bluuebunny/crossref_metadata_2025_split huggingface dataset:
Generation mechanism of intermodulation products in a traveling wave tube
Authors: Hirata Hitoshi , Kanai Hisashi 
Published: July 2007

AbstractTo study methods for improvement of the intermodulation product of a traveling‐wave tube which amplifies multiple frequencies, the general mechanism was investigated by a large signal analysis. the origin of the intermodulation product is in the nonlinearity of the traveling‐wave tube. Previously, the phase nonlinearity has been considered important from the discussion of polynomial expansion of the amplitude and phase transfer functions.In this paper, the relationship between the intermodulation product and the phase nonlinearity is reevaluated theoretically and experimentally for various conditions. At the same time, the modulation components of the electron beam charge density are studied as a factor related directly to the generation of the intermodulation product. As a result, it was found that the fundamental component of the charge modulation components which is in phase with the circuit wave voltage best represents the tendency of the third‐order intermodulation product.
High‐speed (20 Gb/s), low‐drive voltage (2 Vp‐p) strained InGaAsP mqw modulator/DFB laser light source
Authors: Kotaka Isamu , Sato Kenji , Wakita Koichi , Yamamoto Mitsuo , Kataoka Tomoyoshi 
Published: July 2007

AbstractThis paper describes a monolithically integrated light source module of a high‐speed/low‐driving voltage multiquantum well (MQW) optical modulator and DFB laser for 1.55‐μm applications. This paper investigates: (1) device structure suitable for growing high‐quality crystal, (2) efficient performance due to adoption of a strained InGaAsP MQW, (3) reduction of device capacitance using polyimide at the electrodes of the optical modulator, and (4) realization of a monolithically integrated module using lens coupling.In the test device, the oscillation threshold current was below 15 mA, the extinction ratio was over 20 dB when the bias voltage was −2 V, the frequency band was 15 GHz (−3 dB), and the optical power coupled to an optical fiber was 2.5 mW. Optical modulation at 15 Gb/s was carried out at a driving voltage of 1 Vp‐p. When this device was used under 2 Gb/s high‐speed modulation using a driving voltage of 2 Vp‐p for 100‐km transmission, the minimum optical power sensitivity was −23 dBm and the power penalty was 1 dB. This result indicates that this monolithically integrated optical source is suitable for large‐capacity/long‐distance optical communication.
An analysis of striplines with trapezoidal conductor cross sections
Authors: Hasegawa Tsuyoshi , Atsuki Kazuhiko , Li Keren , Yamashita Eikichi 
Published: July 2007

AbstractAs monolithic integration of the microwave circuits progresses, the microstrip line used as a fundamental transmission medium becomes extremely small in size. As the transmission line is miniaturized, it becomes necessary to consider the effect of the shape of the edges of the strip conductor in addition to the thickness. In this paper, an integral equation is derived for the charge density distribution on the strip conductor surface as the unknown. The transmission line characteristics are obtained by discretizing the integration range. Further, the effect of the trapezoidal cross section of the strip conductor formed by etching and plating on the characteristic parameters is specifically studied.
Finite‐element analysis of three‐dimensional chirowaveguides using hybrid edge/nodal elements
Authors: Maruyama Shinji , Koshiba Masanori 
Published: July 2007

AbstractA numerical approach based on the vector finite‐element method using hybrid edge/nodal elements and full components of electric or magnetic field is proposed for analysis of three‐dimensional chirowaveguides. Chiral‐loaded circular waveguides and buried circular chirowaveguides are analyzed using the present method, and then the validity and usefulness of the method are discussed based on the detailed numerical accuracy analysis.
Investigations on multicolor display by organic luminescent devices with optical microcavity structure
Authors: Nakayama Takahiro , Kakuta Atsushi , Nagae Yoshiharu 
Published: July 2007

AbstractThe emitted light of an organic electroluminescent (EL) device has a narrow half‐width in its spectrum and its intensity is high if a semitransparent mirror is placed on the light‐emitting side and the optical distance between the mirror and a metal electrode is set on the order of the emitting wavelength. This phenomenon is believed to be due to microcavity formation. This paper shows that device characteristics can be explained qualitatively by equations derived from the propagations. It is also shown that it is possible to obtain different colors from the same device material using this characteristic. The basic device structure for multicolor display will be shown. The dependence of luminescence on the detecting angle is theoretically and experimentally confirmed, and it is concluded that the device can be used for display applications.
Degradation mechanism of impregnated cathodes
Authors: Mita Nagahisa , Shimokawa Kiyoshi 
Published: July 2007

AbstractTo better understand the degradation mechanism of impregnated cathodes, chemical compositions of impregnated cathodes after extended usage were analyzed using a newly devised integral method. The results indicate that cathode degradation is caused by a decrease in Ba supply rate. This decrease is caused by an inward drift of the reaction front as the reaction between an impregnant and a tungsten substrate proceeds. It is also confirmed that the Ba supply rate is controlled by the Knudsen flow of Ba atoms.To compare cathode lives economically, a new diode tube has been designed with an anode that has a taper hole. The diode tube allowed economical measurement of cathode performance (which is almost identical to that of a traveling wave tube (TWT)). The testing of diode tubes confirms that it is possible to estimate the lives of the cathodes with various compositions by the method based on ΔT90. The methodology has been applied to identify the cathode with the longest life from four impregnated cathodes employed in satellite applications.
Computer‐generated holograms by error‐diffusion method using peano curve
Authors: Tanaka Ken'Ichi , Shimomura Teruo 
Published: July 2007

AbstractSeveral investigations on error‐diffusion methods using raster scan for computer‐generated holograms have been described in the literature. However, very little is known about the influence of the procedure applying the Peano curve to computer‐generated holograms. This is because the Peano curve has become effective in recent years in connection with related fields of application.In this paper, the error‐diffusion method using the Peano curve is discussed in detail for the improvement of reconstructed images with computer‐generated holograms. It is clarified under the limitation of area of noise and brightness of images that the error‐diffusion method using the Peano curve gives superior reconstructed images compared with that using raster scan.
Fast‐fourier transform beam‐propagation method using Fadé approximant operators
Authors: Yamauchi Junji , Shibayama Jun , Nakano Hisamatsu 
Published: July 2007

AbstractThe (1, 1) Fadé approximant operator is applied to the fast Fourier transform beam‐propagation method (FFT‐BPM). The Fadé operator for FFT‐BPM is derived, and its relation to the wide‐angle and paraxial operators is investigated. Next, the propagation error of the fundamental mode of a straight step‐index waveguide is evaluated by the mode mismatch loss. It is proved that, in contrast to the wide‐angle operator, Fadé operator does cot exhibit loss, even at small transverse grid‐widths. Finally, as an example of when transverse propagating waves cannot be neglected, the problem of fundamental mode propagation in a tilt waveguide is investigated. It is clarified that the Paé operator preserves an accuracy comparable to that of the wide‐angle operator, even if the tilt angle is widened up to 25 degrees.
A design and fabrication of millimeter‐wave microstrip antenna with monolithic microwave integrated circuits
Authors: Ohmine Hiroyuki , Matsunaga Makoto 
Published: July 2007

AbstractThis paper describes a design method in the millimeter‐wave frequency region for an aperture‐coupled microstrip antenna which unifies a feed network consisting of a monolithic microwave integrated circuit (MMIC) which affects the antenna characteristics at millimeter‐wave frequencies, the shift of the location of the radiating element which is important in actual configuration in the millimeter‐wave region, and the effect of the adhesives. Based on this design, an antenna was fabricated. A quartz substrate was used for the radiating element, while a GaAs substrate was used for the feed network. A high radiating efficiency of 87.1 percent and a wideband characteristic of 3.1 percent with VSWR < 2 were attained. As an application of this structure, a test fabrication is reported on the aperture coupled microstrip antenna in the 40‐GHz band in which an MMIC frequency converter is integrated.
Millimeter‐wave indoor high‐capacity transmission characteristics
Authors: Nakayama Yuji , Sato Akio , Yoshida Teruaki 
Published: July 2007

AbstractTo realize a high‐capacity wireless access, the millimeter‐wave frequencies have been investigated. Research on indoor multipath propagation has been pursued intensively.This paper proposes an evaluation method for the millimeter‐wave indoor high‐capacity digital transmission characteristics. First, the broadband propagation characteristics under indoor multipath environment were measured so that the multiple‐wave configurations are clarified.Next, to quantify the digital transmission characteristics under the multiple wave environment, the level ratio (D/U) of the desired wave to the interference wave was evaluated for a bit error rate of 10−4by means of a 4 PSK‐100 Mb/s and a multipath fading simulator. It was found that the bit error rate is determined by the level ratio (D/UT) of the desired wave to the total interference waves and not by the delay time of the interference wave if the delay time of the interference wave exceeds the symbol duration and that the desiredD/UTapproaches the signal‐to‐noise (S/N) ratio (N: Gaussian noise) giving such a bit error rate. From the foregoing results, this paper proposes a channel design method using theD/Uin indoor high‐capacity wireless communication.
Analysis of optical directional coupler with nonparallel transition sections
Authors: Yasumoto Kiyotoshi , Shimoyama Nobuko , Hirata Tetsuto 
Published: July 2007

AbstractTwo optical waveguides comprising a directional coupler, approach each other gradually through curved waveguide sections from the input ends where the two are sufficiently distanced with negligible coupling. After the coupling section where the two waveguides are placed in parallel, the two are separated again through curved sections to the output ends where they are sufficiently distanced with negligible coupling.In the treatment taking into account the bends of the waveguides, the optical waves propagating through the two waveguides are approximated for simplicity by a superposition of the even and odd local normal modes. The coupling between the guided modes and the radiation wave at the bends often is neglected.In this paper, the method proposed by Sawa for the analysis of the coupled mode equation taking into account the coupling between the guided modes and the radiation modes in the waveguide system including the curved sections is used for the analysis of the directional coupler including the curved sections. The coupling length and power transfer rate are computed for the directional coupler with curved sections represented by a linear function, a cosine function, and a hyperbolic tangent function. The numerical results indicate that the radiation loss is the smallest and an excellent power transfer rate can be obtained if the shape of the curved section is a hyperbolic tangent function.
An analysis of periodic waveguides by coupled‐mode theory and finite element method
Authors: Ohkawa Yuichi , Koshiba Masanori , Hirayama Koichi 
Published: July 2007

AbstractAs a simple method for evaluating the reflection and transmission characteristics of a grating waveguide, an analysis procedure is proposed and formulated that is a combination of the coupled‐mode theory and the finite‐element method. The finite‐element method is used for the determination of the coupling coefficients in the coupled‐mode equations. Therefore, the present method is capable of analyzing a grating waveguide with an arbitrary shape. In addition, the energy storage effect of the nonpropagating modes is automatically included. Specifically, an index‐modulation type grating reflector is analyzed so that the validity of the method is confirmed. Also, the present method is applied to the design of a grooved grating reflector so that its usefulness is demonstrated.
Development of a simulation technique for thin‐film transistor liquid‐crystal displays
Authors: Ohta Masuyuki , Tsumura Makoto , Ohwada Junichi , Ohida Jun 
Published: July 2007

AbstractFor active matrix liquid crystal displays (LCDs) using amorphous silicon thin‐film transistors (a‐Si TFTs), a novel simulation technique was developed. This simulation technique makes it possible to analyze accurately the fluctuation in the source voltage of the gate voltage trailing edge (feedthrough voltage) that is the main cause of image quality degradation in the TFT‐LCDs; consequently, we can accurately predict the image quality in the TFT‐LCDs. The following are the two features: (1) a‐Si TFT model considering the intrinsic capacitance which causes the dependence of the feedthrough voltage on the drain voltage is constructed; and (2) an analysis method for the gate voltage waveform distortion to calculate the difference of the feedthrough voltage between pixels depending on each pixel position in the TFT‐LCD has been extended from the analysis using an RC delay circuit to a matrix analysis using TFT matrix network. The feedthrough voltage obtained by this simulation method agrees with the measurement within 10 percent.
Tuning bandwidth enhancement in waveguide optical second‐harmonic generation device using phase‐reversed quasi‐phasematching grating
Authors: Fujimura Masatoshi , Suhara Toshiaki , Nishihara Hiroshi , Bortz M. L. , Fejer M. M. 
Published: July 2007

AbstractRecently, the conversion efficiency of waveguide quasi‐phasematched second‐harmonic generation (SHG) devices has improved rapidly so that factors other than conversion efficiency now limit the utility of these devices. One practical problem is the narrow wavelength and temperature‐acceptance bandwidths.This paper demonstrates a technique for enhancement of the bandwidths while maintaining a high SHG efficiency. The experimental results are in excellent agreement with the theoretical calculations. The technique may contribute to the practical utilization of the waveguide quasi‐phasematched frequency conversion devices.
Double‐cylindrical cavity multiple‐device structure for stabilized high‐output power combiners
Authors: Tanaka Satoshi , Nogi Shigeji , Fukui Kiyoshi , Ohshima Hideaki , Ohta Keiichi 
Published: July 2007

AbstractAs a method to overcome the moding problem by injection locking while the number of devices is increased when multiple device power combining is carried out with a cylindrical cavity, a power combiner of a double‐cavity multiple‐device configuration was proposed in which the oversized cavity with the desired mode of TMOnO(n⩾ 2) is connected by a coaxial line to a fundamental mode cavity with the same frequency of the TMOnOMode.First, by means of the modal analysis using the equivalent circuit model of the oscillator, the condition for sustaining the desired mode, the condition for suppression of the undesired mode, and the condition for existence of the double mode are obtained so that the range of stable growth of each mode is found. It was shown that the suppression of the undesired mode can be accomplished and the stable oscillation of the desired mode becomes easier by the present configuration.Further, as the oversized cavity, the TM020‐mode octuple‐device cavity and the TM030‐mode 15‐device cavity were used in the power‐combining experiments. The power‐combining efficiency of 91 and 95.8 percent was accomplished. With respect to the growth range of each mode, the theory and the experiment agreed qualitatively.
High‐frequency analysis of electromagnetic scattering due to a dielectric cylinder
Authors: Sasamori Takayuki , Uno Toru , Adachi Saburo 
Published: July 2007

AbstractAs a canonical problem to understand the electromagnetic scattering by a dielectric body, the scattering characteristics of the plane wave by an infinitely long dielectric cylinder is analyzed by a high‐frequency approximation. The rigorous solution of the scattered electromagnetic field by a circular cylinder is separated into the component scattered by the cylinder surface and the one transmitted into the interior of the cylinder by means of Watson transformation and Debye expansion. By applying appropriate high‐frequency approximations to each component, geometrical optics representations for reflection, transmission, and diffraction are provided. Especially for the diffracted field, an approximate solution more accurate than the conventional approximate solution is obtained.By UTD extended to a dielectric cylinder problem, an approximate solution in the transition region is derived which has not been derived by the conventional high‐frequency approximation. To investigate the validity of these approximate methods, the results of the analysis by the present method are compared numerically with the rigorous solutions in the frequency domain and the time domain. It is proven that the present high‐frequency approximation method is extremely accurate except near the critical scattering angle.
Sticking trouble rate on Cd‐added Ag‐based contacts
Authors: Kubono Takayoshi 
Published: July 2007

AbstractBecause the Ag‐oxide dispersed alloy‐type Ag/CdO electrical contact is supposed to have superior welding resistance, this type of contact has been used for circuit breakers designed for medium current. However, there has been no report made on the comparison between the sticking characteristics of Ag/CdO and Ag/Cd contact members.Contact members made of Ag, Ag/CdO 12 wt% and Ag/Cd 11 wt% were mounted in relays with a breaking force of 15 gf, and the ratio of sticking problems in each contact member was investigated during make‐and‐break operations of a dc 30V‐3Q resistive circuit. When the breakers were used for the make‐and‐break or break‐only operation, there was almost no sticking problem, regardless of contact material type. However, when the Ag/Cd contacts were used for make‐only operation, the sticking problem occurred in as much as 50 percent of the cases. When the Ag/CdO contacts were used for the make‐only operation, it was as high as 90 percent. When the Ag/Cd and Ag/CdO contact members were used for make‐only operation, a large pip and crater were observed on the surfaces of the electrode pairs.In addition to the experimental results described here, when the contact sticking occurred, the difference in the contact resistance values before and after the make‐only operation was evaluated. The main cause of the sticking problem was believed to be the locking between the pip and crater on the surfaces of the contact electrodes.
A built‐in self‐test structure for arithmetic execution units of VLSIs
Authors: Ikenaga Takeshi , Takahashi Jun‐Ichi 
Published: July 2007

AbstractThis paper proposes advanced built‐in self‐test (BIST) structures: a bit‐distributed pattern generator (BDPG) and a multistage space compressor (MSSC) for arithmetic execution units of VLSIs. By focusing on the regularity of the arithmetic execution units, the required area overhead of the BIST circuits is less than that of conventional ones. The experimental result shows that these structures can reduce almost 60 percent of the hardware overhead of conventional BIST circuits while maintaining high‐fault coverage. These BIST configurations will make a significant contribution to test cost reduction for the performance‐orientation digital LSIs, especially digital signal processor LSIs.
A simple model for evaluating offset error characteristics in CMOS autozeroed chopper‐type comparators
Authors: Tsukada Toshiro , Matsuura Tatsuji , Imaizumi Eiki 
Published: July 2007

AbstractA circuit technique is proposed for reducing the offset voltage due to feedthrough charges from the MOS switches in the CMOS autozeroed chopper‐type comparators. However, unavoidable offset voltages are generated if many comparators of this kind are grouped in an array for parallel operation, as is the case for flash analog‐to‐digital (A/D) converters. Using a simple model to analyze the offset generation mechanism and characteristics, simple equations are derived that give the offset errors in terms of the array current and parasitic resistances in the power supply lines. These equations are useful for comparator array design.CMOS autozeroed chopper‐type comparators are used as high‐speed comparators for such applications as flash A/D converters. These comparators have a relatively small offset error voltage due to their autozeroed operation. They occupy a small area and operate from a low power supply voltage because most of their logic circuitry is digital. However, the comparator offset voltages generated by the feedthrough charges from the MOS switches, which are used for the autozeroing (AZ), must often be reduced for implementation. The authors have developed a technique to reduce the offset voltages caused by the feedthrough charges from the AZ switches.
Substrate temperature and post‐annealing effects on perpendicular anisotropy of Ba‐ferrite films with excess iron ions
Authors: Hiratsuka Nobuyuki , Tojo Satoshi , Koshikawa Eiichi , Fujita Minoru 
Published: July 2007

AbstractIn forming barium‐ferrite films by RF magnetron sputtering, a film structure is dependent on the substrate temperature (TS) when the Fe/Ba atomic ratio in the film is between 15 and 16, i.e., the c‐axis is oriented perpendicularly to the film surface, parallel to the film surface, or it is isotropic.The deposition temperature dependence of the crystalline orientation was investigated by evaluating the crystalline phase and structure during heat treatment. The film deposited at room temperature (TS = RT) contained a large amount of Fe2+ prior to heat treatment, where Fe2+ was randomly distributed. When this film was annealed, oxygen diffused into the film and ferrite was formed at low temperatures with a c‐axis parallel to the film surface. As TS increased, the amount of Fe2+ in the film decreased and crystalline {110} FexO was formed. When this film was annealed, the temperature at which barium ferrite formation began increased and the c‐axis was isotropic. When a film was sputtered at TS = 750°C, {111} FexO was already formed in the as‐deposited film. When this film was annealed, FexO was transitionally transformed to Fe3O4, which dissolved into barium‐ferrite; the c‐axis was oriented in a direction perpendicular to the film surface.