bluuebunny/crossref_metadata_2025 huggingface dataset:
Output‐queue contents in a ‘minislot’ synchronized ATM switch
Authors: Xiong Yijun , Bruneel Herwig
Published: July 2007

AnN × Nswitching element with output queueing, as used in a large ATM switching network, is considered. All the inlets of the switching element are synchronized on ‘minislots’, where a minislot is the fixed‐length time unit for the transmission of one ‘minicell’. When entering the switching network, an ATM cell is converted into a ‘minicell‐train’, consisting of a fixed number of minicells. Using an active/silent model, it is assumed that on each inlet of the switching element, the number of minicelltrains in an active period and the length of a silent period are both geometrically distributed, and the arriving minicell‐trains are uniformly distributed among all the outlets. The performance of the switching element can be obtained by analysing one single output queue, which is modeled as a discrete‐time single‐server queuing system with train arrivals. In this paper, an upper bound and an approximate expression for the mean queue length are derived. More importantly, an analytical method is developed to obtain a tight upper bound and a good approximation for the tail distribution of the queue length. This analytical method is very useful in buffer dimensioning of ATM switches.
Proportional rate‐based congestion control under long propagation delay
Authors: Cavendish Dirceu , Oie Yuji , Murata Masayuki , Miyahara Hideo
Published: July 2007

The occurrence of congestion severely degrades the performance, especially in high‐speed networks with long propagation delay relative to packet transmission time. This is because it is very likely that a large number of transit packets are flying over such networks at a time and many of them will get lost if they arrive at some congested node. Among ways of controlling traffic to avoid congestion, this paper deals with a class of rate‐based congestion controls (RBCC) which regulate input traffic based on feedback information about network congestion status. Although such mechanisms have been studied recently, the mechanism to be considered, referred to asproportionalRBCC, differs from them in that the amount of input traffic allowed to enter in the network isproportionalto the network resources available, keeping a closer track of the network resources than the previous ones, where the network status is described by two states, congested or not. The mechanism seeks an optimal network operating point, adapting to dynamic changes of carried traffic. We carry out the stability analysis and the transient analysis of some performance measures related to the proportional RBCC, and also address fairness aspects in providing control to various source‐destination connections, while K. W. Fendicket al.have analysed the stability of a general class of RBCC. Furthermore, by making a comparison between the control mechanism analysed here and the ones based on binary feedback information, we show the effectiveness of the former.
Deterministic rule based traffic descriptors for broadband ISDN: Worst case behaviour and its impact on connection acceptance controls
Authors: Doshi B. T.
Published: July 2007

Deterministic rule based traffic descriptors in general, and leaky bucket based (LBB) traffic descriptors in particular, offer many advantages over statistical descriptors for specifying and monitoring traffic in the ATM based broadband ISDN (BISDN). However, these traffic descriptors do not specify the traffic pattern uniquely. Thus, acceptance of a connection request with specific traffic descriptor parameter values implies that the network has agreed to guaranteeing the quality of service (QOS) for the worst case traffic compliant with the traffic descriptor (and hence allowed by the monitor). This poses challenges which have not been addressed adequately. Two of the important ones are: (i) definition of the worst case behaviour and characterization of the worst case traffic compliant with the traffic descriptor; (ii) connection acceptance controls (CAC) for the worst case traffic sources compliant with the traffic descriptors. In this paper we address these questions for leaky bucket based (LBB) traffic descriptors. The focus is on the first problem. The implications on the second problem are discussed briefly. The performance measure and QOS requirements are in terms of the cell loss ratios.

We first define the worst case behaviour for homogeneous and heterogeneous environments in terms of collective cell loss ratio (CLR)) from the multiplexer. We consider both the unbuffered and buffered cases. However, most of the results here are for the unbuffered case. FOTthe case of an unbuffered multiplexer and homogeneous source environment, we show that a simple on‐off source represents the worst case behaviour of an LBB source. In a heterogeneous source traffic environment, the on‐off behaviour is the worst only in a limited sense and the use of a collective measure results in anomalous relationships between the source behaviour and the CLR. A more appropriate measure should be based on individual cell loss ratios or on the maximum of the individual CLRs. We analyse LBB sources with respect to these measures and unbuffered resources, and obtain further characterization of the worst case behaviour. However, we also uncover some counter‐intuitive relationships. In particular, a seemingly ‘smooth’ source may be worse for the other sources than a seemingly ‘bursty’ source.

For a buffered multiplexer, we show, via an example, that a three‐state source may be worse than an on‐off source even in a homogeneous source traffic environment. A complete characterization of the worst case behaviour for a buffered multiplexer remains an open challenge. Moreover, the LBB sources exhibit deterministic behaviour and their equivalent bandwidth need not be sub‐additive in sources. That is, adding the equivalent bandwidths of individual sources to obtain an ‘estimate’ of the equivalent bandwidth for a collection of such sources could be too optimistic in some situations. A fresh look at the connection acceptance control for such sources is therefore warranted.
Comparison of admission control schemes in ATM networks
Authors: Causey Jeffrey W. , Kim Hyong S.
Published: July 2007

Asynchronous transfer mode (ATM) offers an efficient means of carrying a wide spectrum of BISDN traffic provided that network congestion is prevented. Unfortunately, efficient congestion control is difficult to achieve in integrated broadband networks, owing to the wide range of traffic characteristics and quality of service (QOS) requirements. We have implemented a network simulator that allows us to evaluate many proposed admission control schemes using many different traffic models. We present the results of several simulation studies, including one study of the performance of the admission control schemes in the presence of traffic sources that exhibit long‐term dependence.
Shared buffer ATM switch with doubly linked lists
Authors: Lin Yeong‐Fong , Shung C. Bernard
Published: July 2007

The Shared buffer memory switch (SBMS) architecture was originally proposed as an effective approach to implement ATM switch fabrics. However, in this paper we find that if an error occurs in the address chain memory of one linked list which stores the address of the next cell in the shared buffer memory, the erroneous situation will spread over all linked lists in the SBMS in a short time. In order to prevent the fault spread phenomenon, we propose two doubly linked list based architectures to combat address chain failure; these are referred to as the Flush and In‐Seq schemes. The first scheme flushes the remaining cells in the faulty queue but collect their addresses for later usage. The second scheme outputs the remaining cells in their correct sequence. From our simulation, if the error injection rate is low, the performance of the In‐Seq scheme experiences slight degradation compared with the errorfree situation.
An algorithm for sizing trunks carrying mixtures of constant and variable bit rate traffic
Authors: Rege Kiran M.
Published: July 2007

As new broadband networks based on the asynchronous transfer mode (ATM) protocol emerge to support a variety of services, the need for analytical models and tools for sizing network components carrying mixtures of different kinds of traffic will be increasingly felt. This paper presents a simple, yet efficient algorithm for sizing trunks carrying mixtures of constant and variable bit rate traffic. It combines theoretical results for the multi‐dimensional Erlang model and the concept of equivalent bandwidth with some heuristic arguments to produce an analytic method for sizing trunks subject to blocking and quality of service constraints for traffic classes.
Distortionless theory of one‐dimensional non‐uniform transmission lines
Authors: Ito Chiaka , Sato Risaburo
Published: July 2007

For transmitting distortionless arbitrary waveforms over set‐ups with different impedances, the nonuniform lines have been used for a long time by wide‐band impedance‐transform and matching. But rigorous theory is still lacking in treating the basic problems concerning the relationship between the distortionless waveform and the nonuniform line distribution, i.e., the distortionless conditions or the impedance‐matching conditions for the nonuniform lines. This paper first investigates the voltage/current transfer‐functions over any line interval and the local propagation constant. It is then clarified that there exist on the one‐dimensional nonuniform line essentially six localized distortionless conditions for the voltage/current waveforms. Next, the distortionless wave quantities and characteristics, the finitely long line analysis, as well as method of excitation (matching) of the distortionless wave, are presented. Finally, it is shown that all‐pass impedance transformer, attenuator and phase shifter can be realized by using the distortionless line.
Alpha‐particle‐induced soft errors in high speed bipolar ram
Authors: Mitsusada Kazumichi , Katos Yukio , Yamaguchi Kunihiko , Inadachis Masasaki
Published: July 2007

Soft errors of the bipolar RAM (Random Access Memory) caused by α particles emitted from the radioactive material in the package are investigated. The in‐system test and the particle irradiation test were performed by using a 1 Kbit RAM made especially for this purpose. The relation between the soft error rate and the amount of the α particle irradiation was examined. It was confirmed that even in the static bipolar RAM, soft errors do occur due to α particles from the package. The relation between the soft error rate, memory cell structure and the design condition was discussed. Furthermore, the mechanism of soft errors was investigated and the soft error rate was estimated by considering the effective noise change due to α particles and the charge required to invert data in the flip‐flop cell. These results were compared with the experiment.
A model of failure propagation process
Authors: Kokawa Masasumi , Shioya Makoto , Ohnari Mikihiko
Published: July 2007

With the development of towns, various systems, such as chemical plants, water supply and sewage systems, are growing in size and complexity. Therefore, once a failure occurs at one part of a system, its influence spreads extensively to large peripheral areas. Therefore, the key problem is how to protect the systems against the failure propagation to maintain the system safety and reliability. However, the preventive maintenance design or prearranged measures are hard to prepare due to insufficient analysis of the failure propagation process in complicated systems.

This paper proposes a method of building a model of failure propagation process structurally and quantitatively to help in designing preventive maintenance. This method consists in a failure propagation network based on the failure propagation linkages between a failure element and its adjacent failure elements in the system. In addition, it permits the failure propagation simulation, function survival route search, and assessment of risks caused by the failure propagation, with the help of failure transition probability and matrix operation.
A simplified analysis of ferrite strip
Authors: Araki Kiyomichi , Enjohji Sadao , Naito Yoshiyuki
Published: July 2007

Previously, one of the authors proposed a ferrite strip as a non reciprocal waveguide for millimeter and optical waves. It has many features, e.g., it does not require metal conductors and optical anisotropic material (NbO3), and it generates large field displacement for small anisotropy.

This type of waveguide is analyzed by a generalized transmission equation and variational method. These methods, however, are time‐consuming and cumbersome. This paper proposes a simple analysis method using effective permittivity. The field distribution for weakly guiding waves and the radiation characteristics are discussed in detail. It is clear that the occurrence of large field displacement is attributable to weakly guiding waves. The cut‐off condition for the fundamental wave, the condition of edge guide wave generation, the radiation loss and the asymptotic value of the field displacement, are clarified.
Cut‐off mode filter with the structure of metal‐clad optical strip line
Authors: Itoh Masataka , Kudo Masaaki , Mushiakes Yasuto
Published: July 2007

The three‐dimensional mode filter is realized by use of a buffer layer between the metal clad and core of the metal‐clad optical strip line. The equivalent refractive index method is used for analysis of the waveguide transmission properties in which the guide parameters for operation of a TM mode filter and the modal transmission loss are predicted theoretically. With a simple experiment, the dependence of the cut‐off properties on the polarization is confirmed and the correctness of the theory is also verified.
Fabrication and rf surface resistance of superconducting lead cavity by a press forming technique
Authors: Momose Takashi , Akada Katsuhiro , Yamashita Tsutomu , Onodera Yutaka
Published: July 2007

This paper describes fabrication and characteristics of 10‐GHz‐band TM010‐mode superconducting cavities with electroplated lead films on the walls of press‐formed copper shells. The cavity is made up of two symmetrical pieces of copper, and rf current flows parallel to their joint planes. Homogeneous lead films are obtained on copper substrate by using a lead anode with a hemispheric projection. In order to make the rf joints in the cavity, either (a) lead wires were inserted between the copper subtrates with lead films, or (b) indium wires are used between copper substrates on which lead is electroplated. Temperature dependence of Q‐factors of the lead cavities was measured at low temperatures for input power less than 3 mW in an environment where terrestrial magnetism was compensated to be within 20 mG. Q‐factors on the order of 109 were obtained for cavities prepared by the method (b). They also showed residual rf surface resistances as low as 2 × 10‐8ω, which is less than that of TE‐mode lead cavities reported so far for the same frequency range.
Multistage selective dpcm
Authors: Enomot Hajime , Nitta Katsumi
Published: July 2007

The DPCM, a representative prediction encoding system of picture signals, produces two conflicting noises‐overload and granular. This paper describes the selective DPCM that separates picture signals into edge and slant components, and an optimum encoding is applied for each component to consider the two noises. First, statistical analyses on picture signals conclude that they are composed of the edge component and slant component. Second, the edge component, which shows frames of pictures, is approximated by step waves and the slant component, which shows the smoothness of pictures, is approximated by delta modulation. A new method is proposed here: a statistic adaptation in each block and a constant speed scanning are applied for input picture signals. Finally, it is demonstrated that computer simulations prove the usefulness of the method.
A communication network design with the measure of traffic abnormality
Authors: Murata Hatsuho , Akiyama Minoru
Published: July 2007

As the demand for calls by subscribers in communication networks increases, it is necessary to have sufficient equipment or a high‐degree of control over the communication network to make immediate connection of the calls to the desired parties by subscribers at any time they desire. However, economically, it is impossible in large‐scale, modern communication networks to provide enough equipment for all traffic fluctuations. In this paper, a measure of “abnormality” representing the degree of the fluctuations of the subscribers' demand is used to ensure the connection of the calls by limiting all traffic fluctuations below a specified abnormality. First, for the traffic pattern representing the subscribers' demand, we derive a theoretical formula and an approximate calculation method for the traffic intensity which the communication network must actually carry, taking into consideration the number of subscribers.

Then we calculate the traffic intensity which each equipment must carry in a communication network using a relatively simple method of route selection. We present a method for obtaining a maximum value for the traffic pattern below a specified abnormality. It is adequate enough to provide a sufficient number of equipment for the traffic intensity to be carried. It may be possible by this design method to have a very efficient reinforcement of the equipment for traffic fluctuations by a limited equipment investment.
Constant‐resistance phase equalizers using directional couplers
Authors: Ohue Kenji
Published: July 2007

In realizing high‐efficiency, high‐speed digital transmission systems, waveform distortion due to amplitude and phase distortion is a definite impediment. This paper proposes a phase equalizer using a constant‐resistance stripline directional coupler as its basic circuit. Unlike phase equalizers realized with lumped inductors and capacitors, the proposed equalizer offers excellent frequency response over a range from DC to 1 GHz. It is shown that the equalizer is equivalent to a transversal filter realizable in the time domain, which simplifies its structure. Experimental results are shown to match the theoretical results using a prototype equalizer implemented with thin‐film hybrid ICs.
Stimulated raman scattering by a relativistic electron beam—analysis of a free electron laser
Authors: Shiozawa Toshiyuki
Published: July 2007

This paper investigates a free electron laser using stimulated electromagnetic wave scattering, i.e., stimulated Raman scattering by the electron plasma (negative energy) wave excited in a relativistic electron beam. Rigorous analysis of its oscillation property is given. Special attention has been given to the output power saturation with decreasing pump power and the energy relations. For simplicity, a one‐dimensional relativistic electron beam is considered and a strong plane EM wave (pump wave) impinging on the electron beam from the opposite direction is assumed. First, Maxwell's equations, the relativistic motion equation for the electron, and the continuum equation for the beam are used. Oscillatory components up to the second order are considered. The mode‐coupling equations for the pump, scattered and the electron plasma (negative energy) waves are derived and rigorous solutions are sought. Energy relations involving these three waves are formulated. Due to the effect of the pump wave, energy is found to transfer from the electron beam to the scattered wave and the manner in which the scattered wave grows gradually is clarified quantitatively.
A high sensitive speech detector based on sign bit sequence manipulations
Authors: Yatsuzuka Yohtaro
Published: July 2007

In a speech signal transmission by means of the pause of speech such as the DSI, the speech detection capability is significant and accurate detection of it is indispensable. This paper proposes a detector for operations in each block with improved detection characteristic realizing a shortened hangover time and a high sensitivity. These results are obtained based on the sign bit sequence matrix processing in terms of the short‐time energy, the zero crossing rate and the sign bit sequence of the input signal. Especially in processing the sign bit sequence matrix, a degree of the speech spectrum concentration is investigated by processing the sign bit sequence of the original signal as well as the obtained signal through the pre‐emphasis filter, and the sign bit sequence matrix composed of the sign bit sequence of the fundamental frequency and its harmonic sine and cosine waves. A computer simulation has indicated that a speech level of above ‐51 dB m is detected effectively without any degradation of speech quality. The average activity of speech in an international long‐distance line is reduced remarkably to 36% compared with the conventional one of 40%, and the average talkspurt is shortened to 436 ms which is half that of the conventional ones. Furthermore, it is shown that the detector has an excellent discrimination characteristic for thermal noise.
Considerations on structure of single‐channel counting encoder having μ‐255 companding
Authors: Sasakawa Masa‐Aki , Takas Masahiro
Published: July 2007

Owing to their economy and flexibility, much attention is devoted to single‐channel encoders based on LSI technologies. Various circuit configurations have been proposed. This paper presents a systematic discussion of the types of circuit configuratious with a view to applying a counting encoder with lower element accuracy to a single‐channel encoder. Initially, we propose various circuit configurations types for companding encoding by controlling the pulse width of the counting clock at the power of two. We then classify the counting encoder with regard to the processing pattern of encoding, clarify the relationship between the element accuracy and performance deterioration and describe the circuit type adopted for using LSI. The application conditions for digital networks are examined and a simple method is proposed which permits synchronization of the PCM output signal to the zeroth group even if the counting clock and the zeroth group are functioning asynchronously. In addition, we propose a method of adjusting the levels of analog input signals as appropriate for the counting encoder. It is expected that the above discussions will provide the optimum composition of the single‐channel counting encoder.
Narrow‐bandwidth multichannel system for television fm signal
Authors: Sakata Haruo
Published: July 2007

A new transmission system is proposed in which the television signal is used as the modulation signal and the wideband FM signal with low modulation index is transmitted through a multichannel narrow‐bandwidth transmission path. The signal processing of this system is as follows:

Carrier frequency of broadband FM signal is made equivalent to the sum of the maximum carrier frequency of the modulation signal and half the frequency deviation by using a frequency converter.

Frequency is divided by N by flip‐flop and the signal is transmitted as N channels narrow bandwidth FM signal. The phase difference between each of the channel carrier frequencies is π/N radian.

In the receiver, the broadband FM signal is reformed by an exclusive‐OR circuit after the wave is shaped by the limiter.

This paper analyzes the above‐proposed FM signal and estimates the change of frequency spectrum. Furthermore, it has been confirmed experimentally using the television signal that the output of the 30 MHz and FM modulator having 14 MHz bandwidth (base band of modulation signal is about 5 MHz) can be transmitted through the 4 channels having 3.6 MHz bandwidth.
Is(z) transformation and implementation problems of digital systems designed by is(z) translation
Authors: Sakaguchi Hiromi
Published: July 2007

The Is(z) transformation is essentially nonlinear transformation and has been used widely because of its wide linear range. There were two problems to be solved regarding the implementation of the digital systems: (1) to simplify the stabilizing procedure associated with this transformation; and (2) to improve the accuracy in implementing the digital system due to limited word length. For (1), the synthesis of z functions by pole substitution is adopted to simplify the procedure. For (2), the algorithm is modified to improve the accuracy. Further, the accuracy in implementing the digital systems with different word lengths and filter structures is evaluated in terms of the error rate in locating the poles which are estimated by the linear prediction method.
Reflection of a Gaussian beam at oblique incidence on a stratified dielectric medium
Authors: Tanaka Mitsuru , Saga Nobuhiro , Fukumitsus Otozo
Published: July 2007

The reflected and transmitted fields of a Gaussian beam which is incident upon a stratified dielectric medium at oblique angles are expressed in terms of the fundamental beam modes with proper selection of the propagation axis and beam parameters. The reflected field is expanded into the mode function system with the same propagation axis and same beam parameters as the direct reflected beam and the reflected power is calculated from its expansion coefficients. The reflected field and reflected power can be simplified if the stratified medium is symmetric with respect to the intermediate layer. As an example, the output mirror of the YAG laser resonator is considered and the amplitude distribution of the reflected field and reflected power from the seven‐layered medium is calculated. The effect of the minimum spot size of the incident beam and the incidence angle on the reflection characteristics is analyzed.
Polarization transmission characteristics of optical fibers with elliptical cross section
Authors: Fujii Yoichi , Sanos Koichi
Published: July 2007

In the transmission via optical fibers connected to laser diodes, optical switches, optical filters, etc., or in high‐sensitivity high‐selectivity optical heterodyne detection system, polarization characteristics become important in addition to transmission loss and dispersion. The polarization transmission characteristics of optical fibers with elliptic cross‐section are calculated by characteristic matrix method for large values of ellipticity. For two orthogonal polarization modes (oHE11 and eHE11 modes) the transmission velocity, group velocity and their difference (elliptic double refraction) are obtained. The group delay difference among modes is very small but elliptic double refraction greatly affects the polarization characteristics.
A routing system of single‐layer printed wiring boards
Authors: Futagami Shin , Shirakawa Isao , Ozakis Hiroshi
Published: July 2007

A great part of the layout design of single‐layer printed wiring boards and hybrid IC's is still implemented manually, and hence of practical importance is the layout automation in this field.

This paper describes an automatic routing system which can be applied to single‐layer printed wiring boards and hybrid IC's used for numerous analog appliances. This system is distinctive in that the routing process is implemented through a number of stages such that at each stage an interference relation for the from‐to's which remain to be interconnected is sought. Then according to the interference information thus obtained, a maximal set of wire patterns which do not intersect each other is generated. Several experimental results are also shown to reveal how much the system attains its potentialities to be of great use in the practice of layout design for single‐layer printed wiring boards and hybrid IC's.
Thickness aberrations in two‐photon‐resonant image upconverters
Authors: Sasaki Shinya , Mishima Teruhito , Sakurabas Ichiro
Published: July 2007

An image equation for two‐photon‐resonant image upconverters with finite medium thickness is derived by the ray matrix method and the thickness aberration and coma are obtained theoretically. The thickness aberration and coma become small when two pumping sources and an infrared object are located on the same longitudinal plane. These aberrations can be eliminated if locations of two pumping sources and infrared object, the medium thickness and dispersion characteristics satisfy a certain relation. The image equations are analyzed for three different optical systems and their resolutions are compared.
High‐speed digital PLL using trigger oscillators
Authors: Suzuki Shuji , Kurita Taiichiro , Ozawa Shinji , Moris Shinsaku
Published: July 2007

The conventional digital phase‐locked loop (DPLL) cannot be used for high‐frequency purposes, because the local oscillator frequency of the DPLL is several times the input frequency. This paper proposes a use of trigger oscillators to the DPLL. The first‐ and second‐order DPLL's using trigger oscillators can be used if input frequency is as high as the maximum logic clock frequency. The quantization noises of the second‐order DPLL using two trigger oscillators are lower than those of the conventional DPLL. The trigger oscillators can be used in any type of DPLL. Its input frequency becomes higher or its quantization noises become lower.
Measurement of lifetime and diffusion constant of minority carriers by phase shift technique in EBIC
Authors: Fuyuki Takahashi , Matsunamis Hiroyuki
Published: July 2007

Lifetime and diffusion constant of minority carriers in Si have been measured using phase shift technique in EBIC. The phase of EBIC delays in regard to the recombination in materials when the intensity‐modulated electron beam is used in the line scan method of EBIC. The phase shift between the excitation source and the EBIC is calculated theoretically by solving the three‐dimensional time‐dependent diffusion equation. The phase shift increases linearly with the scanning distance. The phase shift against the distance is a function of lifetime and is not influenced by surface recombination. From the values of the phase shift and the diffusion length, the lifetime and the diffusion constant are determined simultaneously. Experimental results in Si Schottky diodes showed good agreement with the theory.
Length dependence of baseband bandwidth for spliced graded‐index multimode fibers
Authors: Tanifuji Tadatoshi , Horiguchi Tuneo , Tokuda Masamitsu
Published: July 2007

It is important in determining system configuration to understand the length dependence of the baseband bandwidth of a graded‐index fiber. An actual fiber communication system is constructed from a number of connected fibers with different characteristics. In such cases, the length dependence of the baseband bandwidth becomes very complex due to mode conversion and mode dispersion compensation at the junction and no practical method exists to estimate the characteristics. Therefore, actual systems are approximated by setting an appropriate value of γ in the γth power expression. This paper first finds the length dependence (γ value) of the baseband bandwidth measured in a number of fiber systems actually installed. Next, to analyze factors determining the length dependence, experimental and theoretical investigations are conducted. It is found that an important factor determining junction characteristics is the mode dispersion compensation regulated by the group delay difference among principal mode groups as well as within a principal mode group. It is also found that mode conversion at the junction has a negligible effect. In an actual communication channel employing many fibers, correlation in the group delay difference among the principal mode groups and within the principal mode group of each fiber becomes small and the value of γ is restricted. In practice, it is possible to estimate the average baseband bandwidth by setting γ ∼ 0.6.
Preparation of permalloy films using facing‐type targets and a high‐rate and low‐temperature sputtering method
Authors: Hoshi Youichi , Kojima Masaya , Naoe Masahiko , Yamanaka Shun‐Ichi
Published: July 2007

Permalloys are promising as candidates for a thin‐film head and as a material for the soft substrate magnetic layer using normal magnetic memory media. Permalloy films prepared using facing‐type targets and a high‐rate and low‐temperature sputtering process are examined. As a result in the facing‐type target sputtering method, it is desirable to use double targets with a structure consisting of a small satellite target positioned eccentrically inside the mother target.

The morphology and magnetic properties of sputtered films depend strongly on the substrate bias voltage. To obtain a good magnetic film, a substrate bias voltage in the range of ‐120 to ‐150 V and/or a substrate temperature of 350 C is needed. In particular, with the application of bias voltage, in addition to being stress free at low substrate temperature, a thermally stable film is also obtained. It is observed that adhesion of the film to the substrate can be improved by sputter‐cleaning of the substrate before deposition. Perpendicular anisotropy of the films decreases significantly and the magnetic properties of the films improve with increasing substrate bias voltage and substrate temperature. This is probably attributable to the change in film morphology.
On some design examples of a circularly polarized wave array antenna using slot antenna combined with parasitically excited dipoles
Authors: Itoh Kiyohiko , Shinada Hidetoshi , Ariga Toru
Published: July 2007

There are two methods to obtain a circularly polarized array antenna. One is to arrange and feed linearly polarized elements (such as slots) in an appropriate manner. Another is to arrange circularly polarized elements. The second approach is used to design a four‐element circularly‐polarized planar array consisting of a slot and parasitic dipoles. An array antenna having good characteristics is obtained and described. In general, coupling exists between the array elements, and these couplings affect the antenna characteristics, particularly in the case of circularly‐polarized arrays. Before beginning the design, the changes in the circular polarization characteristics of a single element are numerically evaluated as a function of the coupling, and this information is used as a reference in the design of the circularly polarized arrays. Then, with a formulation including the inter‐element coupling, calculations are made for a situation more nearly approximating actual practice. The possibility of obtaining a small antenna with a bandwidth of 1.5 dB axial ratio (6%) and a gain of more than 13 dB is pointed out.
Spread spectrum communication with white gaussian noise
Authors: Takada Kazuhiro , Naito Sachio , Masuda Takao
Published: July 2007

One of the basic problems in the Spread Spectrum Multiple Access (SSMA) system is interchannel interference noise. Noise is an important determinant of the possible number of system characteristics of the SSMA system using White Gaussian Noise (WGN) for the spreading signal. The ratio of signal to interchannel interference noise (S/Ni) obtained herein can be the theoretical upper bound for direct sequence SSMA systems.

This paper also proposes a new SSMA system in which the delayed WGN and the spread information signal are transmitted together. The system has no synchronizing problem between spreading and despreading signals. Therefore, receiver structure can be very simple.
Convergence characteristics of the kalman‐type equalizer in decision‐directed mode
Authors: Sakaki Hiroshi , Shintani Sotokichi
Published: July 2007

In general, in the adjustment of its tap weight, the automatic equalizer requires the reference signal in addition to the input to the equalizer. For the convergence to be correct, the reference signal should be the equalizer output after the convergence is completed correctly. Since this is impossible in practice, a decision‐directed operation occurs wherein the equalizer output during tap weight adjustment is given to the decision part and the output of the decision part is used as the reference signal. In such a case, the adjustment of the tap weight is not exactly correct.

This paper shows first that the characteristics of the cascade system (which consists of the transfer characteristics of a Kalman‐type automatic equalizer after tap weight adjustment, operating by following the reference signal from the decision part) and the characteristics of the transmission channel can be determined directly from the signal type and the characteristics of the transmission channel and the characteristics of the decision part. In the above reasoning, the characteristics of the cascade system are obtained as the cross correlation between the transmitted signal and the output signal from the decision part. Then the mechanism to arrive at the correct convergence is described for the automatic equalizer, based on the knowledge obtained in the analysis of the cascade system. Finally, a Karhunen‐Loéve type decision‐assist fixed equalizer is proposed, which compensates the frequencygain characteristics of the transmission channel and assists the correct decision of the decision part.
Polymer thin film optical waveguide
Authors: Kato Isamu , Komatsu Masatoshi , Kawamoto Shigeharu , Matsumoto Yasushi
Published: July 2007

Polymers that are suitable for thin films are also used as materials for hybrid optical IC's; however, it is not easy in general to get a high refractive index change in the waveguide using these materials. To remove this difficulty, we have used copolymers of glycidyl methacrylic acid and methyl methacrylic acid, doped with cinnamic acid; this acid was directly photolocked, by ultraviolet exposure, to the epoxy rings of glycidyl methacrylic acid. Eventually, a refractive index change as large as 2% was achieved. Single‐mode optical waveguides with various widths were fabricated by means of the present method, and the dependence of the loss on the waveguide width and the loss in a bend were measured.
The theoretical analysis of stoneley waves propagating along an interface between Zno and glass
Authors: Shimizu Yasutaka , Irino Toshio
Published: July 2007

Conventional surface acoustic wave devices mainly use a Rayleigh wave, propagating along the surface of the substrate. Therefore, they require packaging. How—ever, the cost of packaging is high. Also, if the packaging quality is poor, water drops accumulate on the substrate surface at low temperature and the device may malfunction. This paper describes devices that do not require packaging and examine Stoneley waves, propagating along the interface between a piezoelectric ZnO layer, which can excite a surface wave, and a glass layer, in which material constants can be changed relatively easily. We find the range of the material constants of the glass which, in combination with ZnO, can generate Stoneley waves. We obtain the velocity, electromechanical coupling coefficient and energy concentration at the interface within this range. The effect of the material constants on these parameters is also considered. It is found that there are glasses that support Stoneley waves and others that do not.
Distortionless transmission of a quantized signal through band‐limited channels
Authors: Kishi Genya , Sakaniwa Kohichi
Published: July 2007

In this paper, a quantized signal is expressed by step functions defined in a finite time interval. The quantized signal has infinite frequency spectra and is distorted when transmitted through band‐limited channels. This paper examines the recovery of the quantized signal from the received signal after passing through an ideal lowpass band‐limited channel. The isolated signal which is zero out of the finite time interval can be recovered. The proposal recovery algorithm is based on an algebraic method and does not contain limiting operation.
Pattern synthesis of spherical circular array antenna by conjugate gradient method
Authors: Horiguchi Susumu , Sawaya Kunio , Ishizone Takayuki , Mushiakes Yasuto
Published: July 2007

In this paper, the spherical circular array antenna pattern is synthesized and the results are compared with the planar circular array. Since the pattern function is complicated, analysis of pattern syntheses of solid surface arrays such as the spherical array becomes difficult. Herein, pattern synthesis is done numerically by minimizing the mean‐square‐error between the desired and synthesized power patterns using the conjugate gradient method. This method is found to be effective in the pattern synthesis of the spherical array. Calculations show that when elements with sharp patterns are used in the array, phase control is more advantageous in practice than amplitude control. Also shown here is the excitation method by which a circularly polarized pattern along the apex direction can be obtained when turnstile antennas are arrayed conformally on the sphere. With this excitation method, the pattern is synthesized and the axial ratio of polarization for main‐beam scan degrades less for spherical than planar array. Furthermore, for spherical array the axial ratio can be improved by placing the elements on a conducting sphere.
Signal modification schemes facsimile based on majority logic
Authors: Suzuki Teruaki , Takebayashi Tomoyoshi , Imai Hideki
Published: July 2007

Recently, numerous researches have been made on data compression for digital facsimile transmission and several papers reported on the coding system in which certain signal processing is applied to the local part of the original image before encoding. This facilitates the encoding and improves the data compression rate. This paper proposes a new system which utilizes a signal processing based on the majority principle. This system can be implemented relatively easily by hardware. The image quality reproduced by this system is quite acceptable and can be improved by high‐density sampling. In this paper quantitative analysis is made based on the calculation of entropy and the ideal data compression rate when this signal processing system is used as a preprocessing. A considerable improvement of the data compression rate is shown. In addition, comparison between the proposed system and the existing conventional systems is made.
Characteristics of Ta and Mo thin films deposited by high current ion beam sputtering
Authors: Ishii Kiyoshi , Naoe Masahiko , Yamanakas Shun'Ichi
Published: July 2007

This paper uses a convenient ion beam sputtering setup to sputter tantalum and molybdenum. The Ta and Mo films so obtained are investigated concerning their structures, electrical properties and their relations with the processing conditions. The ion source used is a variant of the conventional duoplasmatron type and is operated at an ion current higher than 50 mA in Ar surrounding gas at 10‐4 torr. The Ta film possesses three different crystal structures: amorphous, α and β phases, depending on different sputtering conditions. The relations between structures and conditions are obtained. For the Mo film the structures obtained, on the other hand, are all the same as bulk. However, it is found that with varying processing conditions, the crystallite size of Mo film varies and the resistivity depends strongly on the crystallite size. Consequently, for given suitable deposition rate and substrate temperature, Mo films with low resistivity or resistivities close to the bulk value can be obtained whereas these cannot be obtained by conventional evaporation or other sputtering methods due to crystallite size increase.
Stability of autonomous nonlinear networks and resistance matrix
Authors: Suzuki Yoshihiko
Published: July 2007

The first half of this paper discusses the stability of the zero solution (equilibrium point) of the time‐invariant nonlinear active network. The stability of the zero solution depends on eigenvalues of equilibrium points of the matrix K which is determined by resistance matrix and connection matrix. The matrix K is expressed explicitly in terms of the resistance matrix R and connection matrix Q. Therefore the stability of the zero solution is determined by the connection method and the properties of the resistance. The second half discusses the global behavior and conclusions similar to those in the first half are derived except such additional condition that capacitance and inductance are linear and resistance is nonlinear. The actual passivity of the network can readily be examined by this method.
Stability theorems for two‐dimensional digital filters and two‐dimensional first‐order time‐delay digital filters
Authors: Okamoto Jiro , Yamashita Kazumi
Published: July 2007

There has been some interest in two‐dimensional digital filters (2D‐DF) which deal with multi‐dimensional information, such as pictures, earthquake waves, etc. If a reversal (recursive) 2D‐DF is composed of adders and resistors in an analog manner, the stability of the system differs from that of the ordinary 2D‐2F without any time element due to minor time delay of adders approximated by linear delay elements. However, if the coefficients of the filter take space‐symmetrical values, stability conditions of both are identical. Hence, the difference has never been noted. We found this fact both experimentally and theoretically and studied each stability condition of the filters for both cases, having infinite and finite constructions. Further, studies were made on mutual relationship between those stability conditions. The 2D‐2F with finite construction treated here is restricted to the case where the size of its lattice is a MxN rectangle.
Integration function and modeling of the central nervous system in forearm movement control
Authors: Taguchi Hideo , Fujii Katsuhiko
Published: July 2007

In a description of the function of the central nervous system in forearm movement control, the structure of the central nervous system must be considered, together with the control function produced by that structure. In this paper, the motor signal is assumed to originate from the brain, and the forearm movement is defined as the combined cooperative processes (integration) of the reflexes in various portions of the central nervous system, including the brain reflex. Based on this concept, the macroscopic mechanism of the central nervous system is described insofar as this is possible. The forearm movement induced by visual stimulation is then considered, and the response is measured in the frequency domain. A model is constructed for the central functions that describes the frequency response over a relatively wide range and agrees well with the macroscopic mechanism of the central nervous system. This model can be regarded as representing the control‐information processing mechanism and function of the biological system in response to the external environment, reflecting the functions of the higher‐level portion of the central nervous system, i.e., the brain. With the proposed model the behavior can also correspond to the functions and mechanism of the lower levels, i.e., the brainstem‐spinal system, which seems to imply that the brain and brainstem‐spinal systems are similar in functional structure but process different information.
A new approach to the two‐dimensional placement problem of wire congestion in Master‐Slice LSI layout design
Authors: Jung Junghwa , Hirayama Hiroshi , Goto Satoshi
Published: July 2007

As the objective functions for the placement problems for LSI and printed circuit board, the minimization of the total routing length and the minimization of the maximum min‐cut density have been used. These quantities are considered to reflect the objective of the layout problem (100% wiring ratio) globally. However, since they do not reflect local congestions of wiring, they are often inadequate as an objective function. This paper introduces a new concept of wire‐congestion of segments to represent the degree of local wire congestion. As an objective function, the minimization of the wire conjection of segments is proposed. An efficient heuristic algorithm is developed to minimize this objective function and the results of program experiments are presented to show its effectiveness. As a result of experiments, it was found that the maximum value of the wire‐congestion of segments became smaller as the total routing length became samller and that the former became larger as the latter became larger. Also obtained experimentally was a control parameter (wire‐congestion parameter) which simultaneously makes the total routing length short and the maximum of wire‐congestion small.