Length Of Transmission Line Research Articles

Design of an extremely miniaturized branch-line coupler

In this paper, a new size-reduction approach for branch-line coupler is introduced which uses parallel end-shorted coupled lines with lumped capacitors. The characteristic of the new design was analyzed using even-odd mode method, and simulated on HFSS before fabricated on the FR4 epoxy glass cloth copper-clad plat (CCL) PCB substrate at center frequency of 1 GHz. The electrical length of transmission line was reduced to 15 degrees, therefore the size of branch-line coupler was largely reduced approximately maintaining the same characteristic around the stable center frequency. The insertion loss of the branch-line coupler filter was ?4.39 dB. The size of the overall hybrid is 20 mm × 20 mm. Measurements results were well agreed with the simulated ones.

최소 위상 오차를 갖는 곡선 배열안테나용 Rotman 렌즈의 설계

컨포멀 배열에 적용할 수 있는 곡선 배열안테나용 Rotman 렌즈의 설계 방법을 제안한다. 본 논문에서는 곡선 배열안테나와 연동하여 Rotman 렌즈의 평행판 영역에 존재하는 배열 포트의 위치와, 배열 포트와 배열안테나 소자를 연결하는 전송선의 길이를 구하는 설계식을 유도하고, 이 설계식을 바탕으로 빔 곡선 최적화 절차와 재초점 절차를 통하여 위상 오차를 최소화하고 있다. 제안된 설계식과 설계 절차에 의해 설계된 Rotman 렌즈는 정확히 3초점을 보유한 채 직선 배열안테나뿐만 아니라, 원곡선, 포물선, V자형 곡선 등의 오목하거나 볼록한 배열안테나를 급전할 수 있으며, 최소의 위상 오차를 나타내고 있다. We propose a design method of a Rotman lens for curved array antenna applicable to conformal array. In this paper, design equations are derived to obtain an array curve, transmission line lengths of a Rotman lens in conjunction with a curved array antenna, and the phase error of a Rotman lens based on these design equations is minimized through the beam curve optimization procedure and the refocusing procedure. Rotman lenses designed by the proposed design equations and design procedures still maintain 3 focal points, can feed a convex or concave array antenna with circular curve, parabolic curve, V-shaped curve, etc as well as a straight line array antenna, and have minimal phase error.

Increasing On-Shore Wind Generated Electricity in Germany's Transmission Grid

An increase in the penetration of renewables generated electricity has technical and economic impacts on power transmission systems because of the renewables' variable characteristics. However, due to concerns of energy security, operational information of power infrastructure is scarce, making it challenging for policy-makers and independent power producers to assess these systems for the development of new energy projects. This paper presents an analysis of Germany's power generation and transmission infrastructure using integrated, geographically indexed production, demand. and grid models. The paper assesses the impact of growth of renewables on Germany's grid in a scenario of slow growth of grid infrastructure to show that the length of transmission lines needing reinforcement increases from 650 km in 2011 to 1090 km in 2020, if Germany's transmission grid is to keep pace with the increased penetration of renewable energy. Mesoscale model simulations of the weather are used in the year 2020 scenario to assess the economic development of the competing renewables—wind and solar—in relation to the available grid capacity. It is shown that if the grid development lags the development of then targeted 35% renewables portfolio, then 6.5% of generated power by wind and solar energy will face risk of curtailment.

Power-Line Communication Channel Characteristics Under Transient Model

This paper discusses the channel gain characteristics of a two-conductor power-line communication system under a given transient analytical model. The channel frequency responses are derived with different transmission-line lengths and terminal loads. Compared with previous works on power-line communication, the transient model can more accurately describe the variation of the channel frequency responses, especially when transients occur on the transmission line. Simulation results show higher accuracy is achieved compared with the results under the traditional lumped-circuit π model.

A Compact Gysel Power Divider With Unequal Power-Dividing Ratio Using One Resistor

A novel compact Gysel power divider is proposed and investigated in this paper. The proposed power divider consists of two transmission lines, a pair of coupled lines, and only one grounded resistor for unequal power-dividing ratio. Comparing to the conventional Gysel power divider, the new power divider saves its space by eliminating the 180 ° electrical length transmission line and reduces complicity by using one grounded resistor. The flexibility in choosing the value of the resistor provides favorable freedom in circuit realization. In addition, analytic design formulas of the proposed power divider, for both equal and unequal ratio cases, are given. For the equal radio case, two grounded resistors are required. Two prototype power dividers are simulated, fabricated, and measured. Both prototypes operate at 2 GHz, but with different power divisions, one for power division ratio k = 1 and the other for k = 2. There are good correlation between the measured results and those of the theoretically designed, justifying the circuit configuration and the design theory.

Effect of Transmission Line on Impedance Matching of Atmospheric-Pressure Radio-Frequency Capacitive Microplasma Discharge

In this paper, it is found that the coaxial transmission line between the matching box and the plasma reactor plays an important role in impedance matching of atmospheric-pressure radio-frequency capacitively coupled microplasma discharge characterized by very low capacitance value. The high output voltage across reactor terminal is generated when the external circuit is operating in resonant state driven by power supply. The experimental results show that coaxial transmission line exhibits capacitive characteristics within the working frequency range and its capacitance increases linearly with the length of the transmission lines; the resonant frequency and voltage across the terminal reactor decrease with the length of coaxial transmission line.

가유전체 기판을 이용한 소형화된 링 하이브리드 커플러의 설계

본 논문에서는 가유전체 기판을 이용하여 소형화한 마이크로파 대역의 링 하이브리드 커플러 설계에 대하여 기술한다. 가유전체 기판은 다수의 비어홀을 제 2기판에 삽입하여 유효 커패시턴스를 크게 증가시킨 구조를 갖는다. 가유전체 기판의 유효유전율은 표준형 기판에 비하여 크게 증가하게 되는데, 이에 의하여 동일한 전기적 길이 대비 물리적 길이가 크게 감소하므로 마이크로파 전송선로를 소형화시킬 수 있다. 이런 원리를 마이크로파 무선회로 설계에 적용한 사례를 보이기 위하여 가유전체 기판을 이용하여 3GHz대 링 하이브리드 커플러를 설계하고 실제로 제작 및 측정한 결과를 제시한다. 설계된 소형화된 링 하이브리드 커플러는 표준형에 비하여 전기적 성능은 유사하면서도 65%의 크기를 가진다. 측정된 전력분배비는 각각 -3.05dB와 -3.135dB이며, 두 출력간의 위상차는 동위상일 때 3도, 역위상일 때 176도로 이상적인 값과 매우 유사하다. 이로써 가유전체 기판구조로 소형화된 링 하이브리드 커플러의 설계가 타당함을 보인다. This paper describes the design of a size-reduced ring hybrid coupler for microwave band using an artificial dielectric substrate(ADS). ADS structure adopts the second substrate on which has lots of the metalized via-holes. The effective capacitance and effective dielectric constant per unit length of ADS increases compared to the normal substrate due to the via-holes. This enables the physical length of microstrip transmission line to be reduced by adopting ADS instead of the normal substrate. In order to present an example of size-reduction of microwave wireless circuit by ADS, a size-reduced 3GHz ring hybrid coupler is designed, fabricated and measured in this work. The designed coupler has the smaller size from the normal one by 65% due to the ADS, while no critical degradation from ideal performances is observed. The measured power division ratio at two output ports are -3.05dB and -3.135dB, respectively. In addition, the phase differences are 3o for in-phase division and 176o for out of phase split. The measured performances are so similar to ideal ones, and prove the design of size-reduced ring hybrid coupler using ADS is successful.

HTS DC Transmission Line for Megalopolis Grid Development

Using of HTS AC and DC cables in electric power grids allows increasing of the transferred power, losses diminishing, decreasing of exclusion zone areas, the enhancement of the environmental conditions and fire/explosion safety of electric power systems. However, the use of DC superconducting cable lines together with converters brings additional advantages as reduction of losses in cables and suitable lowering of refrigerating plant capacity, as well as the realization of the function of short-circuit currents limitation by means of the appropriate setting of converter equipment. Russian Federal Grid Company and its R&D Center started the construction of the DC HTS power transmission line which includes the cable itself, cryogenic equipment, AC/DC converters, terminals and cable coupling boxes. This line will connect two substations in Saint-Petersburg – 330 kV "Centralnaya" and 220 kV "RP-9". The length of this HTS transmission line will be about 2500 meters. Nowadays are developed all the elements of the line and technologies of the cable manufacturing. Two HTS cable samples, each 30 m length, have been made. This paper describes the results of cables tests.

An algorithm based on traveling waves for transmission line protection in a TCSC environment

This paper describes a new relaying algorithm for the protection of transmission lines with a Thyristor Controlled Series Compensator (TCSC). The algorithm is based on the pattern of traveling waves generated during a fault event. Several tools like modal analysis, the discrete wavelet transform and a probabilistic neural network trained to work with the energy contained in the wavelet transform coefficients are applied to analyze the high frequency pattern generated during the fault. The proposed algorithm is capable of detecting, locating and classifying faults in a reliable way. The impact of harmonic frequencies generated by the TCSC in the protection algorithm was also analyzed. Several studies were carried out in order to validate and to assess the effect of several fault parameters on the algorithm accuracy. The obtained results show that for a sampling rate of 100kHz, the algorithm error in calculating the distance to the fault is less than one percent of the total transmission line length. A higher sampling rate improves the algorithm accuracy.

High Precision Synthesis of a Richards Immittance Via Parametric Approach

A Richards immitance is a positive real function expressed in terms of the Richards variable λ = tanh(pτ) = Σ+jΩ where p=σ+jω is the classical complex frequency. A Richards immittance can be synthesized as a lossless two port terminated in a resistance as in Darlington's synthesis such that the two-port consists of commensurate transmission lines. In this paper, a high precision method is presented to synthesize a Richards immittance as a lossless two-port constructed with cascade connections of equal length transmission lines, as well as short and open stubs. The new method of synthesis utilizes Bode procedure (or Parametric Method) to correct an immitance function specified in the complex Richards variable λ at each step of the synthesis. It is verified that new technique can synthesize a randomly generated Richards immitance function yielding 25 commensurate lines with the accumulated numerical error less than 10-3. A complete synthesis package is developed in MatLab and successfully integrated with the Real Frequency Technique to design broadband matching networks. Examples are presented to show the merits of the new Richards synthesis tool.

Design and Analysis of Microstrip-Based RF Birdcage Coil for 1.5 T Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) technique is widely used to capture the images of the liquid items inside the human body. The radio-frequency (RF) coil is one of the important modules present inside an MRI system, which plays a major role in image quality. In this work, a microstrip-based high-pass RF birdcage coil is proposed for 1.5 T MRI. The cylindrical-shaped birdcage coil consists of 12 microstrip radiating elements and tuning capacitors to achieve a resonance at 63.85 MHz. The coil is made up of 10 mm polytetrafluoroethylene substrate coated by a conducting transmission line of desired length and width. A finite difference time domain simulation is carried out to analyze the return loss (S11), magnetic field homogeneity and Specific Absorption Rate (SAR) parameters of the RF coil. The SAR values of the proposed microstrip-based 1.5 T birdcage coil was compared with 3 T RF birdcage coil. The simulation results indicate the proposed birdcage coil structure gives optimal values of S11, magnetic field homogeneity and SAR.

Detection of Fault in a 400 kV Transmission Line Using EMTP and ANN Method

Power transmission and distribution networks are important for the supply of quality power to the consumers. The rating of the protective device and the co-ordination play a vital role in improving the power quality in Electrical power systems. Since, generating stations exists far away from the load centers and the transmission lines have to run over long distances, the probability of occurrence of faults in transmission lines are very high. Due to such line faults, the system gets destabilized and requires immediate isolation. Therefore, fault analysis is very critical and essential issue in electrical power system with regard to fault clearance and power supply restoration with minimum interruption. In order to detect fault in transmission line, simulation of fault conditions has been carried out by dividing the total length of transmission line into large number of π sections. The π section comprises the series inductance and resistance of line and capacitance to ground. Single phase, double phase and three phase to ground faults are simulated at various distance from generator transformer and fault currents are calculated using electromagnetic transient programme (EMTP). Fault currents are also calculated by simulating faults at different points on wave to account for randomness of fault occurrence. Various time ~ current characteristics are used to train neural network and tested for detecting a specific fault using the untrained data of several faults at other distances. A comparison was made for efficiency of fault detection between time domain and frequency domain data. The neural network calculation was extended to currents determined from point- on wave switching for fault simulation

Realization of Multi-Band 3-dB Branch-Line Couplers Using Fourier-Based Transmission Line Profiles

A new procedure for the design of multi-band branch-line couplers utilizing microstrip non-uniform transmission lines with Fourier-based profiles is presented in this article. The general method is accomplished by replacing the quarter-wave uniform transmission lines of a conventional coupler with multi-band non-uniform transmission lines of the same lengths, without including additional transmission lines or matching networks. The design of non-uniform transmission line couplers is performed using even- and odd-mode analysis. The proposed structure is relatively simple and is fabricated on a single-layered microstrip board. Two design examples of dual- and triple-band branch-line couplers suitable for global system mobile (GSM), wireless local area networks, and WiFi communications are designed, fabricated, and experimentally evaluated to validate the proposed methodology.

Architecture of the Florida power grid as a complex network

We study the Florida high-voltage power grid as a technological network embedded in space. Measurements of geographical lengths of transmission lines, the mixing of generators and loads, the weighted clustering coefficient, as well as the organization of edge conductance weights show a complex architecture quite different from random-graph models usually considered. In particular, we introduce a parametrized mixing matrix to characterize the mixing pattern of generators and loads in the Florida Grid, which is intermediate between the random mixing case and the semi-bipartite case where generator–generator transmission lines are forbidden. Our observations motivate an investigation of optimization (design) principles leading to the structural organization of power grids. We thus propose two network optimization models for the Florida Grid as a case study. Our results show that the Florida Grid is optimized not only by reducing the construction cost (measured by the total length of power lines), but also through reducing the total pairwise edge resistance in the grid, which increases the robustness of power transmission between generators and loads against random line failures. We then embed our models in spatial areas of different aspect ratios and study how this geometric factor affects the network structure, as well as the box-counting fractal dimension of the grids generated by our models.

ANALYSIS OF EXCITATION PULSED SIGNAL PROPAGATION FOR ATOM PROBE TOMOGRAPHY SYSTEM

The purpose of this paper is on the behavioral modelling of surge voltage pulses used in Atom Probe Tomography. After brief description of the atom probe functioning principle, we examine the excitation electrical pulse signal integrity along the electric pulser (E-pulser) feeding line modelling with respect to the IEC1733/04 standard. This feeding electric line is ended by cylindrical via ground to control the ion emission. By using the transmission line (TL) ultra-broadband RLCG model, the propagating pulsed signals degradation is predicted. The signal propagation was analysed in both frequency and time domains by taking into account the substrate dispersion. The wideband frequency behaviours of the surge signal along the feeding line were examined from DC-to-2GHz. In addition, by considering pulse surge signals with pulse-width and rise-/fall-time parameters (T1 = 9ns, tr1 = tf1 = 1:6ns) and (T2 = 30ns, tr2 = 4ns/tf2 = 18ns), the transient responses from 5cm-to- 20cm length TL are characterized. It was shown that the excitation pulse was signiflcantly distorted. It was emphasized that the operated signal delay varies from 0.3ns-to-1.5ns in function of the via capacitor value. The time-dependent radiated E-fleld on the performance of the atom probe system which enables to characterize the nature of tested materials (ions or atoms) is discussed. The presented analysis approach is particularly useful for E-pulser integrated in measurement scientiflc instruments as Atom Probe Tomography time of ∞ight optimisation, a nano-analysing technique that uses ultra-sharp high vacuum pulse to induce controlled erosion of samples. In this application, the excitation voltage pulse integrity during the propagation is required in order to improve the measurement instrument performances.

New Versions of Terahertz Radiation Sources for Dynamic Nuclear Polarization in Nuclear Magnetic Resonance Spectroscopy

Dynamic nuclear polarization in strong-field nuclear magnetic resonance (NMR) spectroscopy requires terahertz radiation with moderate power levels. Nowadays, conventional gyrotrons are used almost exclusively to generate such radiation. In this review paper, we consider alternative variants of electronic microwave oscillators which require much weaker magnetic fields for their operation, namely, large-orbit gyrotrons operated at high cyclotron-frequency harmonics and Cerenkov-type devices, such as a backward-wave oscillator and a klystron frequency multiplier with tubular electron beams. Additionally, we consider the possibility to use the magnetic field created directly by the solenoid of an NMR spectrometer for operation of both the gyrotron and the backward-wave oscillator. Location of the oscillator in the spectrometer magnet makes it superfluous to use an additional superconducting magnet creating a strong field, significantly reduces the length of the radiation transmission line, and, in the case of Cerenkov-type devices, allows one to increase considerably the output-signal power. According to our calculations, all the electronic devices considered are capable of ensuring the power required for dynamic nuclear polarization (10 W or more) at a frequency of 260 GHz, whereas the gyrotrons, including their versions proposed in this paper, remain a single option at higher frequencies.

A DISTINCTIVE METHOD OF ELIMINATING OUT-BAND INSTABILITY IN CASCADED ACTIVE DEVICE SYSTEM BASED ON NARROW-BAND ATTENUATION

A distinctive connection method in cascaded RF/MW active device system achieving both stability and low gain loss is presented. Unlike traditional methods (isolator and attenuator), the proposed solution introduces an appropriate length of transmission line to change the input impedance at the out-band instable frequency point and uses a narrow-band termination to absorb the instable power without deteriorating in-band signal. Moreover, the reason that instability often occurs in the cascaded system is analysed with S-parameters, and it turns out to be a kind of out-band instability. The solution is verified by an adjustable circuit example whose insertion loss is below 0.3 dB.

Extremely compact phase delay line with CTSRR loaded transmission line

Phase delay characteristics of the complementary triangular split ring resonator (CTSRR) loaded transmission line with capacitive stubs are presented. The phase responses of a reference microstrip transmission line and a transmission line with capacitive stubs, loaded with the CTSRR on the ground plane, are compared. The practical results show that the CTSRR loaded transmission line provides four times more phase delay when compared with a reference transmission line, and thus the proposed configuration provides a 76% transmission line length reduction.

Electrical Behavior of an Ultralow-Energy Plasma-Focus Device

Measurements of electrical signals in discharges performed in a miniature plasma-focus device (5 nF capacitor bank, central electrode diameter and effective free length 2.0 and 0.5 mm, respectively, no outer electrode) are reported. A lumped model is built that gives good agreement between the model and the recorded signals. The main conclusions are as follows: the voltage at which the chamber disk capacitor is charged is limited by the gas filling pressure inside the chamber and not just by the voltage in the capacitor energy source, and the behavior of the discharge current within the vacuum chamber depends on the whole system and not only on the last portion of the circuit, even for longer transmission line lengths.

PEMBUATAN ANTENA MIKROSTRIP PHASED ARRAY DENGAN PENGATURAN FASA MENGGUNAKAN VARIASI PANJANG SALURAN CATU

A microstrip phased array width phase is controlled by length of line feeder is presented in this paper for application in RADAR system. The microstrip array antenna is built from dipolelike individual elemen at center frequency 650 MHz. Five different length transmission lines are used to change current phase feeding in to the antenna which is 2λ, 2.125 λ, 2.025 λ, and 2.5 λ. The measured result reveal exelent agreement width the simaltions. The different length of transmission line able to change the radiation pattern which are 60o, 150o,210o dan 0o.