bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of miniaturized dielectric duplexer with attenuation poles
Authors: Matsumoto Haruo , Nishikawa Toshio 
Published: July 2007

AbstractA design method is conceived for a miniaturized antenna duplexer with attenuation poles. Its effect is indicated by using it as an antenna duplexer for the 800‐MHz portable telephone. The transmitting filter has a band‐rejection filter characteristic of an elliptic function type while the receiving filter has a Chebyshev bandpass filter with attenuation poles. Previously, the design of these filters has been carried out by an optimum design using an iterative approximation from an initial design value. Hence, a large amount of computation time was required.This paper proposes a design method without an iterative approximation. In the transmission filter, resonators with a low characteristic impedance are used. In the conventional band‐rejection filter design of an elliptic function type, the linearity of the reactance slope of the resonators is degraded and the insertion loss near the passband edge increases. A method of compensating for this increase is presented. In the receiving filter, the design equation for the conventional Chebyshev characteristic was modified. It is shown that a bandpass filter characteristic with attenuation poles can easily be designed. A branching circuit is added to these filters, and an antenna duplexer is constructed with a minimum number of components by the circuit transformation. The computed values of the filter characteristic agreed well with the actual example. In comparison with the optimization method based on the iterative approximation, the amount of computation for the design was about one‐twentieth.
Computer numerical analysis of the high‐speed performance of a two‐phase schottky barrier CCD with a metal shielding layer
Authors: Yonei Kenji , Omoto Osamu 
Published: July 2007

AbstractA two‐phase Schottky barrier CCD structure with a metal shielding layer that is designed to be a highspeed transfer device is described, and its performance is numerically analyzed in order to estimate its characteristics. The proposed CCD is a device structure electrically shielded by the metal layer so that the clock pulse applied voltage at the transfer electrode does not influence the external circuit, thus making it suitable for three‐dimensional ICs. The transfer electrodes are formed by arranging 1‐bit, four‐metal electrodes alternately in narrow gaps and wide gaps. The transfer electrodes are driven by a sawtooth pulse voltage, and the charge is transferred between two wide gap regions. In order to theoretically analyze the charge transfer phenomenon and to clarify the high‐speed characteristics, a two‐dimensional computer simulation using the Schottky‐Read‐Hall model and the dependence of electric field on drift velocity is developed. The charge transfer is produced by a potential well moving in the charge transfer direction in the initial period of the charge transfer process and is done by the drift current in a high electric field in the final period. The clock frequency is 3 GHz in the Si‐CCD and 8 GHz in the GaAs‐CCD for an applied voltage of 3.5 V and a charge transfer efficiency of 99.99 percent at a bit length of 4 m̈m.
Use of a finite difference time‐domain method to analyze thin‐film microstrip lines with conductor loss
Authors: Kitamura Toshiaki , Hira Masafumi , Kurazono Sadao 
Published: July 2007

AbstractThin‐film microstrip lines have been proposed in which microwave transmission lines and circuit elements are placed between or on the metal and insulating layered films on a GaAs substrate. These configurations are intended for size reduction of microwave circuits, realization of new circuit topologies, and improvement of design capability. On the other hand, the finite difference time‐domain method has attracted attention as one of the general‐purpose analysis methods for three‐dimensional configurations. It has been demonstrated that this method is capable of analyzing substantially complex geometry.However, in the conventional finite difference time‐domain method, the conductors usually are treated as perfect and infinitely thin metals. Hence, the conventional method cannot be applied to the thin‐film microstrip lines in which the conductor thickness cannot be neglected in comparison with the transmission line dimensions.In the present study, the conductor thickness is taken into consideration and the formulation is carried out including the conductor loss. In the conductor, the discretization spacing is made sufficiently smaller than the conductor thickness while the discretization step is made larger where the field variation is gradual. In this way, the main storage capacity needed is reduced and the computation time is shortened.Thin‐film microstrip lines of several shapes are analyzed and the frequency characteristics of the transmission line parameters, the electromagnetic field distributions and the Poynting power distribution are derived. Thus, the validity of the method and its range of applications are shown.
Image reconstruction in optical frequency‐domain reflectometry by means of maximum entropy method—fourier transform combination
Authors: Yoshizawa Akio , Iwasaki Takashi 
Published: July 2007

AbstractIn the optical frequency domain reflectometry (OFDR), if the Fourier transform is used for image reconstruction, degradation such as a spread of width in the image for an isolated reflection point occurs due to the fact that the frequency sweep range is finite and the sampling spacing is disturbed. On the other hand, it is known that the reflection position resolution can be improved in a nonlinear spectral estimation method such as the maximum entropy method, whereas it is difficult to measure the intensity of reflection.In this paper, a new image reconstruction method is proposed in which the position (distance) resolution is improved by the maximum entropy method while the spectral intensity is determined by the Fourier transform. The method is compared with the image reconstruction by the conventional Fourier transform. If “detection and measurement of several isolated reflection points” are the objective, the image degradation can substantially be alleviated and the location of reflection and reflection intensity can be measured accurately. Also, an optical reflectometer is constructed and experiments of reflection measurement are carried out so that the effectiveness of the proposed “combination method” is confirmed.
Estimation of a phase‐recording characteristic of system for synthesizing a kinoform
Authors: Akahori Hiroshi , Seik Yasuo 
Published: July 2007

AbstractTo satisfy the phase matching condition in the formation of a kinoform, it is necessary to understand the phase‐recording characteristics of the formation system. This paper proposes a method for estimating the phase‐recording characteristics by first recovering the phase actually recorded from the reconstructed image intensity distribution of the kinoform by means of the iterative algorithm by Gerchberg‐Saxton and comparing this with the phase to be recorded. The validity of the solution obtained by this iterative algorithm is investigated and a method is provided for the initial solution which can be converged to a global solution.A computer simulation for this method is carried out. It is shown that there is possibility of estimating the characteristics even if a Gaussian error with a 20‐percent standard deviation of the true values is contained in the reconstructed image intensity data. Also, from an optical experiment, the phase‐recording characteristics of the kinoform formation system with photographic emulsions actually are estimated.Next, kinoforms are formed in the cases with and without phase corrections based on the estimated characteristics. By comparison of these reconstructed images, the effectiveness of the phase correction and the validity of the estimated results are evaluated.
Sense junction response in a capacitively coupled josephson memory cell
Authors: Suzuki Hideo , Imamura Takeshi , Hasuo Shinya 
Published: July 2007

AbstractPreviously, a capacitively coupled Josephson memory cell was proposed in which an rf‐SQUID device couples capacitively with a single junction. Binary data stored in an rf‐SQUID device can be read through a flux change which generates a pulse signal to be detected. The pulse has a very narrow width, i.e., an order of picoseconds. The current would be different in the time before and after the pulse is applied, which is superimposed by an oscillating current after the application of a pulse. The bias current margin of the memory cell is determined by the way in which a memory is read by using such a pulse. When a memory cell of Josephson junction devices is used, the bias current margin of a sense junction would govern the overall margin of the memory circuit. This bias current margin must be made large for the present study. Therefore, by assuming the read mode of a capacitively coupled memory cell, the response of a single junction has been studied for a very narrow‐width pulse current which varies with fluxons.The minimum pulsewidth and amplitude required to switch a junction and a bias current dependence before and after the pulse is applied are calculated analytically on the basis of the coupling energy reported by Dong and Van Duzer [18]. The relation between a minimum pulse‐width and amplitude and a switching time for a sense junction, which cannot be solved analytically, is calculated by computer simulation. Further, the influence of a sinusoidal current superimposed over a bias current also is studied by computer simulation.
A parametric current sensor with feedback loop
Authors: Kutsukake Hiroshi , Tanno Yorimoto , Ichikawa Jun‐Ichi 
Published: July 2007

AbstractThis paper considers a sensor for detecting currents from dc to high frequency without disturbing the circuit current through contact. The current sensor is based on the phenomenon of parametric oscillation and uses the fact that the parametric oscillation voltage is amplitude‐modulated by the magnetic field of the measured current.An examination is made of the previous current sensor circuit with open‐loop construction, and the new circuit construction is closed‐loop and with feedback circuit. In this way, the current‐detecting characteristics are improved greatly, and it was confirmed that a high‐performance current sensor is obtained.
Low‐temperature preparation of poly‐si tft by ar laser annealing at high scanning speed
Authors: Masumo Kunio , Yuki Masanori 
Published: July 2007

AbstractIn an attempt to fabricate poly‐Si TFT with a field‐effect mobility two orders of magnitude higher than a‐Si TFT which can still be made at an equivalent cost as a‐Si TFT, studies have been made of high‐speed scanning Ar laser annealing. This paper proposes that: ±1 based on the result of spin‐density measurements by ESR, the effect of thermal annealing on the improvement of poly‐Si film quality after a laser annealing is most significant at 400°C. Even at 350°C, high‐quality poly‐Si TFT can be fabricated; and ±2 high‐performance poly‐Si TFT can also be obtained with a‐Si films as starting materials which are made not only by plasma CVD but also by the LPCVD method. Therefore, one can choose a fabrication machine suitable for high yield for amorphous silicon films to be used for high‐speed Ar laser annealing.
An optical neuron device capable of optical parallel operations and all‐optical neural networks
Authors: Takimotoww Akio , Akiyama Koji , Ogawa Hisahito 
Published: July 2007

AbstractWe propose a method for implementing an optical neural network system which utilizes a massively parallel processing architecture and aims to provide performance that approximates that of human mental processes. We describe the configuration, fabrication, and functions of an optical neuron device which is capable of performing both summation and threshold operations in optics. We constructed an all‐optical neural network using these devices, a lenslet array for forming optical interconnections between neurons, and a memory mask representing synaptic weights. This optical neural network has 36 neurons in the input layer and an equal number in the output layer. The network demonstrates an associative memory function for three alphabet letters (O, P, and T). It is capable of recalling perfect patterns against imperfect input patterns through purely optical processing without using electric circuits.
Reduction of amplified spontaneous emission (ase) noise from transmitted soliton signals with a nonlinear amplifying optical loop mirror
Authors: Yamada Eiichi , Suzuki Kazunori , Nakazawa Masataka 
Published: July 2007

AbstractSince the storage of the amplified spontaneous emission (ASE) noise of an amplifier is a cause for the degradation of the transmission characteristics in a long distance soliton transmission using an optical amplifier, the reduction of the ASE is a key issue to be solved for a soliton transmission. A new method to remove the ASE noise using the threshold characteristics (self switching) of a nonlinear amplification loop mirror (NALM) which utilizes the difference in intensity between the soliton signal and the ASE noise is presented in this paper and its application to a transmission experiment is discussed. First, the transmission characteristics of the NALM for a pulse signal are examined. It is demonstrated that the ASE noise can be successfully removed from the pulse signal of high level. The present method is applied to a soliton signal transmitted over 500 km at 10 Gbit/s. The ratio in intensity between the soliton signal and the ASE noise is improved when the NALM is used as compared to the case without it. Finally, it is shown that the switching of pulse close to the transform limit is possible when the phase difference of a pulse peak propagating in a nonlinear loop with a high gain optical amplifier is less than 0.3 π.
Feasibility of very‐short‐channel mos transistors with double‐gate structure
Authors: Sekigawa Toshihiro , Hayashia Yutaka , Ishii Kenich 
Published: July 2007

AbstractConventionally, extremely thin gate oxide and high channel‐doping concentration are used to reduce the short channel effect of an MOS transistor below the submicron region. However, with these methods, there are problems such as the degradation in design freedom with respect to the breakdown voltage, the considerable decrease in the carrier mobility and the remarkable variation in characteristics of devices due to the statistical fluctuation of the impurity doping profile; and they need to be solved. Through the numerical analysis of the threshold voltage performance and the experimental fabrication of various devices with effective channel length range from 0.26 μm to 1.26 μm, it has been made clear in this paper that a double‐gate MOS transistor (XMOS) structure with another insulated gate at the lower part of the channel can reduce the short channel effect without the above‐mentioned problems. The results also show that the gate swing has reached about 60 mV/decade that is close to the theoretical limit; the short channel effect can even be reduced with a much shorter channel length if a thinner active channel layer is used and that reduction is independent of the channel doping concentration; and the limit to a possible shorter channel length may be less than 0.1 μm. It is concluded that the problems with the conventional MOS transistor can be solved by using XMOS structure.
Fabrication of poly‐si tfts using laser annealing technique
Authors: Sameshima Toshiyuki 
Published: July 2007

AbstractA low‐temperature fabrication process of high‐performance polycrystalline silicon thin‐film transistors (poly‐Si TFTs) is discussed. The performance of TFT is found to depend strongly on crystallization, plasma hydrogenation of poly‐Si, and the fabrication process of the SiO2 insulator. Especially, a key issue in a low‐temperature processing is how to fabricate a gate insulator without serious damage. A method of remote plasma chemical vapor deposition is shown to be very useful for fabrication of high‐quality SiO2/Si interface of a large area at low temperatures.
Preparation of poly‐si by excimer laser annealing with solidification process control
Authors: Noguchi Shigeru , Kuwahara Takashi , Hanafusa Hiroshi , Nakano Shoichi , Kuriyama Hiroyuki , Kiyama Seiichi 
Published: July 2007

AbstractPolycrystalline silicon (poly‐Si) recrystallized by a conventional excimer laser has a small grain of about a few hundred Å and a mobility of about 100 cm2/Vs at most. It is believed that such small grain size could be due to a fast solidification velocity based on the authors's study of the solidification control of molten Si. A thermal analysis by computer simulation indicates that the solidification velocity can be lowered by heating substrate (400°C) during laser irradiation and thinning an amorphous Si (a‐Si) film (500 Å).Poly‐Si with a large grain (5000 Å) and high mobility (280 cm2/Vs) has been fabricated by excimer laser annealing in the present study. Nonuniformity of characteristics of poly‐Si in an overlapping region of the laser spot also is examined. An uncompleted melting of a mixed region of fine poly‐Si and a‐Si generated at an excimer laser spot edge is the cause for such nonuniformity. An overlapping region of a laser spot is found to become very uniform by using the present solidification control method. Nonuniformity of mobility is improved from ±20 to ±8 percent in the present study. This method is a very useful low‐temperature processing for fabricating large‐sized poly‐Si films.
Polycrystalline‐silicon tfts fabricated at low temperature using ion doping technique
Authors: Yoshinouchi Atsushi , Oda Akihiro , Itoh Masataka , Morita Tatsuo , Tsuchimoto Shuhei 
Published: July 2007

AbstractCrystallization phenomenon induced by ion beam irradiation from an RF plasma source using large‐area ion doping without mass selection (ion doping technique) at low temperature less than 350°C has been investigated. Phosphorus ions and protons are implanted simultaneously into a polycrystalline silicon film. When the proton dose exceeds 4 × 1015ion/cm2, the amorphous film is crystallized and the crystalline grain size is about 50 nm. Since the crystallization depends on the proton dose, it is obvious that the proton beam contributes to crystallization.Using this self‐activation technique, the annealing step to activate the implanted dopant can be eliminated. In the polycrystalline thin‐film transistor (TFT) withL/W= 15 μ/5 μ, the mobilities inndandpchannels are 25 cm2/V.s and 14 cm2/V.s, respectively.
Complex‐valued equivalent circuits which represent the connection of wave functions at the heterointerfaces
Authors: Sanada Hirofumi , Nagai Nobuo , Ohtani Naoki , Miki Nobuhiro , Ohkama Hiroshi 
Published: July 2007

AbstractFor the design of devices using the quantum effect, it is necessary to know the wavefunction of the electrons and holes in the quantum well and multiple barrier structures as well as the characteristic energy levels and resonance levels. It is necessary further to manipulate the potential structures to synthesize a desired phenomenon. to attain these objectives, applications of circuit theory to the analysis and design of quantum effect phenomena have been attempted.In this paper, it is shown that the 2 × 2 interface matrix representing the continuity of the wavefunction and the boundary condition on the wavefunction accompanied by the T‐X mixing are expressed in terms of the lossless two port and four port, respectively. By means of this procedure, it is now possible to carry out a circuit‐oriented treatment of the behaviors of the electrons and holes in the case of superlattices other than GaAs systems requiring the interface matrix and the case where mixing between the minimum points of the conduction band in GaAs/AlxGal ‐ xAs for which no circuit treatment was previously possible. They can now be analyzed systematically with the circuit functions and circuit matrices of the equivalent circuit without special boundary conditions. Also, by means of the proposed circuit representation, analysis examples are presented for the tunneling phenomena in these potential structures.
Theoretical analysis of optical bistability of a faraday medium
Authors: Hirano Masao 
Published: July 2007

AbstractAn optical bistable device can be useful not only for optical memory but also for optical sensing by using its binary signal process characteristics. In this case, if a nonlinear Faraday medium is used in the optical bistable device, some interesting features can be obtained as already shown by the present author. Those unique characteristics are that, by controlling the polarization direction by an external magnetic field, a multiple interference can also be controlled not only by the phase associated with an optical path variation but also the polarization direction.This paper describes a theoretical analysis of the fluctuation of transmission and reflection as a function of an absorption in a medium besides the incident intensity reduction and discusses the bistability characteristics and the threshold values against the parameters. It is shown that the control of the bistable function, the realization of a low threshold value, and the increase of a discontinuous power variation ratio (= optical intensity ratio between on and off in the binary signal process) at the threshold value are accomplished as the result of the introduction of the external magnetic field control method. Therefore, it can be concluded that a Faraday medium is very useful for an optical bistable device.
Effect of the phase transition of Ti silicide on the thermal stability of Si‐interface in the Cu/CuTi2/Ti/Si contact system
Authors: Sasaki Takahiro , Kagomi Shinya , Sasaki Katsutaka , Noya Atsushi , Yoshimoto Ken'Ichi 
Published: July 2007

AbstractIn an attempt to realize a stable Cu metallization in Si‐LSI, a Cu/CuTi2/Ti/Si contact system was prepared and its thermal stability was studied. As a result, although the phase transition from the intermediate CuTi2 phase to the CuTi phase was observed with increasing annealing temperature in the contact system, the interface between the metallization layers (Cu and CuTi) and Si in the system suppressed the excess diffusion of Si at temperatures up to 570°C. the reason is that the Ti silicide formed at the Si interface acts as an Si diffusion barrier until its chemical state transforms into TiSi2, which is the final phase of Ti silicide. However, the contact system failed due to a direct chemical reaction between Ti and/or Cu in CuTi and Si which diffused into the upper layer through TiSi2 when Ti silicide at Ti/Si interface formed TiSi2 at 600°C. Then the contact system resulted in the phase‐separated bilayer structure of silicide. It was revealed from these results with the thermal stability of this contact system is related closely to the phase transition of the Ti silicide layer at the Si interface with increasing annealing temperature.