bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic characteristics of the push‐pull dc‐dc converter
Authors: Shoyama Masahito , Harada Koosuke 
Published: July 2007

AbstractPush‐pull dc‐dc converters are used widely as large‐capacity power supplies for electronic equipment. Previously, the authors have shown that when the transformer magnetizing current in this converter is not negligible, there are six modes of operation determined by the relation between the reactor and the transformer magnetizing currents. They have analyzed the steady‐state characteristics for each mode of operation. This paper considers the analysis of the dynamic characteristics for each mode of operation for small perturbations around the steady‐state operating point. Transfer functions for four of the six modes of operation were derived based on a new model with the ripples of the transformer and the reactor magnetizing currents taken into account; they were shown to be of the first‐order delay system. It turns out that in two of these four modes of operation the reactor current is continuous and by using these modes, a highly stable converter with small output voltage ripple for a relatively large load current can be realized.
Characteristics of a single‐mode fiber beyond the cutoff frequency of the LP11 mode
Authors: Hiratani Yuji , Kawakami Shojiro 
Published: July 2007

AbstractTo clarify the basis of the concept of effective cutoff wavelength useful for design of single mode optical fibers, this paper discusses theoretically and experimentally the mode conversion effect due to fluctuation of the fiber structure in addition to the difference of the attenuation constants of the modes. In the two‐mode region, the scattering matrix elements of the optical fiber are measured with respect to the power of the LP01 and LP11 modes. Based on the measurement, the wavelength dependence of the mode conversion coefficient h and the mode attenuation αi are determined.Next, the multimode dispersion and excess loss of the two‐mode system with mode conversion are related to the parameters h and αi and the significance of the effective cutoff wavelength is discussed. It is found that at frequencies slightly beyond the theoretical cutoff for the measured sample fiber the difference of attenuation constants of two modes is substantial. In addition, since the mode conversion coefficient is small, the degradation of the transmission characteristics due to the higher order mode is reduced, resulting in the effective single mode transmission line. Also found is the condition to be satisfied by h and αi so that the desired transmission characteristics (dispersion and loss) are realized with a necessary length of fiber.
Effect of the heat treatment of tife amorphous alloy thin films
Authors: Konishi Ryösuke , Imai Hiroshi , Ishibe Shoichi , Harada Hisamochi , Sasakuras Hiroshi 
Published: July 2007

AbstractTiFe, which is well known as an oxygen occlusion alloy, was fabricated by using a composite target of Ti and Fe with sputtering. The composition and structure of TiFe alloy thin‐films were analyzed by using XPS, Mössbauer, x‐ray diffraction and electric resistance measurements. The results show that they are amorphous alloy thin‐films consisting of 38 to 45 Ti at %. The TiFe amorphous alloy thin‐film was heat‐treated in ultra‐high vacuum (2 × 10−9 Torr) at 450°C for one hour; then the change was investigated by measuring its depth profile with XPS. It was found that Ti precipitated and Fe decreased in the film surface after the heat treatment, and, at the same time, Fe increased in the lower layer; and that TiFeOx was formed internally in a part of the layer.
Measurement of surface coupling coefficients between nematic liquid crystals and various substrates
Authors: Kuwahara Michio , Onnagawa Hiroyoshi , Miyashita Kazuo 
Published: July 2007

AbstractThere are still problems not fully solved concerning the characteristics and magnitude of interaction between liquid crystals and the surfaces of substrates. It is thought that the number of electrodes in a matrix display device can be increased and its display panel can contain a memory function by the weak boundary‐coupling effect (i.e., by reducing the coupling of the liquid crystal and the substrate surface). Thus, it is necessary to investigate the strength of the coupling between liquid crystals and the surfaces of various substrates. The coupling strength is measured by curve fitting of the electrostatic capacitance–applied voltage characteristic (the C ‐ V characteristic) of a nematic liquid crystal cell. In this method the measured result of the C ‐ V characteristic is compared with the result of calculation in which the surface coupling coefficient is used as parameter. Two kinds of surface treatment (i.e., oblique vacuum‐evaporation of silicon monoxide and rubbing after coating with polyvinyl alcohol film) are investigated. The nematic liquid crystals used in this study are phenyl cyclohexane‐based. The coupling coefficient is of the order of 10−3 J/m2. When the temperature is raised, the coupling coefficient decreases.
Equivalent‐circuit model analyses of the dv/dt characteristics of a complex pnpn switch circuit
Authors: Suzuki Masayoshi , Sagawa Akio , Izaki Naoyuki , Kawakami Hideaki 
Published: July 2007

AbstractThis paper describes a complex pnpn switch (thyristor) circuit which offers high noise‐immunity and high gate‐sensitivity at the same time. The circuit has a protection transistor which short‐circuits the gate and cathode of the thyristor instantaneously when a noise enters. This has a critical slew rate of about 1000 V/μs (= 200 V/0.2 μs) at a gate‐trigger current of 0.1 mA. However, it is found that the thyristor makes a false turn‐on when the storage time of the protection transistor is shorter than the gate recovery time of the thyristor. This phenomenon is designated “a turn‐off time racing false ignition.” To analyze this phenomenon, an equivalent circuit of the complex pnpn switch circuit is proposed. It is found that no false turn‐on occurs when the anodecathode voltage of the thyristor is lower than the dynamic blocking voltage VF.
Effects of metallic‐grating upon leaky saw propagating on 36° YX‐liTaO3
Authors: Hashimoto Ken‐Ya , Yamaguchi Masatsune , Kogo Hiroshi 
Published: July 2007

AbstractPropagation characteristics of leaky SAW under a metallic‐grating structure (grating mode) on 36° YX‐LiTaO3 (36‐LTO) are analyzed and compared with experimental results. First, the velocity dispersion and attenuation for the grating mode are theoretically analyzed. The results show that although the velocity dispersion is similar to that for an SAW, the stopband width of the grating changes with the electrical boundary of the grating. The attenuation depends on how strongly the grating mode couples to bulk waves and leaks its energy into the bulk. The interaction of the grating mode with slow shear waves is markedly weak on 36‐LTO. Hence, the attenuation due to bulk wave radiation is negligible at frequencies where the grating mode couples only to slow shear waves. However, the attenuation increases at frequencies slightly higher than the stopband, where the grating mode strongly couples to fast shear waves. Next, transmission and reflection characteristics are experimentally investigated about the stopband of a metallic‐grating fabricated on 36‐LTO. The results are in good agreement with the theoretical prediction.
Vector variational analysis of the guided modes in the three‐dimensional anisotropic optical waveguides
Authors: Ohtaka Masato , Kobayashi Takao 
Published: July 2007

AbstractThe guided wave characteristics in a three‐dimensional dielectric optical waveguide containing anisotropic materials must be investigated by vectorial analysis. Such analyses are extremely complicated if non‐diagonal terms are contained in the dielectric tensor or more than two anisotropic materials are involved. In this paper the guided modes are analyzed by a variational method in the case where the dielectric tensor contains nondiagonal elements of the transverse components. First, a new variational expression and trial functions suitable for analysis of the guided mode in these waveguides are derived. Next, numerical calculations are performed for a rectangular dielectric waveguide in which both the core and the substrate are made of anisotropic materials. With these calculations, we investigate the effects of the directions of the multiple principal axes on accuracy of the propagation constant near the lower limit, coupling of the guided modes and directions of the electromagnetic vectors. It is found that there are tight hybrid modes and weak hybrid modes. In the case of weak hybrid modes the electromagnetic vectors are straight and almost parallel to the principal axes. On the other hand, in tight hybrid modes the electromagnetic vectors bend significantly and the vector direction is rotated as the normalized frequency is varied.
Acceptance angles of four‐wave parametric upconverters
Authors: Koyanagi Kojiro , Mishima Teruhito , Sakuraba Ichiro 
Published: July 2007

AbstractIn the four‐wave parametric upconverter based on isotropic alkali‐metal vapor which is considered useful as an infrared detector, the acceptance angle characteristics of the infrared ray have been studied theoretically in the case of angle phase matching (or pump phase matching) in which a phase matching is taken by way of small angular difference of two pumping light beams. It is found that various acceptance angle characteristics such as single‐peak, double‐peak, and multi‐peak characteristics can be obtained by adjustment of two pumping light angles, if the collinear phase mismatch is negative due to anomalous dispersion of the metal vapor. The collinear phase mismatch is defined as the magnitude of wave vector of the sum frequency minus the sum of the magnitudes of the wave vectors of two pumping beams and the infrared beam. A flat and broad acceptance angle is obtained in the case of tangential phase matching. It is also found that an optimum state as an image upconverter with a high conversion efficiency and a large acceptance angle exists in the four‐wave parametric upconverter of the two‐photon resonance excitation type in which a large conversion efficiency has been expected.
Design for a single‐mode optical fiber switch
Authors: Kishimoto Ryozo 
Published: July 2007

AbstractBecause of its low loss and broadband characteristics, the optical communication system with single‐mode fibers is promising for long‐distance large‐capacity communication and subscriber video transmission systems. These systems require optical switching techniques for upgrading and for expanding applications. In this paper, with a view to establishing a method for design of a single‐mode optical fiber switch, an optical collimating system employing a focusing rod lens is analyzed by means of a beam mode expansion method. Next, the characteristics of the optical collimating system, the characteristics of a large matrix optical switch collimating system and the displacement, which is important in the optical circuit, are discussed. Finally, a method of construction and test results are described for a 1 × 3 single‐mode fiber optical switch employing a parallelogram prism. A single‐mode optical fiber switch with insertion loss of 0.4 dB and switching reproducibility of less than 0.1 dB is realized. The results confirm the validity of the design method of single‐mode optical fibers.
Silver migration suppression effects of the 2,4‐diamino‐6‐vinyl‐s‐triazine compounds
Authors: Kamagata Kazuo , Kawatas Shunichi , Yamada Toshiaki 
Published: July 2007

AbstractSilver is used widely as an electrode material. It is well known that the silver used in ceramic substrates, paper/phenol resins, and glass cloths/epoxy resin‐laminated boards, tends to migrate when subjected to an electric potential difference under a high temperature/humidity environment, causing a reduction in insulator resistance and ultimately short‐circuiting. This phenomenon arises from the ionization and resulting migration between silver electrodes in the presence of water and an electric potential difference. A known method of inhibiting silver migration is to apply an epoxy resin coating to the substrate surface. It has been determined that an epoxy resin coating containing intermolecular compounds of isocyanuric acid and 2,4‐diamino‐6‐vinyl‐s‐triazine having an s‐triazine ring within the molecule, is substantially more effective in suppressing silver migration than are epoxy resin coatings not containing those compounds. It has also been confirmed that 2,4‐diamino‐6‐vinyl‐s‐triazine easily forms a complex in combination with silver ions in the water. When water droplets containing this compound are discharged onto bare silver electrodes, the amount of time it takes for shorts to occur is significantly greater than when water devoid of the compound is used. On the basis of these observations, it is conjectured that 2,4‐diamino‐6‐vinyl‐s‐triazine is responsible for suppressing silver migration.
Focusing grating for integrated optical‐disk pickup devices
Authors: Ura Shogo , Suhara Toshiaki , Nishihara Hiroshi , Koyama Jiro 
Published: July 2007

AbstractOptical‐disk pickup heads have been constructed with microoptics. Great improvement in producibility and reduction of weight and size are expected by replacing the pickup head with integrated optics. Such an integrated optic device can be constructed by a focusing grating coupler (FGC) which focuses an optical guided wave onto a point in space. This paper describes the theoretical and experimental examinations of the fundamental characteristics of the FGC for the integrated optical disk pickup device. The theoretical analyses show the feasibility of an FGC having a focus spot width larger than the diffraction‐limited value only by 3 percent and the efficiency of 60 percent, by optimizing the device parameters. The analyses of the imaging of the optical system show that the tracking error and the focusing error of a disk can be detected as the displacement of the focal point of the back‐coupled optical guided wave. By fabricating FGCs by an electron‐beam etch method, the focus spot widths were measured to be 3 μm for the laser diode and 1.4 μm for the He‐Ne laser, while the diffraction‐limited values are 1.4 μm and 1.1 μm, respectively, and the imaging relation was confirmed. The efficiency was measured to be 40%. It is necessary for the pickup operation and was confirmed experimentally that the reflected light from the focal plane is coupled back into the waveguide through the FGC.
Analysis of switched capacitor power supplies using finite element method
Authors: Ueno Fumio , Inoue Takahiro , Iida Hitoshi , Oota Ichirou 
Published: July 2007

AbstractA switched capacitor (SC) power supply with a low output power can be made highly efficient, small and lightweight. The finite element method is a numerical technique superior in adaptability and convergence; however, its application to electronic circuits is yet to be explored. In this paper, the finite element method is used as a time domain algorithm for transient and steady‐state analysis of a step‐down, low‐output SC power supply. In the case where the on‐resistances of P‐channel MOS switches and N‐channel MOS switches are not equal, such transient characteristics as the overshoot and rise time of the output voltage and such steady‐state characteristics as the steady output voltage, efficiency and ripple voltages are analyzed. It is found that the parasitic inductance of the wiring reduces the power supply efficiency. Although the results agree well with those by the Hamming method, the computation time is shorter in the finite element method. It is confirmed that the finite element method is efficient for analysis of the problem described by state equations.
Effect of doping carbon in an electromagnetic wave absorber rubber ferrite
Authors: Naito Yoshiyuki , Mizumoto Tetsuya 
Published: July 2007

AbstractFerrite, a ferromagnetic material in the form of sintered ferrite and rubber ferrite, is used for electromagnetic‐wave absorbers. However, there is a certain limit to reducing the thickness of the electromagnetic wave absorber using ferrite. For obtaining thin rubber‐ferrite electromagnetic‐wave absorbers, carbon is added to them and their electromagnetic‐wave absorbing characteristics are examined. The results show that the thickness can be reduced to about 30 percent by adding the order of 1 to 10 percent (volume ratio) of carbon to ferrite. The reduction of the thickness of the absorber also reduces its weight. The mixing of carbon is highly effective in reducing the weight of the absorber, since the specific gravity of carbon is smaller than ferrite. This paper presents the electromagnetic‐wave absorption characteristics of carbon‐added rubber ferrite.
Driving method for pnpn switch with dv/dt protection circuit
Authors: Suzuki Masayoshi , Sagawa Akio , Izaki Naoyuki , Kawakami Hideaki 
Published: July 2007

AbstractA gate driving method is proposed for a pnpn switch with noise protection capability. In relation to a dv/dt protection circuit, on‐and‐off tests of the switch have been carried out so that the operative and inoperative regions due to switch potentials are determined. If the circuit of the driving current source is of a series‐control type, there is an inoperative (nonfiring) region of about 1 V in terms of cathode potential. In a parallel control‐type circuit, driving is possible in all regions because the currents overlap at the time of switching each gate. On the other hand, in the on‐and‐off switch experiment, it is confirmed that only the combination of a parallel control driving‐type circuit and of a dv/dt protection method by a diode can operate correctly regardless of the switch potential.
Analysis of the electromagnetic fields at the facets of optical fibers and dielectric rod antennas
Authors: Toyoda Ichihiko , Matsuhara Masanori , Kumagai Nobuaki 
Published: July 2007

AbstractThe electromagnetic fields at the facets of optical fibers were analyzed by using a three‐dimensional model, unlike a conventional slab waveguide which is a two‐dimensional model. A closed‐type waveguide model of an optical fiber was analyzed by using the eigenmode expansion method, since the radiation mode in an open‐type waveguide (such as an optical fiber) is difficult to treat and compute numerically. The radiation pattern at the facet was obtained by applying the stationary‐phase method to the electromagnetic field. The radiation pattern of the electromagnetic field of a dielectric rod antenna was also analyzed via the same method, since this is a pattern at the facet of a dielectric cylindrical waveguide. Numerical examples of the reflected and transmitted powers in various cases were shown.
A method for real‐time adaptive cancelling of power‐line noise by microprocessor
Authors: Kubo Hiroshi , Uematsu Hitoshi , Takemoto Akira , Nakagawa Takeshi 
Published: July 2007

AbstractThis paper describes a method of cancelling the periodic noise induced from the power‐line during measurement, using the LMS algorithm and the adaptive periodic noise canceller synchronized to the power‐line frequency. To simplify the analysis, a modelling is made whereby the signal is a random variable and the noise is periodic, containing fundamental and a large number of harmonic components with the power‐line frequency as the fundamental component. A parameter for evaluating the noise cancelling performance of the adaptive periodic noise canceller is derived analytically. It is shown that the processing can be performed without multiplication, without degrading the performance. Then a fast algorithm is proposed for adaptive periodic noise cancellation, which can reduce drastically the computational complexity, thereby degrading the performance little. By applying the algorithm, the realtime processing by a microprocessor is realized with a sampling rate of several kilohertz. Finally, a discussion is made of the effect of digital implementation on the performance, and it is shown that the cancellation of the power‐line interference by the fast algorithm is practically useful.
Frequency characteristics of CR double‐tuned amplifier circuits
Authors: Kurokawa Susumu , Kohno Tadashi , Ieyasu Kenzo 
Published: July 2007

AbstractIn the CR single‐tuned amplifier in general, it is difficult to realize high selectivity and high amplification when a high tuning frequency is specified. We succeeded in reducing the body effect by using a high‐frequency, field‐effect transistor as the reactance transistor and grounding the CR tuned circuit which is a load to the driving circuit. When a double‐tuned amplifier is constructed by cascading such a circuit in two stages, the frequency bandwidth can be enlarged. A stable amplifier was realized with the center frequency of 455 kHz and voltage gain of approximately 80 dB. This paper analyzes the frequency characteristics of such a CR double‐tuned amplifier circuit, deriving the formula for realizing the required double‐hump characteristics. When a single‐hump characteristic is composed by aligning the double‐tuned amplifier to the same tuning frequency, the selectivity is increased by approximately 55 percent compared with the characteristics of the singletuned amplifier, together with a considerable improvement in the roll‐off characteristics. An experimental circuit was constructed. The measurement of the frequency characteristics agreed well with the result of calculation. The double‐tuned amplifier circuit can be applied to the IF amplifier of the receiver.
An integrated‐optic disk pickup device
Authors: Ura Shogo , Suhara Toshiaki , Nishihara Hiroshi , Koyama Jiro 
Published: July 2007

AbstractThis paper describes the proposal, design and fabrication, as well as the experimental results of an optical disk pickup constructed with integrated‐optics using thin‐film waveguides. This integrated‐optic device is constructed with a focusing grating coupler, a guided‐wave beam splitter and a photodiode array on an Si substrate which is coupled to a semiconductor laser. The focusing grating coupler and the guided‐wave beam splitter were fabricated by the electron beam direct writing method. The focus spot width of the fabricated device was measured to be close to the diffraction limited value, and the reflected light was detected as photocurrents of the photodiodes. It was confirmed that the device has a capability of detecting focusing/tracking errors.
Architecture of fiber optic broadband interactive distribution system
Authors: Yamagata Jun , Takemoto Kenji , Okada Kenji 
Published: July 2007

AbstractThe ideal situation in constructing a broadband communication network is that all kinds of services are provided by a single network. Such a structure is not necessarily advantageous at the present state of technology. From such a viewpoint, the best approach would be first to construct an economically‐optimum system, mostly considering the CE type broadband distribution service, which is estimated to have the highest demand, and gradually extend the network for other services. This paper first describes that the configuration combining the star‐type subscriber link and the tree‐type trunk lines is economical and has the functional expandability. Next another configuration is considered, in which the optical fiber is used for the subscriber link and the frequency division switch is used for the channel selections in the conversion of network topology. It is shown that the system is the optimum from the viewpoint of the cost per subscriber. By applying the notion of the cross‐contact switch, it is shown that the proposed system can be extended to the CE type video retrieval service and EE type transmission service. The optical distribution system will be utilized effectively in the future new media, providing the basis for the broadband communication network.