Stochastic Testing Simulator for Integrated Circuits and MEMS: Hierarchical and Sparse Techniques

Process variations are a major concern in today's chip design since they can significantly degrade chip performance. To predict such degradation, existing circuit and MEMS simulators rely on Monte Carlo algorithms, which are typically too slow. Therefore, novel fast stochastic simulators are highly desired. This paper first reviews our recently developed stochastic testing simulator that can achieve speedup factors of hundreds to thousands over Monte Carlo. Then, we develop a fast hierarchical stochastic spectral simulator to simulate a complex circuit or system consisting of several blocks. We further present a fast simulation approach based on anchored ANOVA (analysis of variance) for some design problems with many process variations. This approach can reduce the simulation cost and can identify which variation sources have strong impacts on the circuit's performance. The simulation results of some circuit and MEMS examples are reported to show the effectiveness of our simulatorComment: Accepted to IEEE Custom Integrated Circuits Conference in June 2014. arXiv admin note: text overlap with arXiv:1407.302

Methodologies for Transient Simulation of Hybrid Electromagnetic/Circuit Systems with Multiple Time Scales

This work presents methodologies to facilitate the efficient cosimulation of electromagnetic/circuit systems while exploiting the multiple time scales that are often present in the numerical simulation of such systems. Three distinct approaches are presented to expedite such a simulation process, with the common theme that the methodologies should allow for the ability to utilize different timesteps in the simulation procedure for the different components appearing in a hybrid system. The first contribution involves a direct representation of each of Maxwell???s curl equations in terms of SPICE-equivalent circuit stamps. This provides for a full-wave, circuit-compatible description of a distributed structure that can very naturally be incorporated into a circuit simulation environment. This capability can be applied to circuit simulations of distributed structures, or it can facilitate the detailed simulation of an electrically small structure with full electromagnetic accuracy. The second contribution allows for the utilization of different numerical integration schemes and timesteps in the simulation of hybrid structures via a domain decomposition approach. By introducing a novel scheme to combine finite-difference time-domain simulation with SPICE-like circuit simulation, it is shown that the timestep used in the lumped circuit portions need not be limited by the Courant-Friedrichs-Lewy (CFL) limit which governs the timestep used in distributed portions. Additionally, the use of the Crank-Nicolson integration scheme is investigated for the simulation of transmission line structures, and an efficient methodology is proposed by combining the Crank-Nicolson integration of transmission lines and standard integration of circuits. Finally, the third contribution in this work involves efficient simulation of circuits involving multirate signals with widely separated time scales. An efficient representation of multirate signals is found by introducing a different time variable for each time scale in order to overcome the significant oversampling of such signals that arises from more traditional, univariate representations. This representation is then directly applied to the simulation of transmission line structures. It is found that the resulting methodologies provide for a significant speedup in the overall simulation time

Time-domain Analysis of Multiconductor Transmission Lines Excited by Transient Electromagnetic Disturbances Based on the Analog Behavior Modeling

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

Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers

Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method

Transient Optical Picocavities Within Coupled Plasmonic Nanostructures

Plasmonic nanocavities, such as a nanometre scale gap between a gold nanoparticle and gold mirror (NPoM), confine light beyond the free space diffraction limit. While these enhanced field intensities allow resolvable measurements of vibrational scattering from only a few hundred molecules, ensemble averaging destroys all information on individual molecular local environments. In this thesis, I first investigate the single molecule vibrational scattering from a molecule placed into NPoM using a DNA structure. The DNA complicates the response, which is time variant with transient features suggestive of possible picocavity formation. Picocavities are transient atomic scale features on the metal surfaces which further confine fields (effective volume <1 nm3) with strong field gradients that locally alter the rules for vibrational scattering efficiency. These can alter the spectral response of a single nearby molecule (isolating it spectrally) and were previously noted in NPoM at cryogenic temperatures. I change the gap material to a molecular monolayer to simplify the system and explore room temperature picocavities. I use automated analysis of large experimental datasets to detect and isolate transient vibrational scattering. Picocavity generation is found to depend on the local chemical environment near the gold surface. Picocavities are observed to chemically interact with the molecule being optically probed. This perturbs bond strengths across the molecule with the strength and direction of this perturbation being highly sensitive to the relative picocavity location on a < 0.1Å scale. This single molecule – metal atom system is explored by comparing experimental data to a theoretical Density Function Theory model. Next, I extract the spatial distribution of picocavity formation in the gap by comparing transient scattering at two simultaneous wavelengths of light. Picocavities are found to more likely form at regions of higher optical intensity within the NPoM gap. This suggests that light plays a direct role in the yet undetermined picocavity generation mechanism

Electrical performance analysis of high-speed interconnects and circuits by numerical modeling methods

Ph.DDOCTOR OF PHILOSOPH

Comparative study of 220 kV overhead transmission lines models subjected to lightning strike simulation by using electromagnetic and alternative transients program

Introduction. In high voltage networks intended for the transport of electrical energy, lightning can strike an electric line striking either a phase conductor, a pylon or a ground wire, causing significant overvoltage on the transmission lines classified as stresses the most dangerous for transformer stations and electro-energy systems in general. Modeling transmission lines becomes more complicated, if the frequency dependence of resistance and serial inductance due to the effect of lightning strike in the conductors and in the earth is considered. The difficulty increases the fact that the parameters of the line can be defined and calculated only in the frequency domain, while the simulation of transients is wanted to be in the time domain. Problem. Several models (J.R. Marti, Bergeron, nominal PI, Semlyen and Noda) exist for the modeling of transmission lines, the Electromagnetic Transients Program/Alternative Transient Program software (EMTP/ATPDraw) gives the possibility to choose between these models which is delicate due to the fact that we do not have experimental results to validate and justify the choice among the models available in the software. In this context, practical value: the overhead transport line OAT-El Hassi (220 kV) of the city of Sétif located in the north east of Algeria is used for the modeling of lightning strike by using the EMTP/ATPDraw software. Originality. A comparative study of the investigation of a lightning strike on an existing high voltage transmission line by different models of existing lines in the EMTP/ATPDraw software library of this software. Results. It was concluded that the choice of the model of the line is very important given the accuracy and quality of the curves of the voltage presented at the different calculation points. Вступ. У високовольтних мережах, призначених для передачі електроенергії, блискавка може вдарити по лінії електропередач, уразивши або фазний провід, опору, або заземлюючий провід, викликаючи значні перенапруги на лініях електропередач, визначені як загрози, найбільш небезпечні для трансформаторних підстанцій та електроенергетичних систем загалом. Моделювання ліній електропередач ускладнюється, якщо враховувати частотну залежність опору та послідовної індуктивності внаслідок дії удару блискавки у провідниках та землі. Складність підвищується тим, що параметри лінії можуть бути визначені і розраховані тільки в частотній області, в той час як моделювання перехідних процесів бажано проводити в часовій області. Проблема. Існує кілька моделей (J.R. Marti, Bergeron, номінальна П-подібна схема заміщення, Semlyen і Noda) для моделювання ліній електропередач, комп‘ютерна  програма електромагнітних перехідних процесів/альтернативна програма перехідних процесів EMTP/ATPDraw дає можливість вибирати між цими моделями, що є «тонким питанням» через те, що ми не маємо експериментальних результатів для перевірки та обґрунтування вибору серед моделей, доступних у програмному забезпеченні. У цьому контексті, практична цінність: для моделювання удару блискавки за допомогою програмного забезпечення EMTP/ATPDraw використана повітряна лінія електропередачі ОАТ-Ель-Хассі (220 кВ) міста Сетіф, розташованого на північному сході Алжиру. Оригінальність. Порівняльне дослідження вивчення удару блискавки на існуючій високовольтній лінії електропередач за різними моделями існуючих ліній у бібліотеці програм  EMTP/ATPDraw цього програмного забезпечення. Результати. Зроблено висновок, що вибір моделі лінії дуже важливий з урахуванням точності та якості кривих напруг, представлених у різних розрахункових точках.

Lightning Effects in the Payload Changeout Room

Analytical and empirical studies have been performed to provide better understanding of the electromagnetic environment inside the Payload Changeout Room and Orbiter payload bay resulting from lightning strikes to the launch pad lightning protection system. The analytical studies consisted of physical and mathematical modeling of the pad structure and the Payload Changeout Room. Empirical testing was performed using a lightning simulator to simulate controlled (8 kA) lightning strikes to the catenary wire lightning protection system. In addition to the analyses and testing listed above, an analysis of the configuration with the vehicle present was conducted, in lieu of testing, by the Finite Difference, Time Domain method

Realistic modeling of power lines for transient electromagnetic interference studies

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2020.Este trabalho descreve o problema das interferências eletromagnéticas entre linhas de transmissão de energia elétrica em alta tensão e instalações metálicas vizinhas, em condições de regimes permanente e transitório, bem como os principais riscos a que se sujeitam pessoas e as instalações envolvidas. São desenvolvidas ferramentas computacionais com o propósito de realizar simulações realistas de casos de interferências eletromagnéticas, por meio de duas abordagens distintas: o método FDTD e um modelo baseado em teoria de circuitos utilizando o programa ATP (Alternative Transients Program). Uma nova fórmula é proposta para modelar solos multiestratificados em cálculos de impedâncias com caminho de retorno pela terra utilizando as rotinas nativas do ATP. Os códigos são validados por meio de estudos de casos e comparações com resultados obtidos utilizando programas considerados padrão de mercado. Este trabalho é de interesse prático para as indústrias de energia elétrica, óleo, gás, minérios, abastecimento de água e saneamento, por meio do qual se espera contribuir com o desenvolvimento de técnicas avançadas para prever e mitigar riscos às pessoas e ao patrimônio, auxiliando no projeto de instalações mais seguras, com soluções técnica e economicamente viáveis.This work describes the problem of electromagnetic interferences between high voltage power lines and neighboring metallic installations, in steady-state and transient conditions, and the main risks to which people and facilities are exposed to. Computational tools are developed to carry out realistic simulations of electromagnetic interferences, under two different approaches: an FDTD implementation and a circuit- based model using the Alternative Transients Program (ATP). A new formula, fully compatible with the native ATP routines, is proposed to model multilayered soil structures in ground return impedance calculations. All programs are validated through case studies and comparisons with results obtained by using industry-standard software. Of practical interest to the industries of energy, oil \& gas, ore and water distribution/sanitation, this work is expected to contribute with advanced techniques to predict and mitigate risks to which people and installations are subjected, thus assisting in the design of safer facilities, with technically feasible and economical solutions