2,599 research outputs found

    Nonlinear microwave simulation techniques

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    The design of high performance circuits with short manufacturing cycles and low cost demands reliable analysis tools, capable to accurately predict the circuit behaviour prior to manufacturing. In the case of nonlinear circuits, the user must be aware of the possible coexistence of different steady-state solutions for the same element values and the fact that steady-state methods, such as harmonic balance, may converge to unstable solutions that will not be observed experimentally. In this contribution, the main numerical iterative methods for nonlinear analysis, including time-domain integrations, shooting, harmonic balance and envelope transient, are briefly presented and compared. The steady-state methods must be complemented with a stability steady-state analysis to verify the physical existence of the solution. This stability analysis can also be combined with the use of auxiliary generators to simulate the circuit self-oscillation and predict qualitative changes in the solution under the continuous variation of a parameter. The methods will be applied to timely circuit examples that are demanding from the nonlinear analysis point of view.This work has been supported by the Spanish Government under contract TEC2014-60283-C3-1-R and the Parliament of Cantabria (12.JP02.64069)

    Sensitivity analysis of oscillator models in the space of phase-response curves: Oscillators as open systems

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    Oscillator models are central to the study of system properties such as entrainment or synchronization. Due to their nonlinear nature, few system-theoretic tools exist to analyze those models. The paper develops a sensitivity analysis for phase-response curves, a fundamental one-dimensional phase reduction of oscillator models. The proposed theoretical and numerical analysis tools are illustrated on several system-theoretic questions and models arising in the biology of cellular rhythms

    On two generalisations of the final value theorem : scientific relevance, first applications, and physical foundations

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    The present work considers two published generalisations of the Laplace-transform final value theorem (FVT) and some recently appeared applications of one of these generalisations to the fields of physical stochastic processes and Internet queueing. Physical sense of the irrational time functions, involved in the other generalisation, is one of the points of concern. The work strongly extends the conceptual frame of the references and outlines some new research directions for applications of the generalised theorem

    Effective time-domain approach for the assessment of the stability characteristics and other non-linear effects of RF and microwave circuits

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    This study describes a systematic approach for the stability analysis of RF and microwave non-linear circuits in the time-domain and that can be useful also for the verification of other non-linearities, like intermodulation. The time-domain analysis is the most reliable approach for the evaluation of complex non-linear phenomena but, in general, the transient behaviour of non-linear circuits is difficult to verify at high frequencies, where distributed elements are common. The solution here addressed overcomes this limitation and it may be applied, without restrictions, also to monolithic microwave integrated circuits and EM-based designs. Examples of application to hybrid prototypes are provided, and the comparison between simulations and measurements illustrates the accuracy and reliability of the proposed approach

    Dynamics of non-neutral plasmas

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    In this paper the focus is on the dynamics of two-dimensional cylindrical non-neutral plasmas. After reviewing some highlights of the non-neutral plasma dynamics, some recent two-dimensional results are described: vortex dynamics, diocotron instabilities of hollow profiles, collisionless damping of modes and fluid trapping by modes, fluid echoes, the cyclotron center of mass modes and warm plasma Bernstein modes, and temperature determination from fluctuation measurements. Attention is called to some unsolved problems

    Підвищення ефективності розрахунку стаціонарних періодичних режимів електронних кіл на основі спектрального аналізу сигналів

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    Спектральні характеристики сигналів лежать в основі вибору кроку їх дискретизації у часі, якщо для обчислення цих сигналів застосовується метод аналізу стаціонарних періодичних режимів нелінійних елект-ронних кіл на основі ряду Котельникова-Шеннона. Оскільки отримання самих сигналів і є метою застосування цього методу, виникає замкнене коло: щоб отримати сигнали, необхідно визначити крок дискретизації у часі, а щоб визначити крок дискретизації, необхідно знати спектральні властивості сигналу, а саме верхню граничну частоту, яка обмежує його частотний спектр. У роботі запропонований метод визначення кроку дискретизації сигналу на основі обчислення часткової реакції схеми на пробний сигнал у вигляді функції Хевісайда. Реакція визначається будь-яким чисельним методом, придатним для розв'язування систем нелінійних диференціальних рівнянь першого порядку. За спектральною густиною енергії реакції визначається верхня гранична частота і крок дискретизації сигналу у часі, який визначає необхідну кількість відліків. Наведені приклад застосування запропонованого методу та його порівняльна ефективність.A key problem in the periodic steady-state analysis of electronic circuits is that the duration of transient pro-cesses in a circuit might be much larger than the period of a steady-state response. Thus, application of traditional transient methods becomes ineffective due to a huge amount of redundant computations, and special periodic-steady state methods should be used. The method for periodic steady-state analysis using the Kotelnikov-Shannon series is a time-domain method that has proved to be effective for a such type of circuits. In this method the unknown signals are expanded in the Kotelnikov-Shannon series and the derivatives of these signals are calculated as the derivatives of the series. A matrix form of the derivatives approximation leads to simple matrix expressions in a mathematical model. When using the method for periodic steady-state analysis of non-linear circuits using the Kotelnikov-Shannon series to find the steady-state response of a circuit, a time discretization step is chosen based on the spectral characteristics of the signals. As far as the goal of the method is to calculate the unknown signals in a circuit, a vicious circle occurs: to calculate the signals, the time discretization step has to be chosen, and to choose the time discretization step, the spectral characteris-tics of the signals have to be known, namely the upper frequency in these characteristics. In order to choose the time discretization step, we propose to calculate a partial transient response of a circuit for an input signal of the form of the Heaviside step function, which is usually used to obtain a step response of a linear circuit. The response is calculated with any method, suitable for solving a system of non-linear ordinary differential equations, which usually represents the mathematical model of a circuit. The upper frequency in the spectral characteristic of the partial transient response depends on the duration of the computational domain. The upper frequency versus the dura-tion of the computational domain dependency can be approximated with a hyperbolic function. Thus, calculating few values of the upper frequency at different durations of the computational domain, the value of the upper frequency when the duration of the computational domain is equal to the period of a steady-state response can be forecasted using the hyperbolic approximation

    Stimulus-invariant processing and spectrotemporal reverse correlation in primary auditory cortex

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    The spectrotemporal receptive field (STRF) provides a versatile and integrated, spectral and temporal, functional characterization of single cells in primary auditory cortex (AI). In this paper, we explore the origin of, and relationship between, different ways of measuring and analyzing an STRF. We demonstrate that STRFs measured using a spectrotemporally diverse array of broadband stimuli -- such as dynamic ripples, spectrotemporally white noise, and temporally orthogonal ripple combinations (TORCs) -- are very similar, confirming earlier findings that the STRF is a robust linear descriptor of the cell. We also present a new deterministic analysis framework that employs the Fourier series to describe the spectrotemporal modulations contained in the stimuli and responses. Additional insights into the STRF measurements, including the nature and interpretation of measurement errors, is presented using the Fourier transform, coupled to singular-value decomposition (SVD), and variability analyses including bootstrap. The results promote the utility of the STRF as a core functional descriptor of neurons in AI.Comment: 42 pages, 8 Figures; to appear in Journal of Computational Neuroscienc

    34th Midwest Symposium on Circuits and Systems-Final Program

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    Organized by the Naval Postgraduate School Monterey California. Cosponsored by the IEEE Circuits and Systems Society. Symposium Organizing Committee: General Chairman-Sherif Michael, Technical Program-Roberto Cristi, Publications-Michael Soderstrand, Special Sessions- Charles W. Therrien, Publicity: Jeffrey Burl, Finance: Ralph Hippenstiel, and Local Arrangements: Barbara Cristi

    Incorporation of feed-network and circuit modeling into the time-domain finite element analysis of antenna arrays and microwave circuits

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    In this dissertation, accurate and efficient numerical algorithms are developed to incorporate the feed-network and circuit modeling into the time-domain finite element analysis of antenna arrays and microwave circuits. First, simulation of an antenna system requires accurate modeling of interactions between the radiating elements and the associated feeding network. In this work, a feed network is represented in terms of its scattering matrix in a rational function form in the frequency domain that enables its interfacing with the time-domain finite element modeling of the antenna elements through a fast recursive time-convolution algorithm. The exchange of information between the antenna elements and the feed network occurs through the incident and reflected modal voltages/currents at properly defined port interfaces. The proposed numerical scheme allows a full utilization of the advanced antenna simulation techniques, and significantly extends the current antenna modeling capability to the system level. Second, a hybrid field-circuit solver that combines the capabilities of the time-domain finite element method and a lumped circuit analysis is developed for accurate and efficient characterization of complicated microwave circuits that include both distributive and lumped-circuit components. The distributive portion of the device is modeled by the time-domain finite element method to generate a finite element subsystem, while the lumped circuits are analyzed by a SPICE-like circuit solver to generate a circuit subsystem. A global system for both the finite-element and circuit unknowns is established by combining the two subsystems through coupling matrices to model their interactions. For simulations of even more complicated mixed-scale circuit systems that contain pre-characterized blocks of discrete circuit elements, the hybrid field-circuit analysis implemented a systematic and efficient algorithm to incorporate multiport lumped networks in terms of frequency-dependent admittance matrices. Other advanced features in the hybrid field-circuit solver include application of the tree-cotree splitting algorithm and introduction of a flexible time-stepping scheme. Various numerical examples are presented to validate the implementation and demonstrate the accuracy, efficiency, and applications of the proposed numerical algorithms
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