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

Issue 4 • Date April 1998

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Displaying Results 1 - 22 of 22
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  • The influence of the boundary conditions on the robustness of a CNN

    Page(s): 511 - 515
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    We investigate the issue of robustness and how it is affected by the choice of boundary values for a given template set. First we introduce a measure of robustness, and then we show that, in some cases, an appropriate choice of boundary value may increase the attainable robustness. In other cases, the boundary value may be varied within some interval without loss of robustness View full abstract»

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  • Switched-capacitor inverter with high power density and enhanced regulation capability

    Page(s): 336 - 347
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    A DC-AC inverter containing no inductors or transformers is presented. The role of the magnetic devices is played by a switched-capacitor (SC) circuit, formed by two subcircuits. Each SC-subcircuit contains 15 basic cells, each one formed by one capacitor, two MOSFETs and two diodes. The sinusoidal output waveform is realized in a staircase, formed by 64 steps. To achieve each step, the inverter operates like a step-up DC-DC converter: by using a certain number of SC-cells, the input voltage is boosted to the voltage required by the step in consideration. Each step is implemented in a large number of switching cycles. In each cycle, the inverter goes through four phases; according to a designed switching sequence, some of the capacitors of the SC-cells involved in the respective step are in a charging process from line, while the others are in a discharging process to the load. The phases 2 and 4 have a regulation role only. A duty cycle control is used. A Fourier analysis evidences the clean AC output waveform. The inverter exhibits low weight, high power density, and enhanced regulation for large changes in line and load View full abstract»

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  • Chaotic complex spreading sequences for asynchronous DS-CDMA. Part II. Some theoretical performance bounds

    Page(s): 496 - 506
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    For pt.I see G. Mazzini et al., vol.44, pp.937-47 (Oct. 1997). This paper and its companion (Part I) are devoted to the evaluation of the impact of chaos-based techniques on communications systems with asynchronous Code Division Multiple Access. In Part I, a performance index was introduced and exploited to a priori estimate the performance of DS-CDMA communications systems based on chaotic spreading sequences, and to compare it to that of conventional systems. Here, tools from nonlinear dynamical system theory are employed to give a formal ground for those results. Analytical bounds on the expected partial cross correlation between spreading sequences obtained by quantizing and repeating a chaotic time series are derived, ensuring general applicability of such a technique in a real environment. Further analytical arguments guarantee that, when particular chaotic generators are used, expected performance is not worse than that of a well-behaving communications system. This analysis ensures also that, unlike conventional sequences, chaotic spreading codes can be generated for any number of users and allocated bandwidth View full abstract»

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  • Analysis of a bidirectional coupled-inductor Cuk converter operating in sliding mode

    Page(s): 355 - 363
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    Analytic models for a bidirectional coupled-inductor Cuk converter operating in sliding mode are described. Using a linear combination of the converter four state variable errors as a general switching surface, the expression for the equivalent control is derived and the coordinates of the equilibrium point are obtained. Particular cases of the general switching surface are subsequently analyzed in detail: (1) surfaces for ideal line regulation, (2) surfaces for ideal load regulation, and (3) surfaces for hysteretic current control. Simulation results verifying the analytical predictions are presented View full abstract»

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  • OPF chaos control in a circuit containing a feedback voltage pulse generator

    Page(s): 473 - 480
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    In this paper, we discuss occasional proportional feedback (OPF) chaos control in a circuit containing a feedback voltage pulse generator. First, we show that the Poincare map of this oscillator without the chaos control is derived rigorously as a one-dimensional mapping. This mapping satisfies Li-Yorke's extended period three condition (1975). Hence, the mapping has an n-periodic point for any natural number n, and the appearance of chaos in Li-Yorke's sense is explained. Furthermore, OPF for piecewise-linear systems is applied to this oscillator. Each unstable orbit can be stabilized, and periodic orbits with one to ten periods are successfully stabilized in circuit experiments View full abstract»

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  • Digital tracking control for PWM systems with unacceptable zeros

    Page(s): 397 - 407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    Perfect output tracking, which requires inversion of the input-output dynamics, is not always a practical control objective. Difficulties are encountered for systems with zeros which are unstable, or stable but lightly damped. When the zeros are unacceptable in the above sense, perfect output tracking would require the control to be either unbounded, or bounded but highly oscillatory. In this paper, an approximate output tracking control design method is introduced for pulsewidth modulated (PWM) systems with unacceptable zeros. The design method is applied to the nonlinear sampled-data model of the PWM system, and is based on output redefinition. Although the new approach leads to approximate rather than perfect output tracking, it guarantees bounded and nonoscillatory responses View full abstract»

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  • Quantized sampling as sampling with uncertainty in time and amplitude

    Page(s): 458 - 463
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    In classical sampled quantization, the signal is sampled at discrete times and at discrete values, resulting in uncertainty of the signal amplitude. However, the sampling times and the boundaries of the quantization intervals are still assumed to be known with infinite precision. The aim of this paper is to study quantization and sampling when these quantities are not known with infinite precision by considering quantized sampling in a general framework as sampling with uncertainty in time and amplitude. We define the concept of a valid quantized sample and consider a quantized sampling of a signal as a collection of valid quantized samples. We show that for continuous signals, a set of valid quantized samples generates a secondary set of valid quantized samples. We illustrate that oversampling can reduce reconstruction errors because oversampling can reduce the uncertainty in the secondary quantized samples. In particular, these secondary quantized samples have uncertainty approaching zero as oversampling increases, provided the sampling time and quantization thresholds are known with infinite precision. For a class of T-periodic bandlimited signals, this implies that the reconstruction error is a function of the oversampling ratio, the uncertainty in the sampling time, the stepsize of the quantizer, and the uncertainty in the quantization thresholds View full abstract»

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  • Robust filtering, prediction, smoothing, and observability of uncertain systems

    Page(s): 446 - 457
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    This paper is concerned with a class of continuous time uncertain systems which satisfy a certain Integral Quadratic Constraint. The problems of robust filtering, robust prediction, and robust smoothing for such systems are defined, and nonconservative solutions are given in terms of Riccati differential equations. This paper also addresses a problem of robust observability for this class of uncertain systems View full abstract»

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  • An efficient technique for the time-domain simulation of power electronic circuits

    Page(s): 364 - 376
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    A general-oriented time-domain simulation algorithm for power electronic circuits is presented. The methodology is based on stepwise quadratic formulation of circuit state variable trajectory with progressive analysis of switches' operation. At each simulation step, the circuit topology is transformed into a purely resistive network which is analyzed by the modified nodal analysis (MNA) technique. The rate of change of each state variable is determined by its parasitic resistance and instantaneous value. The trajectory of each state variable and switch branch voltage is expressed by a quadratic description. A simple and efficient method is used to determine the switching instants of circuit topologies. The prominent features of this approach include: (1) its simplicity in solving resistive network only throughout the analysis without dealing with any complicated Laplace-transformed equation or differential formula; (2) its generality in determining valid circuit topology without prior understanding of the switching relationships; (3) its directness in calculating the switching instants; and (4) its inherent consideration of the parasitic resistance of each reactive element in the analysis. Two examples illustrating the generality and computational efficiency of the proposed algorithm are presented. The simulated results are favorably compared to the method used in available literature and the commercial software, PSpice View full abstract»

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  • Zero voltage soft-commutation PWM DC-DC converter with saturable reactor switch-cascaded diode rectifier

    Page(s): 348 - 354
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    An improved single-ended push-pull (SEPP) half-bridge type zero-voltage soft-switching pulse width modulation (ZVS-PWM) DC-DC power converter is presented in this paper, which makes use of a saturable reactor-assisted lossless capacitor type zero voltage soft-switching method. The SEPP power converter with a high-frequency forward and flyback hybrid transformer link has some advantages such as lowered switching and conduction losses, soft-switching transition operation over a wide load range, constant frequency PWM regulation and minimized Electro Magnetic Interference (EMI) as well as Radio Frequency Interference (RFI) noises. Its operating principle is illustrated and its periodic steady-state circuit analysis is implemented. In order to demonstrate the remarkable effectiveness of this converter's characteristics, feasibility experiments are conducted with a 150 W/200 kHz prototype of a high-frequency link ZVS-PWM DC-DC converter using power MOSFETs with an ultrafast soft-recovery diode View full abstract»

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  • On stability and equilibria of the M-lattice

    Page(s): 408 - 415
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Both the analog Hopfield network and the cellular neural network are special cases of the M-lattice system, recently introduced to the signal processing community. We prove that a subclass of the M-lattice is totally stable, This result also applies to the original cellular neural network as a rigorous proof of its total stability. By analyzing the stability of fixed points, we derive the conditions for driving the equilibrium outputs of another subclass of the M-lattice to binary values. For the cellular neural network, this analysis is a precise formulation of an earlier argument based on circuit diagrams. And for certain special cases of the analog Hopfield network, this analysis explains why the output variables converge to binary values even with nonzero neuron auto-connections. This behavior, observed in computer simulation by researchers for quite some time, is explained for the first time here View full abstract»

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  • Synchronization of chaos and its itinerancy from a network by occasional linear connection

    Page(s): 464 - 472
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    This paper proposes a network of continuous-time chaotic cells and considers its dynamics. The cell includes a bipolar hysteresis whose thresholds vary periodically. The cell exhibits chaos and various stable periodic orbits. We have classified these phenomena in a bifurcation diagram and have clarified basic generation mechanism of these phenomena. The network is constructed by using the Occasional Linear Connection method that connects the cells occasionally by using a sampled state of each cell. The network exhibits various phenomena: synchronization of stable periodic orbits, synchronization of chaos, and chaotic itinerancy. We have classified these phenomena and have clarified their existence condition. These results are guaranteed theoretically and are verified in the laboratory View full abstract»

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  • A generalization of Brayton-Moser's mixed potential function

    Page(s): 423 - 427
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    In this paper we give algorithms for constructing the Brayton-Moser's mixed potential function for a class of nonlinear reciprocal RLC networks, and we state necessary conditions for their existence. We have attempted to find the largest possible class of networks for which such a scalar function of state variables consisting of capacitor voltages and inductor currents can be constructed explicitly. Our results are applicable to a certain subclass of complete networks. From a mathematical point of view, we show that the corresponding network equations belong to the class of index I systems View full abstract»

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  • Robust stability for noncommensurate time-delay systems

    Page(s): 507 - 511
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    Based on the maximum principle and some properties of matrix measure and matrix norm, several new stability criteria for perturbed multiple noncommensurate time-delays systems are proposed. These criteria ensure all roots of the system's characteristic equation lying on or to the left of Re(s)=-α, α>o. Two approaches are used here, one is a direct test which needs some matrix computations and the other is a loci test in which one needs to draw the loci of eigenvalues. With the aid of the convex combination property, the restricted region where unstable characteristic roots of the system locate could be estimated accurately View full abstract»

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  • Effect of switch duty ratio on the performance of class E amplifiers and frequency multipliers

    Page(s): 325 - 335
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    Class E circuits have usually been analyzed for particular values of the switch duty ratio. This paper presents a systematic analysis of the effects of the switch duty ratio on the design values and performance of Class E amplifiers and frequency multipliers, for various values of the output network Q. Some new and promising design possibilities are pointed out, especially for class E frequency multipliers operating at low Q values View full abstract»

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  • Transmission-line-based gyrator

    Page(s): 428 - 433
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    A new approach to efficient gyrator realization is described. The approach was motivated by the observation that a λ/4 segment of transmission line exhibits gyrator-like behavior. A gyrator that operates at low-frequency band, including dc, is formed by the combination of a λ/4 segment of transmission line and a switching network. Using a switching bridge, the low frequency signal is converted into a high-frequency wave which is applied to the input terminals of the transmission line. Then the original waveform is reconstructed using a second switching bridge. Since the switching bridge, as well as the transmission line, are loss free (in principle), the resulting gyrator is also lossless. Such a gyrator can find applications in power processing circuits. A circuit based on this approach was constructed and tested at the energy conversion laboratory, Tel-Aviv University, Israel View full abstract»

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  • Transistor transient studies including transcapacitive current and distributive gate resistance for inverter circuits

    Page(s): 416 - 422
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    We examine two assumptions commonly used in analytical studies of inverter transient performances, that the transcapacitive current during a transient and the distributive gate resistance are negligible. We derive the additional delay time expressions which need to be added to the delay times calculated with such assumptions. In addition, we propose an equivalent lumped transistor which accurately models the transient behavior of the transistor with a distributive gate resistance View full abstract»

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  • Design considerations for integrated continuous-time chaotic oscillators

    Page(s): 481 - 495
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    This paper presents an optimization procedure to choose the chaotic state equation which is best suited for implementation using Gm-C integrated circuit techniques. The paper also presents an analysis of the most significant hardware nonidealities of Gm-C circuits on the chaotic operation-the basis to design robust integrated circuits with reproducible and easily controllable behavior. The techniques in the paper are illustrated through a circuit fabricated in 2.4-μm double-poly technology View full abstract»

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  • Finding all solutions of piecewise-linear resistive circuits using linear programming

    Page(s): 434 - 445
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    An efficient algorithm is proposed for finding all solutions of piecewise-linear resistive circuits. This algorithm is based on a new test for nonexistence of a solution to a system of piecewise-linear equations fi(x)=0(i=1.2,···,n) in a super-region. Unlike the conventional sign test, which checks whether the solution surfaces of the single piecewise-linear equations exist or not in a super-region, the new test checks whether they intersect or not in the super-region. Such a test can be performed by using linear programming. It is shown that the simplex method can be performed very efficiently by exploiting the adjacency of super-regions in each step. The proposed algorithm is much more efficient than the conventional sign test algorithms and can find all solutions of large scale circuits very efficiently. Moreover, it can find all characteristic curves of piecewise-linear resistive circuits View full abstract»

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  • A general constant-frequency pulsewidth modulator and its applications

    Page(s): 386 - 396
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    Constant-frequency pulsewidth modulation (PWM) is the most frequently used method in the control of switching converters. This paper proposes a general PWM modulator that realizes various control schemes with either trailing-edge or leading-edge modulation. Based on that a general double-edge modulator ran be constructed. The proposed modulator is applied to feedforward control of a family of converters, current-mode control with linear or nonlinear compensating slope, and a family of unity-power-factor rectifiers at continuous or discontinuous conduction mode to demonstrate its generality. Experimental and PSPICE verifications are provided View full abstract»

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  • A new methodology for the stability analysis of large-scale power electronics systems

    Page(s): 377 - 385
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    A new methodology is proposed to investigate the large-signal stability of interconnected power electronics systems. The approach consists of decoupling the system into a source subsystem and a load subsystem, and stability of the entire system can be analyzed based on investigating the feedback loop formed by the interconnected source/load system. The proposed methodology requires two stages: 1) since the source and the load are unknown nonlinear subsystems, system identification, which consists of isolating each subsystem into a series combination of a linear part and a nonlinear part, must be performed; and 2) stability analysis of the interconnected system is conducted thereafter based on a developed stability criterion suitable for the nonlinear interconnected source-load model. Applicability of the methodology is verified through the stability analysis of a typical power electronics system View full abstract»

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