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

Issue 8 • Date Aug. 1996

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Displaying Results 1 - 16 of 16
  • Comment on "How to identify unstable DC operating points"

    Publication Year: 1996 , Page(s): 705 - 707
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    For original paper see M.M. Green and A.N. Willson, Jr., ibid., vol.39, pp.820-32 (1992). The modeling of capacitors and inductors in nonlinear circuits is discussed. In a previous paper by the author a theorem stated that all dependent current (voltage) sources must be terminated by a positive-valued capacitor (inductor). In this letter it is shown that this requirement can be relaxed so that only ports that contain controlling signals are required to be terminated by reactive elements. View full abstract»

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  • Stability analysis of differential inclusions in Banach space with applications to nonlinear systems with time delays

    Publication Year: 1996 , Page(s): 617 - 626
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    We present new stability results for dynamical systems determined by a class of differential inclusions on Banach space. One of the results shows that under reasonable conditions, the same Lyapunov function can be used in analyzing the stability properties of a given differential inclusion and the stability properties of its convexification. We also establish a result for differential inclusions which is analogous to invariance theory type results for differential equations. To demonstrate applicability, we use the above results in the analysis of the absolute stability problem of regulator systems with multinonlinearities and time delays. Also, we apply the above results in the stability analysis of operating points (equilibria) of a class of integrated circuits with time delays, with an emphasis on a class of artificial neural networks for associative memories. In the applications, we reduce the stability problem of some given nonlinear systems with time delays to the stability problem of a finite number of linear systems with time delays View full abstract»

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  • Quasi-stability regions of nonlinear dynamical systems: theory

    Publication Year: 1996 , Page(s): 627 - 635
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (940 KB)  

    The concept of a stability region (region of attraction) of nonlinear dynamical systems is widely accepted in many fields such as engineering and the sciences. When utilizing this concept, the Lyapunov function approach has been found to give rather conservative estimations of the stability regions of many nonlinear systems. In this paper we study the notion of a quasi-stability region and develop a comprehensive theory for it. It is shown that, working on the concept of quasi-stability regions, one can greatly overcome the problem of conservative estimations of stability regions using the Lyapunov function approach. A complete characterization of quasi-stability regions is presented. Dynamical as well as topological properties of quasi-stability regions are also derived. The quasi-stability regions are shown to be robust relative to small perturbations of the underlying vector fields. The class of nonlinear dynamical systems whose stability regions equal their quasi-stability regions is characterized View full abstract»

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  • Elementary canonical state models of Chua's circuit family

    Publication Year: 1996 , Page(s): 702 - 705
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    Two simple state models of the third-order autonomous piecewise-linear (PWL) dynamical system, topologically conjugate to Chua's circuit family, are proposed. Unlike the known canonical systems they are canonical also with respect to the relation between their parameters and the corresponding eigenvalues, i.e., their state equations contain minimum nonzero coefficients directly determined by the equivalent eigenvalue parameters associated with the two regions of PWL vector field in R3. The corresponding circuit models containing integrators and adders are introduced. The mutual linear conjugacy between these two elementary canonical state models and their relation with Chua's circuit family is suggested. The computer generated chaos for the double-scroll attractor using one of the developed models is shown View full abstract»

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  • Quasi-stability regions of nonlinear dynamical systems: optimal estimations

    Publication Year: 1996 , Page(s): 636 - 643
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (804 KB)  

    In this paper, we develop an effective scheme to estimate stability regions by using an energy function that is a generalization of the Lyapunov functions. It is shown that the scheme can optimally estimate stability regions. A fairly comprehensive study for the structure of the constant energy surface lying inside the quasi-stability region is presented. A topological characterization, as well as a dynamical characterization for the point on the quasi-stability boundary and the point on the stability boundary with the minimum value of an energy function are derived. These characterizations are then used in the development of a computational scheme to estimate quasi-stability regions. By utilizing an energy function approach (or Lyapunov function approach), this scheme can significantly reduce conservativeness in estimating the stability region, because the estimated stability region characterized by the corresponding energy function is the largest one within that stability region View full abstract»

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  • On bounds of the parametric range of bifurcation of Chua's circuit

    Publication Year: 1996 , Page(s): 691 - 695
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    This brief presents general representations for bounds on the parametric range of the G-, C1-, L-, and C2-bifurcations of Chua's circuit. The critical points for the appearance of bifurcations are derived. Consequently, chaos can be quenched by adjusting parameters to meet these conditions View full abstract»

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  • Chaotic behavior in first-order autonomous continuous-time systems with delay

    Publication Year: 1996 , Page(s): 700 - 702
    Cited by:  Papers (52)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    In this letter we present a very simple model described by an autonomous continuous-time difference-differential equation with only one variable. By choosing suitable parameters and delay, chaotic behavior has been observed, dynamics of the system are analyzed briefly. This indicates that chaos can occur even in one-dimensional continuous-time systems with delay View full abstract»

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  • Class D current-driven transformer center-tapped controllable synchronous rectifier

    Publication Year: 1996 , Page(s): 670 - 680
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    We present analysis and experimental results for a phase-controlled, synchronous, transformer center-tapped rectifier. The rectifier is driven by a resonant inverter. A digital control adjusts the phase in the driver of the rectifier MOSFET's. The output voltage is regulated while maintaining a 94% maximum and a 80% minimum efficiency for a 30% line swing, and 50% efficiency for a load swing of 400% from full power. Experimental results are presented for a 10 W rectifier with an output voltage of 3.3 V. Theoretical calculations agreed well with the experimental results, with certain deviations due to the nonidealities of the transformer. The center-tapped topology allows for high efficiency even at 3.3 V and simplifies the control design, providing simple regulation View full abstract»

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  • VLSI implementation of locally connected neural network for solving partial differential equations

    Publication Year: 1996 , Page(s): 687 - 690
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    This brief presents a locally connected neural network for solving a class of partial differential equations. Each neural cell is designed using active and passive components. An architecture is described to control the weights between the neurons. The major benefit of the architecture is that it does not require additional space outside of the cell for routing the control lines no matter how many cells are used. The CMOS VLSI implementation of a sixteen cell network was fabricated and measured. The results of this network are compared to the numerical solution of the partial differential equations View full abstract»

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  • Novel single-resistance-controlled-oscillator configuration using current feedback amplifiers

    Publication Year: 1996 , Page(s): 698 - 700
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    A novel configuration is presented which can realize single-resistance controlled active-RC and active-R oscillators and low-pass/band-pass filters from the same structure View full abstract»

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  • A unified approach to the approximate symbolic analysis of large analog integrated circuits

    Publication Year: 1996 , Page(s): 656 - 669
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1212 KB)  

    This paper describes a unified approach to the approximate symbolic analysis of large linearized analog circuits in the complex frequency domain. It combines two new approximation-during-computation strategies with a variation of the classical two-graph tree enumeration method. The first strategy is to generate common trees of the two-graphs, and therefore the product terms in the symbolic network function, in the decreasing order of magnitude. This is made possible by our algorithm for generating color-constrained spanning trees in the order of weight. It avoids the burden of computing all the product terms only to find most of them numerically negligible. The second approximation strategy is the sensitivity-based simplification of two-graphs, which excludes from the two-graphs many of the insignificant circuit elements that have little effect on the network function being derived. It significantly reduces the complexity of the two-graphs before tree enumeration. Our approach is therefore able to symbolically analyze much larger analog integrated circuits than previously reported, using complete small signal models for the semiconductor devices. We show accurate yet reasonably sized symbolic network functions for integrated circuits with up to 39 transistors whereas previous approaches were limited to less than 15. For even larger circuits, the limit is imposed mainly by the interpretability of the generated symbolic network function View full abstract»

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  • Some corrections on “Discrete-time positive-real lemma revisited: the discrete-time counterpart of the Kalman-Yakubovitch lemma”

    Publication Year: 1996 , Page(s): 707 - 708
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    For original paper see K. Premaratne and E.I. Jury, ibid., vol.41, pp.747-50 (1994). In the above paper, a notion that may be considered the discrete-time counterpart of positive realness was presented. The corresponding counterpart to the Kalman-Yakubovitch lemma and algebraic necessary and sufficient conditions were also presented. This note aims to correct some of the inconsistencies that were later realized View full abstract»

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  • Eigenvalue upper and lower bounds of the solution for the continuous algebraic matrix Riccati equation

    Publication Year: 1996 , Page(s): 683 - 686
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    A lower bound and several upper bounds of the solution eigenvalues for the continuous algebraic matrix Riccati equation are developed. It is shown that the lower bound is new and tighter than the previous reported one and the upper bounds are concise and less restrictive than the majority of those appeared in the literature. Furthermore, by these results, some bounds for the extreme eigenvalues of the solution matrix of the continuous Lyapunov equation are also defined View full abstract»

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  • Oversampling architecture for analog harmonic modulation

    Publication Year: 1996 , Page(s): 696 - 698
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    We propose a technique for sinusoidal modulation of analog signals, which requires neither multiplication nor analog sine wave generation. The modulating signal is an oversampled representation of a sine in the form of a periodic binary sequence, optimized to minimize intermodulation distortion. A 2-to-1 multiplexer performs the modulation multiplication. With third-order low-pass filtering of the input signal, the technique achieves 60 dB of linear dynamic range for a sequence of length 256, conveniently generated with an 11-address decoder and an 8-b counter View full abstract»

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  • A direct proof of the additional element theorem

    Publication Year: 1996 , Page(s): 681 - 683
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    A direct proof of a method of calculating the effect of adding an element to a circuit is presented. This proof which is not based on tensor, matrix, or signal flow graph formulation of the problem uses simpler and elementary concepts to arrive at the result View full abstract»

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  • A neural network for detection of signals in communication

    Publication Year: 1996 , Page(s): 644 - 655
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB)  

    An architecture of densely connected compact neural networks is presented for the maximum-likelihood sequence estimation (MLSE) of signals in digital communications. The combinatorial minimization of the detection cost Is performed through the optimization of a concave Lyapunov function associated with the network, and truly paralleled operations can be achieved via the collective computational behaviors. In addition, the MLSE performance can be improved by a paralleled annealing technique which has been developed for obtaining optimal or near-optimal solutions in high-speed, real-time applications. Given a sequence of length n, the network of complexity and throughput rate are O(L) and n/Tc, respectively, where L is the number of symbols the inference spans and Tc is the convergence time. The hardware architecture as well as network models, neuron models, and methods of feeding the input to the network are addressed in terms of the probability of error. Through the simulations, it is demonstrated that the proposed compact neural network approach is an efficient method of realizing the MLSE receiver View full abstract»

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