In this letter, a realization of current-mode active filter using current followers as active element is described. We show the constructions of second-order lowpass, highpass and bandpass filters. The high-order filters can be realized by a cascade connection of these second filters. As examples, the second-order lowpass and highpass filters are designed for frequency of 5 MHz. The effectiveness of the proposed method is demonstrated through SPICE simulation.

In this paper we newly define a generalized edge-ranking of a graph G as follows: for a positive integer c, a c-edge-ranking of G is a labeling (ranking) of the edges of G with integers such that, for any label i, deletion of all edges with labels >i leaves connected components, each having at most c edges with label i. The problem of finding an optimal c-edge-ranking of G, that is, a c-edge-ranking using the minimum number of ranks, has applications in scheduling the manufacture of complex multi-part products; it is equivalent to finding a c-edge-separator tree of G having the minimum height. We present an algorithm to find an optimal c-edge-ranking of a given tree T for any positive integer c in time O(n2log Δ), where n is the number of vertices in T and Δ is the maximum vertex-degree of T. Our algorithm is faster than the best algorithm known for the case c=1.

In a recent paper, Yang proposes an integer labeling algorithm for determining whether an arbitrary simplex P in Rn contains an integer point or not. The problem under consideration is a very difficult one in the sense that it is NP-complete. The algorithm is based on a specific integer labeling rule and a specific triangulation of Rn. In this paper we discuss a practical implementation of the algorithm and present a computer program (ILIN) for solving integer programming using integer labeling algorithm. We also report on the solution of a number of tested examples with up to 500 integer variables. Numerical results indicate that the algorithm is computationally simple, flexible, efficient and stable.

In an iterative decoding algorithm, such as Chase Type-II decoding algorithm and its improvements, candidate codewords for a received vector are generated for test based on a bounded-distance decoder and a set of test error patterns. It is desirable to remove useless test error patterns in these decoding algorithms. This paper presents a sufficient condition for ruling out some useless test error patterns. If this condition holds for a test error patterns e, then e can not produce a candidate codeword with a correlation metric larger than those of the candidate codewords generated already and hence e is useless. This significantly reduces the decoding operations in Chase type-II decoding algorithm or decoding iterations in its improvements.

In [1] a generalized concatenated code was used to construct the t-fold unidirectional b-bit-byte error-correcting/d(dt)-fold unidirectional b-bit-byte error-detecting (t-UbEC/d(t)-UbED) codes. The concatenated code is to choose an inner code satisfying some disjoint sets and each set is a binary b-tuples unordered code. However, [1] gave five methods including trial and error to construct the optimal inner codes. Here, we present a systematic method for constructing the inner codes. It is shown that we can improve the coding efficiency for t-UbEC/d(t)-UbED) codes in some cases by using our inner codes.

Fundamental nonlinear filters including M-filters and order statistic filters are formulated generally by the maximum a-posteriori (MAP) estimation and some filters are derived with the aid of the Bayes formula. This MAP-filters reduces to M-filters if a-priori probability distribution is uniform, while the rank filters are derived when a-priori bias exists in the MAP estimation. This MAP-filters are implemented with an analog electronic circuit and the log-likelihood is shown to be a Liapunov function for the dynamics of this circuit.

In the literatures [5] and [10], a systematic discussion is presented with respect to the optimum interpolation of multi-dimensional signals. However, the measures of error in these literatures are defined only in each limited block separately. Further, in these literatures, most of the discussion is limited to theoretical treatment and, for example, realization of higher order linear phase FIR filter bank is not considered. In this paper, we will present the optimum interpolation functions minimizing various measures of approximation error simultaneously. Firstly, we outline necessary formulation for the time-limited interpolation functions ψm(t) (m=0,1,. . . ,M-1) realizing the optimum approximation in each limited block separately, where m are the index numbers for analysis filters. Secondly, under some assumptions, we will present analytic or piece-wise analytic interpolation functions φm(t) minimizing various measures of approximation error defined at discrete time samples n=0, 1, 2,. . . . In this discussion, φm(n) are equal to ψm(n) n=0, 1, 2,. . . . Since ψm(t) are time-limited, φm(n) vanish outside of finite set of n. Hence, in designing discrete filter bank, one can use FIR filters if one wants to realize discrete synthesis filters which impulse responses are φm(n). Finally, we will present one-dimensional linear phase M channel FIR filter bank with high attenuation characteristic in each stop band. In this design, we adopt the cosine-sine modulation initially, and then, use the iterative approximation based on the reciprocal property.

Experiments were performed to investigate perceptual contributions of static and dynamic features of vocal tract characteristics to talker individuality. An ARX (Auto-regressive with exogenous input) speech production model was used to extract separately voice source and vocal tract parameters from a Japanese sentence, /aoiueoie/ ("Say blue top" in English) uttered by three males. The Discrete Cosine Transform (DCT) was applied to resolve formant trajectories of the speech signal into static and dynamic components. The perceptual contributions were quantitatively studied by systematically replacing the corresponding formant components of the sentences between the three talkers. Results of the experiments show that the static (average) feature of the vocal tract is a primary cue to talker individuality.

In this paper we review the stretched-pulse principle and discuss its inherent advantages for ultrashort pulse generation and transmission. An analytic theory of the stretched-pulse fiber laser is presented and shown to be in good agreement with experimental results. An extension of the stretched-pulse theory is applied to both fiber lasers and dispersion-allocated soliton transmission and then compared to numerical results. We also discuss the design and operation of an environmentally stable stretched-pulse fiber laser.

This paper describes an MOS current-mode sample-and-hold (S/H) circuit that potentially operates with a sub-1. 5 V supply voltage, 20 MHz clock frequency, and less than 0. 1% linearity. A newly developed voltage-to-current converter suppresses the voltage change at an input terminal and achieves low-voltage operation with superior linearity. Sample switches are differentially placed at the inputs of a differential amplifier so that the feedthrough errors from switches cancel out. The MOS current-mode S/H circuit is designed and simulated using CMOS 0. 6 µm device parameters. Simulation results indicate that an operation with 20 MHz clock frequency, linearity error of less than 0. 1%, and 1 MHz input from a 1. 5 V power supply is achievable.

An adaptive infinite impulse response (IIR) filter implemented using an allpass and a minimum phase system has an advantage of its poles converging to the poles of the unknown system when the input is a white signal. However, when the input signal is colored, convergence speed deteriorates considerably, even to the point of lack of convergence for certain colored signals. Furthermore with a colored input signal, there is no guarantee that the poles of the adaptive digital filter (ADF) will converge to the poles of the unknown system. In this paper we propose a method which uses a linear predictor filter to whiten the input signal so as to improve the convergence characteristic. Computer simulation results confirm the increase in convergence speed and the convergence of the poles of the ADF to the poles of the unknown system even when the input is a colored signal.

Fiat-Shamir's identification and signature scheme is efficient as well as provably secure, but it has a problem in that the transmitted information size and memory size cannot simultaneously be small. This paper proposes an identification and signature scheme which overcomes this problem. Our scheme is based on the difficulty of extracting theL-th roots modn (e. g.L=2 1020) when the factors ofnare unknown. We prove that the sequential version of our scheme is a zero knowledge interactive proof system and our parallel version reveals no transferable information if the factoring is difficult. The speed of our scheme's typical implementation is at least one order of magnitude faster than that of the RSA scheme and is relatively slow in comparison with that of the Fiat-Shamir scheme.

Recently reported multidimensional geometrically uniform signal constellations (L MPSK and Decomposed-Lattice constellations) are joined in the term of Generalized Permutation Alphabets (GPA). Possibility of a binary isometric labeling of GPA's is completely characterized. An algorithm for constructing generating groups of PSK-type GPA is proposed. We show that this concept, when is extended to the lattice, gives rise to a class of new coset codes which perform out best codes listed in [11].

A simple method of compensating the DC drift of LiNbO3 Mach-Zehnder intensity modulators for very high speed optical transmission systems is proposed. This method adds low frequency perturbation to the modulator driving signal, and controls the bias voltage using the detected envelope of the modulator output signal. The control circuit is successfully demonstrated to work with less than a 0. 1-dB power penalty.

This paper proposes an architecture for circuit construction for developing single-electron integrated circuits based on majority logic. The majority logic gate circuit proposed consists of a capacitor array for input summation and a single-electron inverter for threshold operation. It accepts an odd number of inputs and produces the corresponding output on the basis of the principle of majority decision; it produces an output of logic "1" if the majority of the inputs is 1, and an output of "0" if the majority is 0. By combining the proposed majority gate circuits, various subsystems can be constructed with a smaller number of devices than that of Boolean-based construction. An adder and a parity generator are designed as examples. It is shown by computer simulation that the designed subsystems produce the correct logic operations. The operation error induced by thermal agitation is also estimated.

This paper presents the results of the best differential characteristic search of FEAL. The search algorithm for the best differential characteristic (best linear expression) was already presented by Matsui, and improvements on this algorithm were presented by Moriai et al. We further improve the speed of the search algorithm. For example, the search time for the 7-round best differential characteristic of FEAL is reduced to about 10 minutes (Pentium/166 MHz), which is about 212. 6 times faster than Matsui's algorithm. Moreover, we determine all the best differential characteristics of FEAL for up to 32 rounds assuming all S-boxes are independent. As a result, we confirm that the N-round (7N32) best differential characteristic probability of FEAL is 2-2N, which was found by Biham. For N=6, we find 6-round differential characteristics with a greater probability, 2-11, than that previously discovered, 2-12.

This paper focuses on competitive learning algorithms for WTA (winner-take-all) networks which perform rotation invariant pattern classification. Although WTA networks may theoretically be possible to achieve rotation invariant pattern classification with infinite memory capacities, actual networks cannot memorize all input data. To effectively memorize input patterns or the vectors to be classified, we present two algorithms for learning vectors in classes (LVC1 and LVC2), where the cells in the network memorize not only weight vectors but also their firing numbers as statistical values of the vectors. The LVC1 algorithm uses simple and ordinary competitive learning functions, but it incorporates the firing number into a coefficient of the weight change equation. In addition to all the functions of the LVC1, the LVC2 algorithm has a function to utilize under-utilized weight vectors. From theoretical analysis, the LVC2 algorithm works to minimize the energy of all weight vectors to form an effective memory. From computer simulation with two-dimensional rotated patterns, the LVC2 is shown to be better than the LVC1 in learning and generalization abilities, and both are better than the conventional Kohonen self-organizing feature map (SOFM) and the learning vector quantization (LVQ1). Furthermore, the incorporation of the firing number into the weight change equation is shown to be efficient for both the LVC1 and the LVC2 to achieve higher learning and generalization abilities. The theoretical analysis given here is not only for rotation invariant pattern classification, but it is also applicable to other WTA networks for learning vector quantization.

In the circumstances we want to deal with, transmission channel is limited and global motion can happen by camera movement, and also there exists a region-of-interest (ROI) which is more important than background. So very low bit rate coding algorithm is required and processing of global motion must be considered. Also ROI must be reconstructed with required quality after decoding because of its importance. But the existing methods such as H. 261, H. 263 are not suitable for such situations because they do not compensate global motion, which needs large amount of transmission bits in motion information and degrades image quality. And also they can not reconstruct ROI's with high quality because they do not consider the fact that ROI's are more important than background. So a new coding scheme is proposed that describes a method for encoding image sequences distinguishing bits between ROI and background. Simulations show that the suggested algorithm performs well especially in the circumstances where background changes and the area of ROI is small enough compared with that of background.

The addition chain (A-chain) and addition-subtraction chain (AS-chain) are efficient tools to calculate power Me (or multiplication eM), where integere is fixed andM is variable. Since the optimization problem to find the shortest A (or AS)-chain is NP-hard, many algorithms to get a sub-optimal A (or AS)-chain in polynomial time are proposed. In this paper, a window method for the AS-chain and an extended window method for the A-chain and AS-chain are proposed and their performances are theoretically evaluated by applying the theory of the optimal variable-to-fixed length code, i. e. , Tunstall code, in data compression. It is shown by theory and simulation that the proposed algorithms are more efficient than other algorithms in practical cases in addition to the asymptotic case.

A new broadband space diversity (B-SD) combining method, which is a key technique in the growth of digital microwave radio system, is proposed. In this B-SD combining method, two received signals, whose bandwidths are 280 MHz, are combined. To develop this combining method, an optimum control algorithm is developed that monitors power levels of all primary carriers and controls the endless phase shifter so that the higher level signal is decreased and the lower level signal is increased. This paper describes the proposed B-SD combining method which effectively operates over a wide bandwidth. Performance evaluations based on simulations and theoretical estimations are given. It is proven that this combining method offers the same performance obtained by the conventional narrowband SD combining method and can be applied to over 50% cases of the propagation paths observed in Japan. The suitability of the proposed combining method and the calculation methods adopted is demonstrated experimentally.