Circuit simulation using distributed waveform relaxation techniques

Simulation plays an important role in the design of integrated circuits. Due to high costs and large delays involved in their fabrication, simulation is commonly used to verify functionality and to predict performance before fabrication. This thesis describes analysis, implementation and performance evaluation of a distributed memory parallel waveform relaxation technique for the electrical circuit simulation of MOS VLSI circuits. The waveform relaxation technique exhibits inherent parallelism due to the partitioning of a circuit into a number of sub-circuits. These subcircuits can be concurrently simulated on parallel processors. Different forms of parallelism in the direct method and the waveform relaxation technique are studied. An analysis of single queue and distributed queue approaches to implement parallel waveform relaxation on distributed memory machines is performed and their performance implications are studied. The distributed queue approach selected for exploiting the coarse grain parallelism across sub-circuits is described. Parallel waveform relaxation programs based on Gauss-Seidel and Gauss-Jacobi techniques are implemented using a network of eight Transputers. Static and dynamic load balancing strategies are studied. A dynamic load balancing algorithm is developed and implemented. Results of parallel implementation are analyzed to identify sources of bottlenecks. This thesis has demonstrated the applicability of a low cost distributed memory multi-computer system for simulation of MOS VLSI circuits. Speed-up measurements prove that a five times improvement in the speed of calculations can be achieved using a full window parallel Gauss-Jacobi waveform relaxation algorithm. Analysis of overheads shows that load imbalance is the major source of overhead and that the fraction of the computation which must be performed sequentially is very low. Communication overhead depends on the nature of the parallel architecture and the design of communication mechanisms. The run-time environment (parallel processing framework) developed in this research exploits features of the Transputer architecture to reduce the effect of the communication overhead by effectively overlapping computation with communications, and running communications processes at a higher priority. This research will contribute to the development of low cost, high performance workstations for computer-aided design and analysis of VLSI circuits

Multiscale simulation of frequency dependent line models and network equivalents

The evaluation of power systems encompasses phenomenon of distinct timeframes and so leads to the adoption of different simulation tools. For instance, fast transients related to switching maneuvers require time-steps of microseconds while slow transients, related to energy exchange between generators, demand timesteps of milliseconds. However, the need to assess conditions where slow frequency oscillations might be combined with fast transients is becoming more common. This research evaluates the use of frequency dependent admittance-based models in the development of multiscale algorithms for phase-coordinate modeling of overhead lines, subsea cables and frequency dependent network equivalents. Unlike the modeling with the Method of Characteristics, the direct fitting of the nodal admittance matrix and two alternative schemes are considered to cope with the trade-off between time-step and traveling times, namely: the Folded Line Equivalent and Idempotent Decomposition. The concept of Latency is also addressed in a distinct way to provide more efficient realization frequency dependent models to allow the so-called multirate simulation. The major advantage of the designed models is the straightforward implementation in EMTP-like programs such as PSCAD, EMTP-RV and ATP since they attain the same Norton-type structure. In addition, dynamic phasors allowed the unification of electromagnetic and electromechanical modeling into a single model. Both numerical performance and accuracy of the proposed schemes are evaluated through several test cases. The Method of Characteristics and the Numerical Laplace Transform are used for comparison. The computational burden is considerably reduced without significant loss of accuracy and with no numerical oscillations or discontinuities in the waveforms.A análise de sistemas elétricos engloba fenômenos com diferentes constantes de tempo, o que acarreta na utilização de diversas ferramentas de simulação. Como exemplo, transitórios rápidos envolvendo surtos de manobra demandam passos de integração na ordem de microssegundos enquanto para transitórios lentos, advindos da troca de energia entre geradores, adotam-se passos de integração de milissegundos. O presente trabalho investiga a utilização de modelos baseados em matrizes de admitância variantes na frequência para representação de linhas de transmissão aéreas, cabos submarinos e equivalentes de rede em coordenadas de fase para o desenvolvimento de algoritmos para simulação multiescala. Ao invés da utilização do Método das Características, a matriz de admitância nodal e duas decomposições alternativas são consideradas de modo a contornar a limitação do passo de integração em função do tempo de tráfego de linhas, a saber: o Folded Line Equivalent e a Decomposição Idempotente. O conceito de Latência será também investigado de modo a prover uma realização mais eficiente de modelos variantes na frequência. As formulações desenvolvidas neste trabalho encontram aplicação imediata em programas para simulação de transitórios eletromagnéticos, tais como PSCAD, EMTP-RV e ATP dado que é mantida a representação através dos equivalentes de Norton. Por meio de fasores dinâmicos, torna-se viável a representação de fenômenos eletromagnéticos e eletromecânicos com o mesmo modelo computacional. Casos teste são empregados na avaliação do desempenho e precisão das formulações propostas. O Método das Características e a transformada numérica de Laplace são utilizados para fins de comparação. Com reduzido esforço computacional, resultados com excelente precisão são obtidos sem a presença de oscilações numéricas ou descontinuidades nas formas de onda

Analysis of multirate behavior in electronic systems

Doutoramento em Engenharia ElectrotécnicaEsta tese insere-se na área da simulação de circuitos de RF e microondas, e visa o estudo de ferramentas computacionais inovadoras que consigam simular, de forma eficiente, circuitos não lineares e muito heterogéneos, contendo uma estrutura combinada de blocos analógicos de RF e de banda base e blocos digitais, a operar em múltiplas escalas de tempo. Os métodos numéricos propostos nesta tese baseiam-se em estratégias multi-dimensionais, as quais usam múltiplas variáveis temporais definidas em domínios de tempo deformados e não deformados, para lidar, de forma eficaz, com as disparidades existentes entre as diversas escalas de tempo. De modo a poder tirar proveito dos diferentes ritmos de evolução temporal existentes entre correntes e tensões com variação muito rápida (variáveis de estado activas) e correntes e tensões com variação lenta (variáveis de estado latentes), são utilizadas algumas técnicas numéricas avançadas para operar dentro dos espaços multi-dimensionais, como, por exemplo, os algoritmos multi-ritmo de Runge-Kutta, ou o método das linhas. São também apresentadas algumas estratégias de partição dos circuitos, as quais permitem dividir um circuito em sub-circuitos de uma forma completamente automática, em função dos ritmos de evolução das suas variáveis de estado. Para problemas acentuadamente não lineares, são propostos vários métodos inovadores de simulação a operar estritamente no domínio do tempo. Para problemas com não linearidades moderadas é proposto um novo método híbrido frequência-tempo, baseado numa combinação entre a integração passo a passo unidimensional e o método seguidor de envolvente com balanço harmónico. O desempenho dos métodos é testado na simulação de alguns exemplos ilustrativos, com resultados bastante promissores. Uma análise comparativa entre os métodos agora propostos e os métodos actualmente existentes para simulação RF, revela ganhos consideráveis em termos de rapidez de computação.This thesis belongs to the field of RF and microwave circuit simulation, and is intended to discuss some innovative computer-aided design tools especially conceived for the efficient numerical simulation of highly heterogeneous nonlinear wireless communication circuits, combining RF and baseband analog and digital circuitry, operating in multiple time scales. The numerical methods proposed in this thesis are based on multivariate strategies, which use multiple time variables defined in warped and unwarped time domains, for efficiently dealing with the time-scale disparities. In order to benefit from the different rates of variation of slowly varying (latent) and fast-varying (active) currents and voltages (circuits’ state variables), several advanced numerical techniques, such as modern multirate Runge-Kutta algorithms, or the mathematical method of lines, are proposed to operate within the multivariate frameworks. Diverse partitioning strategies are also introduced, which allow the simulator to automatically split the circuits into sub-circuits according to the different time rates of change of their state variables. Novel purely time-domain techniques are addressed for the numerical simulation of circuits presenting strong nonlinearities, while a mixed frequency-time engine, based on a combination of univariate time-step integration with multitime envelope transient harmonic balance, is discussed for circuits operating under moderately nonlinear regimes. Tests performed in illustrative circuit examples with the newly proposed methods revealed very promising results. Indeed, compared to previously available RF tools, significant gains in simulation speed are reported

Custom Integrated Circuits

Contains reports on twelve research projects.Analog Devices, Inc.International Business Machines, Inc.Joint Services Electronics Program (Contract DAAL03-86-K-0002)Joint Services Electronics Program (Contract DAAL03-89-C-0001)U.S. Air Force - Office of Scientific Research (Grant AFOSR 86-0164)Rockwell International CorporationOKI Semiconductor, Inc.U.S. Navy - Office of Naval Research (Contract N00014-81-K-0742)Charles Stark Draper LaboratoryNational Science Foundation (Grant MIP 84-07285)National Science Foundation (Grant MIP 87-14969)Battelle LaboratoriesNational Science Foundation (Grant MIP 88-14612)DuPont CorporationDefense Advanced Research Projects Agency/U.S. Navy - Office of Naval Research (Contract N00014-87-K-0825)American Telephone and TelegraphDigital Equipment CorporationNational Science Foundation (Grant MIP-88-58764

Center for Aeronautics and Space Information Sciences

This report summarizes the research done during 1991/92 under the Center for Aeronautics and Space Information Science (CASIS) program. The topics covered are computer architecture, networking, and neural nets

Modelling, Dimensioning and Optimization of 5G Communication Networks, Resources and Services

This reprint aims to collect state-of-the-art research contributions that address challenges in the emerging 5G networks design, dimensioning and optimization. Designing, dimensioning and optimization of communication networks resources and services have been an inseparable part of telecom network development. The latter must convey a large volume of traffic, providing service to traffic streams with highly differentiated requirements in terms of bit-rate and service time, required quality of service and quality of experience parameters. Such a communication infrastructure presents many important challenges, such as the study of necessary multi-layer cooperation, new protocols, performance evaluation of different network parts, low layer network design, network management and security issues, and new technologies in general, which will be discussed in this book

Applications of MATLAB in Science and Engineering

The book consists of 24 chapters illustrating a wide range of areas where MATLAB tools are applied. These areas include mathematics, physics, chemistry and chemical engineering, mechanical engineering, biological (molecular biology) and medical sciences, communication and control systems, digital signal, image and video processing, system modeling and simulation. Many interesting problems have been included throughout the book, and its contents will be beneficial for students and professionals in wide areas of interest

Modelling and Co-simulation of Multi-Energy Systems: Distributed Software Methods and Platforms

L'abstract è presente nell'allegato / the abstract is in the attachmen

JTIT

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