Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (conference, symposium, etc.)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PIERS  

High frequency electromagnetic plane wave scattering by a large rectangular glass window on a conducting wall has been analyzed in this study. Scattering far-fields are formulated by means of the Kirchhoff approximation in which the fields are obtained from radiation integrals due to the equivalent current sources on the virtually closed window apertures. In order to consider the effect of the window glass, a dielectric slab layer has been inserted in the window hole, and the reflection and transmission through the slab are treated via waveguide modal theory. The validity of our formulation has been confirmed by the numerical comparison with another method for an empty window case. The effects of the window dimension, the glass layer, and the polarization have been discussed for practical high frequency mobile communications.

DOI： 10.2528/PIERC22041501

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

In this study, edge diffraction of an electromagnetic plane wave by two-dimensional conducting wedges has been analyzed by the physical optics (PO) method for both E and H polarizations. Non uniform and uniform asymptotic solutions of diffracted fields have been derived. A unified edge diffraction coefficient has also been derived with four cotangent functions from the conventional angle dependent coefficients. Numerical calculations have been made to compare the results with those by other methods, such as the exact solution and the uniform geometrical theory of diffraction (UTD). A good agreement has been observed to confirm the validity of our method.

DOI： 10.1587/transele.2021ECP5031

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

In this paper, the scattering far-field from a circular electric conducting cylinder has been analyzed by physical optics (PO) approximation for both H and E polarizations. The evaluation of radiation integrations due to the PO current is conducted numerically and analytically. While non-uniform and uniform asymptotic solutions have been derived by the saddle point method, a separate approximation has been made for forward scattering direction. Comparisons among our approximation, direct numerical integration and exact solution results yield a good agreement for electrically large cylinders.

DOI： 10.1587/transele.2021REP0001

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICEAA  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

Electromagnetic scattering of an electromagnetic plane wave from a rectangular hole in a thick conducting screen is solved using the Kirchhoff approximation (KA). The scattering fields can be derived as field radiations from equivalent magnetic current sources on the aperture of the hole. Some numerical results are compared with those by the Kobayashi potential (KP) method. The proposed method can be found to be efficient to solve the diffraction problem for high frequency regime.

DOI： 10.1587/transele.2020REP0001

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

Plane wave scattering from a circular conducting cylinder and a circular conducting strip has been formulated by equivalent surface currents which are postulated from the scattering geometrical optics (GO) field. Thus derived radiation far fields are found to be the same as those formulated by a conventional physical optics (PO) approximation for both E and H polarizations.

DOI： 10.1587/tranele.2019ECP5048

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICEAA  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICEAA  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

This study presents an investigation of human skin exposure to obliquely incident electromagnetic waves at frequencies from 6 GHz to 1 THz. We aim to clarify the relationship between the power density and the skin surface temperature elevation under various exposure conditions. A Monte Carlo simulation was conducted to assess the transmittance and surface temperature elevation considering the variation of skin tissue thickness. For the case of TM wave injection, transmittance increases with increasing incidence angle from the normal incidence because of the Brewster effect. The normal incidence is confirmed as the worst-case exposure condition when the incident power density is defined in an area normal to the propagation direction.

DOI： 10.1088/1361-6560/ab057a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

Kirchhoff approximation (KA) method has been applied to analyze the plane wave scattering by conducting thick slits. The scattering fields can be considered as field radiations from equivalent magnetic current sources assumed by closing the aperture of the slit. The obtained results are compared with those of other methods to validate the accuracy of the proposed formulation in different conditions of slit dimension.

DOI： 10.1587/transele.E102.C.21

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

In this study, transverse magnetic electromagnetic plane wave scatterings by rectangular cylinders have been analyzed by a high frequency asymptotic method. Scattering field can be generated by the equivalent electric and magnetic currents which are obtained approximately from the geometrical optics (GO) fields. Our formulation is found to be exactly the same with the physical optics (PO) for the conducting cylinders, and it can also be applicable for dielectric cylinders. Numerical calculations are made to compare the results with those by other methods, such as the geometrical theory of diffraction (GTD) and HFSS simulation. A good agreement has been observed to confirm the validity of our method.

DOI： 10.1587/transele.E102.C.21

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Language：English   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICEAA  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

In this study, the electromagnetic scatterings from conducting bodies have been investigated via a surface equivalence theorem. When one formulates equivalent electric and magnetic currents from geometrical optics (GO) reflected field in the illuminated surface and GO incident field in the shadowed surface, it has been found that the asymptotically derived radiation fields are found to be the same as those formulated from physical optics (PO) approximation.

DOI： 10.1587/transele.E101.C.664

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PIER  

In this paper, a compact metamaterial quad-band antenna is presented. The antenna is designed from a unit cell of asymmetric extended-composite right/left handed transmission line (E- CRLH TL) as the main resonator part and a 50 Ω coplanar waveguide (CPW) as the feeding part. The design concept and resonant frequencies are analyzed and discussed. The results show that the proposed antenna exhibits four frequency bands covering GSM810, WLAN 2.45/5.5 GHz and WiMAX 3.5 GHz bands. The overall size of the fabricated antenna is only 57.2mm×31.2mm×1.6mm and is very small compared with other proposed quad-band antennas. In addition, a good agreement can be seen among the estimated resonant frequencies, HFSS simulated and measured results.

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Language：English   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

High frequency electromagnetic wave diffraction by a window and the window glasses have been analyzed. The problem has been modeled as two dimensional thick slit loaded with a dielectric material layer, and formulated by the Geometrical Theory of Diffraction and the ray-mode conversion technique. The validity of our formulation has been tested by comparing the results with these by the Kobayashi Potential method for relatively narrow slit aperture cases. Then the various numerical calculation results have been made to show the effects of the wall and window thickness, and window's glasses for practical wireless mobile communication frequencies.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A broadband approach to estimate the relative permittivity of dielectric cuboids has been proposed for materials of weak frequency dispersive characteristic. Our method involves a numerical iterative scheme with appropriate initial values carefully selected to solve for the relative permittivity in a wide range of frequencies. Good agreements between our method and references have been observed for nylon and acrylic samples. An applicable range relation between the minimal thickness, the frequency range and the dielectric property of the material has also been discussed.

DOI： 10.1587/transele.E100.C.52

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Theoretical maximum radiation efficiency of electrically small spherical surface antennas has been derived in this study. The current on the antenna surface is described in terms of vector spherical harmonics, and the radiated and the dissipated powers are calculated to obtain the radiation efficiency. It has been found that non-resonant TM10 mode shows the best radiation efficiency, and a proper combination of TM10 and TE10 modes establishes a resonant spherical surface antenna whose radiation efficiency is bounded by those values of non-resonant TM10 and TE10 modes. As a practical example of the spherical surface antennas, the radiation efficiency of the spherical helix antennas has also been computed to check the validity of our formulation.

DOI： 10.1587/transele.E100.C.20

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we derive approximate solution of scattering field by three-layered dielectric slab under high frequency condition. To bundle or collect the multiple reflected rays inside the slab into the primary reflected and transmitted rays, high frequency asymptotic approximation technique is used. We call the derived primary rays "collective rays". By using the new reflection/transmission coefficients in the present collective rays instead of the conventional ones, the internal multiple reflections effect can be easily included in ray tracing method without increase of the computational cost, so one can efficiently carry out propagation analysis through indoor/outdoor environments.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A high-frequency asymptotic method has been applied to formulate E-polarized plane wave diffraction by a thick slit. The slit structure is regarded as an open-ended parallel plane waveguide cavity, and the excitation of the waveguide modes and their reradiation are derived from a ray-mode conversion technique. Comparison with another method reveals the validity and effectiveness of our formulation.

DOI： 10.1109/TAP.2016.2608978

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICEAA  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A simple approach is presented for designing an antipodal Vivaldi antenna in this paper. A new and better estimation of the low frequency end of the operational range is shown. Final dimensions of the antenna parameters are determined by using the High Frequency Structure Simulator (HFSS). The proposed antenna has a simple configuration but exhibits low return loss, good radiation characteristics, and high and flat gain in the operating ultra wideband frequency range (3.1-10.6 GHz). Lastly, the fabrication has been done along with the specification to confirm the properties by measurements.

DOI： 10.1587/transele.E99.C.947

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Aalt University  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

CiNii Books

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

CiNii Books

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this paper, an electromagnetic plane wave diffraction by finite number of loaded thick slits on infinitely long perfectly electric conductor (PEC) screen is analyzed. Here we formulate the problem by utilizing the Kobayashi Potential (KP) method, which is a kind of eigenfunction expansion method in terns of Weber-Schafheitlin discontinuous integrals. The multiple scattering contributions between the slits are analytically included in the formulation. The solution derived here may provide us with precise numerical result, so it may be considered as a reference solution to other numerical and approximate analyses.

DOI： 10.1587/transele.E99.C.72

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A high frequency approximation method is proposed to obtain the scattering from rectangular dielectric cuboids. Our formulation is based on a Kirchhoff type aperture integration of the equivalent current sources over the surface of the scattering bodies. The derived formulae have been used to get the radar cross section of cuboids, and the results are compared with those by other methods, such as physical optics, geometrical theory of diffraction, the HFSS simulation and measurements. Good agreement has been observed to confirm the validity of our method.

DOI： 10.1587/transele.E99.C.11

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A high frequency asymptotic method has been applied to formulate a E-polarized plane wave diffraction by a thick and loaded slit. Internal slit region is considered as a waveguide and the excitations of the waveguide modes are given by a ray-mode conversion method from the multiply bouncing diffracted fields. Comparison with the results by the other method reveals the validity and the effectiveness of our formulation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper analyzes electromagnetic scattering problems for simplified crack models, based on the formulation of the Kobayashi Potential (KP) method. Here, three types of simple crack models, a flanged waveguide, a rectangular trough, and a thick slit, are considered. The derived far zone field representations are utilized to obtain the approximate formulae of the scattered fields for the models.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Ray-mode conversion technique has been applied to formulate a plane wave diffraction by a wide and thick slit perforated in a perfectly conducting screen. The internal field inside the thick slit is first formulated by multiply bouncing reflected and diffracted rays, and this ray summation is converted into a summation of parallel plane waveguide modes through the Poisson summation formula. The total field is then expressed as a summation of successive radiation fields excited by the waveguide modes at the aperture edges. The derived results are used to calculate the far fields and compared with the reference solution. Good agreement has been observed to confirm the validity of our formulation.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Electromagnetics Academy  

In this study, new closed-form solutions are presented for deriving inductance and capacitance elements of the extended-composite right/left-handed transmission line (E-CRLH TL) unit cell from the cutoff frequencies of right-handed (RH) and left-handed (LH) bands. The characteristics of the E-CRLH TL are investigated for unbalanced, balanced, and mixed cases. The dispersion diagram, Bloch impedance, S-parameters are analyzed by the TL, circuit theories and the Bloch-Floquet theorem. Lastly, the usefulness of our method has been shown in detail by designing the desired characteristics for various cases.

DOI： 10.2528/PIERC16080103

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper presents a compact multiband antenna formed from only one cell of dual composite right left handed transmission line (D-CRLH TL), which employs metamaterial loading on a conventional monopole to attain a certain degree of miniaturization. The proposed configuration is simple as uniplanar structure, and is operating at 2.45, 3.60 and 5.60 GHz, covering the WLANs and WiMAX bands, and its dimension is only 20 x 16 x 1.6 mm(3). The design concepts, the simulation and the experimental results are reported.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Radiation efficiency of multi-arm open-ended spherical helix antennas has been discussed in this paper. The numerical electromagnetics code (NEC) engine has been utilized for the calculation of their radiation efficiency. It has been found that single-arm Kim-type winding antennas can achieve higher radiation efficiency than that of the Best-type antennas, and non-feeding multi-arms can increase their radiation efficiency.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

High frequency asymptotic method has been applied to formulate E-polarized plane wave diffraction by a wide and thick slit. Slit aperture region is considered as a waveguide and excitations of the waveguide modes are given by ray-mode conversion technique. Comparison with the other method reveals the validity and the effectiveness of our formulation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Maximum radiation efficiency has been derived for homogeneous electrically small antennas. The spherical wave expansion is utilized to express the radiated field and the current distribution on an antenna, and the radiation efficiency is represented by the current, which is expressed in the spherical wave expansion coefficients and the nonradiating current. By using a concept of the nonradiating current, it is shown that the maximum radiation efficiency is achieved if the antenna shape is spherical. The radiation efficiency of a spherical antenna is maximized by varying the expansion coefficients. This radiation efficiency is compared with that of the antenna which achieves the maximum gain and those of linear antennas. The comparison indicates the validity of our proposed upper limit of the radiation efficiency.

DOI： 10.1587/transele.E98.C.2

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A broadband approach to estimate relative permittivity of dielectric cuboids has been proposed. Our method involves a numerical iterative scheme with appropriate initial values to solve for the permittivity in a wide range of frequency. Good agreement between the method and references has been observed. It is assumed that the material has a weak frequency dispersive characteristic. An applicable range relation between the smallest thickness, the dielectric property of material has also been discussed.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

High frequency ray method has been applied to formulate E-polarized plane wave scattering by a wide and thick slit. Slit aperture region is considered as a waveguide which connects the upper and lower half spaces, and excitations of the waveguide modes are given by edge diffraction at the open end. Multiple edge diffraction effect as well as modal bouncing effect are also considered to improve the accuracy of the scattering field.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Effect of curvature of antipodal structure on Vivaldi antennas is presented in this paper. The results indicate that inner curvature has a significant impact on the return loss S11. In addition, a new estimation of lower frequency limit is shown. Based on our design, an antipodal Vivaldi antenna has been fabricated and verified its properties through measurements.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A method has been proposed here to estimate the facet's size of polygonal dielectric targets using the specular reflected RCS. This algorithm has been tested to estimate the size of dielectric cuboids from the measurement data. Good accuracy has been found and the validity of our method is confirmed.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A compact tri-band metamaterial antenna is presented. The antenna is based on dual composite right/left handed transmission line (D-CRLH TL) which employs metamaterial loading on a conventional monopole to attain a certain degree of miniaturization. The over size of the antenna is 20 x 16 x 1.6 mm(3). The simulated return loss shows that the proposed antenna is suitable for WLAN 2.4/5.5 and WiMAX bands.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEE Japan  

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

Three dimensional visualization has been tested for electromagnetic wave propagation and radiation, which cannot be observed by our own eyes directly. Electric, magnetic, and Poynting vectors radiated from an infinitely small dipole antenna in a free space have been visualized by arrows, which are colored and enlarged according to their strength. Electric and magnetic lines of forces are also calculated from their space distribution, and shown three dimensionally. Radiation from a half-wavelength dipole antenna near a human head model has been simulated by the finite difference time domain (FDTD) method, and resultant time-varying electric field vectors are shown with the head model. The internal electric field inside the human head is utilized to calculate the specific absorption ratio (SAR) at that position, and SAR values are displayed.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICCE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Electromagnetic Academy  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We developed a millimeter-wave (MMW) exposure system for in vivo experiments for operating frequencies ranging from 24.5 to 95 GHz. The MMWs are localized to the rabbit ocular tissue with a spot-focus lens antenna. The MMW energy absorption and consequent temperature elevation are evaluated by numerical simulation using measured antenna distribution and precisely modeled rabbit ocular data. Results suggest that corneal damage occurs at an incident power density of 300 mW/cm(2) with our exposure system at frequencies from 26.5 to 95 GHz.

DOI： 10.1109/TMTT.2014.2323011

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publisher：Building Maintenance & Management Center  

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose efficient reflection and transmission coefficients from two-layered dielectric slab for realizing accurate ray-launching propagation analysis, by approximately including multiple reflections effect inside the dielectric slab. In order to precisely execute the ray-launching analysis through the two-layered slab, which is a simplified model of insulating glass window utilized on side wall of modern building, an efficient high frequency approximation is introduced to bundle or collect the multiple reflected rays inside the two-layered slab into the primary ray component. We here call it "collective ray". By utilizing the derived new reflection/transmission coefficients, one can easily include the multiple reflections effect inside the slab without increase of computational time.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Radiation efficiency of homogeneous antennas has been discussed in this paper. The radiated and dissipated powers are expressed in terms of the radiating and nonradiating currents. It has been found that the maximum radiation efficiency can be accomplished by the homogeneous spherical antenna which circumscribes arbitrary antenna shape.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

An antipodal Vivaldi antenna for UWB applications is presented in this paper. The proposed antenna is designed with simple structure but presents very good plot impedance characteristic. In addition, the antenna offers high gain and flat gain in the operating bandwidth from 3.1 GHz to 10.6 GHz. The antenna design simulation has been performed by using the commercially available simulation software HFSS 14. The antenna is fabricated on popular substrate FR4 with a dielectric constant of 4.4 and thickness 1.6 mm. The fabricated antenna has been tested for its return loss and directional pattern, and compared with simulated results.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Ray-mode conversion technique gives us an alternative description for analyzing electromagnetic scattering from open waveguide/resonance structures. For such structures, modal description may be convenient for expressing the field in the internal structures, while ray description would be suitable for the exterior ones. Ray-modal coupling occurs at the aperture, and its mathematical base is given by the Poisson summation formula.
In this paper, we shall show some recent development of the ray-mode conversion application to improve the accuracy of the field description by considering the multiple edge interaction and the evanescent modes.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper analyzes an electromagnetic plane wave scattering by a crack model on perfectly conducting plane and presents a simple formula for easily calculating two dimensional radar cross section from a material covered crack. Here, a narrow rectangular trough, which is filled by two-layered dielectric material, is utilized as the simple crack model to obtain the rigorous solution of the scattering field. In the formulation, we utilize the Kobayashi Potential (KP) method, which is an eigen function expansion method in terms of Weber-Schafheitlin type discontinuous integrals. Then the simple formula of the scattering field for the case that the aperture width is electrically very narrow is derived by approximating the rigorous solution. By utilizing the derived simple formula, the scattering characteristics for empty, partially material covered, and material filled crack models can be easily investigated.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper presents novel reflection and transmission coefficients for two-layered dielectric slab, which approximately include multiple reflections inside the slab. H polarization or TE case is here considered. In the derivation, an efficient high frequency approximation is introduced to bundle or collect the multiple reflected rays inside the two-layered slab into the primary ray component. We call them "collective rays". By utilizing the present reflection/transmission coefficients, one can easily include the internal multiple reflections effect in ray-launching analysis without increase of computational time, so these are very efficient for propagation analysis through indoor/outdoor interface as propagation through multi-layered insulating glass window on side wall of modern building.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE  

E polarized electromagnetic plane wave diffraction by a wide and thick slit has been analyzed. High frequency ray-mode coupling analysis has been utilized, and the total diffracted field is considered as a summation of successive modal radiation contribution from the slit aperture due to the original modal excitation by the incident plane wave. The derived results are then compared with those obtained by Kobayashi Potential method, and the corresponding H-mode incidence case.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：電気学会  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

For stable high speed wireless communication in urban area, it is necessary to install wireless access base station antennas in proper locations. Specially, for non-LOS (line of sight) propagation in a complex urban environment, edge diffracted ray contribution sometimes plays an important role. Shooting and Bouncing Rays (SBR) method is one of the powerful tool for analyzing high frequency electromagnetic wave propagation estimation including edge|rn|diffracted rays. In this report, new algorithm to include multiple edge diffracted rays has been proposed.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE  

An H polarized electromagnetic plane wave scattering by a V-shape groove on the perfectly conducting ground|rn|has been analyzed. Based on assumption that the groove aperture is sufficiently large compared with wavelength,|rn|Geometrical Theory of Diffraction (GTD) has been utilized for obtaining the edge diffracted waves.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ICEAA  

A general three dimensional formulation of high frequency solution for the scattering field of a dielectric body, which is illuminated by a transverse electric polarized plane wave, is presented. Based on the postulated equivalent currents, scattering far field components are derived. Effects of complex permittivity of material and the multiple bouncing effect caused by the finiteness of scattering body are included in a collective reflection coefficient. Under monostatic conditions, obtained formulae precisely agree with the ones derived from conventional physical optics in the case of a PEC surface. Differences between the two methods are observed in bistatic RCS estimation. Effects of finiteness of scattering body and of polarization on RCS are investigated.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE  

A target re-construction algorithm has been proposed for cylindrical metal scatterers from the angular Radar Cross Section (RCS) variation. This algorithm is based on the fact that the monostatic RCS return from a plate has its peak value at the specular reflection angle, and the RCS lobe width in the angular variation is related with its plate width. By assuming the target is a polygonal convex cylinder, sizes of their facets are estimated by the local maxima|rn|in the angular RCS variation. Then one may be able to reconstruct the target's shape by connecting all facets in the specular reflection order. For this paper, an algorithm for estimating the curvatures and widths of the smooth curved facets has been augmented with the previously proposed algorthm for flat facets. Our reconstruction algorithm has been tested for several cylindrical targets from numerically calculated and measured RCS values. Pretty|rn|good estimation of the target shape has been observed to show the validity of our method.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

In order to study the electromagnetic scattering properties of lossy dielectric polygonal body, Kirchhoff's approximation was used to derive scattering far-field components. Numerical calculations were carried out for some lossy dielectric and metallic rectangular cubes at different frequencies, and then they were compared to measured radar cross section data in order to verify the validity of our approximation. Good agreements were observed in specular reflection directions, especially in the case of electrically large metal cube.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

電気的小型アンテナ(ESA) に対するQ, 利得等の各種諸特性の限界値について議論が進んでいる．こうした議論においては，アンテナからの放射界を球面調和関数の和によって表現し，各モードの展開係数を用いて評価する．本報告では，ESA に対する損失電力について，そのアンテナの各励振モードによる依存性について考察した．

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：APMC  

Electromagnetic TM polarized plane wave scattering by dielectric surfaces is analyzed by high frequency asymptotic method. The scattering field is estimated from the equivalent currents induced by reflected plane wave on the dielectric surface. Effects of material nature, polarization and finiteness of the dielectric bodies are included in a multiple reflection coefficient. A comparison between theoretical estimations and measurement in the case of a rubber cube suggests a strong connection between the thickness of the body and its RCS values. © 2013 IEEE.

DOI： 10.1109/APMC.2013.6695124

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE Computer Society  

In this paper, a small metamaterial antenna with high efficiency is presented. The antenna is proposed for 2.4 GHz Wireless Local Area Network (WLAN) application. The metamaterial resonant antenna is designed with a mushroom structure which based on the zeroth order resonant characteristic of a composite right/left-handed transmission line (CRLH TL). The antenna is designed on the low-cost FR4 substrate with dielectric constant εr = 4.4 and tan δ= 0.02. The antenna is simulated and optimized by HFSS 14. The simulation results show that antenna has small size and a good bandwidth with range from 2.40-2.48 GHz for return loss S11 less than -10 dB. The proposed antenna offers high efficiency 72-75% in operation bandwidth. The overall dimension of the antenna is 20.0×22.0×1.6 mm3 including the antenna substrate. © 2013 IEEE.

DOI： 10.1109/APWC.2013.6624903

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, a compact antenna for broadband operation is depicted. A C-shaped patch that based on Chuo University's logo is used to design a monopole radiator. Transmission line theory and the resonator model are adopted to analyze the operating frequencies of the proposed antenna. The bandwidth was enhanced by using the curve of C-shaped patch and CPW feeding method. The proposed antenna was designed and simulated successfully by using HFSS 14. The simulation results show that the antenna has compact size 18.6x17.2 mm(2), a good impedance band with range from 3.9 to 7.6 GHz for return loss S-11 less than -10 dB. The simulated bandwidth reaches 3.7 GHz which is about 72.5% with respect to the center frequency of 5.1 GHz. The antenna can be integrated into wireless communication products such as HIPERLAN/2, IEEE 802.11 a/h/j/n, and WiMAX (4.9-5.85GHz).

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Antenna radiation efficiency for electrically small antennas has been discussed in this paper. The radiated field is expressed in terms of spherical harmonic TE and TM modes and radiated and dissipated powers are described by this modal excitation coefficients. By carefully evaluating the above coefficients, upper bound of the radiation efficiency has been estimated.

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Language：English   Publishing type：Research paper (international conference proceedings)  

A general three dimensional formulation of high frequency solution for the scattering field of a dielectric body, which is illuminated by a transverse electric polarized plane wave, is presented. Based on the postulated equivalent currents, scattering far field components are derived. Effects of complex permittivity of material and the multiple bouncing effect caused by the finiteness of scattering body are included in a collective reflection coefficient. Under monostatic conditions, obtained formulae precisely agree with the ones derived from conventional physical optics in the case of a PEC surface. Differences between the two methods are observed in bistatic RCS estimation. Effects of finiteness of scattering body and of polarization on RCS are investigated. © 2013 IEEE.

DOI： 10.1109/ICEAA.2013.6632344

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper examines electromagnetic plane wave diffraction by a three-layer dielectric material loaded slit on infinitely long perfect electric conductor (PEC) screen. Here, the Kobayashi Potential (KP) method, which is an analytical eigen function expansion method in terms of the discontinuous characteristics of Weber-Schafheitlin type integrals, is utilized for the analysis. The derived solution obtained by the KP method provides us with precise numerical results, so it may be regarded as a reference solution to other high frequency approximations and numerical techniques. We examine the detailed scattering and diffraction features of the partially loaded slit for H-polarized plane wave incidence, by comparing the results for this analysis with those for empty and material filled cases.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

High frequency asymptotic analysis has been done for obtaining modal excitation coefficients for the flanged parallel plane waveguides. Previously derived formula has been extended to included multiple edge diffracted contribution between two aperture edges. And also, there is a problem that the excitation coefficients with the transitional modes have discontinuous spike at cut-off frequencies. To improve this behavior, diffraction coefficient has been extended to uniform asymptotic theory of diffraction for complex number. Numerical calculations show that the excitation coefficients with multiple diffraction contribution give us better results for the transitional modes.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

For stable high speed wireless communication in urban area, it is necessary to install wireless access base station antennas in proper locations. For such purpose, one needs a reliable tool for estimating electromagnetic propagation. Ray tracing method is one of the powerful methods for high frequency propagation analysis. For non-LOS (line of sight) propagation in a complex urban environment, diffracted ray contribution sometimes play an important role.|rn|In this report, new algorithm for SBR (Shooting and Bouncing Rays) method to include diffracted rays has been proposed.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEE Japan  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

都市部における集中した携帯電話利用の増加とともに，基地局の効率のよい配置が望まれている．こうした基地局の配置は，広い範囲での電波伝搬強度分布を基に考える必要があり，短時間で効率の良い電波伝搬予測を実測で，または計算シミュレーションによって行うことが求められる[1]．|rn|東京を中心とした関東地方の電波伝搬強度について，基地局アンテナ高，使用周波数，伝搬環境，土地利用の状態を考慮して詳細に測定し，その結果をまとめて受信電界強度の中央値を示す曲線を示したOkumura の報告[2] や，その報告から一般化した伝搬環境に対する伝搬損を導出したHata の公式[3] は，世界的にも有名である．|rn|本稿では，広範囲な空間における電波伝搬・散乱量の推定に対して，有力な方法となる光線手法の特徴とその手法を適用する際に注意すべき点について述べる．

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose a simple and useful extension of the previous GTD|rn|solution for diffracted field by a thin and relatively narrow slit on infinitely|rn|long conducting screen, to treat the internal evanescent modes excited by the|rn|higher order terms due to multiple interactions between the illuminated edges|rn|of the slit. Here, complex propagation angle is introduced for appropriately|rn|evaluating the evanescent modes. To confirm the validity of the proposed extension,|rn|we will make a comparison between the derived solution and that|rn|obtained by the rigorous Kobayashi Potential method. In consequence, the|rn|detailed numerical tests using the present solution will make clear how the|rn|multiple interactions between the illuminated edges and the corresponding|rn|internal modal excitation/coupling contribute to the total radiation characteristics,|rn|for variation of the incident angle and the thickness of the slit.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A novel delta-sigma modulator that employs a non-uniform quantizer whose spacing is adjusted by reference to the statistical properties of the input signal is proposed. The proposed delta-sigma modulator has less quantization noise compared to the one that uses a uniform quantizer with the same number of output values. With respect to the quantizer on its own, Lloyd proposed a non-uniform quantizer that is best for minimizing the average quantization noise power. The applicable condition of the method is that the statistical properties of the input signal, the probability density, are given. However, the procedure cannot be directly applied to the quantizer in the delta-sigma modulator because it jeopardizes the modulator's stability. In this paper, a procedure is proposed that determine the spacing of the quantizer with avoiding instability. Simulation results show that the proposed method reduces quantization noise by up to 3.8 dB and 2.8 dB with the input signal having a PAPR of 16 dB and 12 dB, respectively, compared to the one employing a uniform quantizer. Two alternative types of probability density function (PDF) are used in the proposed method for the calculation of the output values. One is the PDF of the input signal to the delta-sigma modulator and the other is an approximated PDF of the input signal to the quantizer inside the delta-sigma modulator. Both approaches are evaluated to find that the latter gives lower quantization noise.

DOI： 10.1587/transcom.E95.B.2257

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose a simple and useful extension of the previous GTD solution for diffracted field by a thin and relatively narrow slit on infinitely long conducting screen, to treat the internal evanescent modes excited by the higher order terms due to multiple interactions between the illuminated edges of the slit. Here, complex propagation angle is introduced for appropriately evaluating the evanescent modes. To confirm the validity of the proposed extension, we will make a comparison between the derived solution and that obtained by the rigorous Kobayashi Potential method. In consequence, the detailed numerical tests using the present solution will make clear how the multiple interactions between the illuminated edges and the corresponding internal modal excitation/coupling contribute to the total radiation characteristics,|rn|for variation of the incident angle and the thickness of the slit.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Diffraction field by a wide and thick slit on a conducting screen has been analyzed. High frequency ray-mode coupling analysis has been utilized, and the total diffracted or radiated field in each region is considered as a summation of successive modal radiation contribution due to the original modal excitation by the incident plane wave. Our derived results are compared with those obtained by other solutions, and good agreement has been observed, and the validity of our formulation is confirmed.

DOI： 10.1587/transele.E95.C.10

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we provide the simulation results for the noise reduction in the delta-sigma modulator with a non-uniform quantizer under various types of input signals. The delta-sigma modulator employs a non-uniform quantizer and adjusts the spacing of the quantizer referring to statistical properties of the input signal to the modulator. It reduces its quantization noise compared to the delta-sigma modulator with the uniform quantizer at the same number of output values. The simulation results showed that the amount of noise reduction varied from 0.15 dB to 4.9 dB depending on the input signal, while the effect is not limited by the architecture of delta-sigma modulators. Moreover, it is shown that the PAPR of the input signal cannot work as an indicator of the amount of the noise reduction. © 2012 IEEE.

DOI： 10.1109/RWS.2012.6175337

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This letter proposes new usage of the binary tree constructed by fundamental GO ray components in shooting and bouncing rays (SBR) for indoor propagation analysis. The node number of the binary tree is here considered as an important parameter. A couple of small size arrays that can store the passing ray information of both the node number and the position of the pixel considered, and the corresponding ray classification algorithm are newly introduced, not to double-count the same ray with slightly different bouncing angle. Consequently, we realize the big reduction of the computer memory resources consumed for the ray classification especially for wide area analysis, keeping the high accuracy of the SBR method.

DOI： 10.1587/elex.9.673

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE COMPUTER SOC  

Ray analysis has been executed for obtaining modal excitation coefficients at the flanged parallel plane waveguides. Previously derived formula has been extended to include multiple edge diffraction contributions between the aperture edges. By comparing the results by other methods, it has been shown that the contribution due to the doubly edge diffracted rays can improve the excitation coefficients for the transitional waveguide mode.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A simple target reconstruction algorithm has been proposed for cylindrical metal scatterers from the angular Radar Cross Section (RCS) variation. This algorithm is based upon the fact that the monostatic RCS return from a plate has its peak value at the specular reflection angle, and the RCS lobe width in the angular variation is related with its plate width. By assuming the target is a polygonal convex cylinder, sizes of their facets are estimated by the local maxima in the angular RCS variation. Then one may be able to reconstruct the target's shape by connecting all facets in the specular reflection order. Our algorithm for the flat facet case can also extend to handle smooth curved facets. We have applied our reconstruction algorithm for several cylindrical targets from numerically calculated and measured RCS values. Good agreement has been observed to show the validity of our method.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

This paper presents an efficient ray-launching method for 2D indoor propagation problem, by including crucial multiple reflection effect inside wall. We hen: focus on the derivation of the reflected and transmitted ray solutions at/through wall when a magnetic source is located in the indoor environment. An efficient approximation, which is called collective ray approximation, is carried out to bundle or collect the internal multiple reflected rays into the primary one. It is resultantly confirmed from the detailed numerical experiments that the derived collective ray solutions can be confidently effective when the internal reflections strongly contribute to the propagation characteristic in the propagation environment, regardless of angle of the incidence.

DOI： 10.1587/transele.E94.C.55

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

Several experiments to investigate ocular effects due to millimeter wave exposure have been performed. In this study, SAR and temperature elevation inside the eye were evaluated numerically using one dimensional model.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper examines specific propagation characteristics for a simple outdoor/indoor interface environment, by analyzing diffraction problem for wide aperture slit in an infinitely long PEC screen. High frequency asymptotic ray technique is applied to analyze the diffraction problem. According to the ray-mode coupling analysis, the total diffracted or radiated field in each region is considered as a summation of successive modal radiation contribution due to the original modal excitation by the incident plane wave. The successive process for generating internal higher modal reflection and external modal radiation fields continues until all the energy inside the slit region is completely consumed. The validity of the derived solution is confirmed by comparing with the other analytical reference one for both width and thickness variations. © 2011 IEEE.

DOI： 10.1109/APS.2011.5996999

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper examines specific propagation characteristics for a simple outdoor/indoor interface environment, by analyzing diffraction problem for wide aperture slit in an infinitely long PEC screen. High frequency asymptotic ray technique is applied to analyze the diffraction problem. According to the ray-mode coupling analysis, the total diffracted or radiated field in each region is considered as a summation of successive modal radiation contribution due to the original modal excitation by the incident plane wave. The successive process for generating internal higher modal reflection and external modal radiation fields continues until all the energy inside the slit region is completely consumed. The validity of the derived solution is confirmed by comparing with the other analytical reference one for both width and thickness variations.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, a novel delta-sigma modulator which has a non-uniform quantizer is proposed. The step sizes of a non-uniform quantizer are, in general, uniquely determined by the probability density function (PDF) of an input signal amplitude, while delta-sigma modulators usually become unstable when the non-uniform quantizer is directly applied to them. It is found that the proposed delta-sigma modulator reduces a quantization noise and works in a stable condition. To guarantee the stability of the delta-sigma modulator, the maximum output value of the quantizer is fixed at a certain value. The rest of the output and threshold values of the non-uniform quantizer are determined by the PDF of the input signal amplitude. The simulation results show that the quantization noise power is reduced by up to 2.90 dB when the non-uniform quantizer is applied.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Science  

The present study describes theoretical parametric analysis of the steady-state temperature elevation in one-dimensional three-layer (skin, fat and muscle) and one-layer (skin only) models due to millimeter-wave exposure. The motivation of this fundamental investigation is that some variability of warmth sensation in the human skin has been reported. An analytical solution for a bioheat equation was derived by using the Laplace transform for the one-dimensional human models. Approximate expressions were obtained to investigate the dependence of temperature elevation on different thermal and tissue thickness parameters.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Non-destructive and non-contacting estimation of the complex permittivity of the solid materials has been proposed using the monostatic RCS measurement from the specular reflection surface. In order to isolate the surface reflection contribution from the total scattering response, time gating method is utilized. The frequency domain RCS is measured first at a certain frequency band, and the corresponding time domain result is calculated via inverse Fourier Transformation. After identifying the surface reflection contribution and selecting it with a certain time width, Fourier transformation is used to obtain the desired surface response in the frequency domain. These RCS results are then utilized to estimate the surface reflection coefficients and their permittivities. The proposed method has been tested to evaluate the permittivities of cubic granite and synthetic phantom material, and the results are compared with those obtained by a coaxial probe method. Good agreement has been found between them and the validity of our method has been confirmed.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BIOMED CENTRAL LTD  

Background: Because the possibility of millimeter wave (MMW) exposure has increased, public concern about the health issues due to electromagnetic radiation has also increased. While many studies have been conducted for MMW exposure, the effect of dielectric permittivities on skin heating in multilayer/heterogeneous human-body models have not been adequately investigated. This is partly due to the fact that a detailed investigation of skin heating in a multilayer model by computational methods is difficult since many parameters are involved. In the present study, therefore, theoretical analyses were conducted to investigate the relationship between dielectric permittivities and MMW-induced skin heating in a one-dimensional three-layer model (skin, fat, and muscle).
Methods: Approximate expressions were derived for the temperature elevation and temperature difference in the skin due to MMW exposure from analytical solutions for the temperature distribution. First, the power absorption distribution was approximated from the analytical solution for a one-layer model (skin only). Then, the analytical expression of the temperature in the three-layer model was simplified on the basis of the proposal in our previous study. By examining the approximate expressions, the dominant term influencing skin heating was clarified to identify the effects of the dielectric permittivities. Finally, the effects of dielectric permittivities were clarified by applying partial differentiation to the derived dominant term.
Results: Skin heating can be characterized by the parameters associated with the dielectric permittivities, independently of morphological and thermal parameters. With the derived expressions, it was first clarified that skin heating correlates with the total power absorbed in the skin rather than the specific absorption rate (SAR) at the skin surface or the incident power density. Using Debye-type expression we next investigated the effect of frequency dispersion on the complex relative permittivity of tissue. The parametric study on the total power absorbed in the skin showed that skin heating increases as the static permittivity and static conductivity decrease. In addition, the maximum temperature elevation on the body surface was approximately 1.6 times that of the minimum case. This difference is smaller than the difference caused by the thermal and morphological parameters reported in our previous study.
Conclusion: This paper analytically clarified the effects of dielectric permittivities on the thermally steady state temperature elevation and the temperature difference in the skin of a one-dimensional three-layer model due to MMW exposure.

DOI： 10.1186/1475-925X-8-20

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Language：Japanese   Publisher：IEICE  

米国大学の大学院への留学を通した、学生生活、Ph.D.取得やポストドクターとしての研究生活等を通して体験した、海外の大学における研究教育活動・環境と日本のそれとの違いについて紹介する。また帰国後、現在までに到る国際共同研究や研究交流を通して日ごろ感じていることについて述べる。

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Incheon University  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper proposes an efficient modification of 2D ray-launching method, by including multiple reflection effect inside wall for indoor environment. An efficient approximation is carried out to bundle or collect the internal multiple reflected rays into the primary one. This approximation is called collective ray approach. We here focus on the derivation of the approximate solution for H (or Vertical) polarized incident case. Resultantly, it is confirmed from the detailed considerations that the present collective ray solutions can be confidently utilized in particular when the internal reflections strongly contribute to the propagation characteristic of the considered indoor environment.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communication, Engineers, IEICE  

This paper presents an easy and efficient modification of simplified 2D ray-launching method, by approximately including multiple reflection effect inside walls for indoor environment. In order to precisely carry out the ray-launching procedure inside lossy wall, a simple modification using a true real refraction angle is first introduced, instead of complex one. Furthermore, an efficient approximation is carried out to collect the internal multiple reflected rays into the primary one. We here call it collective ray approach. Consequently, it is confirmed from the detailed considerations that the present ray representations obtained by introducing the real refraction angle are well suitable for indoor propagation analysis, and in particular the collective ray solution can be utilized confidently even when the internal reflections strongly contribute to the propagation feature of the considered indoor environment. © 2009 The Institute of Electronics, Information and Communication Engineers.

DOI： 10.1587/transele.E92.C.40

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Non Line of Sight (NLOS) path loss has been investigated by using the Shooting and Bouncing Rays (SBR) method. Two building layouts; continuously connected and non-connected building layouts, are used to check the street propagation characteristics and leakage effect due to the building gaps. Based on the statistical data numerically generated buildings are placed along the streets and path loss are evaluated along them. It is found that the predictions by ITU-R model give us somewhat less path loss for our street-cell models.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

This paper investigated the analytical solution of the temperature elevation in one-dimensional human model due to millimeter wave exposure for parametric analysis. The analytical solution of the bioheat equation for the one-dimensional three-layer model has been derived using the Laplace Transform. Temperature distribution obtained from the analytical solution is compared with those derived from a numerical difference method. Good agreement has been found between them, suggesting the validity of our analytical solution. The derived expression is useful to clarify the effects of biological parameters on the temperature elevation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

We investigated the radio propagation characteristics for line-of-sight (LOS) inter-vehicle communication (IVC) at 60 GHz on an actual road with an undulating surface. Radio propagation tests between two moving vehicles were carried out on a test course. From this, it was found that the measured received power on the actual road and the results calculated for a flat road approximately follow logarithmic normal distributions. To investigate this phenomenon in detail, a propagation test between two stationary vehicles on a road was performed. Furthermore, calculations using geometrical optics taking road undulation into consideration demonstrated that undulation in the road can cause variations in the received power that follow a logarithmic normal distribution. Finally, the received power for moving vehicles on an undulating road was calculated using the model.

DOI： 10.1093/ietele/e90-c.9.1807

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICEAA  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Electromagnetic Academy  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The electromagnetic Academy  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

The dependence of the specific absorption rate (SAR) on ear shape and head size have been investigated using human-head and cellular-phone models. Cubical and realistic head models were used. Various ear shapes were used with the cubical head model whereas a low-loss thin ear or a lossy realistic ear was used with the realistic head models. The SAR distribution depends significantly on the shape of the ear, regardless of the head model. The effects of the head size have been investigated using a 90th-percentile head model and a Japanese-average head model. The head size has considerably less effect than the ear shape. The measurement results have been validated by numerical calculation, and support the use of the specific anthropomorphic mannequin (SAM) standard head model.

DOI： 10.1109/TEMC.2007.902189

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

We have developed a code-division-multiplexing (CDM) transmission scheme for future road-vehicle communication systems, which uses cyclic shifted-and-extended (CSE) codes generated from a basic code with superior auto-correlation characteristics. This paper proposes to use a Quasi-Orthogonal (QO) sequence as the basic code. Its auto-correlation values are zero except at zero and middle shifts. When the CDM transmission is performed by the CSE codes based on the QO sequence, a desired correlation value is, at a receiver, interfered by the auto-correlation value at middle shift. Therefore, an elimination technique for the interfered correlation value is proposed and realizes zero cross-correlation characteristics within the cyclical shift interval. The new CDM transmission scheme based on the proposed scheme is evaluated by computer simulations in terms of the bit-error-rate performance.

DOI： 10.1093/ietcom/e89-b.11.2998

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Language：English   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Hanoi University of Technology  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Gebze Institute, Turkey  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Technical University of Catalonia  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Xidian University  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Electromagnetic Academy  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Electromagnetic Academy  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Bioelectromagnetic Society  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Applied Computational Elctromagnetic Society  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Target reconstruction algorithm from its monostatic radar cross section (RCS) has been proposed for polygonal cylinders with curved surfaces. This algorithm is based on our previous finding that the main contribution to the back scattering is due to edge diffracted fields excited at a facet of nearly specular reflection direction. Dimension of this constitutive facet of the target is estimated from the local maxima and its lobe width in the angular RCS variation. Half and quarter circular cylinders are used as canonical scattering objects, and their measured and numerically simulated monostatic RCS values have been studied extensively to find scattering pattern characteristic difference between flat and circularly curved surfaces. Thus estimated constitutive facets are connected in order, and this procedure will be continued until the distance between the first and the final edges would be minimized. Our algorithm has been tested for other targets, and it is found that it works well for predicting metal convex targets with flat and curved facets.

DOI： 10.1093/ietele/e88-c.12.2289

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In software defined radio systems, placing the analog-to-digital converter (ADC) near the antenna part in the block diagram of the receiver is desired to improve the flexibility of the system. The radio frequency (RF) sampling method in which the received signal is sampled at the RF stage, realizes such structure. The undersampling is a potential method to sample the RF signal using the existing consumer ADCs because high speed ADCs are required in the traditional methods, such as Nyquist sampling or the oversampling of the RF signal. This paper presents a technique to determine the minimum sampling frequency to undersample the separated multiple wireless systems simultaneously. In addition, this paper proposes a frequency selecting scheme that enables selection of a lower sampling frequency by receiving at least the desired transmission channels in the wireless system signals. This paper also provides a result of performance analysis of the proposed scheme.

DOI： 10.1093/ietcom/e88-b.11.4170

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICEAA  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Electromagnetic Academy  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Bioelectromagnetic Society  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Bioelectromagnetic Society  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

We have implemented development of millimeter-wave exposure setups for studies on thresholds of biological effects due to millimeter-wave exposure. In developing the previous setups we have used the circular horn antenna, but the beam radiated from the antenna is difficult to illuminate only the object because of widely broadened propagation characteristics. Therefore we have developed two new setups that realize intended exposure. These setups use different-characteristics lens antennas. In this report measurement of incident power density and of reflection loss are described. Consequently we have confirmed that 1000 mW/cm^2 and 2800 mW/cm^2 of incident power density can be available for these setups with 1 W input which is enough performance for the biological studies.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

In software defined radio systems, it is desired to place the analog-to-digital converter (ADC) near the antenna part in the block diagram of the receiver, to improve the flexibility of the system. The radio frequency (RF) sampling method, in which the received signal is sampled at RF stage, realizes such structure. The RF sampling using the undersampling is a potential method to sample the RF signal using the existing consumer ADCs because the high speed ADC is required in the traditional methods, such as the nyquist sampling or the oversampling of the RF signal. This paper presents a technique to determine the minimum sampling frequency to undersample the separated multiple wireless systems simultaneously. In addition, this paper proposes a frequency selecting scheme which enables to select lower sampling frequency by receiving at least the desired transmission channels in the wireless system signals. This paper also provides the estimation of proposed scheme.

CiNii Books

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：World Publishing Corporation  

Virtual reality environment has great potential to display various types of information in three-dimensional space. In this paper, an interactively stereoscopic visual simulation with view-dependent culling and level-of-detail (LOD) is presented, which targets high frequency electromagnetic wave propagation in wireless communication systems such as wireless LAN. Considering a trade-off between interactive visualization and precise representation of volume data of the propagation in large and complex urban space, view-dependent culling of volume data is introduced, which are generated by beam tracing. In addition to applying LOD to the definition of volume data, the number of volume data is restricted within a limit under which can generate and visualize the data interactively. The proposed method is installed and performs well on the CAVE, a multi-faced stereoscopic display system.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CIE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A new hybrid formulation has been derived for analyzing biological electromagnetic compatibility (Bio-EMC) problems by combining the frequency-domain Method of Moments (MoM) and the Finite-Difference Time-Domain (FDTD) method. This hybrid form is different from, and more direct than, the method previously proposed by Mangoud et al. Some numerical examples are given for the human head exposure field due to a half wavelength dipole and a one-wavelength loop antenna. Our iterative method is found to have fast convergence. In addition, our method works well for cases when the radiation antenna wires are not aligned with the FDTD lattice.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A depth estimation method for a crack on metal surfaces has been studied and a simple estimation formula and measurement method have been proposed. This formula is based on our previous theoretical analysis that the backscattering from a crack causes periodical nulls (dips) as the frequency changes, and the first dip occurs when the depth of the crack becomes nearly one-half the incident wavelength. Dependencies of the crack's aperture and the incident angle have also been studied and considered as our depth estimation parameters. Test measurement has been made to check the validity of our estimation procedure.

DOI： 10.1109/TIM.2004830789

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

We have developed a code-division-multiplexing (CDM) transmission scheme for future cellular communication systems, which uses cyclic shifted-and-extended (CSE) codes generated from an M-sequence to enable seamless communication in highly mobile environments. Because the correlation characteristics of CSE codes are determined by the M-sequence, the cross-correlation values are accumulated as a result of combining transmitted signals with opposite polarities in parallel channels. The accumulated cross-correlation values significantly degrade transmission performance, especially with multi-level modulation schemes such as quadrature amplitude modulation (QAM). We thus propose a cancellation technique to eliminate the accumulated cross-correlation values. We have evaluated the transmission performance of the CDM transmission scheme with the proposed technique by computer simulation. The new scheme enables high-quality data transmission in fast-fading channels.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

In this paper, we propose a new desired signal power to undesired signal power ratio estimation (DURE) method for the downlink frame of dynamic-parameter-controlled orthogonal frequency and time division multiple access (DPC-OF/TDMA) and a new subcarrier arrangement of the orthogonal frequency division multiplexing (OFDM) symbols used for DURE. The proposed subcarrier arrangement enables no interference between the signals transmitted form the adjacent cells by employing orthogonal sequence codes, and thus, we can distinguish the desired signal from the undesired ones and estimate DURE accurately. Moreover, we propose another DURE method. We evaluated the effectiveness of the proposed methods by computer simulation in multi cell environment.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

Near-field of a 60-GHz milimeter-wave exposure setup has been measured for developing the exposure system designed to survey the ocular effects of milimeter-wave. To investigate the limited effects of an eye, an antenna and irradiation interval which enable the uniform and local exposure have been examined based on the experimental results. The results show that the circular antenna (QUINSTAR : QWH-VCRROO) exposes relatively uniform and local. Therefore it was confirmed that the exposure to the rabbit eye was uniform and local by setting it 2-3cm away from the antenna.

CiNii Books

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ICNIRP  

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In recent years, a project on the standardization of measurement methods for the head specific absorption rate (SAR) while using cellular phones has been in progress in Japan, Europe, and the United States. In order to achieve international coordination, it is desirable that head phantoms of the same shape be used in all countries
these are based on statistical data on European and American human sizes. However, the validity of application to the Japanese standard head phantoms which are generally of a larger size than the Japanese human size has not been established. Consequently, SAR measurements are made in this study with head phantoms based on the 90th-percentile values of the head shape statistics of Europeans and Americans (E/A) and head phantoms based on the average Japanese adult male head shape (JP) in order to investigate the dependence of the head SAR on the phantom size. A numerical simulation is also performed, and the effect of the head phantom size on the current distribution on a cellular phone is also investigated. Based on these studies, it is found that the effect of the head phantom characteristics on the head SAR is small compared to the effect of the position of the cellular phone in the measurements, and that the effect on the current distribution on the cellular phone is also small. It is shown that for all three types of cellular phone models, that is, thick, thin, and folding types, that the E/A phantoms have roughly the same or larger maximum local SAR values than the JP phantoms. © 2003 Wiley Periodicals, Inc.

DOI： 10.1002/ecja.10083

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

For future cellular communication systems, we have developed a code-division-multiplexing (CDM) transmission scheme based on cyclic shifted-and-extended (CSE) codes generated from a basic code with superior auto-correlation characteristics in order to realize seamless communication in high-speed mobile environment. In this paper, an almost perfect auto-correlation sequence is used as the basic code, and its autocorrelation values are zero except at zero and middle shifts. Moreover. we propose an elimination technique for interference caused by the correlation value at the middle shift. The proposed technique can realize perfect correlation characteristics within the cyclical shifted chips by adding a simple calculation at a receiver. The proposed scheme is evaluated by computer simulations in terms of the bit-error-rate performance for various code lengths of the basic code.

DOI： 10.1109/VETECF.2004.1405068

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper, we propose an adaptive beam division method for a visual simulation of high frequency electromagnetic wave propagation. In order to guarantee the correctness of visualization and calculate electromagnetic wave power within beam (transformation from beam data to, volume data) with low computational cost, an adaptive beam division technique is introduced into the beam data structure. By implementation of the proposed method, one can transform beam, data to volume data more correctly with lower computational cost and visualize the high frequency electromagnetic wave propagation by a so-called ray-casting algorithm, which is one of the most useful methods in computer graphics.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A simple non-destructive depth estimation method for a crack on a metal surface has been proposed. This method is based on our finding that the electromagnetic back scattering from a narrow trough (crack model) on the ground plane causes periodical nulls (dips) as the frequency changes, and the first dip occurs when the depth of the crack becomes nearly one half of the incident wavelength. Dependencies of the crack's aperture and the incident angle have also been studied from rigorous and numerical analyses, and considered as our depth estimation parameters. A simple estimation formula for a crack depth has been derived from these studies. Test measurement has been made to check the accuracy of our estimation formula. Time domain gating process is utilized for isolating the crack scattering spectra buried in the measured frequency RCS data. Tested crack types are a. narrow rectangular, a tapered, and a stair approximated crack shapes. It is found that the depth of these cracks can be measured within 3 percent error by our estimation method.

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Language：Japanese   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

CiNii Books

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

Electromagnetic interference of implanted pacemakers by mobile telephones has been investigated by FDTD method. An implanted cardiac pacemaker, lead wire and an electrode are modeled in realistic voxel models of Japanese adult male and female which were constructed from MRI images. It is shown that the induced voltage at a connector of the pacemaker in European-American voxel model is higher than those in Japanese models. It is also shown that the induced voltage for the Japanese male model is higher than that of Japanese female model. Furthermore, it is shown that the induced voltage evaluated by an experimental method using homogeneouse recutangular model is higer than those of the human models, that is the rectangular model provides the most safety estimation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In order to realize a future seamless high-speed road-vehicle communication system, we have proposed using code division multiplexing (CDM) radio transmission scheme by using cyclic shifted-and-extended (CSE) codes as spread codes. As the CSE codes are generated by cyclically shifting and extending a conventionally used code, the number of codes generated from a code is limited to the length of the shift interval and the tolerable period of delayed waves also depends on the length. In this paper, based on CSE codes, we propose a method to minimize the length of the shift interval and a cancellation technique with a simple calculation in order to eliminate the interference from delayed waves caused by the reduction of the length of shift interval. The concept and the BER performances in AWGN, two-paths, and multi-path fading environments are described in this paper. As a result, the maximum transmission rate of CSE-based-CDM transmission per one-code using the newly proposed transmission scheme is 3 times as large as that using conventional CSE codes and DQPSK-CDM transmission scheme.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

The dose characteristics in a human head exposed to the near field of various fundamental sources have been evaluated numerically by the finite-difference time-domain (FDTD) method. It is shown that the electromagnetic fields in the human head strongly depend on the near-field characteristics of the sources. In the case of the infinitesimal short electric dipole, it is also suggested that the internal E- and H-field as well as current density and SAR are closely related with the incident H-field.

CiNii Books

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEICE  

最近，我が国をはじめ欧米諸国では携帯電話使用時の頭部SAR測定法の標準化作 業が進められており，国際的な整合性を図るために，各国で欧米人体型寸法統計データ に基づいた同一形状の頭部ファントムを使用することが求められている． しかし，日本人と比べて全体的な形状が大きい標準頭部ファントムを日本 人に適用することの妥当性は十分に示されていない． そこで，本研究では，欧米人の頭部形状統計データの90パーセンタイル値に基づく頭部ファントム（E/A）と平均的な日本人成人男性頭部形状に基づく頭部ファントム（JP）を用いたSAR測定を行ない，頭部SARのファントムサイズへの依存性について検討を行なった．

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEE Japan  

An algorithm to estimate non-destructively the depth of a crack has been proposed in this paper using electromagnetic waves. From our theoretical study of the scattering by a trough on a conducting surface, it is found that periodical sharp dips in the scattering return occur as one sweeps the operation frequency, and the first dip frequency corresponds to the crack depth. Based on this observation, corelation curves between the first dip frequency and the crack depth have been made.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

In order to accelerate the previously proposed visual simulation of high frequency electromagnetic wave propagation, a beam tracing method with improved subdivision technique is proposed, in which the beam is defined by three rays. According to reflection of the rays on the buildings or ground, additional rays are generated adaptively and the beam is subdivided automatically with the proposed subdivision algorithm. By using it we can generate the numbers of beams less than ones generated by the previously proposed subdivision technique. After generation of the set of beams, we transform the electromagnetic wave propagation data into volume data. Then one can visualize the data of propagation with interaction at any viewpoints by the so-called ray-casting algorithm, which is one of the most useful methods in computer graphics.

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)  

In order to realize a future seamless high-speed road-vehicle communication system, we have proposed using code division multiplexing (CDM) radio transmission scheme by using cyclic shifted-and-extended (CSE) codes as spread codes. As the CSE codes are generated by cyclically shifting and extending a conventionally used code, the number of codes generated from a code is limited to the length of the shift interval and the tolerable period of delayed waves also depends on the length. In this paper, based on CSE codes, we propose a method to minimize the length of the shift interval and a cancellation technique with a simple calculation in order to eliminate the interference from delayed waves caused by the reduction of the length of shift interval. The concept of the proposed scheme and the BER performances in AWGN, two-paths, and multipath fading environment are described in this paper. As a result, the maximum transmission rate of CSE-based-CDM transmission per one-code using the newly proposed transmission scheme is 3 times as large as that using conventional CSE codes and DQPSK-CDM transmission scheme.

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In order to realize a future seamless high-speed road-vehicle communication system, we have proposed using code division multiplexing (CDM) radio transmission scheme by using cyclic shifted-and-extended (CSE) codes as spread codes. As the CSE codes are generated by cyclically shifting and extending a conventionally used code, the number of codes generated from a code is limited to the length of the shift interval and the tolerable period of delayed waves also depends on the length. In this paper, based on CSE codes, we propose a method to minimize the length of the shift interval:and a cancellation technique with a simple calculation in order to eliminate the interference from delayed waves caused by the reduction of the length of shift interval. The concept of the proposed scheme and the BER performances in AWGN, two-paths, and multipath fading environment are described in this paper. As a result, the maximum transmission rate of CSE-based-CDM transmission per one-code using the newly proposed transmission scheme is 3 times as large as that using conventional CSE codes and DQPSK-CDM transmission scheme.

Web of Science

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：Chuo University  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：Chuo University  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEICE  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：IEEJ  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：KAIST  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：URSI  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A symbol timing synchronization method is proposed for the realization of a multi-mode and multi-service software radio receiver. The method enables an accurate search for the optimum symbol timing without ally redundant hardware such as sampling rate conversion devices. when the system clock is non-integer times for the target systems' symbol rates. Accordingly, a multimode and multi-service receiver can set an arbitrary system clock for the target system's symbol rates, and the number of A/D converters call bo reduced to the minimum. Also, it may lead to a reduction of the implementation time for digital signal processing hardware, and reduce the burden on the memory in a multi-mode and multi-service software radio receiver, since no sampling rate conversion is needed. Thf effectiveness of the proposed method for use with a multi-mode and multi-service software radio receiver for future ITS services. which are CPS (Global Positioning System). ETC (Electric Toll Collection system), and Japanese PHS (Personal Handy-phone System) is assumed, and the supposed system is evaluated by computer simulation. The jitter performance under an AWGN (Additive White Gaussian Noise) environment is first simulated, and the necessary number of over-samples and observation symbols are defined bq the value of jitter which gives a theoretical value of the BER, respectively. Moreover, the bit error rate performance under a fading environment condition where the attenuation of a signal level fluctuates more rapidly than in a noise environment is calculated, and it is shown that the proposed method enables an accurate search for the optimum synchronization timing caused by a cycle slip even if the signal level is quite low, and allows one handset to adopt a system clock for several systems.

Web of Science

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：PIERS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEICE  

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