Modelling of printed discontinuities on open microstrip lines by mode matching techniques

The dynamic analysis of discontinuities in printed circuits has been performed using the mode matching technique. This study concerns the open end of microstrip lines and suspended microstrip lines. The fields on either side of the discontinuity are described by means of the continuous (radiated and evanescent) and guided modes of the structure. The conditions of continuity of the electromagnetic fields are then applied in the plane of the discontinuity. By taking into account the relations of orthogonality of the modes of the same region, a system of coupled Fredholm integral equations is obtained and solved by the iterative method of Neumann's series. The study calls for the use of the continuous spectrum of microstrip lines, which can be obtained analytically only after a great amount of calculation and CPU time. Thus, the first approach consists in neglecting this continuous spectrum. This gives accurate results for the reflection coefficient but it is not sufficient for the derivation of the radiation pattern. So, two simple models for the continuous spectrum, both based on the physical behaviour of such discontinuities, are considered and discussed. © 1997 John Wiley & Sons, Ltd.     

On the responses of strip-line interconnects with discontinuities excited by external fields

An algorithm is developed to evaluate the responses of discontinuous coplanar strip-lines excited by external electromagnetic fields. The algorithm uses the cascade chain matrix method which employs the distributed circuit parameters to model the external field coupling to the line and it is applicable to most commonly encountered discontinuities in microwave integrated circuit interconnects on lossy substrates. A general CAD program is developed based on this model and it is applied to realistic coplanar strip-line interconnections with geometric and resistive discontinuities to illustrate the capabilities of the algorithm. These interconnect models are selected from a practical microwave integrated circuit design. Simplicity and fast speed of the algorithm enable computer-aided analysis of externally induced electromagnetic noise in integrated circuits to be carried out. The effects of dielectric losses in the integrated circuit substrates and the discontinuities in the conducting tracks on the wave coupling are investigated in isolation.     

A generalized CAD model for the full‐wave modelling of microstrip line and its regular and irregular discontinuities

In this paper we present a new theoretical model for the modelling of the microstrip line as well as two types of discontinuities: regular (open end, step, bend and T‐ and cross‐junctions) and irregular (stub and bent‐stub). The two‐dimensional exact dyadic Green function of a grounded dielectric slab has been used with the Galerkin's technique. The subdivision of the discontinuity in a network of juxtaposed unit cells, characterized by their own longitudinal and transversal current distributions, allowed the treatment of a large class of irregular discontinuities in addition to the regular discontinuities. The obtained results have been commented and compared with those of different approaches and with experimental results where a good concordance has been observed. Copyright © 2006 John Wiley & Sons, Ltd.     

A new approach to the network modelling of capacitive irises and steps in waveguide

Classical network representations of waveguide discontinuities assume monomode operation and involve elements which depend not only upon geometry, but also on frequency. Later approaches to the problem consist of numerical techniques. These are unsuitable for synthesis since they do not yield equivalent networks and involve repeating the field analysis at each frequency, which is cumbersome for applications to wideband design. A recent approach permits to derive wideband equivalent networks with elements which depend only upon geometry. In this contribution capacitive irises, steps and combinations are treated. These discontinuities occur in filters, transformers, etc. where higher-order mode interaction cannot be neglected for closely spaced discontinuities. Whatever this spacing may be, higher order mode interaction always occurs in oversize guide. Higher order mode interaction fits naturally into the network modelling presented here. The resulting network representations are either in canonical Foster form of the first type or easily reducible to it. This approach is based on a Rayleigh–Ritz variational solution of the field problem and involves manipulations with small matrices only. The accuracy of the method is demonstrated for a number of basic configurations, while its flexibility is illustrated by providing simpler equivalent networks, applicable when extreme accuracy is not required. The elements involved are given in graphical or in simple analytical form.     

The discrete time domain Green's function or Johns matrix — A new powerful concept in transmission line modelling (TLM)

A new TLM-based concept analogous to the Green's function approach in classical electromagnetic theory is presented. It employs the procedure known as time domain diakoptics. The response of a TLM mesh to a unit impulse excitation at selected input points is interpreted as a discrete Green's function in the time domain, and the term ‘Johns matrix’ is proposed for this characteristic response. As in classical theory, the response of the mesh to an arbitrary excitation is found by convolving the excitation with its Johns matrix. This concept extends the generalized scattering parameter concept into the time dimension, opens unprecedented possibilities for partioning time domain problems at the field level, and permits large-scale preprocessing of substructures for computer-aided design. It also represents and elegant way of modelling broadband absorbing boundary conditions, imperfectly conducting walls and general frequency dispersive boundaries in the time domain.     

A generalized CAD model for the full‐wave modeling of Coplanar striplines discontinuities

In this work, the coplanar stripline (CPS) and its discontinuities: open‐end, short‐end, gaps and resonator have been modeled. New integral equations for the electrical field components are formulated, in the spectral domain, using an exact dyadic Green's function, applied to the CPS structure. The use of this form of Green's function allows the consideration of the effects of the dielectric losses, the surface wave excitation and the space wave radiation on the propagation characteristics of the CPS and its discontinuities. The resulting integral equation has been solved using the two‐dimensional Galerkin's technique. The resolution of the resulting matrix equation gives the scattering parameters of the studied structures. The obtained results are commented and compared with those of other approaches and measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Wave-digital cascade synthesis

The purpose of this paper is to demonstrate the possibility of a wave-digital cascade synthesis. Each section, reciprocal as well as non-reciprocal, being for instance the result of a cascade synthesis based on the factorization of the transfer matrix of an analogue lossless two-port network, is translated into a wave-digital realization. Except for the zero-order sections, it is shown to be sufficient that each section is cascaded with one unit-element in order to obtain an equivalent network which can be translated into wave-digital form. It gives some insight in the price to be paid in terms of complexity of the realization if a perfectly general transfer function is to be realized in wave-digital form. By some examples it is shown how each structure which has been introduced can be ‘passified’ if it cannot be realized by a lossless structure.     

Transmission network expansion planning considering renewable energy target with Taguchi's orthogonal array testing

Nowadays, renewable energy resources are becoming more and more popular. The intermittent nature of renewable energy sources will affect transmission network expansion planning (TNEP). Consequently, this paper presents a new problem formulation and solution procedure for TNEP which can cope with the intermittent characteristics. Taguchi's orthogonal array testing (TOAT) is used to select the scenarios that represent the loads and renewable energy resource uncertainties. In this paper, a new index called the ‘renewable energy leak’ (REL) is proposed to evaluate the ‘unutilized or leaked’ renewable energy in the TNEP. For minimizing the investment cost of transmission network expansion, annual generator operation cost, and annual transmission line loss cost, the meta‐heuristic adaptive Tabu search (ATS) algorithm is used, while the system operating limits including the REL index are taken into account as the optimization constraints. The proposed procedure is tested in a modified IEEE Reliability Test System 79. The results show that the proposed method is efficient and promising. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于RL和总变分的非盲模糊图像复原算法

基于模糊退化过程的空不变卷积模型,依据跳跃边缘的不连续性在总变分最小化过程中的指导性作用,提出一种在已知模糊核情况下,基于Richardson-Lucy和总变分(Total Variation)正则化的两步非盲模糊图像复原方法.Richardson-Lucy算法得到清晰边缘的初始估计,然后以边缘的不连续性指导总变分能量...     

高压配电网负荷转供中的开关动作时序判定策略

转供开关操作时序问题是对高压配电网负荷转供的进一步研究,对系统的可靠供电和系统安全具有切实影响。分析了各转供模式,并在开关操作原则的基础上提出了一种转供风险评估方法,由此建立了与传统旅行商问题中距离矩阵相类似的风险量度矩阵。在时序求解上,采用蚁群算法并结合求解对象的特点和要求对其进行了相应调整。采用某城市局部高压配电网负荷转供算例,求解得到了适用于不同情景的开关时序方案,通过与枚举法和经验法的对比,验证了所提方法的有效性。     

矢量网络分析仪的时频域阻抗测量技术

由于传输线阻抗不连续性导致的串扰问题会严重影响信号传输的质量,从而导致信号完整性问题。从矢量网络分析仪阻抗测试原理出发,通过对比网络仪开路校准及端口补偿后的Smith圆图测量结果、阻抗和相位格式测量结果,说明网络仪频域3种测量格式所表述的阻抗信息;利用矢量网络分析仪时域变换功能从时域上对传输线进行评估,可以获得传输线阻抗不连续点和各位置阻抗信息。最后通过对一段3.5 mm传输线的测试,说明如何利用矢量网络分析仪的频域和时域同时对传输线特性尤其是阻抗特性进行评估,为传输线测试提供了一种新的方法。     

基于主成分分析的用电模式稳定性分析

用电模式稳定性分析是实施用户用电量预测的前提,其本质是考察不同历史时间段用电模式的相似性。过长的基础数据时间跨度会降低用电模式稳定性分析的可行性和准确性,而在短期内基于日用电量数据评估的用电特征指标又受随机因素干扰,难以准确反映用电模式。为此,提出一种以过往几周日用电系数和日用电波动率为原始特征指标提取用电模式主成分,进而用两个历史时间段内用电模式主成分因子载荷的欧氏距离衡量用电模式稳定性的方法。针对某小区的算例结果表明,用所提方法判定为用电模式稳定、不稳定的用户组的用电量预测精度存在明显差异,且相似性距离与预测误差存在正相关性。算例分析表明,合适的历史数据时间跨度对提升方法的适用性和准确性至关重要,所提方法采用16周历史数据较为合理。     

Torsional vibration characteristics analysis of DFIG‐based wind farm and its equivalent model

As large‐scale wind farms (WFs) are integrated with the power grid, the interaction between the WF and the grid may excite torsional vibration of the shaft of the wind turbine. To study the shaft's torsional vibration characteristics of a doubly fed induction generator (DFIG)‐based WF, a detailed small‐signal model of DFIG is established first. Then the small‐signal model for a WF composed of multiple DFIGs is developed on the basis of the single‐machine model. Modal analysis is employed to investigate the torsional vibration characteristics of a WF made up of several identical DFIGs, whose accuracy is also demonstrated through time‐domain simulation. To simplify the torsional vibration analysis for the DFIG‐based WF, a reduced‐order equivalent model is proposed. The results obtained from modal analysis show that the equivalent model not only precisely maintains all the torsional vibration modes of the original small‐signal model but also greatly reduces the computation complexity. With the equivalent model, the ‘curse of dimensionality’ problem is solved in torsional vibration analysis for large WFs, which is of great help in the design of further damping schemes. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于DDPG的柔性伺服系统级联陷波器设计

针对柔性伺服系统的多频谐振抑制问题,提出一种基于DDPG的级联陷波器参数整定方法。以系统速度环开环bode图及陷波器bode图预处理结果作为训练数据,并以相位裕度作为奖励函数训练神经网络,实现所设计的伺服系统级联陷波器深度及宽度参数优化训练。搭建了三质量柔性伺服系统实验平台,并开展了多频谐振抑制实验,实验结果表明所提出的参数选择方法能够 找到具有最大相位裕度的陷波器参数,并有效地抑制系统多频谐振。     

General interpretation of sensitivity functions

A general interpretation of sensitivity functions of linear networks is given in order to determine any nth order sensitivity function with respect to any parameter. The calculation uses an indirect method: ‘transfer function products’ give the desired sensitivities instead of derivation. The interpretation makes it possible to construct a computer program, too, which needs only one matrix inversion for a complete sensitivity analysis (including first- and higher-order sensitivities). It is shown that the adjoint network approach is superfluous and more complicated than the given method.     

Improving Parsing of ‘BA’ Sentences for Machine Translation

The research on Chinese‐Japanese machine translation has been lasting for many years, and now this research field is increasingly thoroughly refined. In practical machine translation system, the processing of a simple and short Chinese sentence has somewhat good results. However, the translation of complex long Chinese sentence still has difficulties. For example, these systems are still unable to solve the translation problem of complex ‘BA’ sentences. In this article a new method of parsing of ‘BA’ sentence for machine translation based on valency theory is proposed. A ‘BA’ sentence is one that has a prepositional word ‘BA’. The structural character of a ‘BA’ sentence is that the original verb is behind the object word. The object word after the ‘BA’ preposition is used as an adverbial modifier of an active word. First, a large number of grammar items from Chinese grammar books are collected, and some elementary judgment rules are set by classifying and including the collected grammar items. Then, these judgment rules are put into use in actual Chinese language and are modified by checking their results instantly. Rules are checked and modified by using the statistical information from an actual corpus. Then, a five‐segment model used for ‘BA’ sentence translation is brought forward after the above mentioned analysis. Finally, we applied this proposed model into our developed machine translation system and evaluated the experimental results. It achieved a 91.3% rate of accuracy and the satisfying result verified effectiveness of our five‐segment model for ‘BA’ sentence translation. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Microwave bandpass filters consisting of rectangular waveguides with 1-dimensional offsets

The computer-aided analysis and design of direct-coupled and quarter-wave-coupled bandpass filters utilizing monomode rectangular waveguides with 1-dimensional offset discontinuities are described. The equivalent networks of these discontinuities, which consist of a shunt reactance and additional transmission lines connected at both sides, have been derived from the rigorous field-theoretical investigations of E-plane and H-plane displacements in rectangular waveguide. Both network elements are tabulated in terms of geometry and wavelength with fine steps to allow accurate interpolation by means of computational methods, Simple design formulae for the filter geometry as a function of the electrical specifications are given which are based upon narrow-band approximations. The analytical relationships required for a computer simulation of the filter's wide-band performance are summarized. The predicted frequency characteristics showed such close agreement with the experimental results obtained on two X-band filter models that neither tuning elements in the waveguide sections nor final adjustments of the offset widths had to be provided.     

Atomistic deconstruction of current flow in graphene based hetero-junctions

We describe the numerical modeling of current flow in graphene heterojunctions, within the Keldysh Landauer Non-equilibrium Green’s function (NEGF) formalism. By implementing a k-space approach along the transverse modes, coupled with partial matrix inversion using the Recursive Green’s function Algorithm (RGFA), we can simulate on an atomistic scale current flow across devices approaching experimental dimensions. We use the numerical platform to deconstruct current flow in graphene, compare with experimental results on conductance, conductivity and quantum Hall, and deconstruct the physics of electron ‘optics’ and pseudospintronics in graphene pn junctions. We also demonstrate how to impose exact open boundary conditions along the edges to minimize spurious edge reflections.