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Circuits and Systems, IEEE Transactions on

Issue 10 • Date October 1987

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Displaying Results 1 - 18 of 18
  • Comments on "Accurate Determination of Threshold Voltage levels of a Schmitt Trigger

    Publication Year: 1987 , Page(s): 1252 - 1253
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    It is shown that for an accurate determination of the two threshold voltages of a Schmitt trigger, the influence of the forward current amplification \beta and the internal ohmic base and emitter resistors R_B and R_E of the transistors T_1 and T_2 may not be neglected. The hysteresis width of a real Schmitt trigger is smaller than calculated with the formula of Roy [1], because neither \beta is infinite nor R_B and R_E are zero. A very accurate but simple formula for the threshold voltages is given, using an analysis similar to that of Roy. View full abstract»

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  • Comments on "Reciprocity, Power Dissipation, and the Thevenin Circuit

    Publication Year: 1987 , Page(s): 1255 - 1257
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB)  

    Theorem 2 in the above paper has a flaw. A correct formulation of this theorem is given, along with other related theorems referring to the relations between the power dissipated in a uniport and in its Thévenin or Norton equivalent models. Internally equivalent models of a uniport are established. View full abstract»

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  • On several variable zero sets and application to MIMO robust feedback stabilization

    Publication Year: 1987 , Page(s): 1208 - 1220
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1432 KB)  

    Given a complex-valued function f which depends on m real variables s_1,\cdots ,s_m and n complex parameters A_1,\cdots ,A_n , we describe a method of finding the zero set V of all zeros of f in some given set G in R^m when each parameter A_i is allowed to vary in some given set K_i in the extended complex plane \overline {\bf C} = {\bf C} cup{\infty } . This mathematical tool is applied in the paper to determine the complete space of output (or state) feedback gains, which allows robust stabilization of a linear MIMO system under uncertainty conditions. The system may be continuous or discrete. Also, the stabilization may be "relative," i.e., with safety margins. Design examples are provided. View full abstract»

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  • Fast algorithms for block FIR adaptive digital filtering

    Publication Year: 1987 , Page(s): 1152 - 1160
    Cited by:  Papers (39)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    Two fast gradient algorithms for block FIR (finite impulse response) adaptive digital filtering are presented in this paper. The proposed algorithms employ a time-varying convergence factor \mu_B(j) which is optimized in a least-squares (LS) sense. In the first algorithm, the optimum block adaptive (OBA) algorithm, the processed signal blocks are disjointed. In the second algorithm, the optimum block adaptive shifting (OBAS) algorithm, the signal blocks are overlapping. Computer simulations and analysis of the computational complexity of the algorithms are given. It is shown that, although OBA and OBAS require a relatively modest increase in computation for each block iteration compared to the existing block least-mean-square (BLMS) algorithm, OBA and OBAS may be found in some applications more computationally efficient due to the considerable reduction in the number of iterations required for a given adaptation accuracy. A comparison between the OBAS algorithm and the recently proposed fast a posteriori error sequential technique (FAEST) is also conducted for adapting to time-varying (unknown) systems, and the results show that OBAS is superior to the FAEST algorithm with respect to speed and accuracy of adaptation, at least for the variety of filters used in the simulations. View full abstract»

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  • A class of FIR Nyquist (Nth-band) filters with zero intersymbol interference

    Publication Year: 1987 , Page(s): 1182 - 1190
    Cited by:  Papers (37)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1064 KB)  

    This paper introduces a new class of linear-phase FIR Nyquist ( N th-band) filters composed of cascaded FIR subfilters with different periodicities in the frequency domain. Each one of the subfilters is itself a Nyquist filter or an N th-band filter. - The composite filters have zero intersymbol interference and they provide a Chebyshev stopband behavior, thereby band-limiting the pulses optimally. A computationally efficient Remez-type procedure is presented for simultaneously optimizing the subfilters. This algorithm is equally applicable to the design of conventional single-stage FIR Nyquist ( N th-band) filters. Examples demonstrate that the proposed multistage filters provide significant advantages over equivalent IIR filters and single-stage FIR filters in terms of reduced multiplication rate and reduced number of multipliers. In addition, it is shown that, in the case of single-stage implementations, the proposed algorithm gives FIR Nyquist filters having higher selectivities than those which have been designed using other methods. View full abstract»

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  • Concurrent cellular VLSI adaptive filter architectures

    Publication Year: 1987 , Page(s): 1141 - 1151
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1344 KB)  

    Previous approaches to high-sampling-rate adaptive filter implementations have been based on word-level pipelined word-parallel (or "block") realizations. In this paper, we show that adaptive filters can be implemented in an area-efficient manner by first using pipelining to the maximum possible extent, and then using block processing in combination with pipelining if further increase in sampling rate is needed. We show that, with the use of a decomposition technique, high-speed realizations can be achieved using pipelining with a logarithmic increase in hardware (the block realizations require a linear increase in hardware). We derive pipelined word-parallel realizations of high-sampling-rate adaptive lattice filters using the techniques of look-ahead computation decomposed state update implementation, and incremental output computation. These three techniques combined make it possible to achieve asymptotically optimal complexity realizations (i.e., the same complexity asymptotically as nonrecursive systems) of high-speed adaptive lattice filters (in both bit-serial and bit-parallel methodologies) and provide a "system solution" to high-speed adaptive filtering. The adaptive lattice filter structures are ideal for high-sampling-rate implementations, since the error residuals of a particular stage are adapted order-recursively based on those of the previous stage, and the coefficient update recursion inside each stage is linear in nature. An example of a normalized stochastic gradient adaptive lattice filter is presented, and its complexity, latency, and implementation methodology tradeoffs are studied. View full abstract»

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  • Design of two-dimensional digital filters by using the singular value decomposition

    Publication Year: 1987 , Page(s): 1191 - 1198
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (856 KB)  

    A method for the design of quadrantally symmetric 2-D digital filters is described. Like the method outlined by Twogood and Mitra, the method proposed here is based on the singular value decomposition. The salient difference between the two methods is that the proposed method uses one or more parallel correction sections which reduce the approximation error. In this way, reduced passband ripple and increased minimum stopband attenuation can easily be achieved. An important merit of the method is that the required 2-D filter is decomposed into a set of 1-D digital subfilters, which are much easier to design by optimization than the original 2-D filter. View full abstract»

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  • A bilateral optocirculation circuit with three ports

    Publication Year: 1987 , Page(s): 1165 - 1170
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    A bilateral circulation circuit using LED-photodiode optoisolators is proposed. It is revealed theoretically and experimentally that bilateral and circular transmission is achieved by the enhancement of the current transfer ratio through optoelectronic positive feedback loops. Since the feedback loops are dispersed among three ports, it is possible to get circular signals in and out of optional ports. This circuit has stable positive gain and stable coupling efficiency because of optoelectronic feed-forwards. The bilateral frequency responses of gain extend over several hundred kilohertz. View full abstract»

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  • New results on stable multidimensional polynomials-Part I: Continuous case

    Publication Year: 1987 , Page(s): 1221 - 1232
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1664 KB)  

    New classes of multivariable polynomials arising in studies of passive multidimensional systems have been identified and their properties have been studied. In particular, polynomials occurring as the numerators and denominators of multivariable reactance functions and positive functions are characterized. Related properties of these and other classes of multivariable Hurwitz polynomials are also studied. Finally, a nontrivial test for the property of positivity of rational functions, holomorphic in a domain, in terms of their behavior on the distinguished boundary is formulated. View full abstract»

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  • A simple general proof of Kharitonov's generalized stability criterion

    Publication Year: 1987 , Page(s): 1233 - 1237
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    In a paper published in 1978 in Russian, Kharitonov proved that the strict Hurwitz property of a set of interval polynomials having complex coefficients may be established from the strict Hurwitz property of eight extreme polynomials. The proof of this significant result is advanced using elementary concepts in circuit theory. The approach not only provides a clear and complete proof of Kharitonov's generalized stability criterion but also has potentialities for generalization to the bivariate and, subsequently, the multivariate polynomial cases. View full abstract»

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  • Universal digital biquads which are free of limit cycles

    Publication Year: 1987 , Page(s): 1243 - 1248
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    Two second-order, multiple-output digital-filter structures are described which realize simultaneously a low-pass, a high-pass, a bandpass, a notch, and an all-pass transfer function. The two structures can be stabilized with respect to limit-cycle oscillations by employing the techniques of magnitude truncation and controlled rounding, and each uses four multipliers and two unit delays. The two structures are attractive for VLSI implementation since each can serve as the basis of a versatile, universal digital-filter chip which can be used for the implementation of Butterworth, Chebyshev, and elliptic digital filters and also for the design of digital equalizers. View full abstract»

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  • A distributed modeling approach for simulation and verification of digital designs

    Publication Year: 1987 , Page(s): 1171 - 1181
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1480 KB)  

    A new modeling approach for simulation and verification of digital designs is presented in this paper and has been implemented for functional and fault simulation and timing verification in the experimental rule-based design verifier (RDV) [5] at. Stanford University that uses Ada [2], [6] as the hardware description language and a simulation environment. In this approach, every component of a digital design is represented as a model-a concurrently executable entity that performs the tasks of scheduling itself for execution, simulation, or verification of the corresponding component, and communication of results to other devices. A model schedules itself for execution when the necessary signals are asserted at all its input ports. New approaches are developed and presented in this paper that permit the functional fault simulation and timing verification tasks to be distributed in all the models. Corresponding to an output signal generated as a result of execution of a component description, the model retrieves a list of components that are connected to its output port and propagates the signal directly to each of them. As a consequence of the distributed scheduling and communication mechanisms, parallelism may be utilized with relative ease. View full abstract»

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  • The loop-gain modulator: A new class of linear amplitude modulators

    Publication Year: 1987 , Page(s): 1161 - 1164
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A new type of class A modulator is introduced. This circuit, called the loop-gain modulator, exhibits a high degree of modulation linearity even for an index of modulation approaching unity. The concept is based on modifying the loop-gain of an oscillator with the modulating voltage. An analysis is done for the RC phase shift oscillator, although the method can be used with any oscillator. Experimental results that verify this analysis are reported. View full abstract»

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  • Sufficiency conditions for the stability of a class of 3-D functions with nonessential singularities of the second kind

    Publication Year: 1987 , Page(s): 1253 - 1255
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    In this correspondence, we state sufficiency conditions for boundedness, and 1_{2^-} and 1_{1^-} stabilities of a 3-D function G(z_1, z_2, z_3) = P(z_1, z_2, z_3)/Q(z_1, z_2, z_3) , where Q is a polynomial which is linear in all its three variables, and P/Q has some second kind nonessential singularities in \overline {U}^3 - U^3 . Some illustrative examples are also given. View full abstract»

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  • Nonstationary learning characteristics of the LMS algorithm

    Publication Year: 1987 , Page(s): 1199 - 1207
    Cited by:  Papers (34)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB)  

    Upper and lower bounding first-order linear recursions for the mean-squared error realized with the LMS algorithm subjected to a sequence of independent nonstationary training vectors are derived. These bounds coincide to give the exact evolution of mean-squared error for the problem of identification of a nonrecursive time-varying system with white-noise excitation. This leads to an exact formula for time-averaged mean-squared error that is used to study optimization of the step-size parameter for minimum time-average misadjustment. New results on dependence of the minimal step size and the minimum misadjustment on the degree of nonstationarity are obtained. View full abstract»

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  • Discrete optimization of digital filters using Gaussian adaptation and quadratic function minimization

    Publication Year: 1987 , Page(s): 1238 - 1242
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    In this paper, a new strategy for discrete optimization of a function F(x) is presented. Let A be the region in the n -dimensional parameter space, where F(x) is less than some constant. First, A is located and characterized by a Gaussian search process, called Gaussian adaptation. This makes it possible to approximate the behavior of F(x) . over A by a quadratic function Q(x) . Q(x) is then optimized for the N best discrete solutions using a branch and bound technique. Finally, these points are evaluated for the best F(x) points. By various digital filter examples it will be demonstrated that the new method is more capable of finding good solutions than methods presented so far. View full abstract»

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  • An extension to a result concerning the stability of 2-D digital filters

    Publication Year: 1987 , Page(s): 1251 - 1252
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    In this correspondence, we extend the range of application of a recently proposed technique [1] for the solution of the open problem regarding the BIBO Stability of 2-D digital filters in the presence of nonessential singularities of the second kind. This extension is accomplished through the use of a certain z -domain transformation. An illustrative example is also given. View full abstract»

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  • The use of a thyristor as a switching device in a Class E tuned power amplifier

    Publication Year: 1987 , Page(s): 1248 - 1250
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    The switching device in a Class E tuned power amplifier can be a thyristor instead of a bipolar or MOS transistor if the load network provides a switch current which nominally has zero value and zero slope at the time the switch turns OFF. The thyristor greatly enhances the powerhandling capabilities of Class E amplifiers and is especially attractive in low-frequency, high-power, high-efficiency applications. It is shown that the thyristor turn-off time is substantially reduced by the Class E amplifier operation which keeps the thyristor at low junction temperature and provides low reapplied voltage rate to it. Laboratory results are given which verify theoretical predictions. View full abstract»

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