bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of optical waveguides in soda‐lime glass by field‐assisted potassium ion migration and the index‐profile formation process
Authors: Sawa Shinnosuke , Ono Kazuo , Ryoshima Tadashi
Published: July 2007

An optical waveguide was formed by thermal diffusion or field‐assisted thermal diffusion of potassium ions (K+) into a soda‐lime glass. The refractive index profile could be estimated precisely by the diffusion equation. Assuming that the exchange between the potassium ions and the sodium ions in the glass takes place, the diffusion equation was derived. Next, the mutual diffusion coefficient was obtained by the measuring the potassium ion density profile by an x‐ray microanalyzer. Using the result, it was shown that the diffusion process of potassium ions in a glass matches the model for the diffusion equation, unlike the case of silver diffusion. In addition, it was also shown that in the case of fieldassisted thermal diffusion, the potassium density profile in the glass can be obtained by numerically solving the diffusion equation using the measured values of the diffusion coefficient and current density. Also, the refractive index profile can be obtained for an arbitrary diffusion time and temperature. This indicates that the waveguide of graded‐index through step‐index types can be fabricated by diffusing potassium ions.
Design for SMF laser diode module using thick lens
Authors: Kishimoto Ryozo , Sumida Masatoyo
Published: July 2007

This paper proposes a laser diode (LD) module using a thick lens. Its configuration and characteristics are discussed. First, to clarify a design guideline of practical accuracy required in fabrication and to establish a design method for a low‐loss LD module, a single‐mode fiber (SMF) focused beam optics using a thick lens is analyzed via the beam mode expansion method. Next, coupling experiments were carried out to prove the validity of the theory. At the same time, a low‐loss coupling system has been realized in which the coupling loss is approximately 3.8 dB. Further, the off‐axis characteristics and the off‐axis tolerance were tested for LD's, lenses and single‐mode fibers. It is found that the LD module using a thick lens can constitute a coupling system with a large off‐axis tolerance. Also, this system has a low insertion loss, and the characteristics are stable against the external variations.
Semiconductor device simulation method using boundary‐fitted curvilinear coordinates and the voronoi discretization
Authors: Tago Kazutami
Published: July 2007

A semiconductor device simulation method using boundary‐fitted curvilinear coordinates and the Voronoi discretization has been developed. In this method, arbitrary curved surfaces can be expressed exactly and easily using geometrical modeling techniques in computer graphics, while curvilinear coordinate points are generated automatically by numerically solving grid‐generation equations. The boundary conditions of the grid generation can be selected from among the following four conditions: (1) fixed boundary, (2) orthogonality, (3) smooth connection of the coordinate lines, and (4) control of concentration and intersection angles between the boundary and coordinate lines. Further, grid points can be concentrated at an arbitrary local region within the whole area. Thus, through control of the grid‐point configurations, improvements in accuracy of the calculation of the physical quantities may be achieved. In discretization of the Poisson and current continuity equations with curvilinear grids, a discretized formula as simple as in the finite difference method with the rectangular grids is developed, using the Voronoi polyhedron at each grid point as the control volume. The accuracy of current conservation is improved by more than four orders of magnitude over the ordinary boundary‐fit method. The simulation method is applied to an isolation passive MOSFET, and the solutions are confirmed to be stable under a bias of 5 V at the drain. An application to a bipolar transistor shows simulations are possible in which the impurity profiles are considered accurately.
Parallel operation of peak–current–controlled forward–type DC–DC converters
Authors: Sato Terukazu , Nakano Tadao , Harada Koosuke
Published: July 2007

The dc‐dc converter with peak‐current control has the following features, compared with the traditional type: (1) the output voltage is affected less by the input voltage variation; (2) it is easy to protect the circuit from the overcurrent due to output short‐circuit, etc.; (3) the power sharing is easy in the parallel operation of converters. Especially, the feature for the parallel operation is interesting from the viewpoint of high‐power, high‐reliability supply. However, the quantitative analysis has not been made for this property. As a typical case of parallel operation, this paper considers the parallel operation of two forward‐type converters with peak‐current control. The static and dynamic characteristics as well as the stability are analyzed for the case where the circuit is used as the constant‐voltage supply with feedback. The result of analysis agreed well with the result of experiment. The condition for power sharing is derived. The result can easily be extended to the case of N converters and provides a guideline for the design of the parallel operation.
Effect of plasma properties on the preparation of tin oxide thin film by means of DC planar magnetron plasma CVD
Authors: Fujita Hiroharu , Ueno Hironobu , Nagano Masamitsu , Matsuo Hisao
Published: July 2007

There have been many recent studies on thin‐film deposition in plasma. However, only a few reports have considered the relation between the film deposition and plasma characteristics. In this study, the influence of the plasma characteristics on the thin‐film deposition was investigated via the dc planar magnetron plasma chemical vapor deposition (CVD) technique. Assuming that the characteristics of inert gas plasma measured by probes are the same qualitatively as those of reactive gas plasma, tinoxide thin films which have been used for transparent electrodes, gas sensors, and so forth, are deposited. The decomposition of source materials is accelerated in the highdensity plasma region where the thin films deposited, are composed of highly densified particles and have a crystalline structure. The electrical conductivity of these films is higher than that of films formed in a low‐density plasma region.
Direct formation of solder bump on Al pad using ultrasonic soldering
Authors: Inaba Michihiko , Iwase Nobuo , Hirata Seiichi , Gonda Makoto , Imai Yasuhiro
Published: July 2007

Although a conventional solder bump formation on Al pad uses an evaporation of Pb and Sn on the underlying metal (Au/Cu/Cr, Au/Pt/Ti, etc.) and reflow, it has the disadvantages of high equipment cost and complex process. By applying an ultrasonic soldering technique, in this work, solder bumps were formed directly and selectively on an Al pad without underlying metal. The sample chip used in the experiment had 118 Al pads which were 1.5 μm thick and 100 μm□, and anticorrosive Sn‐37 Pb‐5 Ag was used as a solder. By examining the factors affecting the bump formation percentage, an optimum condition was selected [(1) chip preheating temperature: above 280°C; (2) solder temperature: 280°C; (3) distance between chip and ultrasonic horn: ≈︁0 mm; (4) dip time: more than 8 s; (5) ultrasonic power: more than 135 W]. Using this condition, bumps were formed without damaging the passivation film, which was also the case on 30 μm □ pads with 50 μm pitch without bridging. The bump height was approximately 36 μm on 100 μm □ pads with a variation of ±6 μm. Since the shear force of the bump was on the average 32.5 g and all the breakage occurred within the bumps, a strong adhesion at the interface is guaranteed. The interface contained a compound several 1000 Å thick with a 4 : 1 composition of Al and Ag.
Characterization of GaAs regrowth interfaces grown by metal‐organic vapor phase epitaxy
Authors: Ikeda Eiji , Hasegawa Hideki , Ohno Hideo
Published: July 2007

If epitaxial growth is interrupted to incorporate processes followed by epitaxial regrowth, the degree of freedom in device designing increases. This paper characterizes the GaAs epitaxial regrowth interface grown by metal‐organic vapor phase epitaxy (MOVPE).

Three basic regrowth processes were evaluated by C‐V carrier profiling, DLTS analysis and I‐V measurements, and the following results have been obtained:

(1) when regrowth is carried out after growth is interrupted in the furnace, carrier accumulation at the interface is observed. This is due to the transitional change of the V/III ratio and can be eliminated by proper control of the gas flow;

(2) when regrowth occurs after exposure to air for a long period of time, carrier depletion/accumulation or carrier accumulation alone is observed. This can be explained by a formation of interface energy levels which are energy‐wise continuous. The cause of the interface energy levels can be explained by our model DIGS (disorder induced gap state);

(3) when regrowth is carried out after the sample is soaked in acetone, a depletion profile due to carbon adsorption is observed.
InP LD with PD fabricated by Br2–reactive—ion–etching technique
Authors: Tsujii Hiraaki , Ohnaka Kiyoshi , Shibata Jun
Published: July 2007

It is important to monitor the optical output of a laser diode (LD) in an opto‐electric integrated circuit (OEIC). Therefore, in monolithic fabrication of an LD with a photodetector (PD), chlorine (Cl)‐based gas has been used to carry out dry etching for forming a laser facet in InP‐based materials. However, in this technique, selectivity of etching is not sufficient. In our study, Br2 was employed as the etching gas using Ti for the etching mask. Our technique can provide a selectivity of etching as high as 34 and has been found to be effective in forming a laser facet.

Using reactive ion etching (RIE) with Br2 gas, a laser facet was formed in a buried heterostructure laser diode (BHLD) with a PD. The threshold current and optical output of the LD were 35 ‐ 50 mA and 5 ‐ 10 mW, respectively, while the sensitivity of the PD was 0.49 A/W. The isolation resistance between the LD and PD was 1 Mω.

The result of this study indicates that our technique will be effective in high‐density integration of OEICs.
An integrated AlGaAs two—beam laser diode—photodiode array fabricated with reactive ion beam etching
Authors: Uchida Mamoru , Asakawa Kiyoshi , Matsumoto Shohei , Kawano Hideo
Published: July 2007

An integrated A1GaAs two‐beam laser diode‐photodiode array for optical disk applications was fabricated monolithically by the reactive ion beam etching technique. The laser cavity was formed by etched and cleaved facets. The threshold current and the external differential quantum efficiency are 18 mA and 28 percent, respectively. These parameters are as good as those of a laser with two cleaved facets. The detection efficiency of the photodetector (PD) was as high as 32.5 percent. The crosstalk due to the neighboring laser diode (LD) was minimized by forming an optical barrier between two PD and LD pairs. The cross‐talk was as low as −20 dB. In the dual cavity‐type laser using the light receiving surface of PD as the external mirror, the optical noise was lower than that in the laser without the external mirror.
Approach to high—speed operation of InGaAs/InP monolithic PIN/Amplifier
Authors: Matsuda Kenichi , Kubo Minoru , Ogura Mototsugu , Shibata Jun
Published: July 2007

We have been developing InGaAs/InP monolithic PIN/Amplifiers. This paper describes the consideration to use self‐aligned FETs with a view to improving the operating speed. To this end, the device structure and the fabrication process have first been discussed for integrating the self‐aligned JFETs and photodiodes. Next, photodiodes and FETs of this configuration have been fabricated and their characteristics evaluated. It was found that the dark current of the photodiode could be reduced to 2.7 nA at −3 V and that the cutoff frequency of the FET was improved to be 3.0 GHz. Finally, a monolithic PIN/Amplifier was fabricated. Presently, the frequency characteristics of fabricated PIN/Amplifiers are not so good. This is believed to be caused by the fact that the gate electrode of the FET is a Schottky electrode. If this problem is settled in the future, a PIN/Amplifier with a 3‐dB bandwidth of about 700 MHz can be realized.
Diffused ion concentration profiles of ion—exchanged glass optical—waveguides
Authors: Tsutsumi Kiyoshi , Mizushima Tetsuya , Hirai Hiroshi , Yuba Yoshiharu
Published: July 2007

Based on diffusion theory and results obtained by using an X‐ray microanalyzer (EPMA), the concentration profile of diffused ions in an ion‐exchanged optical waveguide was investigated. To clarify the features of the concentration profile, the concentration dependence of the diffusion coefficient was discussed. In the EPMA measurement, angle‐lapped samples were used to achieve a high resolution. First, the dependences of the diffused‐ion concentration profile on the exchange time and temperature was investigated by using diffusion theory. Then the concentration dependence of the diffusion coefficient was presented by using the calculated diffusion coefficients for some concentration profiles. Next, potassium concentration profiles were measured with an EPMA, using angle‐lapped K+ ion‐exchanged soda‐lime glass waveguides. By expressing measured concentration profiles using the normalized depth of η = x/2√τ (x: depth, τ: exchange time), it was found that the concentration profiles were much the same, regardless of the exchange time. Furthermore, by comparing the concentration dependence of the diffusion coefficient evaluated from the concentration profile, it was found that, in general, the profile was close to the Gaussian and that near the surface or in the case of zero concentration, the profile was close to a quadratic function. The concentration profile was similar to the refractive index profile obtained by the inverse WKB method.
Preparation and magnetic properties of anodic oxide magnetic films
Authors: Arai Ken Ichi , Ohoka Yohsuke , Wakui Yukio
Published: July 2007

The M‐H curve, coercive force and magnetic anisotropy of magnetic anodic oxide films containing electro‐deposited iron particles in pores were measured for the various pore diameters between 150 and 1200 Å, packing densities between 0.13 ‐ 0.48 and film thicknesses between 0.08 and 1.3 μm. As a result, it was found that the coercive force perpendicular to the film surface depends only on the pore diameter when the length of the iron particle is 15 times larger than its diameter, and that it decreases in inverse proportion to the square of the pore diameter when the pore diameter is larger than 350 Å. This indicates that the mechanism of magnetization reversal in these films follows the curling mode. The coercive force parallel to the film surface is affected by the shape of the initially deposited iron particles. The magnetic anisotropy depends strongly on the packing density of the iron particles. When the packing density is less than 0.32, the direction perpendicular to the film surface is the direction of easy magnetization. When the packing density is higher than 0.32, the direction parallel to the film surface is the direction of easy magnetization.
Analysis of reflective SAW gratings for SH‐type modes using finite‐element method
Authors: Hasegawa Koji , Koshiba Masanori
Published: July 2007

A solution based on the finite‐element method (FEM) is presented for the analysis of SH‐type surface acoustic wave gratings. Although the FEM has already been applied to the discontinuities in elastic waveguides for SH‐type modes, only the isotropic substrate has been treated. Also, it is difficult to apply the FEM directly to many discontinuities such as grating reflectors due to excessive computation time and computer memory requirements.

This paper presents a numerical approach to the analysis of SH‐type surface acoustic wave gratings on anisotropic substrates. To apply the FEM directly to many discontinuities, the substructure method is introduced. As a result, mutual interaction between surface waves and bulk waves is automatically taken into account over the entire discontinuity region. To show the validity and usefulness of this approach, examples are computed for various gratings on PZT‐4, 41° Y‐X LiNbO3, and 36° Y‐X LiTaO3 substrates.
Estimation of acoustic wave radiation from an IDT by use of effective permittivity
Authors: Hashimoto Ken‐Ya , Yamaguchi Masatsune
Published: July 2007

By means of approximate charge distribution on an interdigital transducer (IDT), it is shown that not only the electromechanical coupling coefficient k2 and the radiation conductance for the surface acoustic wave (SAW), but also the radiation conductance due to the radiation of a bulk wave from an IDT can be obtained from the effective permittivity in an analytic, though approximate, form. Next, a simple method is proposed in estimating the spurious level of the bulk wave in an SAW device by using the radiation conductances for the SAW and the bulk wave. In general, the spurious level due to the bulk wave often depends on the geometric shape. The maximum value can readily be computed by the present evaluation method. The analysis results agreed well with the experimental data on Li2B4O7 and LiTaO3 used as SAW device substrates. It is also shown that a program for deriving the effective permittivity can be developed by making use of the computer program for the SAW velocity calculations.
Multinozzle drop generator for continuous ink jet printing
Authors: Morita Naoki
Published: July 2007

Uniform, stable drop generation is the key technology for continuous ink jet printing. Previously, the method to produce the standing wave driven by the high polymer piezoelectric transducer had been utilized for acoustic excitation. However, the characteristics varied from assembly to assembly and were unstable to the environmental changes. As a new alternative approach, the Traveling‐Wave Drop Generator (TWDG) was developed in which the acoustic wave is generated in one end, and then travels to the other end of the jet array. The characteristic results showed that this generator could fully solve the forementioned problems, and it has a simplified structure.
Growth of oxide films on the surface of Cu contact and its effect on the contact resistance property
Authors: Tamai Terutaka
Published: July 2007

From the viewpoints of contact reliability for small‐sized contact components, growth processes of the oxide film on the Cu contact surface were analyzed by studying the film thickness and formation of films. This analysis of the film was conducted in detail by ellipsometry which scarcely applied to the contact phenomena, in combination with an electrochemical reduction method. Moreover, the effect of the growth of the film on the contact resistance property was studied. As a result, in the oxidation by heating in air, Cu2O film grows mainly at the initial stage of the film growth. As the film grows around 1000 Å, CuO appears on the surface of Cu2O.

In this stage, the contact resistance increases sharply and contact failure occurs. Furthermore, it was found that the velocity of growth of the film is slowed which corresponds Co each stage of the oxidation: the initial, the middle, and the latter stage. By application of ellipsometry to the analysis of the contact surface, the measurement of the film thickness together with the possibility of discrimination for the formation of the film by using changes of the optical constants of the film were clarified.
Frequency stabilization of a semiconductor laser under modulation
Authors: Sato Takashi , Koizumi Shungo , Saito Toshinori , Shimba Minoru
Published: July 2007

The laser oscillation frequency of a semiconductor laser becomes unstable under modulation. The stability of the frequency stabilization method using the atomic absorption line is degraded by the oscillation spectrum broadening caused by the sidebands under modulation. Therefore, we designed two methods, the synchronous detection method and the peak‐hold method, to improve the frequency stability under modulation.

From the experiment using the Rb absorption line, the synchronous detection method improved the stability by 3 times compared with the old method. The peak‐hold method improved the stability by 10 times compared with the old method under modulation and by 2 times compared with the old method without modulation.
A synthesis of reduced ripple switched‐capacitor current sources and their applications
Authors: Hyogo Akira , Sekine Keitaro
Published: July 2007

Although the circuit in the conventional switched capacitor (SC) current source (SCCS) is extremely simple, the output current ripple incresaes if the input frequency is reduced. This paper proposes a new reduced ripple SC current source (RRSCCS) in which an integrator circuit is added to the conventional circuit to reduce the ripple. The output current from the proposed circuit can be determined by the voltage, frequency and capacitance as in the conventional circuit. In addition, no current ripple occurs theoretically in the new circuit. As examples of applications, a frequency‐controlled voltage source (FCVS) and a current source proportional to the square of the frequency (F2CCS) are constructed. In the present FCVS, the output voltage can be made proportional to or inversely proportional to the frequency depending on the input frequency and the control frequency. Since the output voltage is determined by the capacitance ratio, frequency ratio and voltage, it is of high precision. Next, it is shown that the present F2CCS is useful for linear control of gm of the MOS‐type OTA. Good results have been obtained by experiments using individual components.
Effects of the cell structure on ZnS:Mn El characteristics
Authors: Abe Yoshio , Fuyama Moriaki , Onisawa Ken'ichi , Ono Yoshimasa A.
Published: July 2007

This paper discusses electroluminescent (EL) characteristics of ZnS : Mn orange‐yellow EL cells. By measuring charage density within the EL cell by means of the Sawyer‐Tower circuit, the dependence of EL characteristics on insulating layer thickness and active layer thickness was determined. Clamp voltage of EL cells estimated from the bend point in the charge density‐voltage characteristic curve was in good agreement with the threshold voltage. It was found that below the clamp voltage, it was possible to treat active layer as an insulator. By decreasing the insulating layer thickness and thus increasing the insulating layer capacitance, we found the following: (1) the voltage of the insulating layer decreased and the clamp voltage decreased; (2) at the same time, the drive voltage margin defined by the difference between the breakdown voltage and the clamp voltage decreased. When the active layer thickness was decreased, the active layer voltage decreased and the insulating layer voltage increased. Furthermore, in the EL cell where the insulating layer capacitance per unit area was 10 nF/cm2, the clamp voltage became smallest when the active layer thickness was taken to be approximately equal to 0.3 μm. Based on these results, an experimental formula was obtained which describes the relation among the clamp voltage, the insulating layer capacitance, and the active layer thickness.
Analysis of soliton pulse propagation in an optical fiber using the finite‐element method
Authors: Eguchi Masashi , Hayata Kazuya , Koshiba Masanori
Published: July 2007

Soliton is one of the key concepts that will support future optical communications with a capability for large‐capacity, longdistance transmission systems. In general, the propagation of soliton pulses in an optical fiber is described by the perturbed nonlinear Schrödinger equation (PNLSE). Without any perturbation, this equation is reduced to the canonical nonlinear Schrödinger equation (NLSE) and can be solved analytically. However, in an attempt to take into account a variety of perturbations such as higher‐order dispersion, nonlinear dispersion, shock effect, induced Raman scattering, dissipation, etc., it is no longer solvable in an analytical fashion.

This paper proposes a useful method based on the finite‐element method to carry out systematically the evolutional analysis that includes these perturbations. This method can easily deal with cases with realistic perturbations. To confirm the validity of this approach, it is applied to solving unperturbed cases, and it is shown that the same results as those using other solution methods are obtained.
Electrical control of laser beam in viscoelastic polymer thin‐film waveguide
Authors: Muto Shinzo , Takauchi Toshimasa , Murakami Michimasa , Ito Hiroshi
Published: July 2007

A thin‐film optical waveguide made of a viscoelastic polymer to which an electric voltage can be applied has been fabricated. Also fabricated is an active thin‐film waveguide device doped with laser dye. Laser light propagation in these devices and the possibilities of electrical control have been studied. It is found that the transmission coefficient of the waveguide and the oscillation wavelength of the thin‐film DFB dye laser can be controlled electrically to a certain extent, although the response is slow.
Uniform asymptotic analysis of guided modes in diffused slab waveguides with polynomial refractive‐index profiles
Authors: Yata Akira , Ikuno Hiroyoshi
Published: July 2007

The propagation constant and the field distribution of the guided modes in a diffused slab waveguide with an inhomogeneous refractive index profile are analyzed by means of the uniform asymptotic series. We used the Airy differential equation as the reference equation to which the Langer transform and the Liouville transform are used repeatedly to construct a uniform asymptotic series solution. If this recursive algorithm is used, an asymptotic solution of an arbitrary approximate degree can be obtained. This uniform asymptotic series solution can be represented analytically by the expansion coefficients of the polynomial approximating the refractive index profile.

The propagation characteristics of the guided modes in a diffused waveguide with an index of refraction expressed in terms of an exponential function or an error function are studied and convergence and accuracy of the uniform asymptotic series solution are investigated. The numerical results confirm that the uniform asymptotic series solution agrees well with the rigorous solution or the numerical solution. The propagation characteristics of the guided modes in a diffused waveguide with an exponential refractive index profile have been found with high accuracy. The determination of the propagating modal index is discussed.
An examination of the lateral mode control of the laser diode
Authors: Shirae Hisazumi , Matsuhara Masanori
Published: July 2007

To avoid the high light output power density which has become the problem of the high‐power laser diode, the light power is assumed to be distributed uniformly. However, the disadvantage is that the laser is apt to operate in higher‐order modes in this case. For optical communications use, the laser must operate in a single fundamental mode. This paper aims at obtaining the single fundamental lateral mode, controlling the modes of an index guided semiconductor laser diode together with the investigations of its theoretic results. The finite element method based on Galerkin's method is used for the analysis presented here. In numerical calulations, we take the broad area laser and the array laser as examples for discussions starting from the modal gain. As a result, it is shown that placing high gain in the middle part of the laser diode cross section is effective for the single fundamental lateral mode operation.
Analysis and operating characteristics of micro gas–flow sensor using magnetic fluid
Authors: Oka Hideo , Biringer Paul P.
Published: July 2007

Presently, the thermal method and the area method are used in practice for measurement of a gas flow of infinitesimal quantity. However, in terms of output format and the response characteristics, several problems exist. To resolve these problems, we have conceived and fabricated a micro gas‐flow sensor that provides the output in an electrical signal format by means of a magnetic fluid with a fast response and has a simple configuration. This paper presents the analysis of operation and the basic characteristics of the sensor. It is found that the gas flow can be derived as a constant multiple of the product of the period and the maximum amplitude of the output signal of the micro gas‐flow sensor.
Planar‐type photosensor with SiN/a‐Si: H double layers
Authors: Kitagawa Masatoshi , Miyauchi Michihiro , Hirao Takashi
Published: July 2007

It is proposed that an a‐Si:H/SiN double‐layer device is promising which has a thin SiN layer between the planar electrode and a‐Si:H so that the deficiency of the slow optical response is improved while the advantage of a high‐optical sensitivity and the easy fabrication process of the planar photoconductor device are retained. A study was carried out for the amount of PH3 inclusion with respect to SiH4 in the a‐Si:H deposition and the SiN film thickness.

By using a double layer of a‐Si:H and SiN, a planar photosensor was realized which has an extinction ratio of more than two orders of magnitude (about 50 dB) and a photocurrent of more than 100 nA with an optical illumination of 150 lx. The optical response speed was more than five times that in a conventional a‐Si:H planar sensor.

By varying the SiN film thickness, the threshold voltage of the photocurrent can be changed. The threshold value increased as the SiN film thickness is increased. As the PH3 concentration was increased, both the photocurrent and the dark current increased while the optical response speed decreased. The spectral sensitivity was similar to that in a conventional a‐Si:H planar sensor. Hence, no advantage of the photosensor using a‐Si:H was lost.
Analysis of slot antennas on a rectangular conducting box by using the fourier series expansion and galerkin's method
Authors: Fujino Yoshiyuki , Sawaya Kunio , Adachi Saburo
Published: July 2007

Solution of the problem of scattering from a rectangular conducting box is important in the cases where the scattering characteristics from buildings must be estimated and where an antenna attached to a portable telephone is designed. Especially, a magnetic source antenna that can be built in a portable telephone has recently been proposed so that the importance of the analysis of antennas placed near a conducting box has increased. However, to date, no analytical results sufficiently valid for these antennas have been available.

In this paper, an analysis technique for the antenna system near a three‐dimensional conducting box is developed. It describes the procedure to derive the impedance matrix using the Fourier series expansion and Galerkin's method as well as the method to introduce the continuity condition of the surface current on each side of the rectangular body. As an example, the present method is applied to a slot antenna located on a surface of a rectangular box and the input admittance and the radiation pattern are analyzed. Through comparison with the experimental results, the validity of the present method is confirmed.
Scattering of electromagnetic plane waves by an inclined parallel strip grating
Authors: Shimoda Michinari , Itakura Tokuya
Published: July 2007

The two‐dimensional scattering problem of electromagnetic wave by an inclined parallel strip grating with a periodic structure is analyzed by means of the formulation using the mutual field. A formulation is presented for the analysis of multiple scattering by a strip system with a periodic structure by means of the representation of the scattered field by one strip. The Wiener‐Hopf equations to be satisfied by each scattered field and the representation of scattered waves based on the solution to these equations are obtained. Since the width of the strip in the grating is finite, it is difficult to carry out rigorously the decomposition in the solution of the Wiener‐Hopf equations.

The sampling theorem is used for expansion of the unknown function corresponding to the surface current on the strip into a series so that the Wiener‐Hopf equations are reduced to a set of simultaneous equations. In this procedure, the numerical analysis can be carried out independently of the Wood anomaly frequencies and the resonant frequencies between the strips.

For evaluation of convergence and errors in the results, the relative error with respect to the extrapolated value and the square error for satisfaction of the boundary condition are computed numerically. The numerical results for the power transmission coefficient by the present method are compared with those by other methods.
Nonradiative dielectric waveguide circuit components using beam‐lead diodes
Authors: Kuroki Futoshi , Yoneyama Tsukasa
Published: July 2007

The nonradiative dielectric waveguide (NRD guide) which has low loss and no radiation at the bends and discontinuities is suitable for millimeter‐wave integrated circuits. In this paper, the NRD guide circuit components using beam‐lead diodes are studied in the 35‐GHz range.

The diode mount proposed in this paper consists of a patch antenna and an RF choke etched together on a thin Teflon substrate. A beam‐lead diode is mounted on this structure and the substrate is inserted transversely in the dielectric waveguide. Since this mount has a compact and rigid structure and can be fabricated only by etching, no fabrication difficulty is expected at higher frequencies.

A simple matching technique, which uses a thin high‐permittivity sheet and an air gap provided in the dielectric strip, is developed. The performance of a Schottky‐barrier diode detector, a balanced mixer, and a PIN diode pulse modulator were found to be quite excellent.
Gas‐sensor characteristics of SnO2 film
Authors: Matsubara Chihiro , Furukawa Kimihiko , Taketoshi Osamu , Konishi Ryōsuke , Sasakura Hiroshi
Published: July 2007

A recent study of the gas sensor device has been aimed at the improvement of gas selectivity and gas distinction. In the present study, to distinguish the kind of gas, three kinds of SnO2 thin films with different resistivities were deposited on glass substrates by vacuum evaporation to evaluate the changes of resistivity and work function due to hydrogen and oxygen in a vacuum system. As a result, it was found that oxygen acts differently in vacuum than in atmosphere.

From the results of these experiments by XPS and XRD, a model of oxygen and hydrogen adsorption was proposed. In hydrogen adsorption, the model of carrier release is adequate and in oxygen adsorption, the model of mobility increase is adequate.
Yasuura method for solving two‐dimensional scattering problems. (I) theory
Authors: Okuno Yoichi , Ikuno Hiroyoshi
Published: July 2007

We describe the theory and algorithm of the Yasuura methods (a conventional mode‐matching method, the mode‐matching method with a smoothing procedure, the mode‐matching method with a singular‐smoothed procedure) for solving the problems of scattering by perfectly conducting cylindrical obstacles. Both the E‐wave and the H‐wave are considered. Two types of scatterers with either smooth or edged contour are treated. After formulating the problem, we explain the methods of solution with the proof of convergence. All the methods are reduced to a canonical form of the least‐squares problem. Some remarks on actual numerical computations are also included.
Precise calculation of space‐potential with the boundary of electron gun‐type
Authors: Kajiyama Yoshino
Published: July 2007

The space potential for a given boundary condition is obtained, in general, by digital simulation. In the case of an electron‐gun‐type boundary with sharp edges, confirmation of the numerical accuracy is not straightforward as singular electric field points are contained. In this paper, an accurate computation algorithm is proposed for such cases based on the Green's function method.

When the computed values were compared with those by the simulation method, it was found that the present method can arrive at a high‐precision solution in a shorter period of time. In general, the analytical solution of a three‐dimensional boundary value problem containing sharp edges contain function series terms with poor convergence. Hence, the conventional acceleration method is not very effective.

This paper obtains a convergence criterion suitable for the nature of the analytical solution and a significant reduction in computational time. From the nature of the basic computation equation, accuracy can be improved easily by an appropriate discretization of the numerical integral. The present method is effective for high‐precision computation of the weak electric field near the cathode. In the aberration analysis of a cathode lens, this method can be used as an effective comparison when the accuracy of the solution by the simulation is confirmed.
Noise characteristics of Er3+‐doped fiber amplifiers pumped by laser diodes
Authors: Yamada Makoto , Shimizu Makoto , Horiguchi Masaharu , Okayasu Masanobu , Sugita Etsuji
Published: July 2007

The noise characteristics of the Er3+‐doped optical fiber amplifier pumped by laser diodes (LD) at 0.98 μm and 1.48 μm are theoretically and experimentally studied. The noise figures of the optical fiber amplifiers pumped by a 0.98–μm band LD and a 1.48–μm band LD estimated from the beat noise between the signal noise and the spontaneous emission were 3.2 and 4.1 dB. It was found that the beat noise between spontaneous emissions and the shot noise of the spontaneous emission were smaller in the 0.98 μm‐band LD than in the 1.48–μm band LD. From these results, it was found that the optical fiber amplifier pumped by the 0.98–μm band LD has lower noise characteristics than those of the amplifier pumped by the 1.48 μm band LD.

Further, the signal gain dependence, fiber length dependence and signal wavelength dependence of each noise component were studied. When the signal gain is kept constant, each noise component is not dependent on the fiber length and can be reduced monotonically by increasing the signal gain. When the wavelength deviates from the signal wavelength giving the maximum signal gain, the beat noise between the spontaneous emissions and the shot noise of the spontaneous emission increase.
New approach of adaptive automatic load shedding
Authors: Terzija V. V. , Koglin H.‐J.
Published: July 2007

In the paper a new approach of adaptive automatic load shedding, a procedure for protecting electric power systems from dynamic instability and frequency collapse is presented. It is consisted of two main stages. In the first stage the frequency and the rate of its change are estimated by nonrecursive Newton type algorithm and least error squares method. In the second stage the magnitude of disturbance, i.e. the difference between the generated and the consumed active power is estimated by applying the simplest form of generator swing equation. Results of multimachine test system computer simulations are presented.
Evaluation of the adaptive behaviour of an artificial neural network controller for a hybrid power compensator
Authors: Van Schoor G. , van Wyk J. D. , Shaw I. S.
Published: July 2007

An artificial neural network (ANN) is used to optimally control a hybrid power compensator (HPC) consisting of a static VAR compensator (SVC) and a dynamic compensator (DC) during the compensation of nonlinear loads. The HPC must be controlled to meet minimum requirements in terms of power factor and harmonic distortion, while at the same time minimising its total cost. The ability of the ANN to adapt its output when subjected to a dynamic power system environment to achieve the above, is evaluated. The power system dynamics in this paper constitute line impedance changes and changes in the load conditions of other consumers coupled to the same network. A state space model of the power distribution network together with the HPC forms the basis of evaluation of the mentioned controller. The results obtained reveal that the ANN can meaningfully adapt its output to optimise the HPC performance.
New approach to standing phase angle reduction for power system restoration
Authors: Ketabi A. , Ranjbar A. M. , Feuillet R.
Published: July 2007

During power system restoration, it is necessary to check the phase angle between two buses before closing circuit breakers to connect a line between them. These angles may occur across a tie line between two systems or between two connected subsystems within a system. In case of large Standing Phase Angle (SPA) difference the synchro‐check relay does not allow closing of the breaker for this line. Therefore, this excessive SPA has to be reduced before attempting to connect the line. In this paper a new and fast method for reducing SPA is presented. For this purpose, the standing phase angle difference between two specific buses is represented in terms of sensitivity factors associated with the change in active power generations and consumption at the buses. Then, the proposed method reschedule generation of selected units or shed load of selected buses to reduce excessive SPA difference between two buses based on sensitivity factors.
The dynamic voltage/current characteristics of vacuum arcs after breakdown at currents in the lower kHz‐range
Authors: Hardt N. , Heimbach M. , Böhme H. , Gentsch D.
Published: July 2007

A test set‐up is presented which is able to measure the arc voltage of vacuum interrupters after breakdown with currents in the lower kHz‐range. Arc voltage measurements from this set‐up are presented. The obtained dynamic voltage/current characteristics are discussed and compared to the known voltage current characteristic of a power frequency arc in vacuum. A simple vacuum arc model is presented describing the voltage current characteristic. The model is applied to assess the energy dissipation in the arc.
Effects of toroidal HVDC ground electrode on earth‐return circuits
Authors: Machczyński W.
Published: July 2007

This paper presents a method of evaluation of currents and potentials, excited by conductive effects of high‐voltage direct‐current (HVDC) transmission system, along two parallel earth‐return circuits such as pipelines and cables buried in the vicinity of a toroidal ground electrode. It is assumed that the system considered is linear and that the earth is an isotropic, homogeneous medium of finite conductivity. Conductive coupling between earth‐return circuits is taken into account, whereas the reaction of the conductors' currents on the electrode current is disregarded. The transmission line model of the conductor with earth‐return, a segmental linear approximation of the curve of the primary earth potential distribution along the conductor and the concept of superposition have been used in the method. It should be pointed out, that the method does not require the time consuming numerical integration. The technical applications of the method are illustrated by examples.
A methodology for optimal planning of capacitor installments in deregulated distribution networks
Authors: Rajakovic N. , Drca R. , Arsenijevic N.
Published: July 2007

In this paper methodology for optimal planning of capacitor installments in deregulated distribution networks is presented. The improvements are performed by using heuristics in practical consideration, reducing the number of combinations in a special division search technique. Deregulation aspects are carefully included in modeling of annual costs. It appears that importance of energy costs versus costs of the yearly peak power increases in a deregulated environment.
Core loss estimation in three‐phase transformer using vector hysteresis model and classical loss model incorporated in 2D magnetodynamics
Authors: Deblecker O. , Lobry J. , Broche C.
Published: July 2007

This paper deals with the computation of the magnetic field and core loss in a three‐phase three‐limb transformer at no‐load. The computational algorithm consists of the vector hysteresis model incorporated in 2D magneto‐dynamics via the differential reluctivity tensor. The hysteretic nonlinearity is handled by a simple iteration scheme. The eddy‐current losses in the laminated steel core are accounted for by considering an additional conductivity matrix in the FE equations. The magnetisation‐dependant vector Preisach model with an analytical expression for the distribution function is adopted for describing the hysteretic constitutive law in the rolling and transverse directions of the laminations. The parameters and mean field term are fitted on the basis of a set of BH‐symmetric (quasistatic) loops. Numerical results are presented that confirm the effectiveness of the proposed method for the no‐load simulation of the transformer in the transient and the steady‐states.
An efficient methodology for security assessment of power systems based on distributed optimal power flow
Authors: Hur D. , Park J.‐K. , Kim B. H.
Published: July 2007

This paper presents an algorithm for the parallel solution of the security constrained optimal power flow (SCOPF) problem in a decentralized framework, consisting of regions, using a price‐based mechanism that models each region as an economic unit. We first solve the distributed optimal power flow (OPF) problem to determine the maximum secure simultaneous transfer capability of each tie‐line between adjacent regions by taking only the security constraints imposed on the tie‐lines into account. In this paper, the line outage distribution factors (LODF) calculated at the current state are used to formulate the appended constraints. Once the secure transfer capability of each tie‐line is determined, the intra‐regional SCOPF is performed using the conventional linear programming (LP) approach. A description on the inclusion of security constraints with distributed OPF algorithm will be given, followed by the case study for Korea Electric Power System.
Novel modelling of residual operating time of transformer oil
Authors: Wahab M. A. A. , Hamada M. M. , Zeitoun A. G. , Ismail G.
Published: July 2007

This paper presents techniques developed to accurately model the characteristics of transformer oil for the purpose of predicting the effect of aging on these characteristics. Aging causes some of the transformer oil characteristics to violate the internationally specified limits. The purpose of this simulation is to develop alternative techniques to predict the operating time after which these characteristics would violate the limits. The results obtained from monitoring of twenty in‐service power transformers for long period of operating time up to ten years have been implemented in developing the proposed models. The physical, chemical and electrical characteristics have been determined periodically by internationally specified testing methods. The patterns of violation sequence of the standard limits, against operating time, by different transformer oil characteristics have been revealed and the most common pattern has been determined. The definition of residual operating time (trot) of the different transformer oil characteristics has been introduced. The choice of transformer oil breakdown voltage trot to represent that of the transformer oil characteristics has been justified. Modelling of trot as a function of transformer oil breakdown voltage, total acidity and water content by multiple‐linear regression has been proposed and verified. Also, polynomial regression model of trot as a function only of transformer oil breakdown voltage has been given. The accuracy and applicability of these models and the different modelling techniques have been discussed and proved.