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[Author] Hirokazu KOBAYASHI(3hit)

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  • Diffraction of Cylindrical Wave by Smooth and Polygonal Cylinders

    Hiroshi SHIRAI  Kohei HONGO  Hirokazu KOBAYASHI  

     
    PAPER-Antenna and Propagation

      Vol:
    E66-E No:2
      Page(s):
    116-123

    Expressions are derived for estimating the scattered and diffracted field in the presence of the polygonal cylinder using high frequency technique which is closely related with equivalent current or equivalent moment method proposed formerly. As the first step, we verified the method by applying it to various kinds of polygonal cylinders. The numerical results for radiation patterns are compared with those obtained by other methods when they are available. The agreement between them is fairly good and difference between them is not recognised in the figures except in a small part of region where observation point lies near a shadow boundary of the polygonal cylinder. The discrepancy is few decibels. Next we study a possibility of estimating the diffracted field of smooth convex cylinder by approximating it with corresponding polygonal cylinder. As an illustration we consider radiation of electric and magnetic line source in the presence of conducting circular cylinder since the exact solution of the problem is readily obtained. The approximation of smooth object with corresponding edged object is found to be useful from the standpoint of diffraction. The method is also applied to estimate the diffracted field by curved wedge and curved half plane.

  • Layer-Aware 3D-IC Partitioning for Area-Overhead Reduction Considering the Power of Interconnections and Pads

    Yung-Hao LAI  Yang-Lang CHANG  Jyh-Perng FANG  Lena CHANG  Hirokazu KOBAYASHI  

     
    PAPER-VLSI Design Technology and CAD

      Vol:
    E99-A No:6
      Page(s):
    1206-1215

    Through-silicon vias (TSV) allow the stacking of dies into multilayer structures, and solve connection problems between neighboring tiers for three-dimensional (3D) integrated circuit (IC) technology. Several studies have investigated the placement and routing in 3D ICs, but not much has focused on circuit partitioning for 3D stacking. However, with the scaling trend of CMOS technology, the influence of the area of I/O pads, power/ground (P/G) pads, and TSVs should not be neglected in 3D partitioning technology. In this paper, we propose an iterative layer-aware partitioning algorithm called EX-iLap, which takes into account the area of I/O pads, P/G pads, and TSVs for area balancing and minimization of inter-tier interconnections in a 3D structure. Minimizing the quantity of TSVs reduces the total silicon die area, which is the main source of recurring costs during fabrication. Furthermore, estimations of the number of TSVs and the total area are somewhat imprecise if P/G TSVs are not taken into account. Therefore, we calculate the power consumption of each cell and estimate the number of P/G TSVs at each layer. Experimental results show that, after considering the power of interconnections and pads, our algorithm can reduce area-overhead by ~39% and area standard deviation by ~69%, while increasing the quantity of TSVs by only 12%, as compared to the algorithm without considering the power of interconnections and pads.

  • Shadow Boundary Currents in the Problem of High-Frequency Electromagnetic Diffraction by a Circular Impedance Cylinder

    Andrey V. OSIPOV  Hirokazu KOBAYASHI  Kohei HONGO  

     
    PAPER-Electromagnetic Theory

      Vol:
    E81-C No:10
      Page(s):
    1655-1666

    A correction of the physical optics approximation by accounting for the presence of specific currents concentrated near shadow boundaries on the surface of a convex non-metallic scatterer is analysed by considering a canonical problem of diffraction of a plane electromagnetic wave incident normally to the axis of an infinite circular cylinder with impedance boundary conditions. The analysis focuses on the development of Fock-type asymptotic representations for magnetic field tangent components on the surface of the scatterer. The Fock-type representation of the surface field is uniformly valid within the penumbra region, providing a continuous transition from the geometrical optics formulas on the lit portion of the surface to the creeping waves approximation in the deep shadow region. A new numerical procedure for evaluating Fock-type integrals is proposed that extracts rapidly varying factors and approximates the rest, slowly varying coefficients via interpolation. This allows us to obtain accurate and simple representations for the shadow boundary currents that can be directly inserted into the radiation integral and effectively integrated. We show that accounting for the shadow boundary currents considerably improves the traditional PO analysis of the high-frequency electromagnetic fields scattered from smooth and convex non-metallic obstacles, particularly near the forward scattering direction.