram and calculate the temperature and dissipation dependence of the array conductivity. We find good agreement with recent experimental results.

Capacitive technology for wireless power transmission has been shown to be a good option for charging the batteries of electric vehicles. It offers better coupling between the transmitter and the receiver than inductive power transmission. On the other hand, it has some disadvantages; for example, it is very sensitive to the distance between plates. Several ideas have recently been proposed to overcome this disadvantage. However, a proper analysis methodology is still lacking, as is a proper design procedure for the circuits used in capacitive transmission. In this paper, an analysis and design methodology is presented for applying the Z-tank resonant circuit to capacitive power transmission, and the theoretical design methodology is based on normalized equations with respect to the operating resonance frequency. The analysis methodology and design procedure result in a circuit where the resonance frequency remains constant despite changes in the distance between the capacitive plat...

Ultra-broad-band star mixers using planar Mouw's hybrid junction [1] are presented in this paper. The planar Mouw's hybrid junction is realized by coplanar waveguide (CPW) to coplanar strip (CPS) or CPW to CPW T-junctions. A new explanation of Mouw's theory based on coupled transmission lines and including the transmission line losses is presented. The modified theory is more suitable for ultra-broad-band mixer design. Some prototype mixers with CPW to CPS or CPW to CPW T-junctions are fabricated with Al 2 O 3 substrate. The prototype mixers show a bandwidth of greater than 20 : 1 if the even-mode resonance has been damped out. Method for damping out the even-mode resonance is also presented. All of the prototype circuits show much broader bandwidth than that of conventional star mixer.

This contribution presents a Distributed MEMS Transmission Line (DMTL) phase shifter for the 24 GHz ISM band fabricated in silicon bulk technology. Using this technology enables the suspension of all capacitive loads on one movable plate and therefore allows wide range analog and homogeneous tuning. To avoid commonly used metallic feed-throughs for signal connection, an electromagnetic signal coupler guides the microwave signal non-galvanically from printed circuit board level, through the chip substrate into the MEMS device. The first available prototypes of the phase shifter are characterized to provide 50°/dB loss normalized differential phase shift at 24 GHz. The achievable normalized insertion loss of the coupling structure has been determined with 0.13-0.17 dB.

This study describes geometric characteristics of a nonvolatile memory (NVM) device with a designed chromium (Cr) nanocrystal (NC) floating gate. By using a block copolymer (BCP) nanotemplate as a mask layer, cone-shaped NCs and disc-shaped NCs were formed. It was found that the NVM device using the cone-shaped NC had a better program efficiency than that of the device using the disc-shaped one. This trend was verified by a theoretical model, which considered an effect of the capacitive-coupling ratio between a control gate and a NC floating gate. Index Terms-Nonvolatile memories (NVM), nanocrystal (NC), geometric effect, block copolymer (BCP) nanotemplate, modeling, capacitive-coupling ratio.

This paper presents an accurate method to evaluate the capacitances of multi-conductor power cables. The method developed can also be applied to cables presenting multilayer dielectrics. Strips of charge are used to represent the electric charge distribution on conductors' surface, as well as to characterize the polarization charge distribution on interfaces separating two different dielectrics. The advantage of using strips of charge is to preserve charge continuity along conductor surfaces and dielectric interfaces. This methodology is accurate since the proximity effects among conductors are taken into account. Validation of the method is performed comparing experimental, other software and analytical results with those obtained by using the proposed numerical method. A cylindrical non-concentric capacitor is used for the analytical validation and a three-phase power cable is used on experimental tests.

Cases of close proximity of high voltage transmission lines and metallic pipelines become more and more frequent in high population density regions. Therefore, there is a growing concern about possible hazards resulting from the influence of electrical systems: safety of people making contact with the pipeline, damage to the pipeline and CP equipment. Hence it is not surprising that there is an industrial need for mitigating AC interference. This paper will discuss capabilities of a software tool to predict AC currents and voltages induced on metallic structures near AC power lines by electromagnetic induction, and resistive coupling effects. Situations can be studied under normal operational conditions as well as for the occurrence of fault currents. Most available computer programs limit the modeling capabilities to parallel or near parallel geometries. In addition, most of them are restricted in the number of pipelines, transmission lines and (direct) bonds that can be modeled. This is a serious restriction since in many corridors a large number of pipelines are bonded together, e.g. for cathodic protection purposes. Furthermore, handling of the software can be cumbersome and time-consuming (e.g. manual adding of routings versus being able to read in GPS coordinates) and requires a computer expert rather than a CP engineer to be able to work with it. For this reason the number of simulations done (especially in the mitigation case for fault currents) is most often very limited due to time and budget restrictions. Given the complexity of the problems dealt with nowadays it is easy to understand that this can have a negative impact on the final design since not all possible scenarios have been accounted for. In this article a software that is linked to the customers asset database will be presented. The software directly converts the complete routing in a numerical model directly taking into account all geometrical and electrical properties. An automated fault current module that faults each individual tower of all power lines allows taking into account all possible scenarios in the mitigation design. It will be demonstrated how field data are used to update the model with realistic coating values and how the model can be used to find anomalies in the input data. Secondly, the effect of different operating scenarios is studied in order to predict mitigation for safe operation conditions.

The voltages induced on gas transmission pipelines by 60 Hz ac power transmission lines sharing a joint right-of-way are predicted using electrical transmission line theory. Thevenin equivalent circuits for pipeline sections are developed which allow the decomposition of complex pipeline-power line geometries. Programmable hand calculator techniques are used to determine inducing fields, pipeline characteristics, and Thevenin circuits.

Considering the massive development that took place in the past two decades, wireless power transfer has yet to show the applicability to be used due to several factors. This work focuses on determining the main parameters like, mutual inductance, and coupling coefficient for a pair of helical coils for wireless power transfer applications. These parameters are important in designing and analyzing a wireless power transfer system based on the phenomenon of inductive/ resonant inductive coupling. Here presents a simple approach based on fundamental laws of physics for determining the coupled coil parameters for single layered helical coils. The results conducted by computer simulation which is MATLAB. Furthermore, this analysis is used to study the effect of change in coil diameter, mutual inductance coefficient and change in distance between coils on parameters like self and mutual inductance of coupled coils which is of great importance in Wireless Power Transfer applications. The r...

This paper presents the design of a wideband low noise amplifier (LNA) for the 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) standard. The proposed LNA uses a common gate topology with a noise cancellation technique for wideband (0.7 to 2.7 GHz) and low noise operation. The capacitive cross coupling technique is adopted for the common gate amplifier. Consequently input matching is achieved with lower transconductance, thereby reducing the power consumption and noise contribution. The LNA is designed in a 0.18 μm process and the simulations show lower than −10 dB input return loss (S11), and 2.4∼2.6 dB noise figure (NF) over the entire operating band (0.7∼2.7 GHz) while drawing 9 mA from a 1.8 V supply.

Kilohertz Frequency Alternating Current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current-and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage-and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms.

Problem 1: D Flip-Flop Characterization a. Is the circuit in Figure P1.2 positive or negative edge-triggered DFF? Describe its functionality using appropriate waveforms on nodes D, Q, and CLK (specify the clock frequency). The circuit shown in Figure P1.2 is a positive edge-triggered D flip-flop. Its functionality is as follows: • The Q output only changes values on the positive (rising) edge of the clock signal CLK. • When the positive clock edge occurs, the value of the D input is transferred to the Q output after the clock-to-output delay time Tclk-to-q.

AbrtractA method is presented, by which a Finite Element Method (FEM) formulation is used for the direct computation of overhead transmission line series and sequence impedances. The method is applied in single and dnuhle circuit line configurations of arbitrary geometry, giving results in perfect ugreement with those available from classical calculation methods. The new method can easily handle cases of nonhnmngenous and/or irregular terrain, where classical methods may fail.

Considering the massive development that took place in the past two decades, wireless power transfer has yet to show the applicability to be used due to several factors. This work focuses on determining the main parameters like, mutual inductance, and coupling coefficient for a pair of helical coils for wireless power transfer applications. These parameters are important in designing and analyzing a wireless power transfer system based on the phenomenon of inductive/ resonant inductive coupling. Here presents a simple approach based on fundamental laws of physics for determining the coupled coil parameters for single layered helical coils. The results conducted by computer simulation which is MATLAB. Furthermore, this analysis is used to study the effect of change in coil diameter, mutual inductance coefficient and change in distance between coils on parameters like self and mutual inductance of coupled coils which is of great importance in Wireless Power Transfer applications. The r...

The Josephson junction phase qubit has been shown to be a viable candidate for quantum computation. The two coupled phase qubit system has been extensively studied theoretically and experimentally. We have analyzed the quantum behavior of systems with more, three and four capacitively-coupled phase qubits, with different possible configurations. We have used anharmonic oscillators to model the systems. We will

AbrtractA method is presented, by which a Finite Element Method (FEM) formulation is used for the direct computation of overhead transmission line series and sequence impedances. The method is applied in single and dnuhle circuit line configurations of arbitrary geometry, giving results in perfect ugreement with those available from classical calculation methods. The new method can easily handle cases of nonhnmngenous and/or irregular terrain, where classical methods may fail.

A general formulation for the determination of the influence of imperfect earth on overhead transmission line impedances and admittances is presented in this paper. The resulting model can be used in the simulation of electromagnetic transients in cases of two-layer earth over a wide frequency range, covering most fast transient phenomena of power engineering interest. The propagation characteristics of an overhead transmission line over homogeneous and two-layer earth are investigated using the proposed model. A systematic comparison of the proposed model with other approaches is also presented and the differences due to earth stratification are reported. Finally, the transmission line parameters calculated by the proposed formulation are used in the simulation of fast transient surges in a transmission line excited by double exponential sources.

Kilohertz Frequency Alternating Current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current-and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage-and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms.