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[Author] Nobuaki TAKAHASHI(7hit)

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  • Separable 2D Lifting Using Discrete-Time Cellular Neural Networks for Lossless Image Coding

    Hisashi AOMORI  Kohei KAWAKAMI  Tsuyoshi OTAKE  Nobuaki TAKAHASHI  Masayuki YAMAUCHI  Mamoru TANAKA  

     
    PAPER

      Vol:
    E88-A No:10
      Page(s):
    2607-2614

    The lifting scheme is an efficient and flexible method for the construction of linear and nonlinear wavelet transforms. In this paper, a novel lossless image coding technique based on the lifting scheme using discrete-time cellular neural networks (DT-CNNs) is proposed. In our proposed method, the image is interpolated by using the nonlinear interpolative dynamics of DT-CNN, and since the output function of DT-CNN works as a multi-level quantization function, our method composes the integer lifting scheme for lossless image coding. Moreover, the nonlinear interpolative dynamics by A-template is used effectively compared with conventional CNN image coding methods using only B-template. The experimental results show a better coding performance compared with the conventional lifting methods using linear filters.

  • High-Speed Adaptive Noise Canceller with Parallel Block Structure

    Kiyoyasu MARUYAMA  Chawalit BENJANGKAPRASERT  Nobuaki TAKAHASHI  Tsuyoshi TAKEBE  

     
    PAPER

      Vol:
    E79-A No:3
      Page(s):
    275-282

    An adaptive algorithm for a single sinusoid detection using IIR bandpass filter with parallel block structure has been proposed by Nishimura et al. However, the algorithm has three problems: First, it has several input frequencies being impossible to converge. Secondly, the convergence rate can not be higher than that of the scalar structure. Finally, it has a large amount of computation. In this paper, a new algorithm is proposed to solve these problems. In addition, a new structure is proposed to reduce the amount of computation, in which the adaptive control signal generator is realized by the paralel block structure. Simulation results are given to illustrate the performance of the proposed algorithm.

  • An IIR SC Filter Utilizing Square Roots of Transfer Function Coefficient Values

    Toshihiro MORI  Nobuaki TAKAHASHI  Tsuyoshi TAKEBE  

     
    PAPER

      Vol:
    E82-A No:3
      Page(s):
    442-449

    Recently, we proposed a low power consumption FIR switched-capacitor filter constructed with capacitors having capacitances in proportion to square roots of transfer function coefficient values. It is referred to as an FIR semi-parallel cyclic type (SPCT) filter. In this paper, we present IIR SPCT filter. It needs only a single operational amplifier, hence being low power consumption. The IIR SPCT filter has smaller total capacitance than one of the IIR parallel cyclic type (PCT) filter and better high frequency response than one of the IIR transfer function coefficient ratio (TCR) filter. As a whole, the IIR SPCT filter has middle performance of the IIR PCT and TCR filters for the total capacitance, the number of types of clock pulses, and high frequency response.

  • Stabilized Fast Adaptive High-Speed Noise Canceller with Parallel Block Structure

    Chawalit BENJANGKAPRASERT  Nobuaki TAKAHASHI  Tsuyoshi TAKEBE  

     
    PAPER-Adaptive Signal Processing

      Vol:
    E87-A No:8
      Page(s):
    1965-1972

    This paper proposes a new implementation of an adaptive noise canceller based upon a parallel block structure, which aims to raise the processing and convergence rates and to improve the steady-state performance. The procedure is as follows: First, an IIR bandpass filter with a variable center angular frequency using adaptive Q-factor control and two adaptive control signal generators are realized by the parallel block structure. Secondly, a new algorithm for adaptive Q-factor control with parallel block structure is proposed to improve the convergence characteristic. In addition, the steady-state performance of the filter is stabilized by using the variable step size parameter in adaptive control of the center frequency and the speed up of the convergence rate is achieved by adopting a normalized gradient algorithm for adaptive control. Finally, simulation results are given to demonstrate the convergence performance.

  • Characteristics of Fiber Bragg Grating Hydrophone

    Nobuaki TAKAHASHI  Kazuto YOSHIMURA  Sumio TAKAHASHI  Kazuo IMAMURA  

     
    PAPER-Physical and Mechanical Sensors

      Vol:
    E83-C No:3
      Page(s):
    275-281

    Characteristics of an FBG hydrophone are described under various conditions. The developed FBG hydrophone detects an acoustic field in water with good performances: linear response,high sensitivity,high stability,wide dynamic range as large as 90 dB and wide operation frequency range from a few kHz to a few MHz. A WDM FBG hydrophone consisting of two FBGs in serial connection can detect simultaneously amplitudes and phases of acoustic fields at different points,which in turn allows a directive measurement of an acoustic field in water.

  • Semi-Parallel Cyclic Type Switched-Capacitor Filter Using Unity Gain Buffer

    Toshihiro MORI  Nobuaki TAKAHASHI  Tsuyoshi TAKEBE  

     
    PAPER-Analog Signal Processing

      Vol:
    E83-A No:7
      Page(s):
    1370-1380

    Recently, we developed a low power consumption and small total capacitance switched-capacitor filter using a single operational amplifier. It is called a semi-parallel cyclic type (SPCT) filter, in which each capacitance is in proportion to the square root of a transfer function coefficient value. In this paper, we propose the SPCT filter using a single unity gain buffer (UGB). It will be referred to a UGB-SPCT filter. It is possible to use the UGB-SPCT filter over a wider frequency range than the SPCT filter since a UGB has nearly unity gain over a wide frequency range.

  • Block Implementation of High-Speed IIR Adaptive Noise Canceller

    Xiaohua WU  Shang LI  Nobuaki TAKAHASHI  Tsuyoshi TAKEBE  

     
    PAPER

      Vol:
    E80-A No:3
      Page(s):
    466-471

    In this paper, a block implementation of high-speed IIR adaptive noise canceller is proposed. First, the block difference equation of an IIR filter is derived by the difference equation for high-speed signal processing. It is shown that the computational complexity for updating the coefficients of IIR adaptive filter can be reduced by using the relations between the elements of coefficient matrices of block difference equation. Secondly, the block implementation of IIR adaptive noise canceller is proposed in which the convergence rate is increased by successively adjusting filter Q-factors. Finally, the usefulness of proposed block implementation is verified by the computer simulations.