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Circuits and Systems I: Fundamental Theory and Applications, IEEE Transactions on

Issue 11 • Date Nov 2000

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Displaying Results 1 - 12 of 12
  • Resynchronization for multiprocessor DSP systems

    Page(s): 1597 - 1609
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    This paper introduces a technique, called resynchronization, for reducing synchronization overhead in multiprocessor implementations of digital signal processing (DSP) systems. The technique applies to arbitrary collections of dedicated, programmable or configurable processors, such as combinations of programmable DSP's, ASICs, and FPGA subsystems. Thus, it is particularly well-suited to the evolving trend toward heterogeneous single-chip multiprocessors in DSP systems. Resynchronization exploits the well-known observation that in a given multiprocessor implementation, certain synchronization operations may be redundant in the sense that their associated sequencing requirements are ensured by other synchronizations in the system. The goal of resynchronization is to introduce new synchronizations in such a way that the number of original synchronizations that become redundant exceeds the number of new synchronizations that are added, and thus, the net synchronization cost is reduced. Our study is based on the context of self-timed execution for iterative dataflow specifications of DSP applications. An iterative dataflow specification consists of a dataflow representation of the body of a loop that is to be iterated indefinitely; dataflow programming in this form has been employed extensively in the DSP domain View full abstract»

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  • A physical contradiction in network theory

    Page(s): 1610 - 1612
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    It may have been believed that the majority of problems in network theory have been solved, but it is not necessarily true. In this paper the Instantaneous Propagation Problem, presented by Debart is shown and the Anti-Causality Problem is introduced as contradicted examples of the Reciprocity Theorem and Anti-Reciprocity Theorem, respectively. Since the circuit of interest is a feedback circuit, the input signal circulates the feedback loop infinitely. We unveil the fact that analyzing the feedback circuit using the Superposition theorem is inaccurate, because the network theory, which is based on Energy Conservation Law, is applied to a circuit that has no relationship with it View full abstract»

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  • A wavelet-based time-domain solution for PEEC circuits

    Page(s): 1634 - 1639
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    This paper deals with a time-domain wavelet-based approach for the PEEC method. Our goal is to investigate a new procedure for the formulation in time domain of the PEEC technique to consider linear as well as nonlinear circuits. By means of the wavelet transform the differential operators in the PEEC equations are substituted by matrices. The high sparsity of these matrices makes this procedure effective for reliable time domain simulation View full abstract»

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  • Self-control of chaotic dynamics using LTI filters

    Page(s): 1649 - 1652
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    In this brief, an algorithm for controlling chaotic systems using small, continuous-time perturbations is presented. Stabilization is achieved by self controlling feedback using low order LTI filters. The algorithm alleviates the need of complex calculations or costly delay elements and can be implemented in a wide variety of systems using simple circuit elements only View full abstract»

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  • A tensor approach to higher order expectations of quantized chaotic trajectories. I. General theory and specialization to piecewise affine Markov systems

    Page(s): 1571 - 1583
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    The problem of computing any-order expectations of trajectories generated by discrete-time one-dimensional chaotic systems is addressed by means of a suitable generalization of the Perron-Frobenius operator and its quantization. Tools from tensor algebra are introduced and analytical expressions for the special case of piecewise-affine Markov maps are obtained. Results are further specialized for a family of maps with quite general features. As an example application, some cross- and self-interference terms are computed, which are involved in the evaluation of the performance of chaos-based DS-CDMA systems in an asynchronous multipath environment View full abstract»

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  • A tensor approach to higher order expectations of chaotic trajectories. II. Application to chaos-based DS-CDMA in multipath environments

    Page(s): 1584 - 1596
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    For pt. I see ibid., vol. 47, no. 11, p. 1571-1583 (2000). Chaos-based DS-CDMA systems in presence of a dispersive channel are analyzed to obtain analytical expression for key quantities involved in performance evaluation. To do so a simple but realistic exponential model for dispersive channel characterization is adopted to derive an estimation of the magnitude of error causes in terms of second-, third- and fourth-order correlation properties of the spreading sequences. These properties are analytically computed by choosing a suitable set of chaotic-maps for sequences generation and using some tools from the general theory developed in the companion paper. Such a theory expresses higher order expectations as products between tensors made of the spreading symbols and tensors accounting for the mixed causal-stochastic nature of the chaotic generators. The factorization of these tensors naturally leads to a handy exponential form for correlations. With this a closed form is given for the variances of disturbing terms which, under the standard Gaussian assumption, determine the system performance. Such closed forms are finally exploited to optimize the performance of the system under different channel and load conditions, showing an improvement over what can be obtained by some classical spreading sequences View full abstract»

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  • CMOS circuits generating arbitrary chaos by using pulsewidth modulation techniques

    Page(s): 1652 - 1657
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    This paper describes CMOS circuits generating arbitrary chaotic signals. The proposed circuits implement discrete-time continuous-state dynamics by means of analog processing in a time domain. Arbitrary nonlinear transformation functions can be generated by using the conversion from an analog voltage to a pulsewidth modulation (PWM) signal; for the transformation, time-domain nonlinear voltage waveforms having the same shape as the inverse function of the desired transformation function are used. The circuit simultaneously outputs both voltage and PWM signals following the desired dynamics. If the nonlinear voltage waveforms are generated by digital circuits and D/A converters with low-pass filters, high flexibility and controllability are obtained. Moreover, the nonlinear dynamics can be changed in real time. Common waveform generators can be shared by many independent chaos generator circuits. Because the proposed circuits mainly consist of capacitors, switches, and CMOS logic gates, they are suitable for scaled VLSI implementation. CMOS circuits generating arbitrary chaos with up to third-order nonlinearity and two variables have been designed and fabricated using a 0.4 μm CMOS process. Chaos has been successfully generated by using tent, logistic, and Henon maps, and a chaotic neuron model View full abstract»

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  • Interaction of transmission network and load phasor dynamics in electric power systems

    Page(s): 1613 - 1620
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    This paper is concerned with modeling and analysis of an interconnected electric power system for frequency ranges in which phasor dynamics of transmission lines and loads may be important to include. In most studies, only phasor dynamics of generators are taken into account. Dynamics of all other system components (transmission lines, loads, and generator stator windings) are assumed stable and instantaneous (static). While several papers have examined phasor dynamics of the transmission lines, particularly when these are equipped with FACTS devices, no systematic investigation has been carried out concerning validity of static load models in this case. It is shown in this paper that problems may arise in particular when a static constant power load model is used at the same time that phasor dynamics of transmission lines are included. Standard singular perturbation-based arguments for neglecting load dynamics are shown not to be applicable in this case. More generally, the paper raises a general concern about consistency of electric power system models in frequency ranges where phasor dynamics of the devices typically assumed to be static must be taken into consideration View full abstract»

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  • Bipolar transistor circuit analysis using the Lambert W-function

    Page(s): 1621 - 1633
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    The generalized diode equation describes conduction in a diode with series resistance. An analytical solution for the generalized diode equation has been elusive; however, one was found based on the transcendental equation w=ln(x/w). The solution of this equation; w=W(x), is traditionally referred to as the Lambert W-function. This function provides a long sought after natural continuity between exponential diode and linear resistor behavior. The W-function also describes more general circuits consisting of a diode or bipolar transistor with local linear negative or positive feedback. The properties of W(x) are reviewed and several iterative methods for its calculation are compared. Three approximations for the W function are derived which can simplify bipolar circuit analysis and design. The practical utility of the proposed solutions are demonstrated in four circuits along with experimental confirmation: a common emitter amplifier with an emitter or collector feedback resistor, Schmitt trigger threshold temperature compensation, bandgap stabilized current source, and a novel current-efficient laser driver View full abstract»

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  • Convergence analysis of waveform relaxation for nonlinear differential-algebraic equations of index one

    Page(s): 1639 - 1645
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    We give a new and simple convergence theorem on the waveform relaxation (WR) solution for a system of nonlinear differential-algebraic equations of index one. We show that if the norms of certain matrices derived from the Jacobians of the system functions are less than one, then the WR solution converges. The new sufficient condition includes previously reported conditions as special cases. Examples are given to confirm the theoretical analysis View full abstract»

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  • Design of a high-efficiency class DE tuned power oscillator

    Page(s): 1645 - 1649
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    This paper presents a high-efficiency class DE tuned power oscillator, along with the analysis, design procedure, and experimental results. It consists of a class DE inverter and a feedback-loop for phase matching and is especially applicable for high frequency performance because it minimizes the power dissipated when turning ON each MOSFET. In contrast to conventional inverters, the proposed oscillator needs an additional complicated circuit including a driver circuit to start the oscillation. The measured efficiency was over 90% at the operating frequency of 1.0 MHz and output of 2.3 W View full abstract»

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  • Effective chaotic orbit tracker: a prediction-based digital redesign approach

    Page(s): 1557 - 1570
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    It has been widely experienced that tracking (targeting) a periodic orbit embedded within a chaotic attractor often encounters an essential issue of numerical sensitivity. In this paper, we develop an effective digital tracker for continuous-time chaotic orbit tracking, which is insensitive to numerical errors. The design is based on some advanced digital redesign techniques equipped with a predictive feature. The new digital tracker allows for a relatively large sampling time, which can be important in some applications such as in chaotic biological systems. A new chaotic attractor is used as an example for illustration and demonstration View full abstract»

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