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

Issue 9 • Date Sep 1998

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Displaying Results 1 - 20 of 20
  • An analytical model for the power spectral density of a voltage-controlled oscillator and its analogy to the laser linewidth theory

    Publication Year: 1998 , Page(s): 904 - 908
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    We calculate the output power density spectrum for a simple voltage-controlled oscillator (VCO) circuit. The power spectral density of the oscillator is composed of a term related to the high-frequency fluctuations in the feedback loop and a term related to the low-frequency fluctuations of the frequency control voltage. The latter is treated stochastically in a similar fashion to the inhomogeneous line broadening of gas lasers due to the Doppler effect. This additional broadening causes a deviation of the power spectral density from the Lorentzian shape, that is, from the phase noise decay of -6 dB per octave. This is specially pronounced at not-too-large frequency offsets. The analogy between electrical oscillators and optical oscillators (lasers) allows the methods used in optical spectroscopy to be applied. The approach may be employed to synthesize oscillator spectra from the equivalent circuit parameters with small numerical effort. Furthermore, it allows experimental power density spectra to be decomposed into the contributions stemming from the high-frequency noise in the feedback loop and the low-frequency noise of the oscillation frequency. This should give better insight into the origin of the phase noise. Besides VCO's, this concept may be useful for oscillators subject to Gaussian supply and substrate noise View full abstract»

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  • An absolute stability criterion for the Lur'e problem with sector and slope restricted nonlinearities

    Publication Year: 1998 , Page(s): 1007 - 1009
    Cited by:  Papers (116)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    In this brief we present a new sufficient condition for global asymptotic stability of Lur'e systems with sector and slope restricted nonlinearities. It is expressed as a matrix inequality and is based on an extended Lur'e-Postnikov Lyapunov function. It is compared based on numerical examples to conditions of Josselson-Raju and Haddad-Kapila View full abstract»

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  • Discrete-time chaotic encryption systems. III. Cryptographical analysis

    Publication Year: 1998 , Page(s): 983 - 988
    Cited by:  Papers (24)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    For pt. 2 see Proc. Workshop Nonlinear Dynamic Electron. Syst.., Seville, p. 27-32 (1996). This work deals with the cryptographical analysis of a class of discrete-time continuous-value encryption systems. The design of these systems has been treated in Part I. Here, approaches and criteria used in applied cryptography are adopted for continuous-value systems. Two different ciphertext-only attacks on the encryption system are presented in detail. Based on the analysis, improvements of the coder system are suggested View full abstract»

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  • Group theoretical approach to eigenvalue problems of symmetrical multiports with gyrotropic media

    Publication Year: 1998 , Page(s): 895 - 903
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    Eigenvalue problems of symmetrical multiports with gyrotropic media are considered. It is shown that the perturbation method known in quantum mechanics may be used for symmetrical structures with gyrotropic media in order to determine the influence of dc magnetic field on the eigenvalue degeneracy. In gyrotropic structures, an additional degeneracy may appear which is not predicted by the unitary subgroup. The eigenvalue equation for [S]-matrix in the case of magnetic groups of the third category and the problem of calculation of eigenvectors for transposed matrix are investigated. The theory is illustrated by some examples View full abstract»

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  • A simple proof of a necessary and sufficient condition for absolute stability of symmetric neural networks

    Publication Year: 1998 , Page(s): 1010 - 1011
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (60 KB)  

    The main result that for a neural circuit of the Hopfield type with a symmetric connection matrix T, the negative semidefiniteness of T is a necessary and sufficient condition for absolute stability was obtained and proved by rather complex procedures by Forti et al. [1994]. This brief gives a very simple proof of this result, using only the well-known total stability result about Hopfield type neural circuits with a symmetric connection matrix and the basic algebraic properties of real symmetric matrices View full abstract»

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  • Stability analysis of continuous time planar systems with state saturation nonlinearity

    Publication Year: 1998 , Page(s): 989 - 993
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    This work establishes easy-to-verify necessary and sufficient conditions for global asymptotic stability of a class of continuous time planar systems which are subject to state saturation nonlinearities on both its state variables View full abstract»

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  • Time-domain simulation of large lossy interconnect systems on conducting substrates

    Publication Year: 1998 , Page(s): 909 - 918
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    The most general class of uniform transmission-line systems is considered, assuming that samples of the frequency dependent parameter matrices R, L, G, and C are given. In particular, substrate effects which influence wave propagation along integrated circuits (IC) interconnects typically over a very broad range of frequencies are included. A time-domain simulation technique which can handle this problem is described in detail. The algorithm can be embedded in general-purpose circuit simulators and is based on modal analysis, mode tracking, modal delay separation, broadband rational function least squares approximation directly in partial fraction form, and recursive convolution. A numerical example for realistic geometry and material parameters of the examined transmission line structure shows the significance of substrate effects in the frequency and-more important-in the time domain View full abstract»

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  • The N Extra Element Theorem

    Publication Year: 1998 , Page(s): 919 - 935
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    The N Extra Element Theorem (NEET) is an alternative means of analysis for any transfer function of any linear system model, not restricted to electrical systems. Its principal distinction from conventional loop or node analysis is that a simpler reference system model in the absence of N designated “extra” elements is solved first, and the N extra elements are then restored via a correction factor. Parameters in the correction factor are various single injection and null double injection driving point immittances seen by the extra elements, and are all calculated upon the reference model. Thus, no calculation is performed upon a model containing any of the designated extra elements, and the final result is obtained by assembly of sequentially obtained results in a “divide and conquer” approach that is potentially easier, shorter, and which produces lower entropy forms than does the conventional approach. The NEET correction factor is a simultaneous bilinear representation of the extra elements, which can be immittances or dependent generators in any combination, and thus exposes explicitly the contribution of each extra element. An especially useful implementation of the NEET is to designate all the reactances as extra elements. The frequency response of the transfer function is then contained entirely in the NEET correction factor, which emerges directly as a ratio of polynomials in complex frequency s. The zeros as well as the poles can thus be obtained directly from the driving point resistances seen by the reactances, and it can also be determined whether any of the zeros or poles are exactly factorable. The approach throughout is to show how the NEET theorem can be useful in practical Design-Oriented Analysis, and emphasis is on the criteria by which the designer-analyst can take maximum advantage of the numerous choices of which elements to designate as “extra” and which of the many versions of the theorem to adopt View full abstract»

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  • Shilnikov orbits in an autonomous third-order chaotic phase-locked loop

    Publication Year: 1998 , Page(s): 979 - 983
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    In this work we investigate the Shilnikov homoclinic bifurcation in a new type of phase-locked loop (PLL) having a second-order loop filter. This system can be represented as a third-order autonomous system with piecewise-linear characteristics. By using piecewise-linear analysis, bifurcation equations for many types of homoclinic orbits are derived. Solving these equations gives many Shilnikov-type homoclinic orbits. We present bifurcation diagrams for the homoclinic orbits in the gain (K0) versus detuning (Δω) plane. Finally, we demonstrate the role of the homoclinic orbits in the global bifurcation of attractors both by computer simulation and experiments, View full abstract»

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  • Hyperchaos from a 4-D manifold piecewise-linear system

    Publication Year: 1998 , Page(s): 889 - 894
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    A piecewise-linear 4-D autonomous system with hyperchaotic behavior is proposed. The system is analyzed by constructing a 2-D return map. We describe this map explicitly and give theoretical evidence for hyperchaos generation. An implementation example is also provided, and its chaotic behavior is demonstrated View full abstract»

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  • Linguistic flow in fuzzy discrete-time cellular neural networks and its stability

    Publication Year: 1998 , Page(s): 869 - 878
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    A type-III fuzzy discrete-time cellular neural network (FDTCNN) structure is presented to implement local linguistic dynamic systems. The theoretical results of equilibrium points and stability of this FDTCNN are presented. The state transient process of this FDTCNN is analyzed by using fuzzy mathematics, Markov chain, and graph theory. An efficient algorithm is presented to check the existence of globally stable equilibrium point. Examples in a two-cell FDTCNN are used to demonstrate theoretical results, Finally, designing examples of a 1-D FDTCNN are presented to simulate the traffic flow of a highway system. Computer simulation results are given View full abstract»

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  • Coefficient sensitivity and structure optimization of multidimensional state-space digital filters

    Publication Year: 1998 , Page(s): 993 - 998
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    In this work, a new coefficient sensitivity measure for multidimensional (n-D) digital systems in state-space representation is proposed. This is motivated by the fact that coefficients equal to 0 or ±1 can be implemented exactly using finite wordlength, and thus have no contribution to coefficient quantization errors. The relationship between commonly used sensitivity measures for 2-D and n-D systems and the new one proposed here is discussed. It is shown that in evaluating the accuracy between a finite wordlength implementation of a transfer function and the ideal one, the proposed sensitivity measure is more useful than the commonly used ones. Furthermore, the proposed measure confirms that realizations with Schur and/or Hessenberg structures can be used to obtain more accurate finite wordlength implementations of transfer functions than the ones obtained using fully parametrized minimum sensitivity structures View full abstract»

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  • The Augmentation Principle of nonlinear circuits and its application to continuation methods

    Publication Year: 1998 , Page(s): 1002 - 1006
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    The Augmentation Principle, which is a generalization of the well-known Substitution Theorem, is presented. This principle establishes that a circuit's DC operating point remains constant over all values of resistors placed in series with a set of properly chosen voltage sources or placed in parallel with a set of properly chosen current sources. A useful application of the Augmentation Principle to circuit simulation using continuation methods is also given View full abstract»

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  • On the existence of robust strictly positive real rational functions

    Publication Year: 1998 , Page(s): 962 - 967
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    A new approach for the analysis of the strict positive real property of rational functions of the form H(s)=p(s)/q(g) is proposed. This approach is based on the interlacing properties of the roots of the even and odd parts of p(s) and q(s) over the imaginary axis. From the analysis of these properties, an algorithm to obtain p(s) such that p(s)/q(s) is strictly positive real (SPR) for a given Hurwitz q(s) is developed. The problem of finding p(s) when q(s) is an uncertain Hurwitz polynomial is also considered, using this new approach. An algorithm for obtaining p(s) such that p(s)/q(s) is SPR, when q(s) has parametric uncertainties, is presented. This algorithm is easy to use and leads to p(s) in cases where previously published methods fail View full abstract»

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  • Symbolic analysis of linear microwave circuits by extension of the polynomial interpolation method

    Publication Year: 1998 , Page(s): 936 - 944
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    This paper describes a new approach for the symbolic analysis of microwave circuits, based on the Polynomial Interpolation (PI) method. The latter has been widely presented in the literature as one of the most suitable symbolic analysis techniques for the computation of network functions when the only circuit variable is the complex frequency p(p=jω). An extension of the polynomial interpolation method that allows us to determine, for arbitrary linear circuits, the transfer functions in a fully symbolic form is presented. Then, a description of how the new method can be used to compute microwave performances, such as scattering parameters and reflection coefficients, is detailed. The proposed method was implemented in a computer program called SYSMIC (symbolic simulator of microwave circuits), for both DOS and IBM Unix environments View full abstract»

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  • Graph coloring via synchronization of coupled oscillators

    Publication Year: 1998 , Page(s): 974 - 978
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    In this work, we study the possibility of coloring graphs by means of synchronized coupled oscillators. We consider an array of coupled oscillators as a graph by associating the oscillators to vertices and the coupling to edges. When the coupled array is synchronized, the phase of the oscillators can be considered as the color associated with the corresponding vertices. We prove that for connected 2-colorable graphs, we can construct a coupled array which generates the 2-coloring for that graph. For the general case, numerical simulation results with connected 3-colorable graphs suggest that the coupled array of oscillators can color graphs with a small number of colors in most cases. Some complexity issues of the system and comparisons to antivoter models of graph coloring are discussed. We also conjecture that the system can be used to approximate the star chromatic number of the graph View full abstract»

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  • Breaking the 2n-bit carry propagation barrier in residue to binary conversion for the [2n-1, 2n, 2n+1] modula set

    Publication Year: 1998 , Page(s): 998 - 1002
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    This work presents a high speed realization of a residue to binary converter for the (2n-1, 2n, 2n+1), moduli set, which improves upon the best known implementation by almost twice in terms of overall conversion delay. This significant speedup is achieved by using just three extra two input logic gates. Interestingly, by exploiting certain symmetry in operands, we also reduce the hardware requirement of the best known implementation by n-1 full adders. Finally, the proposed converter eliminates the redundant representation of zero using no extra logic View full abstract»

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  • Nonlinear system identification by the Haar multiresolution analysis

    Publication Year: 1998 , Page(s): 945 - 961
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The paper deals with the problem of reconstruction of nonlinearities in a certain class of nonlinear systems of composite structure from their input-output observations when prior information about the system is poor, thus excluding the standard parametric approach to the problem. The multiresolution idea, being the fundamental concept of modern wavelet theory, is adopted, and the Haar multiresolution analysis in particular is applied to construct nonparametric identification techniques of nonlinear characteristics. The pointwise convergence properties of the proposed identification algorithms are established. Conditions for the convergence are given; and for nonlinearities satisfying a local Lipschitz condition, the rate of convergence is evaluated, With applications in mind, the problem of data-driven selection of the optimum resolution degree in the identification procedure, essential for the multiresolution analysis, is considered as well. The theory is verified by computer simulations View full abstract»

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  • Area efficient implementations of fixed-template CNN's

    Publication Year: 1998 , Page(s): 968 - 973
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Implementations of fixed-template Cellular Neural Networks (CNN's) with reduced circuit complexity are presented. Considerable improvements in area without performance degradation have been obtained by: (1) using single-polarity signals that reduce the number of transistors required for signal replication and to generate the pseudo-linear output function; (2) using simple current-mode circuits to implement the output pseudo-linear function; and (3) searching for network parameter configurations that solve a particular application using the proposed circuit implementation with less hardware complexity. Experimental results for a CCD-CNN chip prototype with a density of 230 cells per millimetersquared (mm2) are also reported View full abstract»

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  • Transformational DT-CNN design from morphological specifications

    Publication Year: 1998 , Page(s): 879 - 888
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    Morphology provides the algebraic means to specify operations on images. Discrete-time cellular neural networks (DT-CNNs) mechanize the execution of operations on images. The paper first shows the equivalence between morphological functions and DT-CNNs. Then, the argument is extended to the synthesis of optimal DT-CNN structures from complex morphological expressions. It is shown that morphological specifications may be freely derived, to be subsequently transformed and adopted to the needs of a specific target terminology. This process of technology mapping can be automated along the well-trodden path in CAD for microelectronics View full abstract»

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