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Circuits and Systems, IEEE Transactions on

Issue 6 • Date June 1986

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Displaying Results 1 - 17 of 17
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  • Area/bandwidth tradeoffs for CMOS current mirrors

    Page(s): 667 - 669
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    Conventional CMOS current mirrors with large current ratios require very large active areas and have limited bandwidths. It is shown that replacing the inefficient large ratio current mirrors with a cascade of smaller current mirrors can give significant increases in bandwidth and reductions in active area. A simple design strategy is presented which can be used to obtain near optimal tradeoffs between active area and bandwidth. View full abstract»

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  • New VLSI systolic array design for real-time digital signal processing

    Page(s): 673 - 676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The well-known advantages of pipelines systolic array architecture is applied for implementation of a second-order recursive digital filter. The proposed structure achieves five-fold increase in system throughput over standard techniques, and two-fold increase over usual systolic approaches. In this letter, the data flow operation and the basic cell implementation for this design are presented. View full abstract»

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  • Exact design of stray-insensitive switched-capacitor LDI ladder filters from unit element prototypes

    Page(s): 613 - 622
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (944 KB)  

    A new technique is described by means of which stray-insensitive switched-capacitor (SC) low-pass and highpass ladder filters of the LDI type may be designed without the need for network synthesis. These filters exactly simulate the response of a unit element cascade prototype filter and may be designed with a usable frequency range up to one-half the sampling frequency. The method operates by establishing an equivalence between the signal flowgraphs (SFG's) of a voltage-wave filter and a leapfrog LDI filter, and a simple algorithm to effect this transformation is described. Since the resulting SFG contains the original wave filter parameters in symbolic form, the transformation need only be carried out once for each order of prototype. View full abstract»

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  • An alternative approach for designing maximally flat low- pass filters with multiple order imaginary-axis zeros

    Page(s): 642 - 644
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A systematic procedure is introduced to design a maximally flat low-pass filter with multiple order imaginary-axis zeros. The filter characteristics is specified by the passband and stopband edge frequencies, maximum loss in passband and minimum loss in stopband. This approach can lead to an optimal design of this class of filters. View full abstract»

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  • The enhancement and tracking of moving objects in digital images using adaptive three-dimensional recursive filters

    Page(s): 604 - 612
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1088 KB)  

    A three-dimensional (3-D) adaptive filter control system is described which is capable of seeking, tracking and enhancing an object that moves with time on an arbitrary, but smooth, trajectory in a dynamic digital image. Enhancement of the object is performed by employing a time-varying first-order 3-D planar-resonant recursive filter that is adapted via its coefficients at each time interval to correspond to the trajectory of the object. The trajectory of the object is determined at each time interval by tracking the intensity centroid of the object at the output of the adaptive 3-D recursive filter. The system is initialized for tracking by a seek algorithm which searches the image for the first candidate object having uniform motion and intensity. Experimental evidence is provided showing the effectiveness of the system in locating, tracking and enhancing objects in images containing other objects and high levels of noise. View full abstract»

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  • Stability and security assessment of a class of systems governed by LaGrange's equation with application to multi-machine power systems

    Page(s): 623 - 635
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1448 KB)  

    In recent studies, it has been verified heuristically and experimentally (via simulations) that instability in power systems due to a fault occurs when one machine or a group of machines, called the critical group, loses synchronism with the remaining machines. Using energy functions associated with a critical group (rather than system-wide energy functions), transient stability results which are less conservative than other existing results, have recently been obtained. The existence and identity of a critical group is ascertained in these studies by off-line simulations. In the present paper, we first establish some general stability results for a large class of dynamical systems (which are arrived at via a Lagrange formulation). We then show how multi-machine power systems with nonuniform damping are special cases of this class of dynamical systems. Next, we show that our stability results can be used to establish analytically the existence and the identity of the critical group of machines in a power system due to a given fault. Furthermore, we also show that our stability results can be used to obtain an estimate of the domain of attraction of an asymptotically stable equilibrium of a power system. The results presented herein can potentially be used on-line to determine which machines belong to a critical group, and to use this information for corrective action (e.g., shedding of the critical generators or fast valving for these generators.) As such, our results have potential applications in fault diagnosis and security assessment of certain classes of dynamical systems in general and of power systems in particular. The applicability of the present results is explored by means of a specific example (a 162-bus, 17-generator model of the power network of the State of Iowa). Certain limitations of the present results are recognized and avenues for further research are identified. View full abstract»

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  • Multifrequency measurement of testability with application to large linear analog systems

    Page(s): 644 - 648
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    With increasing electronic circuit complexity, assessing the testability features becomes a necessity during the design, implementation, and operational or maintenance phases of an analog system. A quantitative measure of testability, based on several multifrequency stimuli, is adopted which is able to handle multiple faults and may provide information also on the degree of complexity encountered in a specific test. An efficient and practical algorithm is proposed which is associated with the result of Sen and Saeks and has a well-defined interpretation even with a large number of circuit parameters liable to failure. The described technique is a basis for optimizing the number and allocation of the selected test points; furthermore, it may serve as an aid in functional partitioning of the same system to facilitate testing and/or reduce computational complexity. An application to a classical active filter is also given. View full abstract»

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  • Component quantization effects on continuous-time filters

    Page(s): 651 - 659
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1160 KB)  

    Recent trends in precision continuous-time active filter design use post fabrication tunable structures. Digitally adjustable quantization components are often used as tunable elements. It is shown that the trim resolution of continuous-time filters is strongly dependent upon the circuit topology and component quantization schemes. Tradeoffs between number of bits, quantization schemes and resolution for some representative bandpass active filter structures are addressed. It is shown that the optimal circuit structure and component quantization scheme are application dependent. View full abstract»

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  • A coefficient sensitivity bound in 2-D state-space digital filtering

    Page(s): 665 - 667
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    For a SISO two-dimensional (2-D) state-space digital filter, a general upper bound on the sensitivity measurement of the filter's eigenfunctions is proposed. The bound for both equal and unequal word length registers of an optimal realization [11], [12] is calculated. It is shown that for a scaled equal wordlength realization, the bound has its minimum value. View full abstract»

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  • Approximation design of 2-D digital filters with elliptical magnitude response of arbitrary orientation

    Page(s): 597 - 603
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    This paper presents an approximation technique which resuits in simple formulas for fast calculation of the McClellan transform coefficients, and should be useful for real-time and adaptive 2-D digital filtering. The coefficients are calculated by fitting the power series expansion of the transform to the analytical description of the iso-potential contours of the filter. Formulas are also derived for the coefficients of the scaling-free transform, recently proposed by the authors. View full abstract»

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  • Self-sustained oscillation in an R_H - C or R_H - L circuit containing a hysteresis resistor R_H

    Page(s): 636 - 641
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    When thei - vcurve of a resistor exhibits hysteresis jumps alongiorvaxis, this resistor can be connected to an energy storage elementCorLto form a relaxation oscillator. The criteria of oscillation are derived from a point of view somewhat different from those reported in the literature. It is found that only four different combinations ofR_{H} - CorR_{H}- Lwill support sustained oscillations. Theoretical waveforms and frequencies of oscillations are predicted. Experiments employing an op amp realizedR_Hare conducted and agreement between theoretical predictions and experiments is good. A possible application of the theory to the explanation of biological oscillation across an active membrane is proposed. View full abstract»

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  • High frequency effects in MOSFET-CTow - Thomas biquads

    Page(s): 648 - 651
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    The MOSFET-Cversion of the Tow-Thomas activeRC biquadratic filter operated at high frequencies is considered. Formulas for the deviation of quality factor and center frequency due to the finite gain-bandwidth product of the op amps and the intrinsic distributed- RC effects of the MOS transistors are presented and verified by computer simulation. Passive compensation methods are considered for eliminating the degradation of filter performance due to the above effects. View full abstract»

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  • Efficient computation of network sensitivities

    Page(s): 659 - 664
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    A class of methods for generating network functions and their sensitivities, when only one element is allowed to vary, is presented. This class of methods requires either two or three circuit analyses to obtain expressions for the network function and its first order, higher order, and large-scale sensitivities for all values of the variable component. The class of the two circuit analyses methods reduces moderately the computational effort and makes better use of circuit analysis data as compared to the previous methods which employ at least three circuit analysis. The results are applicable to network functions with bilinear characteristics and can be extended to the general class of bilinear systems. View full abstract»

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  • Design of almost minimax FIR filters in one and two dimensions by WLS techniques

    Page(s): 590 - 596
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    The design of Finite Impulse Response (FIR) filters in one or several dimensions can be performed with good computational efficiency using a Weighted Least Square (WLS) design. Minimax design, which is often preferred, is computationally burdensome, principally in two dimensions. This paper draws attention to the design of minimax filters using iterative WLS techniques for one-dimensional filters and extends the approach to two-dimensional filters. For two dimensions the techniques apply to both rectangular and hexagonal sampling grids. Examples demonstrate flexibility and good computational efficiency. The paper also illustrates a promising new approach to filter design which couples the very general WLS methodology to the less manageable but often preferred minimax performance criterion. View full abstract»

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  • Linear systems with transfer functions of bounded type: Canonical factorization

    Page(s): 581 - 589
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1048 KB)  

    This paper deals with linear discrete-time systems with matrix-valued transfer functions each entry of which is represented as a quotient of twoH^{infty}-class functions. The notion of outer functions (or functions of minimum phase) is extended to matrix-valued functions of the Nevanlinna classN, and a canonical factorization theorem for matrix functions of classNis presented. This theorem gives minimum phase systems for these linear systems, and specifies a necessary and sufficient condition for the systems to be causal. The notion of the matrix-fraction descriptions (MFD's) is extended to these systems, and some properties of the MFD's are presented by means of the canonical factorization theorem. View full abstract»

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