bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable bit‐rate video transmission using traffic shaping
Authors: Inoue Masahiro , Kawashima Masahisa , Tominaga Hideyoshi
Published: July 2007

Video transmission that uses traffic shaping to smooth bit‐rate variations in performing a variable bit‐rate transmission while controlling congestion on an ATM network is examined. First, a traffic shaping system is proposed that keeps the transmission delay due to buffering under a fixed permitted value. Next, in simulation, the relationship between the effective bit‐rate smoothing of traffic shaping, the permitted delay, and effective congestion control are shown. Effective congestion control due to the use of average rate control in conjunction with traffic shaping is also shown. Effective bit‐rate smoothing and effective congestion control change in accordance with the size of the permitted delay. In an example experiment, an improvement in effective bit‐rate smoothing in a scene change is evident when the permitted delay increases in a segment of under roughly 100 ms and the rate increase is inversely proportional to the permitted delay.

Consequently, saturation probability decreases. Even when the permitted delay is increased in a segment exceeding 100 ms, saturation probability decreases, although a decrease in the maximum bit rate is not evident due to smoothing. The effect of the two systems is multiplied if the average bit rate and traffic shaping are used together, with the saturation probability being greatly reduced.
Theoretical analysis of stoneley waves propagating along an interface between piezoelectric material and isotropic material
Authors: Irino Toshio , Shimizu Yasutaka
Published: July 2007

Conventional surface acoustic wave (SAW) devices mainly use Rayleigh waves that propagate on the substrate surface. Therefore, they require protective packaging and are expensive as well as unreliable. This paper reports an effort to develop SAW devices that do not require packaging. To this end we study the Stoneley waves propagating along the interface between the piezoelectric and isotropic materials. A range of material constants of isotropic materials is obtained which allows the Stoneley wave if combined with piezoelectric materials with various cuts and propagation directions. We obtain the relation of the allowable range to the maximum velocity of the Stoneley wave and the velocity of the Rayleigh wave. It is found that the Stoneley wave can be supported with a combination of glass and LiTaO3, PZT4 and ZnO. It is not possible to concentrate the energy near the interface if LiNbO3 and Bi12GeO20 are used.
Improved planar magnetron sputtering system and its application for deposition of ALN films
Authors: Takahashi Takakazu
Published: July 2007

An improved planar magnetron sputtering system was constructed, where a solenoid coil is placed surrounding the pyrex glass chamber. the magnetic field distribution, dc discharge and sputtering characteristics are investigated in detail with the dc current (IS) in the solenoid coil as the parameter. The magnetic field distribution was investigated by measuring the field along the target plane (B″) and the direction vertical to the plane (B⟂). The dc discharge and sputtering characteristics were examined in Ar or N2 with pressure of 0.08 to 3 Pa; Ti was used as the target. By setting IS so that B″ increases, the dc discharge voltage and spark voltage decreases and the dc discharge current increases. This tendency is more remarkable when IS is large. It was seen also that the erosion region of the target depends on IS. A reactive AlN film was fabricated by this system, and it was seen that the C axis orientation of the film depends on the kind of atmosphere gas. In N2, the orientation is vertical to the film plane and is parallel in NH3.
Optical fiber loss increase due to hydrogen and long‐term loss stability for optical fiber cables
Authors: Noguchi Kazuhiro , Shibata Nori , Uesugi Naoshi , Ishihara Koushi , Negishi Yukiyasu
Published: July 2007

Recently, it has become clear that the long‐term loss of an optical fiber increases if the fiber is exposed to hydrogen. This phenomenon indicates that the loss in the optical fiber installed in a cable can increase if for some reason hydrogen is generated in the fiber cable. Therefore, this phenomenon is important for reliability design consideration. When the optical communication system with the 1.3 μm band is in actual use and the one with the 1.5 μm band is nearing its preparation for actual use, it is especially important to understand clearly the guarantee of long‐term reliability of an optical fiber cable and prevention of the effects of hydrogen. In this paper, the loss increase characteristics are formulated for optical fiber with germanium as an only dopant placed in a hydrogen atmosphere. The formulation is done from the results of increased temperature tests in hydrogen. From the formula, an allowable level of hydrogen pressure in the cable is calculated such that the loss increase of the fiber is kept below a specified value. It is also shown that the loss increase is sufficiently suppressed for practice by preventing water leakage into the cable.
Development characteristics of photoactive polyimide
Authors: Naito Noboru , Kakuda Nobuhiko , Wada Tsutomu
Published: July 2007

Development characteristics of photosensitive polyimide, which has been applied experimentally to insulation films for multilevel interconnection systems, were examined. Photoactive polyimide, photo‐neece reveals that the thickness of the film (even exposed areas) is reduced remarkably by its development despite the fact that the film is a negative‐type photoresist. It was found that the dissolution rate of the exposed areas by a development, not only depends on the conditions of the exposure but also on the conditions of prebaking. It was also found, notably in the prebake‐dependence of the dissolution rate, that the dissolution rate is determined by the thermal decomposition of the photoactive substance at a temperature above 80°C, and, by the obstruction of crosslinking reaction due to a residual solvent at a temperature below 80°C. The prebake‐temperature dependence of the dissolution rate of unexposed polyimide is determined by the quantity of residue on evaporation of the solvent, since the activation energy agrees approximately with the evaporation heat of solvent N‐methyl 2‐pyrrolidone.
Analysis of semiconductor multilayer and its application to surface emitting lasers
Authors: Morinaga Motoyasu , Chailertvanitkuls Anan , Iga Kenichi
Published: July 2007

A dynamic‐single‐mode laser has become important as a light source for optical fiber communications using a 1.5 μm wavelength band, and a surface emitting laser is promising as one of them. However, a good ohmic contact must serve simultaneously as a mirror and it was difficult by a present technique to obtain a reflective mirror with high reflectivity. In this paper, we apply the multilayer heterostructure with the thick ness of quarter wavelength to the surface emitting laser reflector to solve the difficulty. First: (1) we analyzed the semiconductor multilayer DBR by expanding the multilayer film theory to calculate the complex field reflectivity r and obtained the power reflectivity R and the effective optical path length which is practically effective to the DBR laser. Then we clarify the lasing condition of the surface emitting laser using the semiconductor multilayer DBR.
Finite‐element solution for scattering of lamb waves by asymmetrically located discontinuities in an elastic plate waveguide
Authors: Hasegawa Koji , Koshiba Masanori , Suzuki Michio
Published: July 2007

This paper considers the scattering of Lamb waves due to the discontinuity of elastic plate waveguide. A method of analysis is presented which is a combination of the finite‐element method and analytical solution. The analytical solution is derived taking the cut‐off mode into consideration. Consequently, the region of application of the finite‐element method is reduced drastically compared with the traditional method of analysis by finite‐element method ignoring the cut‐off mode. In the past, the formulation has been made by restricting the discontinuities to symmetrical distribution in regard to the central plane of the plate. In this paper, this restriction is removed and discontinuities of any distribution in regard to the elastic plate can be handled. The effectiveness of taking the cut‐off mode into consideration is verified by applying the proposed method to the scattering of Lamb waves by a free‐edge of the elastic plate and by a slit which is symmetrical in regard to the central plane of the plate. As examples of discontinuities with asymmetrical distribution in regard to the central plane of elastic plate, a slit on one of the surfaces and wedge‐shaped crack are considered. The result of analysis is presented for the scattering characteristics when a fundamental symmetric Lamb wave or fundamental antisymmetric Lamb wave is incident.
Development of high‐performance flexible optical solar reflectors
Authors: Ichino Toshihiro , Sasaki Shigekuni , Hasuda Yoshinori
Published: July 2007

As communication satellites become larger, the flexible optical solar reflector (OSR) controls the temperature of satellites by reducing its weight and thus the assembly work becomes easier. FEP teflon film with vacuum‐deposited silver is a representative flexible OSR, but this deteriorates by radiations in space. This paper investigates the applications of poly(etherimide) (PEI) and poly(etheretherketone) (PEEK), which have excellent radiation‐resistance to the thermal radiation layer of an OSR. Various types of OSRs with PEI and PEEK were fabricated, and their thermal control properties electron‐radiation resistance and UV radiation resistance were investigated. Excellent properties of PEI with vacuum‐deposited silver (PEI/Ag) were confirmed. A new high‐performance flexible OSR, which is superior to FEP teflon with silver, was developed. The results are summarized as:

the initial thermal control properties are represented by the solar absorptance (α s) × 0.15 to 0.17, and the thermal emittance (ϵ) × 0.77 to 0.85; (2) the increase of αs, after an electron irradiation equivalent to 10 years in a geostationary orbit, is 0.01; (3) PEI/Ag can be electric‐conductive without degrading the original characteristics, by coating its surface with indium‐tin‐oxide; and (4) the increase of αs, after an UV irradiation equivalent to 2 years in a geostationary orbit, is 0.03. However, the increase of αs can be prevented by coating the surface with CeO2.
Numerical analysis of magnetization characteristics in the saturation region of magnetic circuits
Authors: Watanabe Hiroyuki , Kato Katsuhiro
Published: July 2007

In the design of such magnetic circuits as electromagnetic relays, it is important to determine how the magnetic body is magnetized by a driving coil and how the inductance seen from the driving coil is related to the shape and the material characteristics of the magnetic material. In this paper, the Newton‐Raphson method is applied to a combination of the analytical solution based on Green's function and the finite element solution. Magnetization characteristics including magnetic saturation are obtained for a magnetic body with a rotationally symmetric bar shape. The relation of the method of element division to the computational error and the computation time is studied first for the inductance of an ellipsoidal magnetic body for which the exact solution is known in the linear region. If the division is such that the dispersion of the magnetic energy in the element to be analyzed is less than 1.0, the inductance can be obtained with a short computation time and a small memory requirement while the error from the exact solution is less than 1.8 percent. Magnetic characteristics are obtained with the material characteristics of the material taken into consideration. A range is found in which the nonlinear solution can be approximated with a linear solution. Further, the present method is applied to a cylindrical magnetic body. It is shown that the nonlinear solution of the magnetization characteristics agrees well with the measured values.
Gas sensing characteristics of reactively sputtered SNO2 films
Authors: Kuriki Shinya , Sano Katsumasa , Konishi Hajime , Matsumoto Goro
Published: July 2007

Sensing characteristics to various flammable gases have been studied for SnO2 thin films made by RF reactive sputtering method. The film has reacted most selectively with ethanol among ethanol, carbon monoxide, hydrogen, methane and propane. The sensitivity is S × 0.5. From the x‐ray photoelectron spectroscopy for the SnO2 films fabricated under different conditions, it is found that there exists a close relationship between the oxygen content in SnO2 and the ethanol gas sensitivity. Conductance, carrier density and Hall mobility have been measured at various temperatures in several gas environments so that their relation to the gas sensitivity is studied. It is found that the variation of the conductance due to ethanol gas is caused by the variation of the electron concentration of the SnO2 film due to adsorption and desorption of oxygen. When very thin Pt is evaporated in islands on the surface of the SnO2 film, the ethanol gas sensitivity was increased as well as the sensitivity to carbon monoxide and hydrogen.
A multimicroelectrode fabricated by silicon dry etching
Authors: Takahashi Kohro , Shoji Shuichi , Matsuo Tadayuki
Published: July 2007

In neuro‐physiology, it is important to record neural impulses from the central neural system simultaneously. For this purpose, a silicon substrate which forms a multimicroelectrode was fabricated and a precise fabrication of a 10 μm thick microelectrode with a 30 μm wide tip was achieved by using Si dry etching. The high‐quality insulation of the electrode in a physiological solution was obtained by using Ta and high‐temperature CVD Si3N4. However, Ta itself is not adequate for the recording site because it is oxidized easily in an electrolyte causing the increase of the electrode impedance. Platinum‐black was electroplated on the titanium surface in order to stabilize and reduce the electrode impedance. The interelectrode crosstalk between electrodes and signal attenuation due to the parasitic capacitances were 0.4% and 4.4%, respectively.
Preparation and properties of Ba‐ferrite films by rf diode sputtering
Authors: Morisako Akimitsu , Matsumoto Mitsunori , Naoe Masahiko
Published: July 2007

Ba‐ferrite films were deposited by rfdiode sputtering which is one of the most conventional methods for complex oxide deposition and the applications of such films in perpendicular magnetic recording are discussed. Because of the bombardment by high‐energy particles, the composition of the deposited film was different from that of the target material. However, we were able to beam films with stoichiometric composition by adjusting the composition of the target. In one case, the first 300 Å layer had spinel‐type crystal structure and the layer above that initial layer had the structure of the magnetoplumbite type of Ba‐ferrite, oriented along the c‐axis. In the other case, the entire film was composed of the Ba‐ferrite layer oriented along the c‐axis. The result of investigating the growth conditions showed that the spinel layer caused a Δθ50 dispersion of the growth orientation in the Ba‐ferrite layer away from the c‐axis. When the growth temperature was around 550°C, the growth occurred in the direction of the c‐axis. The surface roughness of the film was dependent on the distance between the target and the substrate, the partial pressure of oxygen, and the substrate temperature. At high oxygen partial pressures, the deviation of the growth orientation from the c‐axis was especially high, and the surface became rough. The best Ba‐ferrite film had the following properties: Δθ50 = 2 to 3°, Hc1 = 1.2 kOe and Ms = 300 emu/cc. The film surface was smooth and hard enough to serve as a perpendicular magnetic recording medium.
Launching and receiving conditions for optical fiber loss measurements using an OTDR
Authors: Furukawa Shin‐Ichi , Koyamada Yahei
Published: July 2007

Optical pulse measuring instruments (OTDRs) are very useful in locating broken areas and assessing the homogeneity of optical fibers, etc. Until now, the theoretical relation between the measured results of the optical and splicing losses of cut‐back and OTDR methods was not known and OTDRs were not used to measure losses of steady‐state mode distributions. This study investigates the backscattering mode distribution of graded‐index optical fibers using geometrical optics. The launching condition of the light pulse and the receiving condition of back‐scattering, and their relation to the measured optical and splicing losses, are determined. The theoretical and experimental relation between the measured values of backscattering by OTDR and cut‐back methods is also discussed. As a result, it is shown that the steady‐state condition of the received backscattering light is necessary when measuring the losses of steady‐state mode distribution by OTDR method. We propose the possibility of estimating the splicing loss values of the cut‐back method from the difference of the splicing loss measurements under varied launching conditions of OTDR method. Correctness of this method is confirmed experimentally. In this method, no previous preparation is required and by changing the launching conditions at only one end, only two measurements are made and a simple calculation is required. Therefore, it is expected that measurement efforts are significantly reduced by this method.
A 2 ∼ 18‐GHz band distributed MMIC amplifier with single supply bias network
Authors: Seino Kiyoharu , Takagi Tadashi , Ikeda Yukio , Ishikawa Takahide
Published: July 2007

A design concept and experimental results are reported on a distributed amplifier with a flat gain characteristic. To obtain a broadband characteristic, the distributed amplifier is designed in such a way that the input power to each FET is as equal as possible. The obtained performances at 2 to 18 GHz are such that the gain is 7 ± 0.5 dB, the noise figure is less than 5.8 dB, and the VSWR is less than 2. In this amplifier, a self‐bias circuit is installed at the source electrode of each FET so that it can be operated with a single power supply.
Finite‐element solution of three‐dimensional resonator problems. Novel rectangular parallelepiped elements
Authors: Hano Mitsuo
Published: July 2007

New rectangular parallelepiped elements are proposed for analyses by finite elements for problems of three‐dimensional resonators. Earlier methods of finite‐element analysis confirmed the generation of nonphysical spurious solutions which are mixed with physical solutions. New first‐order and second‐order rectangular parallelepiped elements are proposed and the formulations of these finite elements are derived. One of the characteristics of these new elements is that tangential components are used for the electromagnetic fields on the surface of the elements as an unknown parameter. As concrete examples, they are applied to a cubic resonator and a rectangular resonator which contained a dielectric material. It was confirmed that except for a few zero eigenvalues, all nonzero eigenvalues corresponded to resonant modes. Specifically, if new rectangular parallelepiped elements are used, it is shown that no generation of spurious solutions occurs with nonzero eigenvalues.
Recording material characteristics needed for realization of phase‐change type optical disk
Authors: Funakoshi Nobuhiro
Published: July 2007

To apply phase‐change type material to an optical disk, thermal analysis of the material was carried out at a traveling speed of 25 m/s, realizing that the erasing process is based on crystallization of an amorphous material. As a result, the conditions for a circular beam needed to realize phase‐change type recording materials and the relationship between the crystallization energy and frequency factor were clarified. It was found also that if the transformation mode is higher than 3, optical disks compatible with the presently commercialized disks can be fabricated.
Coupled mode theory of parallel multi– and single—mode dielectric waveguide
Authors: Ohke Tadafumi , Tomabechi Yoshiro , Matsumura Kazuhito
Published: July 2007

When Waveguide I supporting several guided modes and Waveguide II supporting a single mode are coupled in a parallel orientation, the electromagnetic field distributions in this coupled guided system are analyzed in such a way that the mode coupling is represented as a weighted sum of the guided modes. In general, when two waveguides are placed closer so that the coupling becomes stronger, the existence of one guide can no longer be neglected by the guided eigenmode of another guide, and its field distribution is perturbed. The method of analysis presented in this paper takes into account this effect by way of weighted expansion coefficients of the mode. Hence, the analysis can be applied even when the coupling is rather dense. As an example, the field distribution of the coupled guided system is analyzed for the case where two rectangular dielectric waveguides having one and two modes, respectively, are placed in parallel. Next, the field distribution along the coupled waveguide is measured and the spatial spectrum is analyzed. A characteristic spatial spectrum is found which is proportional to the difference of the phase constants of the three eigenmodes. It is found that this corresponds to the difference of phase constants of each mode obtained analytically.

The present analysis method can readily be extended to the case in which each of the coupled waveguides has multiple guided modes, including the case where both have only one mode. The theory can be used for the design of couplers, dividers, and mode filters made of dielectric waveguides.
Monolithic integration of LD/HBTs on a semiinsulating InP substrate
Authors: Ohnaka Kiyoshi , Tsujii Hiraaki , Shibata Jun
Published: July 2007

A ridge‐waveguide laser and heterojunction bipolar transistor were integrated monolithically on a semiinsulating InP. In this device, the n‐cladding layer of the laser, the waveguide layer and the active layer were grown epitaxially on a semiinsulating InP. They are common to the collector and double‐layer base of the transistor. Using this device structure, the step height on the device surface was small and the fabrication of the device was simplified.

The threshold current of the laser was 30 mA and the characteristic temperature was 65 K. Since a narrowband gap layer common to the laser active layer exists at the collector side of the base of the heterojunction bipolar transistor, the saturation property of the current‐voltage characteristic in common emitter configuration was good and influenced little by the “Early Effect.” This paper describes the fabrication and analysis of the ridge‐waveguide laser and heterojunction bipolar transistor.
High‐speed Hi‐BiCMOS gate array with RAM
Authors: Nishio Yoji , Murabayashi Fumio , Kotoku Shoichi , Kadono Shinji
Published: July 2007

The newly proposed BiCMOS technology [4] is based on the idea of realizing an LSI with high‐speed and low‐power consumption properties, by combining the bipolar and CMOS technologies in the basic circuit. It was demonstrated in [4] that the designed performance can be realized for logic circuit. This paper reports on the application of the technique to the gate array, where the circuit is constructed by 1.3 μm Hi‐BiCMOS technology and the overall performance as LSI is evaluated experimentally. First, three kinds of master chips suited to the high‐speed processor such as a minicomputer are designed. Among those, a master chip was selected and developed, which includes a multiport RAM and is applicable to the arithmetic logic unit containing a register file. The internal RAM has a structure of 4 kbit and 3‐port, and the access time is less than 10 ns. A basic cell structure to construct the logic circuit by a combination of bipolar and CMOS technologies is devised. A 2‐input NAND gate with a typical delay of 0.45 ns was realized. This type of gate array will be useful in the devices such as those in minicomputer and communication systems, where a high‐speed operation is required.
Measurements on the influence of metallic phase arc on electrode surface for breaking Ag contacts
Authors: Sone Hideaki , Takagi Tasuku , Nakai Masao
Published: July 2007

The influence of metallic phase are discharge on electrode surface was studied for breaking Ag contacts. A whole are duration, metallic phase are duration, contact resistance and electrode material mass change were measured when both conditions of air pressure and circuit current were varied. The result showed that both the material loss and transfer had a close relationship to the metallic phase are duration. The contact resistance increased as the are duration grew in the metallic phase are region, and it became high and almost constant when the are sustained until it transferred to the gaseous phase.
Responses of digital frequency multipliers consisting of coupled‐lines to trains of periodical gaussian pulses
Authors: Sakagami Iwata , Hatori Kozo
Published: July 2007

For the coupled‐line digital frequency multipliers which have been discussed for the impulse train, their output responses are presented for the periodically isolated pulses considered as time‐limited incident signals. In this paper, periodic Gaussian pulse trains are treated as an example. In addition, the physical meaning is given for the nonnegative constant which is determined by the relationship between the reflection and transmission coefficients as the transfer function of the circuit. By means of this constant, it is shown that the attenuation constant of the discrete frequency component passing the circuit is minimum. Similar to the case of unit impulse train input, the input frequency components are discrete at an equal interval on the frequency axis. The amplitude is determined by the Fourier transform of the isolated purse constituting the periodic pulse train. Since the input frequency components are discrete, simulation of the output response requires only the sampled values of the frequency characteristics of the circuit. Since the Fourier transform of a Gaussian waveform is Gaussian, it is possible to determine the transmission frequency range in which most of the energy of the Gaussian pulse train is concentrated. Although the characteristic of the distributed circuit degrades as the frequency is increased, an almost desirable output can be obtained if the frequency characteristics are satisfied within a transmission frequency bandwidth.
Properties of polyimide films cured on copper
Authors: Miura Osamu , Watanabe Hiroshi , Miyazaki Kunio , Numata Shunichi
Published: July 2007

A polyimide film (varnish) on a copper film tends to change in color and to show degradation of the thermal and mechanical properties during the thermal‐curing process. The causes of these property changes were investigated by observing the film appearance and analyzing the molecular structure of films and the infrared absorption spectrum. As a result, it was found that copper diffuses into the polyimide film during the imidization process, causing the decomposition of the imide‐bonds which further causes the changes in color and properties of the film.
Finite‐element formulation of quantum wells using transfer matrix
Authors: Nakamura Kenji , Shimizu Akira , Koshiba Masanori , Hayata Kazuya
Published: July 2007

When the effective mass approximation is used for analysis of electrons bound in a quantum well, the envelope function generally is not continuous at the heterojunction. The boundary condition at the junction is expressed in terms of the transfer matrix. In this paper, an analysis method based on the finite‐element formulation is proposed for electrons bound in a quantum well made of arbitrary materials. It is shown that by using 3rd‐order Hermitian line elements as the approximation functions, the continuities of the envelope function and its derivative are ensured outside the heterojunction, and that introduction of the transfer matrix becomes possible. It is also shown that the problem becomes an asymmetric generalized eigenvalue problem by means of this formulation. As numerical examples, rectangular quantum wells are analyzed in the cases where the envelope function, and its derivative divided by the effective mass, are continuous at the heterojunction (GaAs/A1GaAs quantum well) where also the function and its derivative are discontinuous (InAs/GaSb quantum well). The validity of the calculations is confirmed by comparison with the analytical solutions.
A proposal for polynomial transformer and its design using 3‐D VLSI technology
Authors: Kurokawa Takakazu , Aiso Hideo
Published: July 2007

Any relationship among finite fields, or Galois fields, can be transformed into a unique polynomial consisting of one variable using Galois Fields. In this paper, the 3‐D design of the “Polynomial Transformer” which executes this transformation is discussed.

The Polynomial Transformer consists of very simple and iterative logic, and it is very suitable for parallel and pipelined VLSI implementation. Moreover, it is possible to transform 3‐D construction. From the 2‐D and 3‐D layout result of the Polynomial Transformer, it appears that 3‐D construction is effective.

Some applications of the Polynomial Transformer are substitution in cipher, random number generation, and hashing which is used in compiler.
12‐GHz band triple‐mode filters with waveguide ports—comparison and consideration of two kinds of filter structures
Authors: Nomoto Toshihiro
Published: July 2007

This paper describes the design and development of triple‐mode filters which make possible compact size for use as 12 GHz band broadcast satellite transponder filters. Compared with dual‐mode filters, the realization of triple‐mode filters has further difficulty in controlling the resonant frequency and excitation of the degenerate modes, and in designing the intercavity iris. Two kinds of six‐pole triple‐mode filters which are different in mode‐coupling structures, are presented, and intercavity aperture shapes for each filter capable of a true elliptic function response are newly proposed in this paper. The experimental results showed that these two filters could exhibit almost equal electrical performance, and the proposed intercavity aperture shapes are widely available for controlling three pairs of mode‐couplings between two physical cavities simultaneously and independently. Finally, consideration for application to waveguide manifold multiplexers are made from various viewpoints.
Microwave band push‐pull power amplifiers
Authors: Toyoda Sachihiro
Published: July 2007

This paper describes the push‐pull power amplifier using GaAs power FETs. Two types of phase inverters indispensable for configuration of a push‐pull power amplifier were conceived. The push‐pull amplifiers fabricated for trial were tested at 5‐ and 10‐GHz bands. The bandwidth of the power amplifiers for the 5‐GHz band was 1.48 and 1.8 GHz and the output power was 7.5 W (38.8 dBm). The bandwidth of the power amplifiers for the 10‐GHz band was 1.85 and 2.35 GHz and the output power was 4.5 W (36.5 dBm).
An SOI/CMOS flash A/D converter
Authors: Kumamoto Toshio , Nakaya Masao , Kusunoki Shigeru , Nishimura Tadashi , Yazawa Nobuharu , Akasaka Yoichi , Horiba Yasutaka
Published: July 2007

It is important from the viewpoint of increasing the application range of the three‐dimensional circuit to construct analog circuits such as A/D converters on a silicon substrate formed on an insulating oxide film, or silicon on insulator (SOI) devices. Analog devices on a silicon on sapphire (SOS) substrate have been reported. However, no work on analog circuits has been reported with conventional SOI technology because of the lack of uniformity of the transistor characteristics. Due to the substrate floating effects represented by the kink phenomena characteristic to the configuration, the characteristics of the analog device are degraded. The laser recrystallization technique is improved and the chopper‐type comparator is used which is less susceptible to the variations of the device parameters. Furthermore, a transistor structure that suppresses the kink phenomena is introduced in the amplifier inverter. With these approaches, a 4‐bit flash A/D converter is fabricated successfully with the SOI/CMOS process. As a result, the basic operation is confirmed up to the power supply voltage of 5 V, input signal of 10 kHz, and conversion speed of 30 MS/s. In this paper, the design and evaluation are described for the SOI/CMOS A/D converter for three‐dimensional circuits.
Memory cell design of optically coupled three‐dimensional common memory
Authors: Takata Hirokazu , Mori Hiroki , Hirose Masataka , Koyanagi Mitsumasa
Published: July 2007

An optically coupled three‐dimensional common memory has been proposed for more functional and faster parallel processing of information with several CPUs. A detailed design of the memory cell was carried out. First, the effect of stray light which is a significant problem in the design of the optically coupled three‐dimensional common memory was studied quantitatively by deriving the optical coupling efficiency between the light‐emitting and detecting devices. Next, by means of the static analysis taking into account the fluctuations of the device dimensions, alignment error between the layers and the variation of the power supply voltage, the safe operating region of the memory cell was evaluated. As a result, an optimum condition was found on the transverse pitch between the light‐emitting and detecting devices and the supply current to the emitting device for a stable operation of the memory without being affected by the stray light. Further, with this optimum condition, a dynamic analysis was carried out for the memory cell circuit to which the bit‐line peripheral circuit is attached. In the analysis, the reduction of the load resistance of the memory cell by the optical writing was described with an equivalent circuit consisting of resistors and MOSFETs. The analysis was carried out with the driving circuit for the light‐emitting device characteristic to the optically coupled three‐dimensional common memory taken into account. It was confirmed that the memory cell designed by means of this dynamic analysis operates correctly.
Fundamental properties of ultrathin SOI MOSFETs fabricated by electron‐beam anneal recrystallization
Authors: Yoshimi Makoto , Takahashi Minoru , Hazama Hiroaki , Kambayashi Shigeru , Natori Kenji
Published: July 2007

Thin‐film SOI MOSFETs made in completely depleted SOI films were fabricated by electron‐beam annealing and their electrical properties were compared with those of conventional SOI MOSFETs. The threshold voltage agreed with the calculated value. With complete depletion of the SOI film, the threshold voltage decreased toward the value determined by the work function difference between the gate material and SOI film as the film thickness decreased. The low field mobility increased with the depletion of the SOI film.

When the SOI film was 500 Å thick, the mobility exceeded that of a bulk MOS device fabricated with the same doping concentration. The current overshoot during switching in the thin‐film SOI device was too small to observe.
A novel beam propagation method based on the Galerkin method
Authors: Matsuhara Masanori
Published: July 2007

In the conventional beam propagation method based on the WKB approximation, the spacing between the sampling points is restricted to be sufficiently larger than one‐half the wavelength. This restriction has limited the applicability of the beam propagation method. In this paper, a new beam propagation method is proposed which is based on Galerkin's method. In the new beam propagation method, the forementioned restriction does not apply and a spacing between the sampling points smaller than a half wavelength can be chosen. Hence, it is possible to treat accurately an optical wave with a narrow beam.
Optimum design of high–density circuit boards
Authors: Matsui Norio
Published: July 2007

The method is discussed of determining wire width that minimizes the delay time and crosstalk of the average wiring length of wiring board under the condition that the wiring dimension is scaled down keeping the characteristic impedance of the transmission line constant. By employing the sending‐gate matching method suitable for the fine‐pattern wiring with high resistance, the equation for the relation between the wiring width and the average wiring length is determined from the condition of the gate count, terminal expansion, power consumption and LSI mount area for the multiple wiring layer board that places and routes many LSI chips. The delay time and crosstalk under high wiring resistance are analyzed with the distributed constant circuit model. Then the existence of the optimum wiring width that minimizes simultaneously the delay time and crosstalk for the average wiring length is proved.

If the wiring width exceeds this value, the wiring length increases and the delay time and crosstalk are almost proportional to the wiring length. This is because the gate count determines the wiring count and the increase in wiring width increases the wiring board area. If the wiring width is less than the optimum value, only the wiring resistance increases. The wiring length does not decrease because the power consumption and LSI mount area determine the wiring board area. Moreover, the approximated equation that gives the optimum wiring width, delay time and crosstalk is determined to obtain the guidance for the design of the high‐density wiring board.
Design of CMOS multiple–valued logic circuits using only one voltage source
Authors: Taniguchi Kazutaka , Ueno Fumio , Inoue Takahiro
Published: July 2007

This paper presents the design of CMOS multiple‐valued logic circuits using only one voltage source. The circuits designed by the proposed method have only two lines for voltage sources compared with that of the conventional circuits which require many voltage sources in proportion to the number of logical values.

The circuit simulation for the proposed circuits has been performed by using the SPICE‐2G program. Their performance and usefulness in the design of multiple‐valued digital systems have been confirmed.
Fabrication of single‐mode optical fiber preforms by sol‐gel method
Authors: Kitagawa Takeshi , Shibata Shuichi , Horiguchi Masaharu
Published: July 2007

Single‐mode optical fibers have been fabricated using fluorine‐doped silica glasses made by the sol‐gel method. A liquid‐phase fluorine doping technique for controlling a refractive index in a fluorine‐doped silica glass was developed and the optimum condition in a sintering process for fabricating a highly transparent glass was clarified. A fluorine out‐diffusion method for making optical fiber preforms is proposed. Using this technique, optical fibers have been obtained with an optical loss of 0.43 dB/km at 1.30 μm wavelength.
Analysis of polarization characteristics of cylindrical waveguide containing anisotropic dielectric using spatial network method
Authors: Ko Youngho , Yoshida Norinobu , Fukai Ichiro
Published: July 2007

Recently, various anisotropic materials have been used in the applications to the microwave and millimeter wave circuits. In such a structure, it is indispensable to analyze systematically the medium conditions, boundary conditions and resultant propagation characteristics of complicated electromagnetic fields. Of the electromagnetic characteristics associated with the anisotropic materials, the polarization characteristic is particularly important. Especially, the circular polarization recently has been used extensively as the fundamental propagation mode in satellite communication due to the stability of its propagation characteristics. The polarization characteristics are expected to be applied to the modulation/demodulation in the optical region and to the erasable optical disk memory.

The present analysis considers the generating mechanism of these polarizations and carries out a numerical simulation of the fundamental mechanism by means of the spatial network method as applied to a structure made of an anisotropic dielectric disk or plate inserted in a circular waveguide. By taking advantage of the method, studies in the time domain are carried out so that the variations of the amplitude and phase of the electric field components at each spatial point are presented. From their mutual relationship, as the variation of the electric vector, the analysis determines the process in which the polarization plane characteristics are caused, including the rotation of the polarization plane from the linear polarization through elliptic polarizations and, finally, to the circular polarization depending on the rotation of the principal axis of the anisotropy.
Fabrication of dielectric‐coated rectangular hollow waveguides for CO2 laser light transmission
Authors: Karasawa Satoru , Miyagi Mitsunobu , Nakamura Tsutomu , Ishikawa Hitoshi
Published: July 2007

A germanium coated rectangular wave‐guide with a square cross section for CO2 laser light was fabricated by plating of germanium and soldering. A coated waveguide with a cross section of 2 mm2, a length of 80 cm and a loss of less than 0.1 dB/m was obtained. It was demonstrated experimentally that the waveguide has a low loss even for a bend.
Low‐temperature annealing of heavily ion‐implanted layer
Authors: Ohmi Tadahiro , Ishihara Yoshio , Shibata Tadashi , Okita Akira
Published: July 2007

Crystallinity recovery, impurity activation and stress relief in a heavily ion‐implanted layer by ultrahigh‐vacuum ion‐implantation during low‐temperature annealing were investigated and the following results were obtained. The crystallinity of the layer heavily doped with arsenic ions was recovered at 550°C for 75 min and the impurities were activated sufficiently. Furthermore, the impurity level distribution supported the LSS theory and the maximum carrier concentration was 1.6 × 1020 cm−3.

The reverse current of the p‐n junction formed by this method was two orders of magnitude lower than that in a conventional device. In the p‐n junction formed by continuous ion implantation of arsenic and phosphorus to relieve the stress in the implanted layer, the reverse current decreased further. When the stress was most relieved, the carrier activation rate was highest and the p‐n junction reverse current was lowest.
Magnetic properties of cobalt electrodeposited anodic oxide magnetic films
Authors: Arai Ken Ichi , Ohoka Yohsuke , Ishiyama Kazushi , Kang Hee Woo
Published: July 2007

A magnetic film was fabricated by electrodeposition of cobalt in the pores of an aluminum anodic oxide. The dependence of coercive force and magnetic anisotropy energy on the packing density and diameter of the cobalt particles was investigated when the pore diameter was kept constant.

The dependence of coercive force on the electrodeposition condition of cobalt was also investigated. The coercive force perpendicular to the film surface decreased when the packing density increased because the c‐axis, which is the axis of easy magnetization in a cobalt crystal, tended to incline to the film surface direction when the packing density increased.

Magnetic anisotropy energy depended strongly on packing density. When the packing density was less than 0.26, the direction perpendicular to the film surface became the axis of easy magnetization.

The perpendicular magnetic anisotropy energy was smaller than the calculated value of the magnetostatic energy because of the in‐plane orientation of the c‐axis. In a magnetic film with a pore diameter of 200 Å, the perpendicular coercive force was varied from 2000 to 1200 Oe by controlling the pH and the temperature of the cobalt electro‐depositing bath.
Analysis of electromagnetic scattering problems by the combination of the FEM and BEM
Authors: Toyoda Ichihiko , Matsuhara Masanori
Published: July 2007

A new numerical method is proposed for the analysis of the electromagnetic scattering problem by an inhomogeneous scatterer. Although the finite‐element method and the boundary‐element method have a high degree of generality, several difficulties occur if they are applied to the electromagnetic scattering problem.

First, in the case of the finite‐element method, treatment of inhomogeneous regions is easy, but that of an open region is difficult. Hence, the finite‐element method is not suited for the scattering problems in which open regions such as the exterior of the scattering body need to be treated.

On the other hand, in the case of the boundary‐element method, treatment of the open region is easy but that of inhomogeneous regions is difficult.

In this paper, a new combination of the finite‐element and boundary–element methods is proposed in which the advantages of both are incorporated. The new combined method proposed in this paper solves several difficulties of the conventional combination method by means of the boundary‐element method using the extended integral equation for which observation points are placed on the closed loop inside the scatterer. Numerical computations are carried out for a number of examples so that it is proven that the present method can be applied to scatterers with arbitrary shapes and arbitrary permittivity distributions. Further, it is shown that in addition to the far field, the near field can be found.
Scattering of guided mode by atoms in optical fiber and energy flow
Authors: Kuroda Michiko
Published: July 2007

Recently, a significant effort has been spent on research related to radiating X‐rays, and new X‐ray optical devices have been developed. However, in this case, the problem has arisen of scattering of the incident light or the X‐ray by atoms in the medium. When an X‐ray or a short wavelength optical beam is incident on a fiber, the incident light is scattered by the atoms and a part of the scattered light is radiated so that the energy ratio captured in the fiber is decreased. To minimize this effect, it is necessary to optimize the shape and the refractive index of the fiber.

In this paper, the theory of radiation from an electric dipole which has been used in atmospheric communication is used for the first time to study the problem of scattering by the atoms. By the application of this theory, the scattering problem can be solved easily.

The energy fraction captured in the fiber for the normalized fiber thickness, which has been obtained only for each mode, is now computed adding the higher‐order modes. The results are compared with those in the absence of scattering. It is found that, although the power can be trapped well inside the fiber by increasing the normalized fiber thickness in the case without scattering, the loss cannot be eliminated if scattering exists.
Improved finite element analysis of axisymmetrical resonators
Authors: Yoneda Naofumi , Yoneyama Tsukasa
Published: July 2007

Resonant frequencies and the unloaded Q's of an axially symmetric resonator are calculated via a finite element method using three magnetic field components. In general, triangular elements are used in the finite element method. However, such elements are not necessarily convenient since the computational accuracy is degraded for the resonant modes with circumferential modal number of 0 or 1.

In this paper, such difficulty is resolved by introduction of axial elements near the center axis. To reduce computation time, infinite elements also are introduced. The resonant frequencies actually are computed for dielectric disk resonators placed in a parallel plate cutoff waveguide and a conducting cylindrical cavity. It is confirmed that the computed results agree well with measured results or other available computed data.