Kengo Sugahara

Generalized Strategic Dual Image Method for Open Boundary Axisymmetrical Magnetic Field Problems

During the early 1990s, the strategic dual image (SDI) method for axisymmetric open boundary magnetic field problems was proposed. Although the method is powerful, the specific axis ratio of the ellipsoidal boundary has not been clarified, and therefore no further research has been done so far. Our aims are to clarify the relationship between the specific axis ratio of the ellipsoidal boundary and the harmonic solutions of Laplace equation, and to extend the strategic dual image method in general form. We have investigated the harmonic solutions of the Laplace equation in the oblate spheroidal coordinate to derive the explicit formula regarding the axis ratio and the averaging factor of Dirichlet and Neumann boundary value problems. Numerical analyses have also been carried out to verify the formula. We have determined the explicit formula regarding the axis ratio and averaging factor of Dirichlet and Neumann solutions, thus extending the SDI method in general form. Utilizing the derived formula, one can obtain the open boundary solutions of axisymmetrical magnetic field problems without alternating the existing software which are widely distributed through the Internet.

Electromagnetic field distribution inside an automobile vehicle

Electromagnetic radiation phenomena due to electronic equipment inside an automobile have been analyzed from both numerical and experimental viewpoints. The numerical procedure is carried out using a hybrid method of a finite difference time domain (FDTD) and a transmission line technique (TL technique). This combined procedure is suitable for solving an automobile with long wires connected to an electric control in it. Numerical results were compared with experimental measurements with a real automobile, showing in a good agreement between them. Finally an FM radio antenna position that minimizes noise intensity caused by electronic control units was determined by the hybrid method.

Generalized Electrical Image Method for Field Reconstruction

A technique for magnetic field reconstruction is proposed with the use of a generalized electrical image method (GEIM). The basic idea behind the GEIM is that by understanding fundamental properties of the strategic dual image (SDI) method and applying the equivalence principle on the SDI boundary, a simple form of the interior/exterior magnetic field can be determined. As an example of this technique, a field reconstruction of a quadruple magnet is demonstrated.

Numerical analysis of low-frequency electromagnetic scattering from axially symmetric bodies using an inductance matrix

We have proposed a numerical method for calculating low-frequency electromagnetic scattering from axially symmetric conducting bodies with and without apertures. The surface of the perfectly conducting scatterer is modeled by a set of inductively coupled coil elements, and the current in each coil element is computed by solving an inductance matrix equation. A disadvantage of a conventional method for a scatterer with apertures is discussed. Scattering from various axially symmetric conducting bodies with or without apertures is calculated and the resulting fields are in good agreement with those obtained by finite-element method.

Improvised absorbing boundary conditions for three-dimensional electromagnetic finite elements

Improvised absorbing boundary conditions for high frequency electromagnetic problems have been studied. This method approximated unbounded space as series of isotropic spherical shells so as to emulate open boundaries without the need for additional code to any finite element solver. Previous work addressed applications of this technique to magnetostatic and electrostatic problems. This present work studies the wide-range frequency dependence of the IABC when applied to three-dimensional electromagnetic radiation problems.

Gigahertz frequency band inductors with magnetic films and gigahertz circuit analysis including inductance

The design and equivalent circuit of an inductor with a ferromagnetic film is described. High-frequency circuit simulation including inductance is carried out by two methods: 1) a SPICE-based simulation in which the distributed linear circuit is converted into a GCRL equivalent circuit and 2) an harmonic balance method in which the nonlinear active part of the circuit is solved in terms of sinusoidal harmonics in the frequency domain. High-frequency circuits including inductors and active elements such as low noise amplifiers are analyzed by these methods.

A simple and low-cost permanent magnet system for NMR

We have developed a simple, easy to build, and low-cost magnet system for NMR, of which homogeneity is about 4×10-4 at 57mT, with a pair of two commercially available ferrite magnets. This homogeneity corresponds to about 90Hz spectral resolution at 2.45MHz of the hydrogen Larmor frequency. The material cost of this NMR magnet system is little more than

Perturbation approach for open boundary problems based on the equivalence theorem

100. The components can be printed by a 3D printer.

Periodic Image Method for Open Boundary Axisymmetrical Magnetic Field Problems

The perturbation method for open boundary problems based on the equivalence theorem has been proposed. Most of the open boundary techniques in electromagnetic analysis are approximate, whereas more accurate techniques require large computational resources. In order to improve the accuracy of the open boundary solution, the equivalence theorem has been employed as a perturbation correction to the electromagnetic analysis with the approximate open boundary conditions. In this manuscript, the proposed method has been verified with numerical examples.

Investigation of a Boundary Integral Equation

A simple and efficient method for solving open boundary axisymmetric magnetic field problems is proposed. This technique uses two ellipsoidal analysis domains which are connected through the periodic boundary conditions. One of the domains acts as an exterior region which produces no reflection of low-order multipoles. The harmonic solutions of the Laplace equation in an oblate spheroidal coordinate have been investigated and a formula for the axis ratio of the ellipsoidal boundary and the permeability of the exterior region has been derived. To verify the formula, we have demonstrated some numerical examples and compared with spectrum-domain solutions. Based on the results, we concluded that the methodology is proven to be valid.