Norinobu Yoshida

Transient analysis of a magnetized plasma in three-dimensional space

The time-domain formation, in terms of unified nodal equations, of a magnetized cold plasma in three-dimensional space using the Bergeron method is described. The validity of this treatment is shown by simulations of both transverse propagation and longitudinal propagation. In the formulation of the characteristic equation in the time domain, the authors introduce variables corresponding to the first and second derivates of the electric polarization. Thus the iterative computation can be performed by using only the values obtained at the previous time step. This procedure very closely matches the architecture for high-speed computation in the vector processor of a supercomputer. This property can render practical the simulation of three-dimensional fields involving gyroelectric anisotropic media and expand the generality of the numerical vector analysis method in the time domain. >

Transient analysis of ferrite in three-dimensional space

The authors present Bergerons formulation of vector analysis for magnetized ferrite in a three-dimensional space and time domain. Results are provided for two cases with respect to the relative angle between the directions of the DC magnetic field and wave propagation. For both cases, the results are compared with analytical ones, and the validity of the formulation is verified. >

Transient Analysis of Microstrip Gap in Three-Dimensional Space (Short Paper)

In this paper, we deal with the microstrip gap that should be analyzed in three-dimensional space. The time variations of the electric field at each surface of the stripline having a finite metallization thickness are analyzed. Our method of analysis is based on both an equivalent circuit of Maxwells equations and Bergerons method. The former has advantages in the vector analysis by using all electromagnetic components. The latter has advantages in the time-domain analysis of the field. Therefore, our method can analyze field variations in three-dimensional space and time. We present the time variation of the instantaneous electric-field distributions below the strip, at the side of the strip, and at the gap end surface. These results show how the steady-state field distribution grows in the gap.

Transient Analysis of Coupling Between Crossing Lines in Three-Dimensional Space

Coupling of crossing lines has not been studied extensively since it is very complicated and difficult to estimate. But recently with the development of high density wiring and large-scale integration rigorous analysis of coupling effects has become more important. In this analysis not only the electric and magnetic fields but also the Poynting vector are important. Especially, the variation of the spatial pattern of the Poynting vector in the time domain clarifies the dynamic coupling characteristics. In this paper the fundamental phenomena of coupling are demonstrated by considering the time variation of the distribution of the Poynting vector and the magnetic and electric fields for a Gaussian pulse in three-dimensional space.

Transient analysis of microstrip line on anisotropic substrate in three-dimensional space

The authors describe how anisotropy, with the permittivity tensor involving off-diagonal elements, may be generally formulated by Bergerons method. The formulation is discussed for the propagation characteristics of single and parallel striplines on a sapphire substrate with tilted optical axis. To show the distinctive influence of anisotropy on the coupling property between lines, a parallel-line-type directional coupler on such a substrate is analyzed. >

Transient Analysis of a Directional Coupler Using a Coupled Mlcrostrip Slot Line in Three-Dimensional Space (Short Paper)

In recent MIC techniques, double-sided MIC has been studied because its advantages in propagation characteristics are greater than that conventional MICs. A coupled microstrip slotline is one of them. Its application to various circuit elements has often been discussed. But the coupled microstrip slotline is essentially three-dimensional structure, so the analysis demands a rigorous three-dimensional treatment. Also, the recent high-speed pulse technique demands analysis in the time domain. The present paper treats a directional coupler using the coupled microstrip slotline in three-dimensional space and time. The results of the directional coupler analysis is presented with the complicated time variation of the three-dimensional electromagnetic field. So, the mechanism of the directional coupling phenomena that is produced by the propagation characteristics of the even and odd modes is presented in the time domain, In particular, the instantaneous diagram of the Poynting vector details the energy flow in the transient process. For the analysis of the characteristics of the complex microwave device, these results present the utilities of the various field distributions that are obtained by the three-dimensional vector analysis in the time domain.

Robust speech analysis in noisy environment using running spectrum filtering

A new robust adaptive processing algorithm is proposed for speech parameters estimation in noisy environments; it is based on the extended least squares (ELS) method with running spectrum filtering (RSF). By utilizing RSF, we can retain speech characteristics while noise is effectively eliminated. Then, by using ELS, formants of ARMA parameters can be estimated accurately. In experiments with real speech contaminated by white Gaussian noise, it is shown that the proposed method provides robust spectrum estimation against additive noise.

Transient Analysis of the Electromagnetic Field for a Wave Absorber in Three-Dimensional Space

In recent years, large-scale structures such as tall buildings, large bridges, and towers cause severe reflection and diffraction in the propagation of electromagnetic waves. The most effective means for improvement of these characteristics is coating an electromagnetic wave absorber on the surfaces of structures. At the present time, determination of the performance of a coating and the estimation of its effects are carried out on a practical basis. Beforehand, however, theoretical clarification of absorbing characteristics is necessary for better design of a structure. This analysis demands the unified treatment involving both characteristics of absorber materials and the shapes in three-dimensional space of structures to which they are applied. Also, the analysis of propagation characteristics of a pulse wave in the time domain will be important. In this paper, we report the fundamental treatment of absorbing characteristics, including boundary conditions of the structure. The method of time-domain analysis in three-dimensional space and time is used. This method is formulated by Bergerons method and based upon the equivalent circuit of both Maxwells equation and characteristics of the medium. As an example, the performance of a very thin coating of absorber with magnetic loss is presented. The variations of field distribution for changes of magnetic-loss term including permeability and the frequency of incident wave, are shown. The absorbing characteristics for a pulse wave in the time domain are also given as a parameter of incidence angle.

Transient analysis of vector potential in three-dimensional space by spatial network

Recently, for many kinds of complex engineering problems, numerical analysis methods have become very useful with the remarkable development of the digital computer, especially the super computer. I have recently proposed a new method for the vector analysis of the electromagnetic field, which is called as the spatial network method (SNM). This method is based on both the three-dimensional spatial lattice network of Maxwells equations and the formulation by the Bergeron method in the time domain. For the analysis of some problems involving sources such as currents or charges it is known that the formulation by the vector potential is effective. This paper describes that the SNM can be easily applied to the vector potential fields with the gauge condition in that the divergence of the vector potential is zero. The formulation is performed in the same spatial lattice network as that for Maxwells equation, and both the magnetic and electric vector potential variables are introduced. Therefore the proposed method succeeds the advantages of SNM for analyses of electromagnetic fields. For examining the fundamental characteristics and the validity of the formulation the electromagnetic field distributions around a line current and a small loop current are computed.

Three-dimensional analysis of a through hole with radiation characteristics by the spatial network method

Through holes generate complicated distributions of electromagnetic fields owing to their three-dimensional structures. Rigorous vectorial analyses must be performed for three-dimensional fields by using all field components, boundary conditions, and properties of the medium. The spatial network method, which has many features for analysis of three-dimensional electromagnetic fields in the time domain, was applied to this analysis. The variation of Poynting vector distributions near the through hole is simulated in the time domain. From the distribution of the electric field on the top plane of the through hole containing the connected stripline and the land, the far-field patterns are computed by the Fourier transform. Fundamental characteristics of the radiation from the through hole are thereby obtained. >