bluuebunny/crossref_metadata_2025_split huggingface dataset:
Focusing characteristics of cylindrical luneburg lens‐numerical analysis in wave optics
Authors: Mori Kensuke , Yamaguchi Shoji , Hosono Toshio 
Published: July 2007

AbstractAlthough Luneburg lenses are already in practical use, few papers have been published on their wave‐optical analysis. This is due to the difficulty in the wave‐optical analysis of the electromagnetic field in an inhomogeneous medium with a large radius, in addition to the fact that most researchers have been interested so far in a geometrical‐optic analysis. Increased applications of this type of lens to a microwave band require more precise analysis from the wave‐optics viewpoint. This paper deals with the wave‐optical analysis of a cylindrical Luneburg lens. Taking several numerical analysis methods, the relationship between the number of terms of a truncated series and the accuracy of the analysis, and the relationship between the computation time and the accuracy of the analysis are examined. A method is proposed which can be applied to a lens having a large radius compared with the wavelength. By using this method, actual numerical analyses are carried out, and the focus characteristics and the distribution of the heat generation (the power dissipation density) in the lens are shown. These are compared with the results of published numerical analyses. Some interesting results, which cannot be obtained from a conventional geometrical‐optic analysis, are obtained by the proposed method.
A high‐speed AC power clock for josephson logic circuits
Authors: Ohhata Masanobu , Tokumitsu Masami , Tazoh Yasuo , Aoki Katsuhiko 
Published: July 2007

AbstractWith a view to high‐speed operation of a power clock, a power supply circuit with a high cut filter is proposed. The harmonic noise generated by the nonlinearity of the regulator distorts the sinusoidal current as the clock speed is increased and hence the duty factor is degraded. Hence, it is important to eliminate this noise. The filter has a function to pass the fundamental sinusoidal wave but stop the harmonic noise generated at the regulator. First, the determination of filter parameters is described. It is demonstrated by a computer simulation that the filter is extremely effective at a high frequency. Next, a three‐dimensional high‐density model has been fabricated and the output current waveform of the regulator at 400 MHz (machine cycle time of 1.25 ns) has been measured. By means of this measurement, the validity of the approach is demonstrated.
Analysis of finite periodic waveguides for elastic waves using finite‐element method
Authors: Hasegawa Koji , Koshiba Masanori , Suzuki Michio 
Published: July 2007

AbstractA solution based on a finite‐element method is proposed for calculation of the reflection and transmission characteristics of a finite periodic waveguide for elastic waves. Although finite‐element methods have already been applied to the discontinuity problem in an acoustic waveguide, it has not been possible due to excessive computation time and memory requirement to apply directly the finite‐element method to many discontinuities such as a periodic acoustic waveguide. In this paper, formulations have been undertaken with the substructure which is a related technology of the finite‐element method. Hence, the finite‐element method can be applied directly to all the discontinuities. As a result, in the finite periodic waveguides for acoustic waves, the mutual interaction of the surface wave and the bulk wave can be taken into account over all the discontinuities. The present method has been applied to a groove‐type grating reflector and the validity and effectiveness of the method has been confirmed by comparison with experimental results. An analysis has also been carried out for the positive and negative reflection‐type reflector proposed recently in which the grooves and ridges are combined. It has been confirmed numerically that this reflector has a larger reflection coefficient and smaller bulk wave conversion loss than the conventional reflector.
Heat analysis on pseudo‐line EB annealing using two‐dimensional finite element method
Authors: Yoshimi Makoto , Takahashi Minoru , Taniguchi Kenji 
Published: July 2007

AbstractThe seeding lateral epitaxial process for SOI by the pseudo‐line electron beam annealing method has been stimulated by the two‐dimensional finite element method. The experimental fact that the SOI film is hard to melt on a seed window and easy to overheat on an insulator has been reproduced. The time‐dependent melting process near the seed window was simulated. Moreover, it was found that by depositing a metal film with a high thermal conductivity on the SOI film surface, the temperature difference between the films on the insulator and on the seed window decreased and the lateral epitaxy takes place much more smoothly. The temperature distribution in the case where devices are present in the underlying layer and the relationship between temperature of the SOI film and the diameter of the electron beam have been clarified.
Design and characteristics of an optical fiber cable for emergency use
Authors: Mihara Katsumi , Tanaka Chihaya , Uesugi Naoshi 
Published: July 2007

AbstractCommunication lines damaged during a disaster must be restored quickly since this seriously affects society. This paper examines the applications of optical cables to restore communication lines quickly in a large‐scale disaster area where mechanical tools cannot be used. The paper also offers the conditions required for the structure design of the cable. Based on these examinations, an optical cable for emergency use was developed which contains four optical fibers, and weighs about 25 kg (including its reel), and can be carried by one man. The unit piece of the cable is 1 km; the numbers of pieces can be connected as required. Disaster cases where damaged cable sections are scattered on interoffice lines were examined, and the number of the sections which can be restored was estimated.
Configuration of fuzzy membership function circuits using current mode
Authors: Shirai Yuji , Ueno Fumio , Inoue Takahiro 
Published: July 2007

AbstractThis paper presents a realization of the membership functions (S, Z, ir and U functions) which serve as the input units of the fuzzy logical system, using the bounded difference of the fuzzy logic. The bounded‐difference circuit is constructed by the current mode using the current mirror based on the bipolar transistor array. The circuit for each membership function is realized and the modification of the circuit to other functions is discussed. The multifunction membership function (called N function) is proposed anew, which can realize the four forementioned membership functions flexibly by adjusting the parameters. The circuit for N function is constructed in the same way as the four preceding functions. The optimum circuit construction is presented based on theory and experiment. It is also shown that the membership circuit can be simplified using Nand P‐channel FET arrays. An FET circuit is presented which can eliminate the essential error in the current mirror composed of bipolar transistors.
Optimum design of vertical power MOSFET with thick drain oxide
Authors: Ueda Daisuke , Takagi Hiromitsu , Kano Gota , Kuroda Keiji 
Published: July 2007

AbstractThe optimum design of a vertical power MOSFET with thick drain oxide is described, taking into account such dc characteristics as the on‐resistance and breakdown voltage.Introducing the empirical ideality of the edge‐termination which determines the breakdown voltage of the device, the optimum doping density and thickness of the epitaxial layer have been determined to minimize the on‐resistance.Using two‐dimensional simulation to evaluate the optimum design of the device, the thickness of the drain oxide and the relationship between the layout pitch and the product of on‐resistance and active area have been determined. As a result, the following conclusions have been obtained.1) Based on the ideality for the edge‐termination, the optimum combination between the thickness and the doping density of the epitaxial layer can be determined.2) The optimum layout pitch depends on the decrease in the electron concentration in the accumulation layer at the drain surface and the parasitic JEET effect.3) The optimum layout pitch decreases as the thickness of the drain oxide increases.Finally, the design of a vertical MOSFET with a breakdown voltage of 500 V will be described.
Design of microwave power combiner with circular TMOmo mode cavity
Authors: Matsumura Hajime , Mizuno Haruhiko 
Published: July 2007

AbstractPresently, realization of a high‐output FET amplifier with more than several tens of watts at microwave frequencies requires power combining. This paper proposes a low loss and broadband power combiner with a simple structure in which a cylindrical TMOmO mode (m × 2, 3, …) cavity with coaxial input and output lines is used. The effects of modes m and the number of devices to be combined are studied by means of an equivalent circuit. Since the spurious modes in the resonator degrade the reliability of the power‐combined FET amplifier, a structure is proposed in which slits and subcavity are attached to the TMOmO mode cavity for suppression of spurious modes. To verify the effectiveness of these structures, the spurious modes are excited and their reflection characteristics are measured. The insertion losses of the 4‐ and 8‐way combiners designed with m × 2 and 4 in the 12‐GHz band are 0.25 and 0.45 dB, respectively. An FET amplifier with a maximal output of 40 W is realized with the present power combiner.
A cyclic switched capacitor A–D, D–A converter
Authors: Onodera Hidetoshi , Tateishi Tetsuo , Tamaru Keikichi 
Published: July 2007

AbstractThis paper proposes a new circuit configuration of a cyclic A‐D, D‐A converter using a switched‐capacitor integrator, which is insensitive to parasitic capacitances. Independently of the conversion bit‐length, the circuit consists of one amplifier (opamp), three‐unit capacitors, and one capacitor to compensate the offset voltage of the OP‐amplifier. An n‐bit conversion is carried out in n clock cycles (2n steps). The conversion accuracy is determined by the accuracy of the capacitance ratio between the unit capacitors. For example, to obtain an accuracy better than 2/3 LSB, it is necessary to keep the capacitor ratio within 0.4 percent (0.39%) and 0.10 percent (0.10%) for 8 bit and 10 bit A‐D (D‐A) converters, respectively. These values are comparable to those in the charge‐redistribution type A‐D, D‐A converter using a capacitor array. The experiment on an 8‐bit A‐D, D‐A conversion with a breadboard circuit showed the exactly expected result. In the experiment, the effect of the charge injection of the analog switch was investigated. Also, it was confirmed that the parasitic capacitances and the offset voltage of the operational amplifier do not affect the conversion characteristics.
Stress–applied optical fiber having inhomogeneous core
Authors: Hayata Kazuya , Koshiba Masanori , Suzuki Michio 
Published: July 2007

AbstractTo extend the freedom in the design of polarization‐maintaining single‐mode optical fiber, a stress‐applied fiber with inhomogeneous core has been investigated. The refractive index in the core has an α‐power profile, and the refractive index of the stress‐applying parts is decreased by doping. The fiber characteristics are evaluated by stress analysis and modal analysis, using the finite‐element method useful for arbitrary refractive‐index profile. For modal analysis, a new scalar variational expression useful for the analysis of weakly guiding birefringent fibers is presented. Using this expression, the polarization‐mode properties of the fiber are studied in detail. From this analysis, it is found that the absolutely single‐polarization operation can be realized in stress‐applied fibers by proper selection of refractive‐index profile in the core.
Animal–resistant telecommunication cable sheath covered by a thin hard metal layer
Authors: Kuwabara Tsuneo , Koga Hiroaki , Kitamura Toshihiro 
Published: July 2007

AbstractAerial cable lines running in forests are often damaged by animals. This paper introduces an animal‐resistant cable design by analyses of the fracture of metals when a shearing force is applied. As a result of the analyses, it is understood that when shearing forces are applied repeatedly to a metal plate without strain relaxation (similar to the case in which animals attack the cables), the metal does not fracture as long as the shearing energy is below a critical energy. This critical energy can be estimated from tensile strain at the yield point and the tensile stress at the fracture point. Therefore, it is possible to realize an animal‐resistant metal sheath by making the critical energy higher than the shearing energy which an animal can apply on one impact. It was found that the animal‐resistant cable designed and fabricated by this method could withstand animal attacks.
Temperature dependence of electrical conduction in carbon–Epoxy resin resistors
Authors: Nakamura Shuhei , Ito Atsushi , Katos Hikaru , Ogasawara Sachio , Sawa Goro , Orita Satoru , Tsubotas Kazunari 
Published: July 2007

AbstractIt is well known that the carbon black (CB)—polymer resin resistor is advantageous because of its cheap manufacturing cost. However, there are also disadvantages such as: large temperature coefficient of resistance (TCR), and large humidity dependence of resistance. This paper attempts to clarify the mechanism of electrical conduction, especially its temperature dependence, experimentally and theoretically to obtain more information about producing low TCR resistors.In general, the temperature dependence of the resistors shows a decrease in resistance at low temperatures and an increase at high temperatures with incremental temperature. Mixtures consisting of conducting particles dispersed in an insulating medium have been discussed with a split in the conduction path or a change in the barrier between conducting particles. However, it is shown that the fluctuation‐induced tunneling (FIT) model cannot explain adequately the temperature dependence of resistivity at high temperatures.Temperature dependence of resistivity for the mixture made of CB and epoxy resin can be explained well with a deliberately modified conduction mechanism based upon Scarisbrick's model, incorporating the thermal expansion of resin and the thermally activated conduction process in the model.
Structural design of resin gas–tight dam for optical fiber cables
Authors: Sato Masaji 
Published: July 2007

AbstractResins such as epoxy have been used to form a gas‐tight dam in communication cables. However, they have disadvantages due to the volume shrinkage during the curing period and thermal expansion. This causes reliability problems such as the breakage at the contact surface. Thus when resins are used in the optical fiber, the influence of their properties on the gas‐tightness and optical loss must be well understood. This paper discusses the influence of the strain caused by the curing process of the resins on the optical loss and air‐tightness. In addition, the structural design of a resin gas‐tight dam is described. First, the influence of the strain caused by the resin on the strain in the optical fiber will be described and the design condition of the use of the resin to minimize the optical loss will be shown. Next, the design condition for air‐tightness is discussed by obtaining the relationship between the hardness of the resin and gas‐tightness, the method of experimentally obtaining the strain distribution in the strain at various temperatures during the curing process, and the application of the gas‐tight dam for an optical fiber cable. From these results, a gas‐tight dam with two layers of resin for strain absorbing to protect the optical fiber is designed. As a result of the evaluation of the properties of the designed structure, we decided that it is applicable to the optical fiber cable from the point of air‐tightness and optical loss characteristic.
Analysis of nonplanar DSA MOS (V‐MOS) transistor by capacitance measurements
Authors: Ohashi Hiroshi , Fujita Takeshi , Tarui Yasuo 
Published: July 2007

AbstractA nondestructive method to determine the parameter of the DSA transistor by capacitance measurement is proposed. Determined parameters are the gate oxide thickness (dOX), the drain impurity density (ND), the drain area (SD), the drain flat‐band voltage (VFB), and the lateral profile along the channel which is one of the features of the DSA MOS transistor.In this method, both depletion and inversion characteristics of gate‐drain capacitance (CGD) are analyzed mainly by fitting them to the measured characteristics.A nonplanar DSA MOS (V‐MOS) transistor is used as a sample to apply this method and the error factors caused by a few assumptions in the analysis are discussed.
Frequency stability of emitter follower type crystal oscillators
Authors: Member Kohei Nakamura, 
Published: July 2007

AbstractRecently, crystal oscillators are used increasingly with the advances of electronic components. Particularly, the adjustmentfree crystal oscillators with only a few circuit elements are used widely since they are suited for IC's. Hence, stabilization of their frequency is very important. In this paper, the simplest emitter follower type crystal oscillator made of a transistor, a quartz crystal, a capacitor, and three resistors is studied in terms of its frequency stability. From the calculations and experiments, the following results have been obtained.The oscillation frequency is more stable against the change of an external capacitance if larger values are chosen for the collector capacitance CC, the grounded base current gain α, and the α cutoff frequency fα. Against the change of the power supply voltage, the optimum value of fα can be determined after CC is selected from the forementioned condition. The oscillation frequency deviation is smaller for a larger equivalent inductance L1 regardless of the Q value of the crystal. Based on these results, it is found that the improvement is more than sixfold against the variation of the power supply voltage, and more than elevenfold against that of the circuit capacitance.
Single transverse mode condition of surface‐emitting injection lasers
Authors: Moriki Kazunori , Nakahara Hidetoshi , Hattori Takeo , Iga Kenichi 
Published: July 2007

AbstractThe surface‐emitting laser can be fabricated monolithically via planar technology and mass‐produced for applications to laser discs and optical IC's for optical communication. However, the transverse mode control in the surface‐emitting laser, which is important to laser oscillation, has not been well studied. This paper discusses the transverse mode control for the surfaceemitting laser and clarifies the shape of the single transverse mode in the structure. As a result of the calculation for a laser wavelength of 1.3 μm, if the composition of the waveguide core (the carrier‐confining layer) is λ = 0.93 μm in a structure where a waveguide is built in the cavity, the waveguide radius must be less than 2 μm. For a structure where only the active layer is embedded, the radius of the reflector must be 3 to 4 μm or the radius of the active region must be 5 to 7 μm when the reflector radius is 10 μm. Therefore, even in the surface‐emitting laser, the transverse mode control can be achieved relatively easily.
High‐convergence matrix‐solving scheme for device simulator
Authors: Satou Shigeo , Hane Kunio , Suzuki Tokio 
Published: July 2007

AbstractThis paper proposes pre‐processing and matrix computation to improve the convergence, accuracy and computation speed required in the device simulator. In the pre‐conditioning, a method to increase the number of elements and Gustafsson's modification are employed. The result of application indicated that the element‐increasing method is more effective. In the solution of the problem represented by a symmetrical matrix derived from Poisson's equation, the element‐increasing incomplete Cholesky decomposition conjugate complex gradient method (ICCG (2, 4)) is seen to be suitable. Three methods to solve the problem represented by an asymmetrical matrix, which is derived from the current continuity, are examined; the ORTHOMIN method; the bi‐conjugate gradient method; and the CG‐square (CGS) method. From the viewpoint of the convergence and the computation time, the element‐increasing incomplete LU‐decomposition CGS method (ILUCGS (2, 4)) is seen to be the best. It is demonstrated that by those matrix manipulations, the convergence of the device simulator is improved, and a solution with a satisfactory accuracy is obtained in a short computation time.
Influence of crosstalk in transmission line on accuracy in inductive radio system for detecting the position of linear motor vehicles
Authors: Hatta Tohru , Kusakabe Takashi , Asai Takahiro 
Published: July 2007

AbstractThe three‐phase three‐conductor transmission line can be used in an inductive radio system for detecting the position of a vehicle of a linear synchronous motor car. A quantitative investigation is developed on the relation between the crosstalk between positive and negative‐phase‐sequence components in a helically wound transmission line and deviations of the line conductors from their normal positions. The authors have derived the required accuracy in a manufacturing process of a line for the desired accuracy in detecting the vehicle position. Cases where line conductors deviate randomly from their normal positions and cases where there exist manufacturing imperfections similar to “asymmetrical twisting,” which occasionally happens in manufacturing “star quads” used in ordinary telephone cables, are analyzed. It is clarified that the position detection error is affected mainly by the near‐end crosstalk between positive and negative phase circuits, which is maximized when a vehicle approaches the nearest start terminal of the transmission line. Moreover, it is expected that the fairly satisfactory accuracy in the vehicle position detection is obtained if we can make the layout accuracy of line conductors within a few percent of the helical radius. The obtained results are expected to be applied analogously also to the flat‐type three‐phase three‐conductor line.
NMR fresnel transform imaging using a scannable nonlinear field gradient
Authors: Yamada Yoshifumi , Tanaka Kunio , Abe Zenmon 
Published: July 2007

AbstractA new NMR imaging method is proposed, where the data with contributions from the whole imaging area are examined, and the spin distribution image is reconstructed by computer processing. The method uses a weak scanning nonlinear gradient field which is an extension of the magnetic focusing method. The experimental result is described. It is shown that the detected signal is given by the Fresnel transform of the spin distribution, and a solution is obtained by a convolution integral. Based on the theory, imaging experiments were performed using a phantom, realizing a clear spin density distribution image. In the experiment, a magnetic field of B0 = 0.0192 Tesla was used, which is one order of magnitude weaker than the field in the usual NMR‐CT. The image was obtained with the resolution of approximately 1 mm by collecting the data for 32 s to 8 min. Some discussions are made on the spatial resolution of the method and the application to a large‐scale system, indicating that the method is highly promising.