bluuebunny/crossref_metadata_2025 huggingface dataset:
A method for solving the inverse problem in electrocardiography using a nonlinear torso model
Authors: Akamatsu Norio
Published: July 2007

In the inverse problem in electrocardiography, the information concerning the tissue is known, and the electrical phenomenon in the heart is to be estimated using the measured body surface potential. In the already‐estimated solution of the inverse problem in electrocardiography, the forward solution is determined first, and then the backward solution is derived using the forward solution. In this procedure, an ill‐posed problem may be generated, resulting in an unstable solution, necessitating smoothing. This paper proposes a new method of solution where the backward solution is calculated directly from the surface potential. Due to the ill‐posed condition inherent in the inverse problem in electrocardiography, the potential distribution derived inside the body is oscillatory. The local spatial smoothing is applied to suppress the oscillation. The tissue information is given from Computerized Tomography through an image‐input device. Then a nonlinear network is constructed. The earlier solution method for the inverse problem in electro‐cardiography can only be applied to the linear electrical medium. The proposed method can also be applied to the nonlinear system. This paper describes the solution method for the inverse problem in electrocar‐diography taking the nonlinear conductance into consideration. Examples solved by applying this method are shown. In this method, the deficit of information by excessive smoothing can be avoided. Especially, in the precardial part, the epicardial potential close to the true distribution can be estimated. The proposed method does not require the forward solution. The computation time can be reduced. By employing a successive solution method the memory capacity can be reduced.
Low‐temperature characteristics of buried channel charge‐coupled devices
Authors: Kimata Masafumi , Denda Masahiko , Yutani Naoki , Iwade Syuhei , Tsubouchi Natsuro
Published: July 2007

This paper aims at the improvement of the characteristics of the buried‐channel charge‐coupled device (BCCD), which is used in such low‐temperature operation as the infrared image sensor. The measurement and analysis are performed for the transfer loss of BCCD below 100°K. The transfer loss in this temperature region is dominated by the carrier freeze‐out to the impurity level composing the n‐well of the buried‐channel. The loss in this temperature region depends on the period and the fall‐time of the driving clock. The dependence of the loss on the driving condition can be accounted for by the model in which two time‐constants exist for the emission from the trap. The reason for the different emission time‐constants from a trap depending on time is that the fringing field in the channel depends on time. When a large fringing field exists, the effective barrier of the trap is lowered by the Poole‐Frenkel effect, thereby decreasing the emission time‐constant. To reduce the transfer loss in this temperature region, there are several methods, such as utilization of impurity with shallow donor level in the n‐well of the buried‐channel, reduction of the impurity concentration, and increase of the fringing field.
SAW MSK matched filter and its application
Authors: Tominaga Jun‐Ichi , Shibayama Kimio
Published: July 2007

The SAW device can realize a high‐speed and wide‐band operation. Recently, the application of SAW to the signal‐processing device is considered in the spread‐spectrum communication and in other problems. This paper presents the theoretical and experimental investigations on the construction and characteristics of the SAW MSK matched filter. The device is obtained by combining the SAW filter with the tapped delay‐line and the MSK modulation, which is noted as an excellent means of concentrating the band energy. The construction of the electrode pattern is presented first together with the discussions for the impulse response, frequency response and the correlation characteristics. By experiment and simulation, a method is shown which can improve the amplitude distortion due to the velocity dispersion in the SAW device (substrate) by adjusting the tap intervals. One of the features of this kind of device is that the structure is simple and the signal processing by MSK, such as spread‐spectrum modulation and correlation detection, can be realized by a single kind of element. By utilizing this property, the structure of the communication system can be simplified. As an example of application, a system is constructed where the spread‐spectrum modulation is performed by the proposed device, and the demodulation is made by the correlation detection. Thus, it is demonstrated that such a kind of communication can be realized by a simple structure, indicating the usefulness of the proposed device.
Josephson resistor‐coupled gate considering current density limit
Authors: Yamada Hajime , Tanaka Toshiro
Published: July 2007

This proposes a resistor‐coupled gate with high current density using Josephson elements. In a superconductive logic circuit the input‐output connections must be made using strip lines when the distance between logic gates is increased. In such a case the logic gate must be designed with consideration of the characteristic impedance of the strip line. In the usual design of the logic gate, however, the current density of the Josephson element is limited at the upper and lower sides by the characteristic impedance of the strip line, when the probabilities of punchthrough and misoperation by thermal noise are to be suppressed below a certain value. Then the operating speed of the logic gate is accordingly limited. In order to overcome such limitation, this paper first indicates by calculation that the output voltage should be increased. By connecting two Josephson elements in series, a resistor‐coupled step‐up gate is constructed. This logic gate has the feature that the Josephson current density is increased and the probability of punchthrough misoperation is drastically decreased. A high‐speed logic gate with better overdrive characteristics can be realized. Consequently, the proposed resistor‐coupled gate with high current density can be applied to high‐speed logic circuits.
Fabrication and characterization of titanium dioxide (TiO2)/selenium thin‐film solar cells
Authors: Nakada Tokio , Kunioka Akio
Published: July 2007

Recently, Se‐based low‐cost thin‐film solar cells have been developed, resulting in an improvement of the conversion efficiency over conventional Se photocells. Although these solar cells enable increasing the photocurrent increase by designing a thin Se layer, no considerations have been given for the open‐circuit voltage.

The TiO2/Se solar cell described in this paper uses n‐type TiO2 with remarkable photoconductivity as a window material. In addition, it reduces the dark current and improves the open‐circuit voltage by operating as an MIS (Metal‐Insulator‐Semiconductor) diode in the dark and as a pn junction under the light illumination. As a result, the open‐circuit voltage has been improved, and a cell with a conversion efficiency of 5.0 percent (short‐circuit current is 10.8 mA/cm2, open‐circuit voltage 0.88 V, fill factor FF 0.53) under simulated AM 1.5 (100 mW/cm2) illumination has been realized. This is the highest efficiency reported to date for Se solar cells.

Additionally, since the spectral response is close to the emission spectrum of fluorescent lights, the efficiency improves to 11 ‐ 13 percent under fluorescent lights (500 lux). Furthermore, since these cells have advantages of high sensitivity in short wavelengths, good photocurrent‐illumination characteristics and low dark current, applications not only for solar cells but for light sensors such as color sensors and power meters are also expected.
Analysis of surge and noise generation mechanism in a forward DC‐to‐DC‐converter
Authors: Nakahara Masatoshi , Ninomiya Tamotsu , Harada Koosuke
Published: July 2007

The surge and noise generation in a switching converter depends heavily on the switching speed of the transistor, the recovery characteristics of the diode, the leakage inductances of the transformer and other parasitic inductances, and capacitances. Therefore its mechanism is so complicated that to obtain a complete understanding of the mechanism of surge and noise generation, it is definitely necessary to introduce the analytical procedure through which the quantitative discussions are made. This paper clarifies the mechanism of surge and noise generation in a forward dc‐to‐dc converter which is one of the most popular types of converter. The analysis is performed by partitioning the switching time into several states and deriving a high‐frequency equivalent circuit for each state. The equivalent circuits include not only inductive and capacitive parasitic parameters, but also the parameters related to the switching speed of the transistor and the recovery characteristics of the diode. As a result, the effects of these various parameters on the surge and noise generation are clarified quantitatively.
Evaluation of modal distribution of optical branching waveguide by phase space
Authors: Kokubun Yasuo , Suzuki Senichi , Fuse Tsuneaki , Iga Kenichi
Published: July 2007

Optical multimode branching waveguides are very important devices in optical communication systems, but the evaluation method of their characteristics has not been established yet. The design and evaluation of these elements, because of their characteristic dependency on modal distribution, have encountered some problems.

This paper proposes a new method to evaluate the characteristics of optical multimode branching waveguides. The discussion covers the two branching waveguides of step‐and graded‐index distributions. First, using the ray‐tracing method, the branching characteristics of multimode branching waveguides are investigated and the condition of equal light intensity is obtained. Then as a new method for evaluating the modal distribution at the output, phase space expression in terms of the ray position and its slope, is proposed. It is shown that the optimum condition for the branching ratio does not necessarily agree with the optimum condition if modal distribution is also considered. Further, a diffused branching waveguide is fabricated and a qualitative discussion is given by comparing theoretical and experimental results.
Analysis of reference‐tap‐voltage fluctuation in flash A/D converter
Authors: Nakaya Masao , Kumamoto Toshio , Miki Takahiro , Horiba Yasutaka
Published: July 2007

To improve the speed and accuracy of the CMOS flash A/D converter using a copper‐type comparator, an analysis has been performed for the voltage variation at each reference terminal of the ladder resistor providing a reference voltage. A model has been developed in which the circuit made of the ladder resistor and the input capacitance of the comparator is treated as a distributed network. A theoretical formula is derived which analytically provides transient behavior of each reference terminal voltage due to change in the comparator. With this formula, it is found that the maximum error of the reference terminal voltage occurs when the input voltage is either 0 or V ref. The error decreases exponentially with reduction of ladder resistors and comparator input capacitances and with increase of time. It is found that the product of the ladder resistor and the comparator input capacitance between adjacent terminals must be less than 5 × 10−13 F.Ω in order to obtain an 8 bit A/D converter with 20 MS/s. Variation is decreased if the midpoint of the ladder resistor is fixed. For instance, when the midpoint is fixed, the product of the ladder resistor and the comparator input capacitance is allowed to increase up to 2 × 10−12 F.Ω.
High‐speed spectroscopic measuring apparatus for contact arc discharges using CCD image sensor
Authors: Sato Kiminori , Sone Hideaki , Echigo Hiroshi , Takagi Tasuku
Published: July 2007

Numerous studies have been made on contact arc discharges. However, little has been reported on the detailed measurement of discharge phenomena. With a view to obtaining basic data to be used for the improvement of contact performance, an apparatus has been developed which performs parallel spectroscopic measurement of spectral arc intensities. The arc passing through the spectroscopic analyzer is focused on a CCD image sensor by means of a lens. Each spectral line is correlated to CCD picture elements. CCD has 128 pixels and the apparatus can measure arc spectral lines at 350 ∼ 700 nm in parallel and with a 1 ms interval. The arc voltage and current forms can also be measured. All the data undergo an A/D conversion and are stored on a floppy disk. Hence, the arc discharge can be studied quantitatively and the fine structures in the arc may be analyzed. From the present experiment it is found that the arc is maintained with a larger variety of ambient atoms in the Pb contact arc than in Ag. A transition from the metallic phase to the gaseous phase has been confirmed for the Ag contact arc.
Characteristics of simulation reactance circuits using converter‐type mutators
Authors: Ikeda Katsuji , Tomita Yasushi
Published: July 2007

The mutator proposed by Chua can be classified into two types converter type and inverter type. This paper proposes circuit configurations realizing various converter‐type mutators and studies simulation reactance circuits. It is shown that various converter‐type mutators can be realized by the use of specific two‐ports of active building blocks made of three current converters in which the basic structure is a voltage‐controlled current source and RC elements. Next, for practical simulation reactance circuits made of C‐R, L‐R and D‐R mutators, an analysis has been carried out based on the actual characteristics of current conveyors and an equivalent circuit has been derived. As a result, parasitic elements causing instability of the circuits are identified. The effect of the parasitic elements has been reduced with a passive compensation made of a ground capacitance so that a stable reactance circuit is realized. Further, theoretical and experimental results have been compared and discussed. The validity of the equivalent circuit is confirmed.
Bit‐map CAD system of IC design employing BIT‐I language
Authors: Koide Hideki , Kim Chol , Shono Katsufusa
Published: July 2007

This paper describes the IC design language BIT‐I implemented on a personal computer, and the bit‐map CAD system employing the language. The system is composed of several programs covering the mask pattern design, design rule check, extraction of circuit parameters, function simulations, and conversion of data formats. Actual data processing in the program of design rule check and extraction of circuit parameters consists of the combinations of basic logic operations. The basic logic operations are described in the subprograms and their combinations are described in the main program. Therefore when new programs are to be developed for different water fabrication process or different devices, only the development or modification of new main programs can manage them.
Electrically deposited germanium–coated circular metallic hollow waveguides for infrared radiation
Authors: Miyagi Mitsunobu , Shimada Youichi , Nishida Shigeo , Hongo Akihito
Published: July 2007

An electrically plated germaniumcoated circular metallic hollow waveguide was fabricated to transmit CO2 laser light. The conditions for the plating current, the temperature of the plating bath, and the plating period have been established. The transmission characteristic of a circular hollow waveguide 4 mm in diameter and 1 m long has been measured and its low‐loss characteristic has been confirmed.
Focusing characteristics of cylindrical luneburg lens‐numerical analysis in wave optics
Authors: Mori Kensuke , Yamaguchi Shoji , Hosono Toshio
Published: July 2007

Although 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

With 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

A 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

The 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

Communication 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

This 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

The 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

Presently, 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

This 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

To 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

Aerial 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

It 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

Resins 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

A 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

Recently, 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

The 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

This 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

The 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

A 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.
Annealing technology under arsenic overpressure for GaAs LSI–influence on dislocation and threshold voltage
Authors: Egawa Takashi , Sano Yoshiaki , Nakamura Hiroshi , Kaminishi Katsuzo
Published: July 2007

Since the microscopic uniformity of the threshold voltage (Vth) of an FET is important to obtain GaAs LSI, the cause of the threshold voltage uniformity was researched by investigating the annealing dependencies of the dislocations in the semiinsulating substrate of LEC GaAs and the microscopic uniformity ofVth. Annealing under arsenic overpressure decreased the dislocation density on the substrate surface and formed a uniform distribution of dislocations. This is believed to be caused by the supply of arsenic to the substrate surface. When annealing was carried out under low arsenic pressure,Vthshifted toward the negative direction at the area with clustered pits, and a clear dislocation network was formed. On the other hand, when annealing was carried out under arsenic overpressure using arsene, the shift ofVthin a negative direction becomes small andVthwas distributed uniformly. When annealing was carried out using a protective PCVD SiNxfilm, the distribution ofVthwas consistently uniform, regardless of the dislocation distribution. As described in the preceding, it was found that a high concentration of AsGaexists in the area of the clustered pits, the uniformity ofVthis independent of the dislocation density but dependent on the stoichiometry of the substrate prior to or after annealing, and the distribution ofVthbecomes more uniform with an increase of arsenic concentration.
A MESFET model for the design of GaAs digital integrated circuits
Authors: Tanaka Koutarou , Kawakami Yasushi
Published: July 2007

As in the case of Si IC's, it is important to carry out circuit simulation in the development of GaAs digital IC's. This paper discusses a GaAs MESFET model for digital IC design. Since in the Shichman‐Hodges model the parameters are obtained only for the saturation region of the drain current, the model is not accurate in the nonsaturation region. Therefore, we utilized additional parameters in the model for the nonsaturation region to increase accuracy. Approximating the potential distribution in an MESFET channel by that in the MOSFET model, the internal capacitance was obtained analytically as a function of the gate and drain voltages. Using the model obtained as described in the foregoing, the transfer characteristic and operational speed of the DCFL circuit were calculated and the results were in excellent agreement with the experimental results.
Study on GaAs monolithic dynamic divider
Authors: Shigaki Masafumi , Yokogawa Shigeru
Published: July 2007

The GaAs monolithic dynamic divider, a high speed divider for microwave phase locked oscillators, has been studied. It can be operated at a higher speed than static dividers. The load in the inverter section is a passive resistor. Improved circuit topology at interstage buffers and reduction of gate resistance by the Au/WSi self‐aligned process have been used for superior characteristics of a single FET. For a 1 μm gate length, both division and frequencies ranging from 4.3 GHz to 7.3 GHz have been observed. As a system application, the divider has been implemented in a 13 GHz frequency synthesizer of oscillator‐multiplier type. The divider has been operated in the 6.5 GHz band and an operation with 1 MHz steps has been confirmed at the 13 GHz band. The phase noise has been 90 dBc/Hz at the off‐carrier frequency of 10 kHz. This value is sufficient for conventional microwave circuits.
Multilayer thin‐film waveguide polarizer with metal cladding
Authors: Kato Isamu , Hara Ryoichi , Sugiyama Yasuyuki
Published: July 2007

A metal‐clad optical waveguide can be used as a polarizer which passes the TE mode but blocks the TM mode. Numerous studies have been reported on metal loaded on slab waveguides. However, little has been reported on practical three‐dimensional waveguides. In this paper, a multilayered guided polarizer is fabricated by loading an AL film on a polymer thin‐film waveguide via a low‐index buffer layer. The polarization characteristics have been studied. In the case of a slab waveguide, the extinction of ratio of the guided wave intensities of the TE and TM modes increases with the film thickness of the buffer layer. It becomes a maximum of 34 dB for a film thickness of 0.18 μm and then decreases gradually. In the case of three‐dimensional waveguide, the electric field distribution of the hybrid guided mode is a mixture of the TE and TM modes. Hence, the extinction ratio is somewhat lower. However, the buffer layer thickness dependence of the extinction ratio is about the same as the one in the slabe waveguide. In the case of waveguide widths of 50 and 5 μm, the extinction ratio of the polarizer has been 30 and 22 dB, respectively, for a buffer layer thickness of 0.18 μm.
Monte carlo simulation of energy broadening in electron beams
Authors: Matsuda Jin‐Ichi , Kubo Mitsunori , Iriguchi Chiharu , Kato Kazuo , Masuda Takao
Published: July 2007

A numerical analysis based on the Monte Carlo simulation has been carried out for the space‐charge effect affecting the longitudinal energy broadening of the electron beams. The collisions of the electrons are treated as a many‐body problem. For (1) a cross‐over model, and (2) a triode electrode gun model, the electron beam current dependence of the energy distribution and the current density distribution is studied. It is found that the anomalous energy broadening that has not been explained fully by the existing theoretical analysis based on the two‐body problem approximation can now be understood quantitatively. The validity of our analysis method is thus demonstrated.
Proposal for a fiber‐optic endlessly rotatable fractional wave device and its applications to lightwave technologies
Authors: Matsumoto Takao , Nagase Ryo , Kano Haruo
Published: July 2007

In the fields of single‐mode fiber‐optics, polarization control is an important technique to control undesirable polarization fluctuations. This paper presents a new fiber‐optic fractional wave device which can endlessly and continuously rotate to compensate for polarization fluctuations. A design method is described and factors determining the performance of the device are presented. Characteristics of fabricated devices are described and their applications are introduced. This fiber‐optic fractional device utilizes birefringence induced in a bent fiber. The unique feature is that the fiber is coiled between two rotaing parallel plates with only loose support. This structure makes it possible to achieve a compact endlessly rotatable device. For design comparisons, a figure of merit relating to the characteristics of the bent fiber is proposed. The shape of the fiber bending changes according to the rotation of the device. The effect of this transformation on the characteristics of the device is studied theoretically. Experimental studies are carried out on the effect of coating materials, on fiber durability, and on its characteristics during high‐speed operation. Half‐and quarter‐wave devices for 1.52 μm wavelength are fabricated with losses and birefringence accuracies better than 0.2 dB and ±5%, respectively. A polarization controller realized by utilizing this device is used in a 400 Mb/s optical FSK transmission over 270‐km fiber. It also is used in an LD spectrum width measuring instrument.
Anomalous charging characteristics of Se photoreceptor and its stabilization in high‐speed reversal‐development electrophotography
Authors: Anzai Masayasu
Published: July 2007

In high‐speed electrophotography using the reversal development method, the photoreceptor repeatedly receives positive and negative corona charges. If its period is short (less than about 1 s), the charging voltage varies significantly and the printing is hindered. The charging characteristics in this case have been studied with an Se photoreceptor. The following observations have been obtained: (1) if the negative charge for toner transfer becomes strong, the residual voltage increases more than in the case of the positive charging only; (2) when the negative charging is terminated after positive and negative chargings were repeated, both the charging voltage and the residual voltage increase; (3) this phenomenon is more significant if the temperature is lower. To suppress this anomalous charging phenomenon, a uniform exposure and a recharging process are added before toner transfer so that the operating point of charging is shifted. This method has been confirmed experimentally.