bluuebunny/crossref_metadata_2025 huggingface dataset:
Avoiding accumulation of deterioration caused by iterated dct image coding
Authors: Ando Dai , Higashino Suguru , Yanaka Kazuhisa
Published: July 2007

Discrete 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

This 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

A 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

With 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

The 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

In 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

A 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

In 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

In 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

Unwanted 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

Since 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

When 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

This 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

This 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

It 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

It 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

In 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

The 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.
A variable bit rate video codec for ATM networks and its robustness against cell losses
Authors: Manabe Katsutoshi , Tanaka Tomoaki , Ohtsuka Sakuichi
Published: July 2007

A video codec for ATM (Asynchronous data Transfer Mode), which is the transfer scheme in the era of B‐ISDN (broadband aspects of ISDN) is constructed and the performance is evaluated. The experimental equipment can realize the variable‐rate coded video transmission corresponding to CCIR 601 recommendation, through the experimental switching network. The periodic cyclic refresh, packeting of the coded information, and the interframe prediction DCT layered coding are employed, realizing a robustness against the cell loss which is the cause of a drastic image quality deterioration in ATM.

As a result of the subjective evaluation experiment, the image quality of MOS 3.5 or above is obtained for the cell loss ratio of 10−6 using only the cyclic refresh and the packeting of the coded information, and 10−2 to 10−4 of low‐priority order information using the interframe prediction DCT layered coding.
Optimum dimensioning of circuit‐switched networks handling heterogeneous traffic with application to multiple bit‐rate network dimensioning
Authors: Shinohara Masaaki
Published: July 2007

ISDN network resources such as links and nodes can be shared by various classes of calls with different bit‐rate service quality, holding time characteristics, etc., raising expectations for economical design and efficient operation of the networks. Heterogeneous‐traffic network dimensioning is defined as a problem of determining each link size so as to minimize the total network cost while satisfying the individual loss probability specifications. This is formulated as a nonlinear programming problem and an iterative algorithm for solving it is proposed.

The iterative algorithm is similar to the one used in single‐class traffic network dimensioning, but the optimality conditions are constructed by temporarily using the individual loss probability constraints for the traffic classes for which the equality is held in the preceding iteration. The algorithm then is applied to dimensioning networks serving multiple bit‐rate traffic, and its dimensioning examples are shown. The result shows design characteristics peculiar to a heterogeneous traffic environment, such as the possibility of two local minima, and network topologies with zero direct link size and nonzero direct link size are shown.
Novel automatic bias voltage control for LiNbo3 mach‐zehnder optical modulators using probe light
Authors: Kataoka Tomoyoshi , Hagimoto Kazuo
Published: July 2007

LiNbO3 Mach‐Zehnder optical modulators, which are expected to be used for multi‐Gbit/s optical transmission scheme, have one problem which is a dc drift phenomenon. In order to operate this modulator for a long time, a control unit to adjust a bias voltage for such dc drift is therefore necessary. So far, a method to superimpose a control signal with a main signal has been commonly used. However, the control signal may influence the output signal in this method. A novel automatic bias voltage control scheme utilizing the feature of Mach‐Zehnder modulator with traveling‐wave electrodes is proposed in this paper. A dc drift can be detected with a probe light propagating along a direction opposite to that of a modulated voltage waveform, and therefore very little influence of the probe signal on the output signal would be expected. A theoretical discussion on a dc drift detection and control method is described. This method has been successfully demonstrated to work for a mark density of 1/4, 1/2, and 3/4.
Multiple differential detection with adaptive sequence estimation (MDD‐ASE)–‐mobile radio transmission performance in frequency selective fading environment
Authors: Nakajima Tatsuhiro , Horikoshi Jun , Fukawa Kazuhiko , Suzuki Hiroshi
Published: July 2007

This paper aims at the improvement of the transmission performance of the differential detection system in the mobile radio transmission channel in a frequency selective environment. The multiple differential detection with adaptive sequence estimation (MDD‐ASE) is proposed, and the performance is analyzed by a computer simulation. In MDD‐ASE, not only the differential detection by one‐symbol delay but also the differential detection by two‐ or more‐symbol delays are applied. The soft decision is applied to the output of the multiple differential detection, and the symbol sequence is estimated by Viterbi algorithm (VA).

The bit error rate (BER) performance is improved by the extended observation time by the multiple differential detection and the sequence estimation. The number of states in VA and the processing complexity of the adaptive algorithm increases exponentially with the extension of the observation time. Consequently, the following method is proposed: (i) the number of parameters to be estimated is reduced; and (ii) the sequence candidates stored in each path of VA are fed back.

In this paper, the configuration and operation of MDD‐ASE are described first and then the transmission performance of the 40 kbit/s QPSK modulation system is presented. As a result of analysis for the static and the dynamic performances of ADD‐MSE using one‐ and two‐symbol differential detection, it is shown that the improvement effect is almost the same as in coherent detection DFE.
A high‐accuracy positioning service for land‐based mobile communication systems using the DGPS method
Authors: Ishikawa Hiroyasu , Kobayashi Hideo , Mizuno Toshio
Published: July 2007

This paper proposes a high‐accuracy positioning service for terrestrial mobile communication systems which employs the global positioning system (GPS) with the differential method (DGPS). The proposed system provides a high‐accuracy navigation service to land‐based mobile communication users. The proposed system also provides a comprehensive vehicle control service to the transportation companies when both forward and return links are available in the terrestrial‐based mobile communication systems.

This paper also assesses the performance of the DGPS method by computer simulations and a field experiment in an urban area to identify the viability of the proposed system under an actual environment. The relationship between average ranging time rate and the average visible number of satellites in various operating environments also is investigated.
An estimation method of buried pipe location by using zero‐crossed synthetic aperture
Authors: Nagashima Yuji , Yoshida Hirotaka , Masuda Jun‐Ichi , Komatsu Kouji
Published: July 2007

In the buried‐object search technique using a pulsed radar, the estimation method for the buried‐pipe location and the underground propagation velocity of the electromagnetic wave by means of a synthetic aperture method has been studied. In general, the electromagnetic wave attenuates as it propagates in the underground and the amplitude of the received signal often becomes extremely small. Therefore, it has been difficult in the signal processing using the amplitude value to recognize several buried objects at different depths by an identical discrimination standard.

To resolve this difficulty, a new zero‐crossed synthetic aperture method is developed. In the underground cross‐sectional image, the waves reflected from a buried pipe form a hyperbolic pattern dependent on the underground propagation velocity of the electromagnetic wave. By evaluating only the edge of this hyperbolic pattern, the underground propagation velocity of the electromagnetic wave and the location of the buried object are estimated.

First, to extract the edge, the amplitude value at the time when the observed signal has a “0” amplitude is replaced with “1” if the phase of the original waveform changes from minus to plus whereas with “‐1” if it changes from plus to minus. The amplitude at other time points is replaced with “0.” Subsequently, a synthetic aperture process (addition process) is carried out. Since the absolute value of the amplitude is 1 or 0, it is not necessary to consider the effect of the attenuation of the amplitude due to propagation of the electromagnetic wave as a discrimination reference in the estimation of the location of the buried pipe after the addition process. The location of the buried pipe can be detected accurately.
Widening the bandwidth of ferrite electromagnetic wave absorbers by attaching rubber ferrite
Authors: Naito Yoshiyuki , Mizumoto Tetsuya , Wakita Yuuichi , Takahashi Michiharu
Published: July 2007

With a view to increasing the bandwidth of ferrite electromagnetic wave absorbers, the reflection characteristics were studied for an absorber made of sintered ferrite loaded with rubber ferrite via an appropriate dielectric layer.

First, by means of calculations, it is shown that this structure has a bandwidth wider than that for the sintered ferrite single‐layer absorber. Also, the bandwidth of the absorber increases as the permittivity of the dielectric material inserted in between is lower. By loading an appropriately thick rubber ferrite plate via an air layer on a sintered ferrite plate, an absorber can be constructed for which the reflection is less than ‐20 dB over the frequency range from 30 to 1830 MHz. By loading another air/rubber ferrite pair, an even further increase of the bandwidth is possible. For an existing ferrite single‐layer absorber, it is effective for increase of the bandwidth to load the air/rubber ferrite by attaching a sheet resistance on the ferrite surface.

Finally, by an experiment, it is shown that a broader bandwidth can be obtained than the ferrite single‐layer absorber by loading a rubber ferrite via a low‐permittivity layer.
Application of modulation level‐controlled radio system to ATM networks
Authors: Ohuchi Mikihiro , Lee Hee‐Jin , Komaki Shozo , Morinaga Norihiko
Published: July 2007

This paper considers the application of the modulation level‐controlled variable capacity radio channel to asynchronous transfer mode (ATM) networks and analyzes the cell loss characteristic. A system is proposed in which the transmission capacity of the overall system can be enlarged by controlling the number of modulation levels. This helps to enhance the absorption effect for the traffic variation in ATM networks. Therefore, the proposed system can reduce the cell loss probability.

As a result of quantitative analysis of the system, it is shown that the cell loss improvement is by the factor of several hundreds to several thousands compared to the virtual path fixed‐capacity transmission system and several to several thousands compared to the virtual path capacity control system proposed up to present.
capacity assignment algorithm for packet switching network with different grades of service
Authors: Sugano Masashi , Murata Masayuki , Miyahara Hideo
Published: July 2007

A multimedia communication network is expected to treat various kinds of information, e.g., voice, image, and data which have different demands of grade of service. Furthermore, in new high‐speed networks, end‐to‐end delay distributions or packet‐loss probabilities rather than average delays become more important performance measures.

This paper presents a new heuristic design algorithm for packet switching communication networks in which the end‐to‐end delay distribution and packet‐loss probabilities are adopted as design constraints. It is shown that, while the total cost is increased slightly when compared with the former approach, end‐to‐end delays and packet‐loss probabilities between every two end‐nodes can satisfy predefined constraint as expected.
Two‐dimensional interpolation in the wavenumber domain for radar image reconstruction
Authors: Furusawa Akira , Wakayama Toshio , Sato Toru , Kimura Iwane
Published: July 2007

In the two‐dimensional radar image reconstruction using diffraction tomography, missing data become a significant problem if the observation direction and the scan range are restricted. A method is proposed in which these missing data are interpolated in the wavenumber domain. As an object image, a collection of the point targets is assumed. By means of a method which minimizes repetitively the square residual of the observed values and the reconstructed image in the wavenumber space, it is shown by simulation that a good image reconstruction is possible even if the missing rate is as high as 50 percent.

As a method to provide the initial value for the repetitive method, an interpolation method using the autocorrelation function is proposed. It is shown that this scheme works well in a stable manner even for a high missing rate and a poor SN ratio. Further, an objective discrimination criterion is proposed for estimation of the number of targets. It is shown that the true target can easily be discriminated if the SN is good and that a stable estimation is still possible even if the SN is poor and the extraction of a weak image is difficult.
High‐frequency analysis of electromagnetic fields on variable radius of concave‐conducting boundary
Authors: Ishihara Toyohiko , Goto Keiji
Published: July 2007

By extending the electromagnetic field representation on a cylindrical concave boundary with a constant radius of curvature, two types of representations are proposed for analysis of high‐frequency electromagnetic field on a concave boundary in which the radius of curvature depends on the location. They are: (1) a combination of the ray‐tracing method and the adiabatic whispering gallery (WG) mode; and (2) a combination of the ray‐tracing and the modified integral‐type interference waves. The limitations of the application of these field representations also are presented.

Especially, the adiabatic WG mode is obtained by an approximate analysis of a parabolic equation in a curvilinear coordinate system under the condition that the radius of curvature changes slowly. A transformation equation is obtained from the lower‐order WG modal solution on a cylindrical concave boundary to the adiabatic WG mode.

The foregoing transformation which is similar to the one proposed in the problem of diffraction of a creeping wave on a convex boundary is applied to an integral‐type interference wave and subsequently a modified integral‐type interference wave is derived which can be applied to the case where the radius of curvature changes as an adiabatic approximation. Further, a ray‐tracing algorithm is proposed for determination of the geometrical rays arriving at an arbitrary observation point within a concave surface and its usefulness is clarified.
Transmission power control for TDMA satellite communication systems
Authors: Kazama Hiroshi , Sakata Tetsu , Kato Shuzo , Saka Tsutomu
Published: July 2007

This paper aims at solving the problem of channel quality deterioration due to the reduced D/U and C/N by the rain attenuation. A method is proposed to improve the control accuracy in the transmission power control method. In the proposed method, the feedback‐loop control is applied to control the traffic earth station, and the set‐back closed‐loop control is applied to the control of the reference earth station. The site diversity is employed in the reference earth station, and the reference of the transmission power control is determined independently of the TDMA synchronization reference.

It is verified as a result of computer simulation and RF set‐back experiment for the proposed method that the control error for the reference earth station in Ku and Ka bands is within ±2.5 dB, and the control error for the traffic earth station is within ±2.0 dB, which is an excellent performance. The proposed method is applied to the actual system, and an excellent performance is obtained in the control through a satellite.
A modular cable‐mesh deployable structure for large‐scale satellite communication antennas
Authors: Meguro Akira , Mitsugi Jin , Ando Kazuhide
Published: July 2007

This paper describes a concept and key technologies for a modular mesh deployable antenna. A modular concent is suggested. The advantage of the modular concept and the influence of alignment errors on the surface accuracy are estimated quantitatively. The antenna reflector consists of a mesh surface, a cable network, and deployable truss modules. The cable network comprises three kinds of cables–surface, tie, and back cables. Adjustment of tie cable lengths improves the surface accuracy. Synchronous deployment truss structures are considered as a supporting structure. Their design method, bread board models, and deployment analysis are explained.
Evaluation of acknowledgement methods for high‐speed data transmission
Authors: Saito Tadao , Aida Hitoshi , Tomiyama Tadahiro , Fu Hong
Published: July 2007

The protocol in the open system interconnection (OSI) basic reference model is specified as a system with a multilayer structure. The performance of the network is related closely to the network configuration and the protocol parameters. The authors have been attempting to evaluate the transmission efficiency of the network using the multilayered protocol, with the transmission speed, the window size, and the transmission delay as the parameters.

It is assumed in the studies that the acknowledgement is returned at the end of each window. On the other hand, it is seen that the throughput of the network in the high‐speed transmission is affected greatly by the acknowledgement method. This paper notes this point and evaluates the relation between the acknowledgement method and the transmission efficiency. To achieve the desired transmission speed, the conditions for the window size, the acknowledgement method, and the protocol processing time are presented.
Virtual path test function and its mechanism for ATM transport networks
Authors: Matsunaga Haruhiko , Uematsu Hitoshi , Kanayama Yukiharu , Ueda Hiromi
Published: July 2007

This paper considers a function to improve the efficiency of the operation administration and maintenance (OAM) of the virtual path (VP) in the ATM network. A VP test method is proposed which can test the connectivity and performance at new VP establishment and locate the fault point at VP failure. The implementation of the method is discussed. The feature of proposed method is that the number of error bits, the number of lost cells, and the number of misdelivered cells can be measured by transmitting and receiving the test OAM cell in any test section of VP.

In this paper, the purpose and requirements for the VP test system are described first. Then the mechanisms in the proposed system and the allocation of test functions are considered. A transmission performance measurement algorithm is proposed for the test OAM receiver so that the bit error, the cell loss, and the cell misdelivery can accurately be counted. The structure of the VP test OAM cell to realize the proposed algorithm is presented. Finally, the system parameters of the proposed method are evaluated quantitatively.
Ranging and positioning experiments for an aircraft using a geostationary satellite–the effect of a flight route and orbit elements
Authors: Ito Ken
Published: July 2007

A ranging and positioning system using a geostationary satellite has been developed and its performance has been evaluated using an aircraft. This system can be applied to oceanic air traffic control and can be used at a ground station to determine positions of aircraft. An experimental system consists of a geostationary satellite, a ground station, an aircraft, and a pseudo‐satellite, which is installed inside the ground station and used as the substitute for another geostationary satellite. The Engineering Test Satellite V (ETS‐V) of Japan was used in the experiment.

It is known that the positioning error increases as a user approaches the equator in a positioning system using two geostationary satellites. This fact has been confirmed in this paper by experiment. It has also been shown that positioning errors can be decreased by using relative positioning in which the position of the ground station is used as a reference station. The use of old orbit elements increases the error of the predicted position of the geostationary satellite and therefore increases the positioning error of the aircraft. This has also been confirmed in the experiment. Furthermore, it has been shown that, in relative positioning, positioning errors do not increase much even with old orbit elements and the epoch of orbit elements does not have much influence on positioning errors.
Design of large‐circle rogowski coil for measuring lightning current in building columns and girders
Authors: Sato Masaji , Kuramoto Shoichi , Matsuoka Koichi , Ohta Minoru , Takemoto Koji
Published: July 2007

When observation of a direct lightning strike to a building is performed or in an experiment for applying lightning using a building, one needs current sensors that can measure the current in building columns, girders, and walls. As the current sensor, the Rogowski coil commonly is used. The coil is placed around the object to be measured, and the inductive voltage is obtained. Although there are many commercially available units, these sensors are too small for measuring building columns and girders.

This paper studies Rogowski coils which are long enough to encircle the building columns and girders and flexible enough to set up the structure according to the practical situation. First, the coil and the integrator are described by their lumped element equivalent circuits. In addition, the target values were set for the frequency bandwidth and the sensitivity. A structure optimum for these characteristics was found. From the results, a hollow core coil using a vinyl pipe was fabricated. A Rogowski coil 1 to 10 m long was realized which has a frequency of 300 kHz and a current‐voltage conversion factor of 1/100. Further, the position dependence of the current to be measured was observed. Sufficiently practical characteristics were obtained with the present coil with a long structure.
A hyperdistributed switching system architecture for B‐ISDN
Authors: Tanabe Shiro , Sakurai Yoshito
Published: July 2007

The broadband integrated services digital network (B‐ISDN) is expected to realize a high‐speed network. Information with diversified classes of quality must be transmitted on the network, from the 64‐kbit/s voice signal to the several tens Mbit/s video signal. Another aspect is that the voice and the video signals are sensitive to the delay, and severe requirements are imposed on the data error. For the switching system in B‐ISDN, an architecture is required which fully utilizes the advantages of the asynchronous transfer mode (ATM) communication system, where the effective use of the network is considered by multiplexing the multimedia.

This paper proposes the hyperdistributed architecture to be applied to such a broadband communication environment. In the proposed system, front‐end processing modules (FPM), which are independent ATM nodes with the call processing functions, are placed according to the scale of system. The central switching module (CSM) with the single‐stage distributed ATM switch to connect FPM is provided only with the self‐routing function based on the routing information in the ATM cell header. For the proposed hyperdistributed architecture, the design for the communication channel based on the ATM nonblocking condition, as well as the transfer route determination, are discussed. Then the allocation of the quality class control using the shared buffer ATM switch is discussed which can construct an efficient network satisfying the diversified quality requirements.
Performance evaluation of burst‐based bandwidth‐reservation method in ATM networks
Authors: Wakamiya Naoki , Baba Ken‐Ichi , Murata Masayuki , Miyahara Hideo
Published: July 2007

This paper considers the asynchronous transfer mode (ATM) network and evaluates the burst‐based allocation of the virtual channel (VC) bandwidth. In the traditional call‐based bandwidth allocation by statistical multiplexing based on the bursty property of the traffic, the cell loss is inevitable due to the short‐term traffic congestion.

This paper also considers the data terminal where the transmission rate can be adjusted through the negotiation with the network and evaluates the burst‐based bandwidth allocation mechanism. It is assumed in the proposed method that the virtual path (VP) is already divided into a number of channels and the channel is allocated for each burst. The data transfer by such a bandwidth‐reservation method is evaluated quantitatively by an analytical approach, and an adequate division into VP channels is indicated.