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Circuits and Systems II: Analog and Digital Signal Processing, IEEE Transactions on

Issue 4 • Date Apr 1996

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Displaying Results 1 - 9 of 9
  • ACE: a VLSI chip for Galois field GF(2m) based exponentiation

    Publication Year: 1996 , Page(s): 289 - 297
    Cited by:  Papers (1)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1004 KB)  

    Finite or Galois fields are used in numerous applications like error correcting codes, digital signal processing and cryptography. These applications often require computing exponentiations in GF(2m ) which is a very computationally intensive operation. The methods proposed in the literature achieve exponentiation by iterative methods using repeated multiplications and the hardware implementations use a number of Galois field multipliers in parallel resulting in expensive hardware. In this paper, we present a new algorithm based on a pattern matching technique for computing exponentiations in GF(2m), for values of m⩽8. A systolic array processor architecture was developed by the authors for performing multiplication and division in GF(2m) in [13]. A similar strategy is proposed in this paper for achieving exponentiation at the rate of a new result every clock cycle. A prototype VLSI chip Called ACE implementing the proposed architecture for Galois field GF(24) has been designed and verified using CMOS 2 μm technology. The chip can yield a computational rate of 40 million exponentiations per second View full abstract»

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  • Choosing nonuniform tap spacings for a tapped-delay-line filter

    Publication Year: 1996 , Page(s): 298 - 303
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    The family of frequency responses that can be generated by adjusting the weights on a tapped-delay-line filter with nonuniformly spaced taps is just the span of a basis set whose elements are arbitrary (as long as linear independence is preserved) frequency shifts of the characterizing function of the set of delays. The characterizing function is just the frequency response that results when uniform weights are applied at those delays. If the delays are chosen to provide a unimodal characterizing function with low sidelobes (probability theory provides one approach), then it tends to be easy to approximate a desired frequency response from linear combinations of various frequency shifts of the characterizing function. If the characterizing function is severely multimodal, it is relatively difficult to get the linear combination of the characterizing-function shifts to approximate a desired response. Though this intuition about what is possible comes from visualizing the manual construction of the desired response, the conclusions reached generally also predict the degree of success that will be obtained from an optimal design of the filter weights. Further and most importantly, the characterizing-function idea offers guidance in the choice of the delays themselves View full abstract»

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  • Efficient fast design of three- and higher-dimensional FIR digital filters by analytical least squares method

    Publication Year: 1996 , Page(s): 339 - 344
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    An effective method is proposed for designing three- and higher-dimensional FIR digital filters in this paper. The method is based on deriving the closed-form matrix called by the inverse frequency response transformation matrix, such that the filter's coefficients can be computed directly from the given specifications without any iterative procedures and optimization techniques. Design examples are presented to demonstrate the flexibility and the efficiency of the method, and it is shown that even for filter lengths up to 21×21×21 only 0.4 s CPU time is needed View full abstract»

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  • A fast response split-path median LMS algorithm

    Publication Year: 1996 , Page(s): 344 - 346
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    An adaptive median LMS algorithm based on a split FIR filter structure is presented. The algorithm has a better tracking capability and a faster convergence rate by means of reducing the eigenvalue spread of the input correlation matrix. The performance of the adaptive system is evaluated in a line enhancement application. It is found that the algorithm is effective in both the suppression of impulsive interference and preservation of edge details of the desired signal View full abstract»

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  • Improving the robustness of winner-take-all cellular neural networks

    Publication Year: 1996 , Page(s): 329 - 334
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    This paper describes two improvements on a recently proposed winner-take-all (WTA) architecture with linear circuit complexity based on the cellular neural network paradigm. The general design technique originally used to select parameter values is extended to allow values to be optimized for robustness against relative parameter variations as well as absolute variations. In addition, a modified architecture, called clipped total feedback winner-take-all (CTF-WTA) is proposed. This architecture is shown to share most properties of standard cellular neural networks, but is shown to be better suited to the WTA application. It is shown to be less sensitive to parameter variations and under some conditions to converge faster than the standard cellular version. In addition, the effect of asymmetry between the neurons on the reliability of the circuit is examined, and CTF-WTA is found to be superior View full abstract»

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  • A hyperstable adaptive line enhancer for fast tracking of sinusoidal inputs

    Publication Year: 1996 , Page(s): 304 - 315
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    An IIR adaptive filter is presented for the application of tracking sinusoidal inputs. The filter uses a hyperstable update to provide very fast convergence, and is capable of tracking multiple sinusoids, with the order of the filter being twice the number of sinusoids. The convergence of the filter depends on a certain transfer function being strictly positive real (SPR), and necessary conditions are derived, for this transfer function to be SPR. These conditions hold for the completely general case, and can be very simply expressed in terms of the input sinusoidal frequencies, because of the specific application that is addressed, and because of the filter topology (a resonator-based filter structure) that is used. Further, these conditions are derived under the assumption that no post-error filter is used (unlike most hyperstable schemes). Further, these conditions are also shown to be sufficient for convergence, for the case of up to two input sinusoids (4th order filter). For a larger number of input sinusoids, though it has not been possible to prove the sufficiency of these conditions, we have conducted several experiments and obtained convergence in all cases, leading to the conjecture that the conditions are sufficient for convergence, for the general case as well. Simulations of the performance of the filter structure are also provided to support the theory and the conjectured condition for convergence. The capability of the adaptive filter to track fast changes in frequency make it a candidate for applications like demodulating MFSK signals. Alternatively, the speed can be traded for complexity because for slow adaptation (low μ), the algorithm reduces to a pseudo-gradient-based update that can be implemented very simply View full abstract»

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  • Simultaneous spatial separation and direction-of-arrival estimation of wideband sources using bootstrapped algorithms

    Publication Year: 1996 , Page(s): 316 - 328
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1076 KB)  

    This paper presents two versions of a novel adaptive algorithm for simultaneous spatial separation and direction finding of two wideband, uncorrelated sources received by two separated sensors. The algorithm provides estimates of the spatial location of the sources (direction of arrival-DOA) and outputs two signals which are filtered versions of the source signals. We describe the different configurations of the separation system and study sensitivity of the two signal estimates to the accuracy in estimating the DOA of the sources. We show that perfect separation is achieved even if the DOAs are not perfectly estimated, at the cost of degradation in the output signal-to-noise-ratio. Then we propose implementation of an adaptive control algorithm and we discuss the steady state performance in the presence of an additive noise. We compare the complexity, performance and noise immunity of the two versions of the proposed algorithm View full abstract»

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  • A level-crossing sampling scheme for A/D conversion

    Publication Year: 1996 , Page(s): 335 - 339
    Cited by:  Papers (70)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    A sampling scheme that is based on multiple level-crossings is presented. This scheme generates samples of the input signal that are nonuniformly spaced in time by recording the time instants at which the signal crosses any of the fixed quantization levels. The nonuniform sample sequence is transformed to uniform samples by polynomial interpolation. The resolution is further increased by employing decimation. Various trade-offs involved in terms of speed, resolution and hardware complexity are discussed View full abstract»

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  • One-chip endless phase shifter IC's for space diversity combiner

    Publication Year: 1996 , Page(s): 281 - 288
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    This paper describes a one-chip endless phase shifter IC for a space diversity (SD) combiner in multi-carrier digital microwave radio systems; the combiner has an in-phase control circuit in each carrier. The endless phase shifter, which is the key device for this combiner, was miniaturized by using bipolar IC technology, and embedded on a single chip. First, the design methods of this monolithic endless phase shifter which focus on obtaining highly accurate characteristics in the UHF frequency bands are described. Thereafter, the characteristics of the endless phase shifter in the UHF band are examined in detail. This one chip endless phase shifter IC is found to be applicable to multilevel QAM (16-QAM) systems. Then, a new 90° combiner that achieves higher frequency response in the microwave frequency band is proposed and its effects are examined. Based on the design methods for the individual elemental circuits (90° combiner and balanced modulator), it is expected that the endless phase shifter can also be achieved in the microwave frequency band View full abstract»

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Aims & Scope

This title ceased production in 2003. The current updated title is IEEE Transactions on Circuits and Systems II: Express Briefs.

Full Aims & Scope