bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of josephson triode
Authors: Yoshimori Shigeru , Kawamura Mitsuo
Published: July 2007

The Josephson junction is an oscillator driven by constant current. Therefore, the integrated device of the weak‐link type Josephson junction for detecting electromagnetic waves using the junction as a local oscillator can be considered. The superconducting device proposed by Likharev based on this concept is the Josephson triode consisting of three Josephson junctions. This paper describes the analysis of the Josephson triode which is the superconducting device for the heterodyne detection. First, the static characteristics are analyzed by use of the equivalent circuit and the fundamental equations. The necessary conditions for the normal resistances are derived. It is shown by numerical analysis that the millimeter wave heterodyne detection characteristics of the triode are identical with the theory and experiment for a tunnel junction. Moreover, the results analyzed numerically can be explained by analytical considerations and the simplified equivalent circuit of the Josephson triode is derived. The relations between the intermediate frequency output power and the local oscillator power are represented analytically via the simplified equivalent circuit of the triode.
Characteristics of β‐SIC films grown from an SiHC13‐C3H8‐H2 system
Authors: Furumura Yuji , Doki Masahiko , Mieno Fumitake , Maeda Mamoru
Published: July 2007

Beta‐phase silicon carbine (β‐SiC) layers have been grown on silicon substrates at a growth temperature of 1000°C and at a low pressure of 200 Pa from an SiHC13‐C3H8‐H2 system. Silicon substrates are 4‐inch silicon wafers, and (111) tilted substrates with 4° off‐axis and (100) substrates with no off‐axis are both used. It was found from X‐ray diffraction and reflection high‐energy electron diffraction (RHEED) analysis that β‐SiC single‐crystal films are obtained on (111) tilted substrates, but not on (100) substrates under the conditions used in this experiment. By forming an n‐p heterojunction between a P‐doped β‐SiC layer and a p‐type substrate and measuring its rectifying characteristics, the saturation current density at 2 V in the reverse‐biased region was found to be below 2 × 10−6 A/cm2.
Theoretical determination of equivalent circuit parameters for reflective SAW metallic gratings
Authors: Mitobe Seiichi , Koshiba Masanori , Suzuki Michio
Published: July 2007

A theoretical method is described for determining equivalent circuit parameters for metallic gratings on arbitrary piezoelectric substrates. In this paper, to consider an energy storage effect, we adopt the equivalent circuit model proposed by Li et al. The finite‐element method is used to calculate the upper and lower cutoff frequencies of the stop band for metallic gratings of infinite periodic structure, and circuit parameters are determined from these values. Therefore, in this equivalent circuit, all the effects of piezoelectric perturbation, mechanical perturbation, and energy storage are taken into account. To show the validity and usefulness of this approach, for aluminum strips on some useful piezoelectric substrates (LiNbO3, quartz, LiTaO3, Li2B4O7), equivalent circuit parameters for each of the metallic gratings are determined and SAW reflection characteristics are computed. Result show that for the Li2B4O7 substrate, the reflection magnitude per strip is large and the influence of the change of strip thickness on the center frequency shift is small.
Inspection device for testing the mounted condition of chip components on printed wiring boards
Authors: Yabuzaki Syunichi , Yamataka Yasuo
Published: July 2007

An automatic inspection device has been developed for detecting chip components missing from or improperly positioned on printed wiring boards after the components have been attached temporarily with adhesive and then soldered. Errors are detected by illuminating the back of a mask with holes that correspond to the component locations against the board and observing light leakage. The locations of defect signals are displayed on a TV monitor and memorized as coordinates on a rectangular coordinate system that corresponds to the visual field of the TV camera to provide quantitative data on defect locations. Defect signals and external noise are recorded simultaneously for the first few frames. Succeeding frames are checked for a continuous signal to eliminate problems due to external noise. If a continuous signal is not detected, it is assumed that only noise exists. Device performance is as follows: 1) inspection time–2 s or less for boards with 500 chips or less; 2) inspection accuracy—±0.3 mm maximum. Although the simple structure of the device ensures low cost, the device is extremely effective in actual use.
Speed performance optimization in ECL gate array
Authors: Kato Shuichi , Tatsuki Makoto , Kuramitsu Yohichi , Horiba Yasutaka
Published: July 2007

In ECL circuits with multiple current paths, the delay time depends on the current distributions between the switching stage and the emitter‐follower stage. An optimum current distribution ratio exists for the load capacitance. However, in the application to the gate array, it is not possible to provide an optimum current distribution ratio for each gate. In this paper, the speed performance of the gate array is studied statistically for multiple gate groups. Also, the delay time of the ECL circuit is given as an analytical expression. As a result, the current distribution ratio optimizing the speed performance of the gate array in the ECL circuit structure is analyzed. It is found that the optimum current distribution ratio is regulated by the average load capacitance applied to the gate and the capacitance added to the collector node of the basic gate circuit. Although the ratio decreases in proportion to the increase of the average load capacitance, it does not depend on the current level of the basic gate circuit.

A gate array consisting of 900 internal gate cells with different current distribution ratios has been fabricated. The measured delay time characteristics of various basic gate circuits and the load capacitance distributions in the LSI have been combined and the distribution of the delay time has been derived. Although there is some discrepancy between the calculated and measured data for the average delay time, the measured optimum current distribution agrees very well with the calculated value. Hence, a design of mask patterns optimizing the current distribution for the speed performance has become possible.
Switching noise in josephson AC power circuits
Authors: Ohhata Masanobu , Yoshikiyo Haruo
Published: July 2007

To find a way to reduce the switching noise in Josephson gates, the circuit connecting the regulator and the gate is analyzed so that a quantitive design guideline for the noise is obtained. First, to simplify the mechanism of noise generation, the regulator and the gate are simplified. It is shown that the regulator can be approximated by grounding of the power bus and the gate by a ramp function generator. By these simplifications, the switching noise generated in the circuit connecting the regulator and the gate is analyzed and a simple approximate formula for noise voltage amplitudes is presented. Finally, a circuit is fabricated for trial and the noise is analyzed with a Josephson sampling circuit to confirm the effectiveness of the approximate formula.
Noise in an IMPATT diode oscillator with second harmonic signals
Authors: Fukushima Makoto
Published: July 2007

Multifrequency operation of IMPATT diode oscillators is important for the improvement of the oscillation efficiency of fundamental signals and for the extraction of higher‐order harmonics.

This paper proposes a method to analyze the noise characteristics of IMPATT diodes in multifrequency operations with higher‐order harmonics, and shows the calculation results.

In the analysis, a Read diode model is assumed first and the diode noise is analyzed for fundamental and second harmonic operations. Then numerical calculations are carried out to show the characteristics of the noise generated in the diode as AM and FM oscillator noise. In this numerical calculation, AM and FM noises are represented, respectively, as an N/C ratio and as a frequency fluctuation, and their variations with the amplitude and phase relation of the electric field for fundamental and second harmonic signals. Furthermore, the dependences of output power and external Q value of the oscillator on the phase of fundamental and second harmonic signals are also shown, and the optimum phase relation is described.
Study of impulsive noise characteristics in telecommunication line
Authors: Kuribayashi Masashi , Ishida Yukinori , Fujiwara Mitsugu , Ideguchi Tsuyoshi
Published: July 2007

This paper discusses the duration time rate as an evaluation measure of the impulsive (nonstationary) telecommunication line noise. The expression for the duration time rate is derived by applying the excursion probability theory of the nonstationary random process. The validity of the expression was verified by experiment. First, the non‐stationary property of the impulsive noise is demonstrated. The duration time rate for the impulsive noise is derived using the expected number of excursions, which is the solution of the excursion probability problem, as well as the expected excursion duration time. Then it is shown that the impulsive noise passed through the equalizer can be approximated by the quasi‐stationary noise, considering the frequency response of the equalizer. From a practical viewpoint, the impulsive noise before equalization is assumed as the quasi‐normal stationary noise, and the expressions are derived for the mean duration time rate and the mean error rate after equalization, using the solution of the excursion probability problem. Finally, the contact noise is considered as an example of the impulsive noise. The power spectrum and the auto‐correlation function are derived for the noise at the output of the equalizer. It is shown experimentally that the equalized impulsive noise can be considered as the quasi‐stationary noise. Numerical investigations are made for the mean duration time rate and the mean error rate derived in this paper. As a result, it is indicated that the expressions for the mean duration time rate and the mean error rate derived in this paper are useful for the evaluation of the impulsive noise.
Water propagation blocking properties of submarine optical fiber cables
Authors: Yoshizawa Nobuyuki , Ohnishi Masatoshi , Ishihara Koushi , Negishi Yukiyasu
Published: July 2007

A transit transmission system for a long‐distance digital transmission line using a submarine optical fiber cable is expected to be used at water depth of 8000 m and transit distance of 40 km. This paper introduces a fundamental design for a submarine optical‐fiber cable for deep‐sea use, which can block water propagation within the cable if it is cut accidentally on the sea bed. Evaluations of the water‐blocking properties and signal transmission characteristics of the cable are presented also. The water propagation in the cable can be approximated by the stationary laminar flow of viscous fluid in a capillary tube. The distance of the water propagated is proportional to 0.5 power of the water pressure and 0.3 to 0.5 power of time. The transmission loss of the prototype submarine optical cable (with the water propagation blocking properties) is less than 0.04 dB/km. The propagation of water within the cable is estimated to be less than 800 m per month at water depth of 8000 m. This shows that the cable has practical application.
Improvement in crystalline quality of silicon on fused silica by zone melting recrystallization
Authors: Fukami Akira , Kobayashi Yutaka
Published: July 2007

In the silicon‐on‐insulator (SOI) zonemelting crystallization method using a high‐frequency induction heating, an improvement has been examined for the crystalline quality of recrystallized silicon on a silica substrate. It is easy to obtain the (100) crystalline‐orientation by connecting island‐shaped areas with wide and short bridges (both made of polycrystal Si on a silica substrate). The (100) crystalline‐orientation can more easily be formed with a hexagon island area which has small angles to the bridge rather than a simple square. The reason can be explained by a thermal resistance during their recrystallization. When the bridge is wide and short so that its thermal resistance is small, there is an adequate thermal flow through it. This helps the recrystallization, otherwise it is supercooled. There was no subboundary in the side where the recrystallization occurred earlier, while subboundaries as crystalline defects were generally observed. This is considered to be due to the fact that the solid‐liquid boundary during the recrystallization has no significant micro irregularity. By utilizing this property, and by choosing appropriately the dimensions of the island and bridge, recrystallized Si with no subboundaries can be obtained.
Lift‐off technology for preparation of josephson junction integrated circuits using deep‐UV photoresist
Authors: Hirano Mikio , Yano Shinichiro , Yamada Hiroji , Kawabe Ushio
Published: July 2007

A new lift‐off process for a microscopic pattern formation in a Josephson junction integrated circuit has been developed using high resolution deep‐UV photoresist (MRS). The single‐layer photomask with an overhang structure suitable for a lift‐off process was fabricated using a deep UV contact exposure and development process. Using a low temperature (70°C) lift‐off process with MRS, it was possible to form a Pb‐alloy pattern with the line width and line spacing of 0.8 μm and obtain the 1.5 μm □ contact window through the SiO film.

With the new lift‐off process using MRS, experimental Pb‐alloy type Josephson junction integrated circuit chips, which were formed by 1.0 μm design rule, were fabricated. As a result, it was confirmed that this process was suitable for forming patterns with dimensions less than 1 μm. However, the remains of MRS in the lower electrode surface in the window caused the scattering of the junction currents. The remains could then be removed with a cleaning treatment of the lower electrode using ozone (O3) generated by a UV with ultrashort wavelengths.
Study of matching load on nonuniform coaxial transmission line and its application to wideband impedance transformer
Authors: Sano Seigo , Mochizuki Manabu , Muto Shinzo , Ito Chiaki , Ito Hiroshi
Published: July 2007

Two nonuniform coaxial transmission lines have been fabricated in which the primary parameters of the line vary parabol‐ically and cosinusoidally. The characteristic impedances and the matched loads have been measured and the application to a broadband impedance transformer has been studied. The results show that the characteristic impedance distribution of the nonuniform coaxial transmission line does not coincide with the nominal characteristic impedance Z0(x) but agrees with the solution Zp+ (x) of the differential equation for the impedance derived from the telegrapher's equation. It is also demonstrated experimentally that the standing wave in the transmission line vanishes completely if Zp+(l) is connected at the terminal (x = l) and, hence, this value provides an effective matched load. It is found that under this matched condition both of the nonuniform coaxial transmission line eleoents operate as an impedance transformer over an extremely wide frequency range exceeding 0.5 GHz.
Electrical properties and characterization of Al‐Nb amorphous films
Authors: Sasaki Katsutaka , Noya Atsushi , Umezawa Toshiji
Published: July 2007

To take advantage of the high resistivity and small TCR in amorphous alloys, an Al‐Nb amorphous alloy thin film was prepared by dc sputtering. The thermal aging stability of the film was investigated by the heat treatment in the atmosphere. The film surface was characterized by AEC and XPS analyses. As a result of characterization, it was found that the segregated Al atoms to surface were oxidized preferentially and that a protective oxide film was formed on the surface. The oxidized film did not grow by the heat treatment at 300°C but the structure of the alloy film prepared showed relaxation. The increase in ρ and TCR due to the structural relaxation was discussed in accordance with the electric condition mechanism of liquid alloy. Moreover, nitrogen doping into the film was attempted in order to control the structural relaxation.
Quasi‐matched‐velocity traveling‐wave‐type electrodes for light modulators and their analysis
Authors: Sanagi Minoru , Nakajima Masamitsu
Published: July 2007

To increase the bandwidth of the traveling‐wave‐type light modulator, it is necessary to decrease the difference between the velocity of the modulation wave and that of light. The velocity mismatch was improved by incorporating a buffer material with low dielectric constant between the electrodes and substrate so that the modulation efficiency does not deteriorate and the capacitance between the electrodes is minimized. Considering not only the bandwidth but also the ratio between the driving power and the bandwidth (P/Δf), three types of structures have been proposed.

For the theoretical analysis, the modulation wave traveling through the electrodes was assumed to be a TEM wave and the model of the two‐dimensional static electric field was adopted. However, since the structure was complicated, a numerical calculation was needed in which the boundary element method was used. The structure with least P/Δf ratio was chosen by using the result of the calculation. As a result of further calculation on the chosen structure with the various thickness of the buffer layer, it was found that the bandwidth is improved drastically and the ratio of P/Δf becomes small by increasing the width of the buffer layer.
Circular to rectangular waveguide mode conversion through a parabolic cylinder waveguide–TEON incident
Authors: Wada Osami , Nakajima Masamitsu
Published: July 2007

The output mode of the gyrotron used as a high‐power millimeter wave source for nuclear fusion plasma heating is the TEOn of a circular waveguide. It is desirable that this mode be converted to a linearly polarized mode such as the TEmO in a rectangular waveguide. This paper discusses mode conversion from a circular TEOn mode to rectangular waveguide modes in an oversized waveguide system in which a parabolic cylinder waveguide with its axis as a focal axis is inserted between the circular and rectangular waveguides. First, an approximate analysis is introduced based on the geometrical optics approximation by taking advantage of an oversized waveguide system. Subsequently, the mode matching method is used by expanding the fields into eigen‐modes. The results for the optimum length of the parabolic cylinder waveguide obtained by the mode matching period agreed with those from the geometrical optics approximation. Hence, to a certain extent, an estimate based on the geometrical optics is effective in the oversized waveguide system. Since no accurate eigenvalues have been reported for the parabolic cylinder waveguide, the computed results are presented.
Two–dimensional image–reconstruction method from holograms sampled by fresnel zone plates
Authors: Suzuki Yoichi , Yamashita Eikichi
Published: July 2007

The hologram of a single‐point object is called a Fresnel zone plate (FZP), and the hologram of a general object is represented as a superposition of FZP's. Since a point image can be reconstructed from the FZP at a reasonable location, there can be considered an image reconstruction method based on FZP. This paper proposes the FZP sampled hologram and the corresponding two‐dimensional image reconstruction method. The FZP sampled hologram is sampled with small interval at the central part and large interval at the periphery. By multiplying the phase function with the one‐dimensional hologram and performing the Fourier transform, the two‐dimensional image distribution can be determined for the azimuth and range. By analyzing the point‐image distribution, it is seen that the azimuth resolution of 6 mrad is obtained for the millimeter wave frequency of 35 GHz and the hologram length of 25 cm. It is seen also from the distribution that there exist side peaks of −4.8 dB at an azimuth angle of ± 11 mrad apart from the peak. An experiment was made for the millimeter‐wave holography with a simple object, and a satisfactory agreement with the theory was observed.
Substrate temperature dependence of perpendicular anisotropy for amorphous nickel ferrite films
Authors: Hiratsuka Nobuyuki
Published: July 2007

An amorphous nickel ferrite film was deposited by double source vacuum evaporation using Ni – Fe2 alloy and P2O5 sources. The film formed at the substrate temperature between 100 and 573 K showed an increase in the perpendicular anisotropy (Ku) as the substrate temperature increased. One reason for the increase in ku appeared to be due to a shape anisotropy caused by the formation of a columnar structure. Another reason seemed to be the decrease in the concentration of Fe2+ ions in the film. Specifically, since the deposited films were oxidized with an increase of the substrate temperature, the concentration of Fe2+ ions decreased and Ku increased. As the substrate temperature increased, the film became amorphous because the P2O5 content increased although the Ni/Fe ratio remained constant; P2O5 not only provided the oxygen to the NiFe2 film, but also played an important role in the formation of the amorphous state. The forementioned reaction accelerated as the substrate temperature increased. Therefore, this deposition method has been determined to be a kind of reactive evaporation technique.
Carrier conduction characteristics of si gate mnos memory device
Authors: Sato Kazuo , Hirano Kanji , Fukutomis Tsuyoshi , Misaki Hirozumi
Published: July 2007

The carrier conduction characteristics during erase and write in Si‐gate‐type MNOS memory devices with thin oxide (∼2 nm) have been investigated by comparison with the conventional Al‐gate type. As a result, it has been confirmed that as in Al‐gate type, the carrier injection between the substrate and the gate insulator is dominated by electron injection from the substrate into the gate insulator under positive gate bias, and by hole injection from the substrate into the gate insulator under negative gate bias. However, unlike in the conventional Al‐gate type, the carrier conduction mechanism in nitride for Si‐gate MNOS memory is determined by different mechanisms under positive and negative gate biases, attributed mainly to the difference in carrier injection from the gate electrode.
Lightning–surge observation using optical fiber
Authors: Kuwabara Nobuo , Koga Hiroaki , Motomitsu Tamio
Published: July 2007

This paper describes lightning‐surge characteristics induced in different terminations of subscriber paired cable due to the same lightning discharge and its measurement method using optical fibers. Lightning‐surge‐inducing mechanisms in telecommunication lines have been developed from lightning‐surge data and calculated lightning‐surge values. From the results of study, it has been clarified that: (1) lightning surges in the telecommunication line are induced mainly from the horizontal component of electromagnetic fields based on the lightning discharge; (2) lightning‐surge voltage in underground cable is almost the same value as the surge in aerial cable; and (3) lightning‐surge voltage is reduced by the metalsheath shielding effect based on the metal sheath grounding.
Characteristic of hydrogen storage of TixFe100‐x alloy thin film
Authors: Konish Ryösuke , Okasaka Yasuhiko , Imai Hiroshi , Osaki Tomoyuki , Harada Hisamochi , Sasakura Hiroshi
Published: July 2007

The dependence of amounts of absorbed hydrogen upon compositions of TixFe100‐x thin film is studied. The bonding states of these hydrogenated metal films also are investigated.

The films of various compositions were prepared by a sputtering method using face‐to‐face targets. Compositions and structures of the films were measured by XPS, x‐ray diffraction and Mössbauer spectroscopy methods.

After introduction of hydrogen into these films under the pressure 1 kg/cm2, the maximum amount of hydrogen was absorbed in Ti89Fe11 film. XPS measurements indicated that 2 p spectra of Fe and Ti shifted to the lower energy side, and the maximum shift was observed in Ti45Fe55 film. These results suggested that stable TiFe hydride was not formed in the film which absorbed the maximum amount of hydrogen, and large amounts of absorbed hydrogen were present as solid solution in the film.
Interface circuit between solar cell and commercial AC bus
Authors: Harada Koosuke , Murata Katsuaki
Published: July 2007

Since the power generated by a solar cell depends strongly on the weather condition, particularly the intensity of the solar light, these cells are usually employed in combination with secondary batteries. However, the latter has problems in maintainability and safety. Therefore it is desirable to use ac power in place of a secondary battery if the solar cells are used in general households. For such a purpose, it is necessary to insert between the solar cell and the ac power source an inexpensive interface circuit that is simple and reliable. In this paper, an interface circuit made of a voltage‐controlled variable‐frequency oscillator, an inverter and a coupling inductor is reported. With this circuit, it became possible to extract an almost maximum power from the solar cell at the varying solar intensity. The output is converted to ac and connected automatically with the commercial ac source. The operating principle and the experimental results will be reported.
Cerenkov radiation from a relativistic electron beam propagating through a circular waveguide
Authors: Tanaka Toshiyuki , Yasumoto Kiyotoshi
Published: July 2007

The problem of Cerenkov instability by the relativistic electron beam propagating along a constant static magnetic field applied in the axial direction of the slow‐wave structure with a circular cross section is analyzed based on the relativistic equation of motion for cold electrons and Maxwell's equations. As practical slow‐wave structures, a circular corrugated waveguide, a coaxial corrugated waveguide, and a dielectric loaded waveguide have been assumed. The maximum growth rates of the space charge and cyclotron Cerenkov instabilities are calculated numerically for each structure. It is found that for both instabilities, the growth rate is the maximum in the case of a corrugated coaxial waveguide in which the electron beam is propagating near the waveguide wall. In all three slow‐wave structures, the growth rate of the cyclotron Cerenkov instability can be made substantially smaller than that of the space‐charge Cerenkov instability.
Detection of faults in optical fibers by the phase compensated reflectometer
Authors: Hangai Seiichiro , Kosaka Yoshihiro , Taki Yasuo
Published: July 2007

The Fresnel reflection is influenced strongly by defects in the optical fiber. As the fiber attenuation is decreased, the Fresnel reflection becomes useful for fault detection if it is measured accurately.

This paper proves theoretically that the phase‐compensated reflectometer can be the optimum detection system of the Fresnel reflection when it is used for fiber‐defect detection. In addition, the results of computer simulations for some typical operating conditions for defect detection are shown.
Characteristics of the transient wafer temperature distribution in a furnace for semiconductor fabrication processes
Authors: Mokuya Kinji , Matsuba Ikuo , Aoshima Takaaki
Published: July 2007

In the high‐temperature process of semiconductors, the temperature distribution on the wafer surface during the procedures of the wafer insertion into and removal from the oxidation or diffusion furnace is important in determining the density of the dislocation due to the thermal stress and the uniformities of both the oxide thickness and the diffusion depth. As the size of a wafer and the density of integration increase, the analysis of the thermal transient characteristics becomes more important.

This paper analyzes the model of the temperature transient characteristics proposed previously and describes the transient characteristics on a wafer by measuring the temperature distribution en a wafer in a furnace using an infrared radiometer.

The simulation for a case where a wafer of 150 mm in diameter is inserted into a furnace at a speed of 20 cm/min indicates that the temperature variation on a wafer at every moment is as high as 150°C. This result agrees with the experimental result within an accuracy of 25°C. When the insertion speed is 100 cm/min, the temperature variation increases by 20 to 30 percent and is maintained until the wafer reaches the high‐temperature zone. This is caused by the increase in the rate of temperature change with time due to the radiation from the tube wall which is the external heat source. This tendency is more noticeable for waters located at the middle row.
Improved circular disk 3–dB hybrids
Authors: Ohta Isao , Hagino Ichiro , Kaneko Takenori
Published: July 2007

Methods of improvement on a planar‐circuit‐type 3‐dB hybrid consisting of a four‐port circular disk‐shaped resonator are proposed and described. The characteristics of a conventional circular disk hybrid are degraded gradually by higher‐order modes of the disk resonator as the ratio of the disk radius to the port width decreases, i.e., as the center frequency becomes higher. This is caused mainly by the fact that the ports arrangement is based only upon the field distribution of the fundamental (1, 1) resonant mode (dipole mode). It is important in practice to prevent the deterioration of the hybrid characteristics because of the suitability of the hybrid for application at relatively high microwave frequencies. This is due to simplicity of its structure, and a small value of the ratio is desired for broadening the bandwidth. From the foregoing viewpoint, the purpose of this paper is to improve the hybrid characteristics without loss of simplicity. Great improvement is obtained by rearrangement of the four ports upon consideration of the higher‐order resonant modes and/or addition of a capacitive stub at the circumference of the resonator. Furthermore, the bandwidth of the hybrid is broadened considerably by adding an impedance step between the resonator and each 50‐Ω coupling port. These improvements also are confirmed experimentally.
High‐frequency switching regulator controlled by magnetic amplifier
Authors: Harada Koosuke , Member Takashi Nabeshima,
Published: July 2007

By taking a forward‐type converter, the control characteristics of a switching regulator controlled by a half‐wave magnetic amplifier were analyzed using the models of the dc‐magnetizing characteristic and the reverse recovery of the diode so that the relationship between the switching frequency and the controllable region were described quantitatively. The results show that the dead angle in a magnetic amplifier can represent a function of the dynamic resistance of the core and the magnetic permeability of the core, and that this in a high‐frequency operation cannot be determined by the rectangularity alone. When the magnetic amplifier is used for a pulse‐width modulator of a converter, the reverse recovery of rectifier diodes considerably affects the control characteristic of the magnetic amplifier, limiting its maximum on‐time at the frequency above a few hundred kilohertz. By using the model of the dc‐magnetizing characteristic, the power loss of the core is represented by a function of the parameters of the core and switching frequency so that the iron loss of the magnetic amplifier is expressed quantitatively.
Electromagnetic fields excited by an electric dipole located over a conducting concave spherical surface
Authors: Sawaya Kunio , Maeda Tadahiko , Members Saburo Adachi, , Member Yasuto Mushiake,
Published: July 2007

The dome antenna has been proposed for high‐speed scanning of the main beam of the antenna in a wide‐angle range. For the design of the dome antenna, an analysis for the electromagnetic field in the concave side of the conducting sphere is indispensable. In connection with this problem, several studies have been reported on the cylindrical concave surface. However, no report is available to date on the electromagnetic field for a practical concave conducting sphere for which both the source and the observation points are removed from the boundary. This paper describes the results of analysis for this type of electromagnetic problems. First, the integral expressions for the electric field are obtained in the form of a sum of Whispering Gallery (WG) modes and a continuous spectrum. In the derivation of the field expression, spurious diffracted waves are included due to a hypothetical conical absorber, and these waves are eliminated. A scheme is implemented in which the pole contribution of the wavenumbe in the zenith angle θ so that the numerical difficulty is removed. Actual numerical calculations have been performed and the validity and range of applicability have been studied for the expression. It is found that the expression derived in this paper provides a valid field solution for the case where kα (k is the wavenumber and α is the sphere radius) is sufficiently larger than unity and is an integral multiple of π/2.
Characteristics of a‐Si films prepared by compressed magnetic field (CMF)‐magnetron sputtering
Authors: Hata Tomonobu , Kamide Yukihiro , Nakagawa Shigeki , Hattori Kouji
Published: July 2007

Iraditionally, Ar gas has been used forring. However, when a hydrogenized amourphous film is formed by reactive sputtering the disturbance of the bonding network in Si by the incorporated Ar atoms and the collision of the highly energized Ar particles to the Si substrate cause a high density defects in the film.

The compressed magnetic field magnetron sputerring system has been developed to minimize the damage to the substrate and to enable film deposition at low temperature. High‐quality a‐Si:H film has been formed by using He whose atomic radius is smaller than of Ar. In this paper, the characteris of the compressed magnetic field‐magneting sputtering system are described. The film is characterized by using the pressure of hydrogen as a parameter. over, the characteristics and thermoprotion of the film by He sputtering are computer with those of the film by Ar sputter.

As a result: (1) in case where He was the film characteristics depended higly on the partial pressure of H2 when low (<1.0 mtorr). The best film was when the partial pressure of hydroling was 0.5 mtorr; and (2) the film by He harring did not show degradation by the treatment at temperatures up to 400°C.
Energy theory on discharges of E x B type devices
Authors: Tanizuka Noboru
Published: July 2007

A systematic theory to interpret discharge phenomena generated in E x B structural discharge devices (magnetron type, PIG type, concentric quasi‐spherical type, and so forth) is developed by applying the classical magnetron theory to E x B structural systems. The transforming efficiency h, γ) from the electrostatic energy of a charged particle (mass m) in an electrode system (voltage between the electrodes VCA) to the discharge energy and the coefficient ε(η, r)/(JQVCA/r2) of the energy ε per unit time in unit volume of the discharge bulk are obtained where a device constant k = e (r2 B)2 gives the dimensionless quantity h = √m/k; γ(<1) is a ratio of the electrodes' radii, JQ is the current density at the inner electrode γr2, r2 is the outer‐electrode radius, the potential U2 is U2 = VCA/(1 ‐ r2), and B is the magnetic flux density.

The discharge occurs under the condition h2 + r2 < 1. Because 1 ‐ η is consumed for heating electrodes (raising the temperature of a device), one may select the optimum condition of h and γ for η → 1 if possible. The coefficient of ε is advantageous for γ +1, but care must be taken because it has a maximum value with the parameter h. The energy ε is related to the density and the temperature of discharge products, and the purposes of the device use.

As for experimental examples of the forementioned types of devices, considerations and comparisons with calculated results of h, γ η and ε are given.

The theory presented in this paper is useful for designing such devices as ion sources for ion beam technology, and fundamental researches on cosmic plasmas and nuclear fusion plasmas and for interpreting discharge phenomena generated in these types of devices.
Effects of heat‐treatment on dielectric properties of anodized Al‐Ta double oxide layer thin‐film capacitors
Authors: Dobashi Tsuyoshi , Umezawa Toshiji , Sasaki Katsutaka
Published: July 2007

The effect of the heat‐treatment on the dielectric properties of capacitors with the structures of Al‐Ta2O5‐Al2O3‐Al and Al‐Al2O3‐Ta2O5‐Ta were investigated. The Ta and Al films were deposited by sputtering in the Ar‐N2 gas mixture (2.5% N2 in volume) and Ar gas, respectively. The layers of Ta and Al were anodized to form Ta2O5 and Al2O3. As the treatment temperature is increased up to 200°C, the improvements on tan δ and TCC were observed. However, when the capacitors were treated at 300°C, the loss characteristic of the Al‐Ta2O5‐Al2O3 type capacitor degraded. However, the Al‐Al2O3‐Ta2O5‐ type capacitor did not show any degradation and tan δ decreased to 0.0023. To discuss the difference in the losses between the two capacitors, the devices were investigated by Auger analysis. The loss degradation in the Al‐Ta2O5‐Al2O3‐Al type capacitor was related to the nonstoichiometric interface layer between the aluminum oxide and the base metal layers, while the decrease of the loss in the Al‐Al2O3‐Ta2O5‐Ta type capacitor was due to both the recovery of the stoichiometry in the interface between the tantalum oxide and the base metal and the decrease of the metallic aluminum atoms in the aluminum oxide which degraded the stoichiometry of the aluminum oxide layer.
InP metal‐insulator‐semiconductor field‐effect transistors using vacuum‐evaporated films
Authors: Takagi Shinichi , Sugano Takuo
Published: July 2007

The characteristic of the interface between InP and an insulator was investigated using an MIS structure on an InP substrate fabricated by using vacuum‐evaporated SiO or ZnS for the gate insulator and vacuum‐evaporated aluminum for the gate electrode. An interface state density of 5 × 1011 cm−2 eV−1 was obtained from the C ‐ V characteristic of the MIS diode fabricated on an n‐type InP. Annealing at a temperature between 100 and 200°C was effective in decreasing the hysteresis and the interface state density. InP MIS FET transistors were fabricated using vacuum‐evaporated SiO and ZnS films for the gate insulator, resulting in an excellent dc FET characteristic. The effective mobilities were as high as 3100 cm−2/V.s and 1400 cm−2/V.s when SiO was used on semiinsulating and p‐type InP substrates, respectively. When ZnS was used on a semiinsulating substrate, the effective mobility was 1800 cm−2/V.s.

The mobility of the device was influenced strongly by the activation temperature of the ion‐implanted substrate. When the activation temperature was increased from 660°C to 700°C, the mobility decreased. This mobility decrease is considered to be due to Coulomb scattering in the channel.
Phase‐matched second harmonic generation of an Nd: YAG laser in a 2‐methyl‐4‐nitroaniline (MNA) single‐crystal thin‐film waveguide
Authors: Itoh Hiroshi , Hotta Kazushi , Takara Hidehiko , Sasaki Keisuke
Published: July 2007

A single‐crystal thin‐film of 2‐methyl‐4‐nitroaniline (MNA), which is an organic compound with a very large optical nonlinearity was formed on a pyrex substrate. Using the structure as a waveguide, the phase‐matched second harmonic generation (SHG) of a YAG laser (wavelength 1.064 μm) was observed. The phase‐matching was achieved utilizing the TE mode phase‐dispersion of the guided wave. This is the first report where MNA thin‐film is used as a waveguide. The conversion efficiency for SHG is estimated as approximately 0.3 percent for the input power of 10 W, waveguide‐length of 2 mm and beam diameter of 0.2 mm.
Effect of compositionally grading on DC characteristics of A1GaAs heterojunction bipolar transistors
Authors: Takano Chiaki , Taira Kenichi , Kawai Hiroji , Arai Michio
Published: July 2007

An A1GaAs bipolar transistor which is expected to be a superhigh‐speed device for the future, was fabricated by using the MOCVD technique. The dependencies of the collector current, base current, and current gain on the vertical structure, especially, A1 compositionally grading in the emitter and base, were investigated. The effective barrier height between the emitter and base was evaluated from the temperature characteristic of the collector current. The base current was evaluated from the dependence on the n value and the size. The base current is due mainly to the surface recombination current and the recombination current in the neutral base layer. The reverse injection of holes from the base is negligible. The ratio of the base current which is due to the recombination in the neutral base layer to the collector current can be decreased by grading in the base. Finally, to improve the uniformity of the collector current, the emitter should be graded and the base should be formed of GaAs.
Transport analysis of a resonant‐tunneling hot electron transistor (RHET)
Authors: Ohnishi Hiroaki , Yokoyama Naoki , Shibatomi Akihiro
Published: July 2007

Resonant‐Tunneling Hot Electron Transistors (RHETs) are expected to be an ultra‐high speed and new‐functional device. In this paper the operating principles of RHETs are analyzed and the optimization of the device structure is discussed. For the analysis of the resonant tunneling barrier at the base‐emitter, a self‐consistent method using the Schrödinger and Poisson equations is adopted. To analyze the transport properties of hot electrons in the base, the Monte Carlo method is used. The transfer ratio and device transit time are investigated. Also, a comparison is made between the calculated and measured results.
Device analysis of two‐dimensional electron gas (2DEG)FET
Authors: Usagawa Toshiyuki , Araki Nobuko Mishima
Published: July 2007

A one‐dimensional analytical model of 2DEG‐FETs has been developed in which the effect of the source‐gate resistance Rsq and velocity saturation are included. When the electron mobility μ, the electron drift peak velocity Ve, the source‐gate resistance Rsg and the AlGaAs film thickness d are varied, the corresponding transconductance gm and the conductance coefficient K are numerically studied in detail. With the present model, the device characteristics of the “MIS”‐like 2DEG‐FET with a thick n+‐GaAs cap layer and an undoped AlGaAs gate have been analyzed. From the point of application of 2DEG‐FETs to a high speed LSI, the design guideline of the device has been studied. For the device parameters of the gate length Lg = 0.2 μm, the transistor width W = 10 μm, Rsg = 15 Ω, d = 22 mm, μ = 8000 cm2/Vs and Ve = 2 × 107 cm/s, the expected device characteristics are K = 10.0 mA/V2, the sourcegate capacitance Cgs = 10.0 fF, gm = 700 mS/mm and fT = 110 GHz.
Systematic design approach for AlGaAs/GaAs HBT using two‐dimensional device simulator and circuit simulator
Authors: Honjo Kazuhiko , Madihian Mohammad , Kumashiro Shigetaka
Published: July 2007

A systematic design method for HBT's is described which is based on a two‐dimensional device simulator and a circuit simulator. The validity of this method has been studied by applying it to an AlGaAs/GaAs HBT with a base electrode sandwiched by two emitter electrodes. This structure has a performance better than that of a conventional structure. It is found that the designed values agree well with the measured results for hFE, CBE, CBC and fT. It is shown that the design accuracy of fT and CBE can be improved if the hot electron effect is introduced in the device simulator. A large signal modeling method is proposed by the circuit simulator SPICE‐F' which is modified so that the collector‐emitter offset voltage characteristic to the HBT can be expressed. By way of this new method, the bias dependence of equivalent circuit parameters of the HBT, such as fmax, fT, CBE and CBC, can be computed with good correlation with the experimental data.
Coherent backscatter‐induced noise in optical fiber gyroscopes with serrodyne modulation
Authors: Suzuki Yoichi , Yamashita Eikichi
Published: July 2007

Coherent backscattered light produces considerable noise in optical fiber gyroscopes. The noise in serrodyne‐modulated optical‐fiber gyroscopes with a low‐coherence source is studied theoretically for various forms of serrodyne‐modulation functions. The noise in output signals from the lock‐in amplifier is analyzed for the closed‐loop gyroscope. The coherent backscatter‐induced noise against the maximum phase of serrodyne‐modulation is estimated for finite flyback time or exponential ramp. It is found that the ideal serrodyne‐modulation function with the maximum phase of π and without flyback time cancels the noise in the signals of these gyroscopes.
A design theory of mode transducers utilizing coupling effects of multimode coupling system and its application
Authors: Sawa Shinnosuke
Published: July 2007

This paper considers the case where a mode transducer consisting of a multimode coupling system exists between the input and output waveguides. The former has no coupling and the latter consists of another multimode coupling system. A design theory is proposed for the mode transducer. That is, the condition is clarified for the complete power transfer from any one of the normal modes of the input waveguide to that of the outgoing waveguide, the so‐called “complete coupling condition.” As a typical example of optical circuits, we apply the present theory to the circular bend, the taper and the branch of optical waveguides, and derive the low‐loss comprising conditions, respectively. As a result, we prove that the present theory includes as a special case the low‐loss design methods proposed so far for the circular bend and taper. Further, we propose a new comprising method of the branching waveguide based on the new design theory. Numerical calculations of the mode conversion properties show that the new branching waveguide not only possesses a simpler structure, but can also achieve lower loss characteristics than the previous one.
Propagation of boundary acoustic waves along a ZnO layer between two materials
Authors: Irino Toshio , Shirosaki Yoshimasa , Shimizu Yasutaka
Published: July 2007

This paper describes the theoretical and experimental results on the propagation of boundary acoustic waves along a ZnO layer between two materials. It was proven theoretically that the boundary acoustic waves propagate in SiO2/ZnO/SiO2, SiO2/ZnO/PYREX and SiO2/ZnO/(Z – X)Si structures. The propagation velocity, electromechanical coupling coefficient K2, and the concentration of energy to the mid‐layer were calculated as a function of the ZnO film thickness. The thermal coefficient of delay time TCD was also calculated for the SiO2/ZnO/SiO2 and SiO2/ZnO/(Z – X)Si structures, showing that a certain ZnO film thickness provides zero TCD. Next, requirements of a glass substrate for propagation of boundary acoustic waves along the ZnO film sandwiched by SiO2 and glass substrate or glass film and glass substrate is discussed. As a result, as the thickness of the ZnO film and the second velocity increase, the boundary acoustic wave has a better chance to exist. Finally, the device with SiO2/ZnO/SiO2 structure was actually fabricated and it was confirmed that the boundary acoustic wave was excited and propagated in the device. If the Rayleigh wave characteristic is taken into account, the experimental and theoretical results agree.