Toshihiko Shibazaki

Numerical analysis of the periodic waveguide by thick iris using the FDTD method

In this paper, using the FDTD method, a numerical calculation method is described for obtaining the k-β characteristics of a periodic waveguide of arbitrary shape.

Numerical modeling of thick conducting irises using FDTD method-comparison with the modified residue-calculus method

In this paper, we investigate the accuracy of the finite-difference time-domain (FDTD) method for approximating a waveguide consisting of a periodic structure with a conducting iris of nonzero thickness. We consider a model for a single stage of a periodic structure - an individual conducting iris of nonzero thickness - and determine optimal grid spacings for FDTD calculations. We determine the optimal grid spacings using benchmark numerical solutions obtained with the modified residue-calculus method (MRCM), an accurate solution procedure that incorporates boundary conditions. We obtain agreement by choosing a grid spacing on the order of 1/100th of the wavelength λg.

Calculation method of EM field diffracted from a conductive circular disk for vertically polarized electric dipole incidence

The electromagnetic scattered field by a perfectly conducting circular disk is analyzed by using a technique developed by Y. Nomura and S. Katsura (J. J. Bowman, T. B. A. Senior and P. L. E. Uslenghi, Electromagnetic and Acoustic Scattering by Simple Shapes, 1969, pp.557–561), while a vertically polarized electric dipole source is located near the disk (see Fig. 1). A Hertz vector of the scattered field is expanded as follows: equation and П z (s) = 0, where equation are expansion coefficients, e n = 2, (n ≠ 0), = 1, (n = 0). Function S m n (ρ, z) is seen in the literature (Y. Nomura and S. Katsura, J. Phys. Soc. of Jap., 10, 1955, pp.285–304). In the case of vertically polarized dipole incidence, i.e. equation from the boundary condition on the disk, the scattered Hertz vector is presented in the form equation on the disk (z = 0, ρ < a), where equation, and U is a scalar function and satisfies a following two dimensional inhomogeneous wave equation: equation Applying the solution of Eq. (3) to Eq. (2), and matching with Eq. (1) on the disk, an infinite set of simultaneous linear equation of the expansion coefficients is obtained. After truncating the infinite equation and considering the edge condition, we can solve the equation, and the coefficients are evaluated numerically.