bluuebunny/crossref_metadata_2025_split huggingface dataset:
Avoiding accumulation of deterioration caused by iterated dct image coding
Authors: Ando Dai , Higashino Suguru , Yanaka Kazuhisa 
Published: July 2007

AbstractDiscrete coding transform (DCT) coding is a highly efficient coding method for still images with continuous intensity. It has a feature that a drastic image compression can be realized. Among the coding methods considered by JPEG for international standardization, it is adopted as the most basic baseline system which is a cooperative organization of CCITT and ISO. However, the method is an irreversible coding.When the coding/decoding is applied iteratively to the image once coded and decoded, the image deterioration progresses due to the accumulation of the error. The major causes of the error accumulation are the quantization of the transform coefficient after DCT and the rounding off of the value when the intensity is converted to the integer value in the decoding.This paper shows theoretically the following property. When the quantization step Q satisfies a certain condition and if the image after coding/decoding stays within the range that can be represented by the same number of bits as the original image, no further image deterioration takes place in the following sense. When the decoded image is encoded again using the same quantization table, the result is the same as the previous value. When the image after coding/decoding is outside the range that can be represented by the number of bits of the original image, the value must be restricted.Thus, it is not necessarily true that the DCT transform coefficient of the image after encoding the image is the same as in the previous image. However, it is seen by the result of simulation that even in such a case, the process converges by a finite number of iterative codings, with only a slight deterioration of the signal‐to‐noise (SN) ratio.
A comparison of construction methods for mac and llc protocols in satellite packet communication networks
Authors: Suzuki Takahiro , Tasaka Shuji 
Published: July 2007

AbstractThis paper discusses the layered construction of the OSI second layer (data link layer) in the satellite packet communication network from the viewpoint of the system performance. The isolated‐type system, where the media access control (MAC) sublayer and logical link control (LLC) sublayer are defined independently, and the combined‐type system, where they are defined in a related way, are considered. The performances of those two systems are compared, using the throughput and the average response time as the evaluation criteria.The TDMA‐Reservation and the slotted‐ALOHA are considered as the MAC protocol. The connection‐oriented type is considered as the LLC protocol. As to the TDMA‐Reservation communication network, the isolated‐type system is analyzed by the equilibrium point analysis. Then the performances of the isolated type and the combined type are compared by the analysis and simulation.It is shown quantitatively by comparison that the performance of the isolated type is always better than that of the combined type. As to the slotted‐ALOHA communication network, it is shown by simulation that little difference is observed in the performances of the isolated and the combined types.
Analysis of switching characteristics of a mosfet synchronous rectifier
Authors: Sakai Eiji , Harada Koosuke 
Published: July 2007

AbstractA MOSFET synchronous rectifier is used to reduce power loss due to forward voltage in the rectifier device in the output rectifier circuit of a dc‐dc converter. In this paper, the switching characteristics of the MOSFET synchronous rectifier at the time of turn‐off is analyzed. In the analysis, a model is used in which the parasitic capacitance between the source and the drain of the MOSFET and the reverse recovery characteristics of the parasitic diode are taken into account.The delay time of the switching of the MOSFET is taken into consideration in the analysis. The effects of these parameters on the reverse recovery time and the reverse recovery current of the MOSFET at the turn‐off are determined. It is found that there are two modes in the turn‐off of the MOSFET synchronous rectifier and that both the reverse recovery time and the reverse current can be minimized by operation at the boundary of these modes.
Copy distribution stages for broadband broadcast connecting networks
Authors: Member Toru Maruta , Ji Yusheng , Asano Shoichiro 
Published: July 2007

AbstractWith the widespread use of high‐speed broadband communication, nonblocking switching networks in video distribution and other applications for the broadcast distribution connection will be required. Numerous studies have been made of performance analysis for switching networks for one‐to‐one switching connections, but it is anticipated that a future study is needed for one‐to‐many switching connections.This paper presents a construction for the copy distribution stage, which copies the cell for the broadcast distribution. The copy distribution stage is composed of a multistage connection network. The basic principle of operation is that the cells are arranged appropriately and are copied by the differential address driving.The proposed network is suited to high‐speed operation since nonblocking self‐routing is realized and the control logic is simple. The proposed network assumes that it precedes the network for one‐to‐one switching connection. Then one‐to‐many broadcast distribution connection is realized.
Characteristics of space‐diversity branch using parallel dipole antennas in mobile radio communications
Authors: Taga Tokio 
Published: July 2007

AbstractThe configuration of two parallel half‐wave dipoles is the basic space‐diversity branch for space‐diversity reception in mobile radio communications.This paper presents theoretical and experimental study on the antenna diversity branch connected to a 50‐ohm receiver. Post‐detection selection diversity is applied to determine the relation of the mean effective gain (MEG) and the correlation coefficient with the variation of angle of antenna inclination from the vertical direction, cross‐polarization power ratio (XPR) of the propagation path, and the distribution of the incident wave.First, it is clarified theoretically that, if antenna spacing is made less than 0.2 wavelength, then efficiency is reduced due to the coupling between the antenna elements and MEG is greatly deteriorated. Moreover, minimum antenna spacing for better MEG characteristics is in the range of 0.3 to 0.4 wavelengths.Next, it is clarified that the correlation coefficient is less than 0.1 for variation of antenna inclination, XPR, and the distribution of incident wave when the antenna spacing ranges from 0.2 to 0.3 wavelengths. Thus, an optimum antenna spacing exists in the forementioned space‐diversity branch, which theoretically is found to be about 0.3 wavelength. The validity of the theoretical results is confirmed by 900‐MHz band indoor experiments.
Distortion and cnr characteristics in fm‐fdm optical catv transmission
Authors: Maeda Mikio 
Published: July 2007

AbstractIn the multichannel frequency division multiplex (FDM) optical transmission, the intermodulation distortion generated by the nonlinearity of the LD is a problem. In this paper, it is analyzed that for the number of transmission channel, N, and the optical modulation index per channel, m, the CSO and CTB are constant for a different value of N if the effective optical modulation index, is maintained. The results are compared with experiments. In the present analysis, two types of nonlinearity of the current‐to‐optical conversion characteristics are considered. One of them is the nonlinearity near the bias current of the LD and is predominant in the region of a small effective optical modulation index. Another is the nonlinearity at the threshold value of the LD and is dominant when the effective optical modulation index is large. It is shown by means of the probability density function that the CSO and CTB degrade suddenly if the effect of the nonlinearity of the threshold value appears. In the FM‐FDM optical transmission, many distortions in the transmission bandwidth behave as the white noise due to frequency modulation when the carrier is frequency modulated by a video signal. Hence, the CN ratio is effectively degraded. In this paper, it is further presented that the CN ratio degraded by the distortions can be derived from the CSO and CTB by taking into consideration the frequency allocation of the FM signal.
Optics design for a millimeter‐wave phase‐imaging system and its application to plasma diagnostics
Authors: Uehara Kazuhiro , Yonekura Takeshi , Nishimura Hiroshi , Miyashita Kazuhito , Mizuno Koji 
Published: July 2007

AbstractA ten‐element imaging array which consists of an integrated antenna‐detector system that incorporates trap‐loaded Yagi antennas and Schottky diodes has been developed for operation in the millimeter‐wave band around 70 GHz. Also, a prototype optical system that comprises a millimeter‐wave phase‐imaging interferometer has been designed and fabricated. They were fitted to the GAMMA 10 tandem mirror at Tsukuba University. A real‐time measurement of the radial distribution of the plasma electron density was successfully demonstrated using those systems.
Crosstalk allocation method in design of broadband analog switching equipment
Authors: Oikawa Yoshinori , Hiraide Kazuhiro , Kataoka Hideki 
Published: July 2007

AbstractIn the design of concentration and distribution stages of analog video signal systems, the use of broadband analog switches helps to reduce the number of expensive bandwidth‐reduction CODECs. However, these switches must satisfy severe crosstalk attenuation requirements. To suppress the crosstalk, switch components and packaging must be chosen carefully and switch configurations and their implementation must also be considered. Moreover, the conventional design for one‐to‐one crosstalk cannot be applied to a distribution service for video signals, and a more detailed design that considers crosstalk phase conditions is required. However, no method of allocating the crosstalk attenuation objective to each component in the switch has yet been established for connecting one inlet to multiple outlets.This paper presents a model for crosstalk addition based on the generation mechanism of crosstalk and proposes the concept of equivalent power sum multiplicity. Using this model and concept, a method is proposed of allocating a crosstalk attenuation objective to each component of the switch in order to satisfy the overall quality.
Optical Nonlinearities in Coherent Optical Time Domain Reflectometry Enhanced with Optical Fiber Amplifiers
Authors: Izumita Hisashi , Koyamada Yahei , Furukawa Shin‐Ichi , Sankawa Izumi 
Published: July 2007

AbstractIn order to elucidate the incident pulsed power limit in coherent optical time domain reflectometry (OTDR) using erbium‐doped optical fiber amplifiers (EDFA), experimental data on the nonlinear optical phenomena in a single‐mode optical fiber by a high‐power coherent optical pulse and the resultant degradation of the coherent OTDR are presented and discussed. Previously, the stimulated Brillouin scattering and the stimulated Raman scattering have been considered as the limiting factors for the incident pulse power. However, two nonlinear optical phenomena have been observed which occur at power levels lower than the critical powers of the two phenomena.For a pulsewidth of 1 μs, the intensity gradient occurs in the incident pulse due to reduction of the inversion profile in the EDFA, and an optical frequency shift of the optical pulse occurs in the test optical fiber by the self‐phase modulation. As a result, the beat frequency of the back‐scattered light and the local frequency light falls outside the receiver bandwidth of the coherent OTDR.For a pulsewidth of 100 ns, the intensity gradient of the optical pulse is small, as is the effect of the self‐phase modulation. However, the incident pulse induces a 4‐wave mixing with the spontaneous emission from the EDFA and is transformed to the Stokes light and anti‐Stokes light. Hence, the backscattered light intensity within the receiver bandwidth is decreased, and the performance of the coherent OTDR is degraded. The foregoing results provide important guidelines for understanding the performance limitation of the coherent OTDR.
Suppression of radar clutter with a weighted moving average filter
Authors: Takahashi Satoshi , Miwa Susumu 
Published: July 2007

AbstractUnwanted radar echos, called clutter, make the detection of a target difficult. Therefore various methods have been proposed to suppress such clutters. However, since most of these methods are intended to improve single‐pulse detection performance, the target often disappears by pulse‐to‐pulse fluctuations.In this paper, as a method of suppressing radar clutter, an application of a moving average and a weighted moving average to the data after pulse integration is proposed. First, with the K‐distribution model proposed for modeling the clutter, the signal‐to‐clutter ratio is obtained in the case where infinite pulses are integrated. Next, a method is shown for derivation of the weights to be used for the weighted moving average. The results are shown for the process, using these weights for the sea clutter observed with an X‐band radar. By using the moving average method in the experiment with an X‐band radar, the signal‐to‐clutter ratio is improved by 4.2 dB compared with mere threshold detection, whereas the weighted moving average provides 5.0 dB improvement, which gives the better results.
An electromagnetic environmental monitoring system that interlocks with malfunctions
Authors: Masugi Masao , Takagi Kusuo , Sato Masaharu , Amemiya Fujio , Tokuda Masamitsu 
Published: July 2007

AbstractSince most electromagnetic malfunctions are of high speed and of a passing nature, it is difficult to specify the cause. The objective of this paper is to propose a monitoring system which can detect the electromagnetic waves in the time domain when malfunctions of electrical equipment occurs. The peak value of the detected waveform, the duration of the waveform, and the energy in an arbitrary frequency region were used as procedures to evaluate the measurement data. In this system, by integrating, the energy is defined as the energy spectrum of the detected waveform over arbitrary frequency regions.The monitoring system fabricated for trial was investigated in terms of the processing time such as the data transfer time. It was confirmed that almost 1 s is needed for storing the measured data and that this time duration is the maximum delay in the control of the present system.Using the transmission module as the equipment under test, we performed an experiment to apply the lightning surge on a building which simulates a telephone exchange office to verify the effectiveness of the monitoring system. The measurement results indicate that the amplitude and the energy of the current waveform flowing into the equipment from the grounding wire become several ten times those from other lines. As a result, the detected waveform raised the possibility of significant cause of trouble to the equipment.
Adaptive antennas using a kalman filter for fast mobile communications
Authors: Wang Jinkuan , Hagino Kojiro , Takano Tadashi 
Published: July 2007

AbstractWhen an adaptive antenna is used for a mobile station in a vehicle, it is necessary to quickly adapt the weight coefficients for a changing electromagnetic environment. In this paper, for a nonstationary state in which the signal arrival direction changes as the vehicle moves, the dynamic behavior of the weight coefficients is studied, and a state transition matrix of the optimum weight coefficients is derived.The proposed method is applied to a Kalman filter, and a method for controlling the weight coefficients in a nonstationary state is discussed. Further, by means of a simulation with a simple model, the effectiveness of the proposed model is verified. It is indicated that an accurate control is possible even if the electromagnetic environment changes rapidly in time. It is found that the proposed method has a superior adaptability over the least mean square (LMS) method and can be applied for high‐speed mobile communication.
Development of multibeam phased array antenna on ets‐vi for s‐band intersatellite communications
Authors: Tanaka Masato , Kimura Shigeru , Teshirogi Tasuku , Matsumoto Yasushi , Ito Takeo , Akaishi Akira , Mizutamari Hitoshi , Okubo Shigeru 
Published: July 2007

AbstractThis paper describes the S‐band intersatellite communication (SIC) antenna to be carried on the Engineering Test Satellite VI scheduled for launch in 1994, to undertake the first intersatellite data relay experiments in Japan. The SIC antenna is an on‐board formed multibeam phased array antenna, the first of this kind in the world to be carried on a satellite. The SIC antenna is capable of simultaneous data relays to several orbiting satellites (user satellites) by means of an electrically scanned beam. With an on‐board microprocessor, the location of a user satellite can be computed, and the beam is pointed toward that direction automatically.In comparison with the system used in the data relay satellite of the United States, the on‐board beam‐forming system has several advantages, such as the effective use of power and frequency in the case in which the number of user satellites is small, as in Japan. In this paper, the function and the configuration of an SIC antenna are described first. Next, analysis of the antenna is presented, including the effect of the phase and amplitude errors caused by temperature fluctuations. Further, as the main components, the newly developed broadband microstrip antenna, a small beam‐forming network with small phase errors, and the phase shifter controller making the computation of the orbit of the user satellite are presented. Finally, the total test results of the on‐board model of the SIC antenna are described.
Performance analysis of zone‐structured packet radio network for mobile terminals
Authors: Mukumoto Kaiji , Fukuda Akira 
Published: July 2007

AbstractThis paper studies the system performance of a zone‐structured packet radio network with mobile terminals to which the slotted ALOHA protocol is applied. Conventional performance analyses of the zone‐structured packet radio network have not considered the effect of terminal mobile speed. Here, a model is developed for such a zone‐structured network where a Markov model is used as the mobility model of a terminal and analytical techniques to evaluate static and dynamic performance of the system are presented. Numerical results and their intuitive interpretations are discussed to examine the effect of zone overlapping, mobile speed, etc.
Meteor burst broadcast systems with repeating scheme
Authors: Nagasawa Masashi , Mukumoto Kaiji , Fukuda Akira 
Published: July 2007

AbstractIt is known that the beyond‐line‐of‐sight radio communication channel can be set probabilistically by a column of ionized particles generated when a meteor penetrates into the atmosphere. Numerous transmission control procedures have been reported for an efficient data transmission with this communication channel. Since this communication channel appears independently between two points, it is possible to transmit identical messages from several different locations to one station, thereby improving the receiving probability of a specific message. Because of this characteristic, the transmission time can be reduced by relay transmission of the message by the station successful in receiving the message to other stations. However, to date, little has been reported on relay systems of this type.The present paper proposes a relay system called the unconditional diffusion repeating broadcast scheme and analyzes its characteristics. In this system, the station successful in receiving a message unconditionally broadcasts it. In the case of typical numerical examples studied here, it is shown that the broadcasting time in which the probability of stations without reception is less than 1 percent can be reduced to about two‐thirds when the number of receiving stations is 2. For more than two receiving stations, the reduction is even greater while the improvement effect is saturated when the number of stations is about 20. The situation worsens for more than 30 stations.
Automatic derivation of test cases for LOTOS expressions with data parameters
Authors: Li Xiang Dong , Higashino Teruo , Taniguchi Kenichi 
Published: July 2007

AbstractIt is known as generally impossible to generate automatically the test cases for arbitrary LOTOS expression containing data parameters. A subclass of LOTOS, called P‐LOTOS, is defined. In P‐LOTOS, the data type is restricted to be integer and Boolean and the operation on the integer is restricted to be the addition/subtraction and comparison.This paper presents an algorithm for automatic generation of the test cases for this class of LOTOS descriptions. Algorithms also are presented solving the detection problems for the deadlocks, the unexecutable edges, and the nondeterministic branches. The proposed algorithm is applied to a simplified OSI session protocol, and the result is reported in this paper.
Analysis of meteor burst communication systems with n pairs of stations
Authors: Nagasawa Masashi , Mukumoto Kaiji , Fukuda Akira 
Published: July 2007

AbstractIn the two‐way beyond line‐of‐sight communication using meteor burst, several station pairs can operate on the same frequency band. To date, however, no quantitative studies have been carried out to determine how many station pairs can use a given frequency band.In this paper, the characteristics are analyzed quantitatively in the case where n station pairs commonly use the same frequency band. As the simplest system, a meteor burst system with full‐duplex station pairs is considered. The throughput, optimum number of station pairs, and channel utilization are analyzed.First, an ideal case is studied in which neither the overhead by the header nor the loss of division into blocks is considered. Next, the case with a header and then the case with constant block size are considered. In each case, the relationship of the number of the station pairs to the throughput and channel utilization is derived. Some numerical results for practical models are presented. It is shown that such a configuration is useful for improving the utilization of frequency band.
Configuration of ATM switching networks which are nonblocking at call level
Authors: Sezaki Kaoru , Yasuda Yasuhiko 
Published: July 2007

AbstractThe construction of large‐scale ATM switching networks is done mainly to configure switching networks only with buffered unit switches and to establish a simple path on a call‐by‐call basis. With this approach it is desired that ATM switching networks be nonblocking at call level qr there always exists a path consisting only of inner links with sufficient idle capacity.An efficient configuration of a new class of ATM switching networks is proposed which are nonblocking at the call level. First, the proposed network is shown in the most generalized form and the nonblocking condition is derived. Then, by reforming this generalized configuration into a more practical one, two types of configurations are derived. Through comparison of the two types, it is clarified that Parallel Benes Configuration is optimum. It has the following features: (1) It can be composed by only one kind of n × n square unit switches; (2) it is very fault‐tolerant; (3) besides non‐blocking at the call level, good cell‐level traffic performance is expected. It is shown also that a high‐speed unit switch is mandatory for very large‐scale ATM switching networks to reduce the hardware volume and the number of inner links.