The Technical Committee on Electromagnetic Theory has organized a special issue on 2002 Electromagnetic Theory Symposium. This paper reviews the outline of Electromagnetic Theory Symposium and the papers selected for the present special issue.

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Three-dimensional optical waveguide with periodic structure is playing an important role in optical IC, and more accurate analysis on such waveguides with arbitrary number of periods is required. In this paper, revised Fourier series expansion method for larger number of periods and higher accuracy in which Floquet’s theorem is introduced is applied to numerical analysis of lamellar grating type periodic optical waveguides with rectangular cross-section (glass substrate). Referring to the numerical results, the characteristics for reflected and transmitted powers of guided and radiation fields vs. wavelength are investigated for various depths of the grating groove and for each number of periods(100-1000). Then the effects of the groove depth and the number of period on the powers of each mode are made clear, and the appropriate parameters preferred for the dominant guided mode propagation in the periodic waveguide concerned are exemplified.

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In order to study earthquake-related ULF geomagnetic field changes, it is important to discriminate the signal from the other noises such as magnetic pulsations originated from solar activity and artificial noises from the DC driven train and factories. For this aim, the interstation transfer function method with wavelet transform has been applied to data observed in the ULF electromagnetic sensor array at Boso Peninsula, Japan. The results indicate that the proposed method has a capacity to eliminate the global signal.

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This paper describes a simple analyzing method on the optical resonator compose of the nonlinear directional coupler. Assumed the coupler made in the semiconductor-doped glass with the K⁺-ion diffused technique, the transmitted- and reflected-characteristics are calculated and demonstrated. The parameter dependence of the bistability appearing the transmitted and reflected lights is also presented.

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This paper proposes a new type of comb-line filter suitable for miniaturization utilizing stratifying technology. The filter consists of a couple of quarter-wavelength resonators. Each resonator is composed of two sections of CPW (coplanar waveguide) and MSL (microstrip line) which is fabricated on the other side of the CPW. Both sections are connected to each other with a piece of bonding wire at an open end to set up a new type of folded comb-line filter. The filtering characteristics are investigated through experiments as well as numerical simulations by means of the FD-TD method. It is shown that the filtering characteristics are improved by adjusting coupling between the resonators. It is also shown that the filter can be miniaturized by introducing stepped impedance structure in the resonators.

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A new band elimination filter for coplanar waveguide using a patch of conductor is proposed. The proposed structure is composed of a coplanar waveguide (CPW) to which a patch of conductor on the opposite surface of the substrate is wired through a narrow hole drilled in the substrate. It is shown through numerical simulations by means of the FD-TD method that the structure provides excellent bandstop characteristics and that frequencies of stopband can be controlled by dimensions of the patch. We also investigate, both numerically and experimentally, the characteristics of a filter with several patches aligned periodically.

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Physical optics(PO) is an approximation method for high-frequency scattering and diffraction problems. But PO fields are inaccurate in the shadow region where the source is screened by the scatterer. Two key factors of the error for PO are (i) edge diffraction coefficients and (ii) existence of fictitious penetrating rays. The correction with respect to the former has been extensively investigated by many author using the ray techniques such as GTD, UTD and UAT. On the other hand, the latter was identified recently by the authors. This paper proposes a novel PO-based calculation procedures named PO-AF and PTD-AF, where PO and Aperture Field Integration Method (AFIM) are merged with the help of special elementary diffraction coefficients. These can uniformly cover whole the angular region and only the error factor (ii) is removed in PO-AF while both of (i) and (ii) are removed in PTD-AF. The theoretical backgrounds of PO currents are discussed in terms of field equivalence theorem and visualization of EM waves. Then new methods are proposed and their validity is numerically demonstrated for 2-D scattering problems of a strip, a corner reflector and a cylinder of circular arc.

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The analysis of wave scattering in a random medium plays one of important roles in the development of remote sensing technology. As a theoretical approach to the subject of measuring soil moisture by active microwave remote sensing, this paper considers a simple model of moist soil composed of air and three layers of random medium with many particles. A radiative transfer equation with coefficients estimated by the multiple scattering method developed by us is used to calculate the scattering cross section of the layers by changing the polarization and frequency of incident waves, layer thickness, and particle distribution in the depth direction. The calculation makes clear the characteristics of scattering cross sections of the layers. We also discuss the possibility of the detection of water content in moist soil on the basis of the characteristics.

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In this paper, a directional coupler is proposed for rectangular waveguides. Coupling and scattering problems are analyzed when the fundamental compound mode is incident by the mode-matching method in the sense of least squares. This coupler is composed of two rectangular waveguides placed in dielectric media. A periodic groove structure of finite extent is formed on the surface of one of two waveguides. The incident fundamental compound mode is coupled with other higher compound modes through the periodic groove structure.

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The virtual reality is one in the intelligence information carrier technology. As the application to the education field of the virtual reality, we examine a support system for the calligraphy mastering. The purpose of this system is to realize the model where the information during writing progress can be real time displayed. As a result, we can learn calligraphy casually without being limited to the place and the time. We use 3-D computer graphics (CG) for the virtual image to decrease memory capacity and we examine about the learning effect of this system. We can not get the sense of the writing brush from the tablet pen of the conventional system. Therefore, we developed the writing brush type input device which is near the sense of the writing brush. Moreover, we developed the automatic animation generation processing used 3-D CG. The practice person can experience the subtle writing progress of calligraphy from the eye of calligraphy teacher using this animation. We are using a semitransparent screen and a half mirror instead of HMD to use in general VR. Practice persons improve at the short time by learning their writing brush forming die input pen synchronous with virtual writing brush.

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Late in 1990, a short circuit accident occurred on a GEO satellite due to sustained arc on high voltage solar array. The arc plasma generated by a trigger arc absorbs the electrical charge on coverglass and the conductivity increases. The high density arc plasma short-circuits the adjacent array strings and the solar array supplies the current to the trigger arc, that becomes the sustained arc. The purpose of this paper is to investigate the charge absorption by the arc plasma via a laboratory experiment. Solar array coupons are irradiated by an energetic electron beam in a vacuum chamber. The amount of charge absorbed by the arc plasma is proportional to the differential voltage before the arc. When the initial energy of the trigger arc is small, the charge absorption depends on the distribution of surface potential.

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Traffic information boards have a vital role in promoting safe and efficient road traffic, by providing the drivers with relevant traffic information on a real-time basis. To achieve good visibility and eye-catching quality, we must know the optimum number of display colors and their chromaticity regions so that the road users can correctly recognize displayed information in a short time. We attempted to determine an optimum number of display colors based on the categorical color (basic perceived color) technique, as well as to define the chromaticity regions for display colors so that a given color is most effectively discriminated from the others. The results showed that the optimum number of display colors is ten, and categorization of the so-defined ten display colors on the chromaticity diagram is extremely useful in designing a traffic information board.

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The harmonics of the response wave, the nonlinear dielectric properties of yeast cells, have particular patterns according to the biological activity of the cells, and the measurement of these patterns is a technique for determining the activity of living cells. In this study, we examined the generation of nonlinear dielectric properties by comparing data for the cases in which the cells were near and away from the electrodes with an electrochemical cell mounted with a membrane filter. Measurements were made with living yeast cells in the induction phase, the logarithmic growth phase, and the stationary phase, as well as with sterilized yeast cells. Our measurements of the nonlinear dielectric property of living yeast cells demonstrated that the pattern of harmonics varied depending on the growth phase of the cells. We found that harmonics appeared for yeast cells in every growth phase when the cells existed near the electrodes. When yeast cells existed away from the electrodes, the harmonics were barely apparent for living yeast cells in the induction and stationary phases and for sterilized yeast cells; however, living cells in the logarithmic growth phase (rapidly proliferating yeast cells) displayed substantial second and fourth harmonics. The activity state of yeast cells is one of the factors determining the harmonics pattern generated, and the particular relationship between the activity of the yeast cells and the electrodes affects the cells’ nonlinear dielectric properties.

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FDTD simulations of electromagnetic waves in wave guide mode (or hybrid surface wave mode) discharges have been done. The results show that Transverse Magnetic waves travel along the axis of the dielectric window and penetrate into an over dense plasma as evanescent waves, which would excite electron plasma waves resonantly at the cutoff density and be efficiently absorbed. It has been also shown numerically that there is the maximum absorption energy between relative permittivity 3.6 and 4.6 at the dielectric thickness 15 mm and the diameter 132mmφ. The experiments to imitate it have indicated that there is the maximum density between relative permittivity 3.6 and 4.6.

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We have studied the feasibility of a hybrid discharge method (to guide the discharge with strongly and weakly ionized plasma channels) of a long guiding laser plasma channel. Charged particle densities in a weakly ionized plasma channel were measured as a function of the laser intensity. Critical condition of the weakly ionized plasma to guide an electrical streamer was determined. The electrical resistibility of plasma channel to generate the self-propagating streamer is smaller than 3.5 Ωm. The self-propagating streamer could heat the channel and leads to a main discharge.

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The influence of O₂ gas addition (˜1%) on discharge properties of high-pressure Xe dielectric barrier discharges was investigated using one-dimensional fluid model. In calculated voltage-current characteristics, sharp and shallow current pulses were observed during a half cycle in pure xenon case. With an increase in the mixture ratio r_O2 of oxygen, only a sharp current pulse was observed. The electronegativity in a discharge gap, which depends on r_O2, was varied spatially and temporally. Even in r_O2=1%, the maximum of electronegativity was reached to 53.1 at the phase of maximum value of discharge gap voltage. Despite of small r_O2, dominant positive and negative charged species were changed from Xe₂⁺ ions and electrons to O₂⁺ and O^- ions rapidly.

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We confirmed significant increase in the magnetic reconnection rate caused by a new phenomenon called the current sheet ejection. We focused on the relation between the shape distortion of the current sheet and the reconnection rate (inflow velocity), and concluded that a new simple current sheet model explain our experimental results qualitatively using mass conservation law.

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