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

Issue 3 • Date March 2002

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Displaying Results 1 - 23 of 23
  • Correction to guest editorial for the December 2001 issue

    Publication Year: 2002 , Page(s): 408 - 410
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (173 KB) |  | HTML iconHTML  

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  • Generalized state-space observers for chaotic synchronization and secure communication

    Publication Year: 2002 , Page(s): 345 - 349
    Cited by:  Papers (97)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    In this brief, a simple and useful technique for both synchronization and secure communication of chaotic systems is developed. The proposed approach is based on generalized state space observer design for a class of nonlinear systems. By means of regular transformations we show that asymptotic stability is assured under mild conditions. To show accuracy and high performances of the proposed method, the well-known chaotic Lorentz system will be considered as an illustrative example View full abstract»

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  • Zero location of polynomials with respect to the unit-circle unhampered by nonessential singularities

    Publication Year: 2002 , Page(s): 305 - 314
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (346 KB) |  | HTML iconHTML  

    A method to determine the distribution of the zeros of a polynomial with respect to the unit-circle, proposed by this author in the past, is revisited and refined. The revised procedure remains recursive and nonsingular for polynomials whose Schur-Cohn matrix is not singular. Other nonessential singularities that previously caused interruption of the recursion are assimilated into a more general regular form of the three-term recursion of symmetric polynomials that underlies the method. The new form of the procedure does not compromise the simplicity of the rules to extract the information on the distribution that are proved using a different and more direct proof, based on the evaluation of the Cauchy index along the unit-circle. The low count of operations of the original procedure (recognized as the least cost solution for the problem) is maintained and actually gets better by the elimination of nonessential singularities. The improved features make the revised procedure a better all-around unit-circle zero location method for any real or complex polynomial. Its wider range of regularity should also benefit a variety of related signal processing and algebraic problems including some that were already affected by the original formulation View full abstract»

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  • Consistency of a time-stepping method for a class of piecewise-linear networks

    Publication Year: 2002 , Page(s): 349 - 357
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (455 KB) |  | HTML iconHTML  

    In this brief, we will study the computation of transient solutions of a class of piecewise-linear (PL) circuits. The network models will be so-called linear complementarity systems, which can be seen as dynamical extensions of the PL modeling structure. In particular, the numerical simulation will be based on a time-stepping method using the well-known backward Euler scheme. It will be demonstrated, by means of an example, that this widely applied time-stepping method does not necessarily produce useful output for arbitrary linear dynamical systems with ideal diode characteristics. Next the consistency of the method will be proven for PL networks that can be realized by linear passive circuit elements and ideal diodes by showing that the approximations generated by the method converge to the true solution of the system in a suitable sense. To give such a consistency proof, a fundamental framework developed previously is indispensable as it proposes a precise definition of a "solution" of a linear complementarity system and provides conditions under which solutions exist and are unique View full abstract»

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  • Complex dynamic phenomena in space-invariant cellular neural networks

    Publication Year: 2002 , Page(s): 340 - 345
    Cited by:  Papers (9)
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    It is shown that first-order autonomous space-invariant cellular neural networks (CNNs) may exhibit a complex dynamic behavior (i.e., equilibrium point and limit cycle bifurcation, strange and chaotic attractors). The most significant limit cycle bifurcation processes, leading to chaos, are investigated through the computation of the corresponding Floquet's multipliers and Lyapunov exponents. It is worth noting that most practical CNN implementations exploit first-order cells and space-invariant templates: so far no example of complex dynamics has been shown in first-order autonomous space-invariant CNNs View full abstract»

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  • Sense amplifier signal margins and process sensitivities [DRAM]

    Publication Year: 2002 , Page(s): 269 - 275
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    A method for determining the signal margins of a sense amplifier based on the time required for the sense amplifier to achieve a given voltage separation is presented. The sense-time method generates a continuous curve whose peak value corresponds to the desired signal margin voltage and can be easily refined to provide additional precision. The method is illustrated by examining the behavior of a DRAM sense amplifier/bitline system with respect to the effects of imbalance in the parameters that most significantly affect its operation. The results of this study provide a link between the fluctuations inherent in integrated circuit processing technology and the variability of DRAM refresh times View full abstract»

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  • On the dynamic analysis of piecewise-linear networks

    Publication Year: 2002 , Page(s): 315 - 327
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    Piecewise-linear (PL) modeling is often used to approximate the behavior of nonlinear circuits. One of the possible PL modeling methodologies is based on the linear complementarity problem, and this approach has already been used extensively in the circuits and systems community for static networks. In this paper, the object of study is dynamic electrical circuits that can be recast as linear complementarity systems, i.e. as interconnections of linear time-invariant differential equations and complementarity conditions (ideal diode characteristics). A mathematically precise framework is developed that formalizes the mixed discrete and continuous behavior of these switched networks. Within this framework, the fundamental question of well-posedness (existence and uniqueness of solution trajectories given an initial condition) is studied and additional properties of the behavior are derived. For instance, a full characterization is presented of the inconsistent states View full abstract»

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  • Perturbation theory for inhomogeneous transmission lines

    Publication Year: 2002 , Page(s): 289 - 297
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB) |  | HTML iconHTML  

    We present a novel technique to calculate the transmission and reflection properties of inhomogeneous lossy transmission lines. It is based on a perturbation expansion of the relevant telegrapher's equation around the homogeneous solution. The method reveals that the transmission properties are unaffected to first order in the impedance and admittance, while reflection properties are modified by first-order terms. Extending the analysis to second order, we find correction terms for both transmission and reflection. These allow us to understand the statistical properties of the information bearing capacity and the echo of the inhomogeneous transmission line. The correction to the transmission properties is fully reciprocal, despite the absence of any symmetry properties. We compute scaling laws for echo and capacity View full abstract»

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  • Theory and experimental realization of observer-based discrete-time hyperchaos synchronization

    Publication Year: 2002 , Page(s): 373 - 378
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    Research in the synchronization of dynamical systems has been mainly focused on chaotic rather than hyperchaotic systems and on continuous-time rather than discrete-time systems. Numerical simulations dominate these studies and results typically lack experimental data. This brief fills these gaps by 1) presenting a technique for the exact (dead-beat) synchronization of hyperchaotic discrete-time systems; and 2) describing an electronic implementation of this technique for the generalized Henon map. The synchronization strategy is based on the observer concept and enables a wide class of hyperchaotic discrete-time systems to be synchronized via a scalar signal. An electronic implementation provides verification of the theoretical results and confirms the feasibility of realizing this approach in hardware View full abstract»

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  • Two-channel RSNS dynamic range

    Publication Year: 2002 , Page(s): 395 - 397
    Cited by:  Papers (9)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (218 KB) |  | HTML iconHTML  

    Symmetrical number systems have been explored for many applications in both analog and digital signal processing due to the common availability of symmetrical folding waveforms (e.g., cos2 ). The robust symmetrical number system (RSNS) is a modular scheme in which the integer values within each modulus, when considered together, change one at a time at the next code position (Gray code properties). Although the RSNS has a smaller dynamic range than the optimum symmetrical number system, the RSNS Gray code properties make it particularly attractive for error control. In the past, computer search algorithms have been used to determine the RSNS dynamic range (length of unambiguous vectors). In this brief, we define the two-channel RSKS and present a theorem that gives its dynamic range for relatively prime moduli m1, m2, 5 ⩽ m1 ⩽ m2 View full abstract»

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  • Algebraic phase unwrapping and zero distribution of polynomial for continuous-time systems

    Publication Year: 2002 , Page(s): 298 - 304
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (346 KB) |  | HTML iconHTML  

    An analytic solution is provided to the symbolic algebra-based computational problem for the unwrapped phase (that can be uniquely expressed as an integral involving itself and its derivative) of a continuous-time linear time-invariant system whose characteristic polynomial has coefficients belonging to the algebraically closed field of complex numbers. This solution is based on the use of the classical Cauchy indices. Application and adaptation of this analytic solution to an arbitrary univariate polynomial, yields its zero distribution with respect to the unbounded imaginary axis in the complex plane. Importantly, the algorithm that yields this zero distribution is designed to enforce the nonoccurrence of singular cases and can be implemented to any desired accuracy by rational operations View full abstract»

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  • Discretization schemes for fractional-order differentiators and integrators

    Publication Year: 2002 , Page(s): 363 - 367
    Cited by:  Papers (132)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB) |  | HTML iconHTML  

    For fractional-order differentiator sr where r is a real number, its discretization is a key step in digital implementation. Two discretization methods are presented. The first scheme is a direct recursive discretization of the Tustin operator. The second one is a direct discretization method using the Al-Alaoui operator via continued fraction expansion (CFE). The approximate discretization is minimum phase and stable. Detailed discretization procedures and short MATLAB scripts are given. Examples are included for illustration View full abstract»

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  • A CNN algorithm for real time analysis of DNA microarrays

    Publication Year: 2002 , Page(s): 335 - 340
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    The work focuses on a new approach for DNA-chip image processing by using the cellular neural network (CNN) paradigm. In particular, the work aims to solve the main issues in automatic classification and spot validation that arise during an automatic DNA microarray analysis procedure. This contribution briefly presents the basic DNA micro-array technique and the state-of-the-art technologies, and introduces the idea of processing DNA chip data via CNNs, reporting suitable examples. The algorithm described has been developed using a high level language, dedicated to CNN universal machine (CNNUM) chip programming, and validated on a typical fluorescence image from a DNA microarray after hybridization View full abstract»

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  • Bifurcations and chaos in a permanent-magnet synchronous motor

    Publication Year: 2002 , Page(s): 383 - 387
    Cited by:  Papers (50)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (281 KB) |  | HTML iconHTML  

    This brief studies dynamic characteristics of a permanent-magnet synchronous motor (PMSM). The mathematical model of the PMSM is first derived, which is fit for carrying out the bifurcation and chaos analysis. Then, the steady-state characteristics of the system, when subject to constant input voltage and constant external torque, are formulated. Three cases are discussed and, for each case, conditions are derived under which the dynamic characteristics of the system are either of steady-state type, limit cycles or chaotic, thus by properly adjusting some system parameters, the system can exhibit limit cycles (LCs) or chaotic behaviors at will. Finally, computer simulations are presented to verify the existence of strange attractors in the PMSM View full abstract»

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  • Hopf bifurcation for maps: a frequency-domain approach

    Publication Year: 2002 , Page(s): 281 - 288
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (361 KB)  

    The application of the graphical Hopf theorem (GHT) as a tool for detecting invariant cycles in maps is presented. The invariant cycle emerging from the bifurcation is approximated using an analogous version of the GHT for continuous-time systems. This technique is formulated in the so-called frequency domain and it involves the use of the Nyquist stability criterion and the harmonic balance method. Some examples are included for illustration View full abstract»

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  • Nonlinear effects of radio-frequency interference in operational amplifiers

    Publication Year: 2002 , Page(s): 367 - 372
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    In this brief, the susceptibility of operational amplifiers to radio frequency interference (RFI) is studied by a new analytical model. The proposed model, in particular, points out the dependence of the RFI induced dc offset voltage shift in operational amplifiers on design parameters and parasitics, giving both a good insight into the nonlinear mechanisms involved in the phenomenon and a support to integrated circuit designers in order to develop high immunity operational amplifiers. The validity of the proposed approach is discussed comparing model predictions with the results of computer simulations and experimental measurements View full abstract»

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  • Competitively coupled orientation selective cellular neural networks

    Publication Year: 2002 , Page(s): 388 - 394
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (434 KB) |  | HTML iconHTML  

    We extend previous work in orientation selective cellular neural networks to include competitive couplings between different layers tuned to different orientations and spatial frequencies. The presence of these interactions sharpens the spatial frequency tuning of the filters in two ways, when compared to a similar architecture proposed previously which lacks these interactions. The first is the introduction of nulls in the frequency response. The second is the introduction of constraints on the passbands of the coupled layers. Based on an understanding of these two effects, we propose a method for choosing spatial frequency tunings of the individual layers to enhance orientation selectivity in the coupled system View full abstract»

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  • Study of lasers as nonlinear dynamical systems

    Publication Year: 2002 , Page(s): 328 - 334
    Cited by:  Papers (1)
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    The rate equations of a large class of lasers are considered. These equations represent the evolution of photon and carrier densities in the laser, where the laser output is proportional to the photon density. By applying techniques from the theory of dynamical systems to the rate equations, four important properties of the lasers are rigorously proved. These properties are: (1) for positive and bounded inputs, the laser outputs are bounded; (2) for positive constant inputs, the laser does not exhibit a limit cycle behavior; (3) for a positive constant input, the laser output settles at a positive steady-state value; (4) for positive constant inputs, the relaxation oscillations in the laser output can be attenuated if the coefficient of the spontaneous emission factor is increased View full abstract»

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  • CDS noise reduction of partially reset charge-detection nodes

    Publication Year: 2002 , Page(s): 276 - 280
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (275 KB) |  | HTML iconHTML  

    The paper describes noise reduction obtained by using the correlated double sampling (CDS) technique to process signals from destructively reset charge detection nodes where the resetting process has not been fully completed. In standard cases, the charge-detection-node-reset time constant is very short, which allows the node Fermi level to fully equilibrate with the reference. This article focuses on cases where the clocking frequency is high and the charge-detection-node-reset time constant is comparable or larger than the reset time interval. The derived formulas for the noise power spectral density and variance are thus more general and apply to a wider range of applications. Despite the generality, the obtained results have a closed analytic form and are useful for simple circuit and device parameter optimization programs. The results and derivations are based on a simple model and first principles to avoid tacit assumptions that are sometimes present in other previously published results View full abstract»

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  • On positive realness of descriptor systems

    Publication Year: 2002 , Page(s): 401 - 407
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    In this paper, the positive realness of descriptor systems is studied. For the continuous-time case, two positive real lemmas are given, based on a generalized algebraic Riccati equation and inequality respectively. For the discrete-time case, the positive real lemma is given in terms of a generalized algebraic Riccati inequality View full abstract»

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  • Using the cyclostationary properties of chaotic signals for communications

    Publication Year: 2002 , Page(s): 357 - 362
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    Cyclostationary signals have an expectation value which varies periodically in time. Chaotic signals that have large components at some discrete frequencies in their power spectra can be cyclostationary. The cyclostationarity persists even if the discrete frequency components are removed from the chaotic signal, leaving a signal with a purely broad band frequency spectrum. In this brief, a communications system is created by modulating information onto the periodic parts of a chaotic signal and then removing the periodic parts from the frequency spectrum. At the receiver, the periodic parts of the spectrum are restored by means of a nonlinear operation. This system is demonstrated both in simulations and real circuits, and the performance of this system is measured in simulations. Finally, some of the reasons why such a scheme might be useful are discussed View full abstract»

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  • Generation of frequency-response templates for linear systems with an uncertain time delay and multilinearly-correlated parameter perturbations

    Publication Year: 2002 , Page(s): 378 - 383
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB) |  | HTML iconHTML  

    A simplicial algorithm is applied in this brief to generate frequency-response templates for a class of transfer functions having an uncertain time delay and multilinearly correlated parameter perturbations. It relies on developing a new zero-inclusion test algorithm for checking whether the origin is included in the image of a box T × Q = [τ-, τ+] × Π i=1m-1[qi-, qi +] under a mapping of the form f (τ, q) = g(q) + h(q)e -jωτ, where g(q) and h(q) are multilinear complex-valued functions of q ∈ Q. We present easy-to-check sufficient conditions for the zero inclusion and exclusion of the value set f (T, Q). Using these sufficient conditions on subdivisions in the parameter box T × Q, we implement a branch-and-bound zero-inclusion test algorithm. To illustrate the proposed algorithm, we provide a numerical example View full abstract»

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  • An efficient parallel algorithm for planarization problem

    Publication Year: 2002 , Page(s): 397 - 401
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (289 KB) |  | HTML iconHTML  

    A parallel algorithm for solving the planarization problem using a gradient ascent learning of Hopfield network is presented. This algorithm which is designed to embed a graph on a plane, uses the Hopfield neural network to get a near-maximal planar subgraph, and increase the energy by modifying weights in a gradient ascent direction to help the network escape from the state of the near-maximal planar subgraph to the state of the maximal planar subgraph or better one. The proposed algorithm is verified by a large number of simulation runs and compared with other parallel algorithms for the planarization problem. The experimental results show that the proposed algorithm can generate as good as or better solutions than the other existing parallel algorithm for the planarization problem View full abstract»

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