bluuebunny/crossref_metadata_2025 huggingface dataset:
A consideration for measure of information based on the dempster‐shafer theory
Authors: Kobayashi Kunikatsu , Suzuki Nobuaki , Nemoto Yoshiaki , Sato Risaburo
Published: July 2007

This paper discusses the measure of information for the event using the probability theory by Dempster and Shafer. By providing various kinds of information to the event containing an ambiguity, the ambiguity is gradually decreased to define the event in a clearer way. The combination rule by Dempster is most suited to represent the combination of information. This paper shows first that several representations can be made for Dempster's combination rule. Then using the upper and lower probabilities defined by the basic probability of the event, the upper and lower information measures are defined, followed by the discussion of their properties. The lower probability of a set (event) is defined as the sum of basic probabilities of all subsets in the set, and the upper probability is defined as the sum of basic probabilities of all sets which contain an element of the set. Thus, the upper and lower information measures can be interpreted as the measures of information concerning the message with ambiguity. Finally, several examples are discussed, determining the information measure for the message containing ambiguity.
A/D and D/A converters using a switched capacitor amplifier
Authors: Seki Hideaki , Mori Shinsaku
Published: July 2007

With the development of microcomputers and signal processors in recent years, A/D and D/A converters have increased their importance as analog/digital interfacing circuits. In the past, various types of A/D and D/A converters have been proposed and implemented for practical use. However, they do not necessarily satisfy the requirements for miniaturization, power saving, and low cost. In this paper we have proposed two A/D converters and one D/A converter which utilize the characteristics of a switched capacitor amplifier with switched capacitor bias and load circuits. Their principle, circuit configurations and experimental results are presented. In the proposed A/D and D/A converters only one active element is used. Also the capacitor is much smaller than in the conventional converters. Therefore, the proposed converters are advantageous as an analog/digital interfacing circuit with respect to miniaturization, power saving, and low cost. Experimentally, 5‐bit A/D and D/A converters were built with discrete components and tested. The obtained result confirmed their proper application with a linearity of ± 1/2 LSB.
A charge simulation method with boundary shape taken into account
Authors: Suzuki Yoshihiko , Inoue Yasushi
Published: July 2007

The charge simulation method is used to obtain an approximate solution of the Laplace equation and others but it has several problems including the charge arrangement. This method determines the charge quantitites, the unknown coefficients, by satisfying the boundary values only at the constraint points arranged on the boundary. For a smooth boundary, a small number of charges suffices; however, for a complex boundary the number of constraint points must be increased to represent the boundary shape. The product paper proposes a new charge simulation method with the boundary shape taken into account by utilizing the orthogonal property of the equipotential lines and electric force lines at the constraint points in order to represent a given boundary shape. In other words, the charge quantities are determined such that not only the boundary values but also the forementioned orthogonality are satisfied at the constraint points. It is shown that in this way the boundary shape is taken into account and the error dependence on the charge arrangement as seen in the conventional method can be relaxed.
Suppression of anharmonic spurious modes in quartz resonators by modified electrode design using charge cancellation
Authors: Sekimoto Hitoshi , Ihara Toshiyuki , Nakata Hozumi , Miura Masaaki
Published: July 2007

One of the most important problems in the design of the thickness vibration resonator is how to suppress the anharmonic higher‐order spurious mode which is generated near the main resonant frequency. It is easy to realize a single resonant characteristic by the design based on the trapped energy theory, but the area of the electrode and, consequently, the inductance, are limited. This paper proposes a method which improves this point and increases the degrees of freedom in the design, suppressing the anharmonic spurious mode by adding a mass to the edge of the electrode and by cancelling the charge. In other words, a modified circular electrode structure is proposed in which the peripheral part (ring) of the electrode has a larger thickness. The third overtone resonator is analyzed in detail, and it is shown theoretically that the dominant (3, 3, 1) spurious mode is suppressed by the charge cancellation, thereby realizing a resonator with an essentially single resonant characteristic over a wide frequency range. It is noted that the charge cancellation characteristics for the spurious mode are strongly dependent on the platebacking of the ring electrode. The data for the optimum design are summarized in a table which will be utilized in the future design.
Design centering for analog‐integrated circuits using spherical surface random numbers
Authors: Jyo Yoichi , Ikeda Hiroshi , Minamoto Suemitsu , Kojima Yoshiaki
Published: July 2007

This paper considers the semiconductor integrated circuit, and proposes a solution to the decision problem for the optimum design, where circuit‐element values are determined so that the yield is maximized. The spherical surface random number is employed in the calculation of the yield. Although various nonlinear programming methods can be applied to the optimization problem, this paper applies Newton's algorithm to the optimization algorithm. It is shown that the first‐ and the second‐order derivatives of the yield to the design value, which are needed in the calculation of the search vector in Newton's method, can also be derived using the spherical surface random numbers. I is also shown that the center of the element value determined by the design specification can be calculated using the spherical surface random numbers, and the optimization can be performed efficiently using the center as the initial point for the optimization. Applying the proposed method to the 5th‐order leapfrog‐type switched‐capacitor filter, the processing time is reduced to approximately onefourth compared with the case of the Monte‐Carlo method.
Hybrid ARQ system employing soft decoding algorithm
Authors: Kobayashi Hideo
Published: July 2007

It is known that by applying a soft decoding algorithm to the error‐detecting code in the ARQ system, a hybrid ARQ system can be realized in which error detection and correction are possible. This paper discusses the application of the soft decoding algorithm to the ARQ system, where the multivalued digital modulation is employed. A scheme for a practical system is proposed, including the detection of channel measurement information in the multivalued digital modulation system and estimation of error patterns. By the proposed method, the hybrid ARQ system can easily be realized by adding some peripheral circuits to the conventional ARQ receiver. Theoretical study is made on the number of error patterns that can be estimated for a long block length as well as the probability of miss and the probability of retransmission request. The proposed scheme was applied experimentally to the ARQ system employing SG VIII V.29 modem based on CCITT recommendation, and the usefulness of the proposed scheme was verified by experiment.
Round‐off error analysis for deadbeat control system using observer
Authors: Imai Nobuyuki , Hirai Kazumasa
Published: July 2007

In the control system using a digital computer with finite word‐length, the control performance is degraded by the quantization error of the signal and the control parameter, as well as the round‐off error in the computation. Consequently, one of the important problems is to establish the design method which can reduce the effect of the quantization error. This paper considers the deadbeat control system with an observer, and analyzes the round‐off error in the floating‐point computation. The effect of the round‐off error on the control system is evaluated quantitatively. Finally, a numerical example is presented demonstrating the validity of the result in this paper, as well as the effectiveness of the parameter determination method for the observer to reduce the effect of the error.
Processing of ultrasonic pulse‐echo signals to remove electroacoustic conversion distortion
Authors: Yamada Akira , Abe Kenichi
Published: July 2007

In the ultrasonic pulse‐echo system, the reflection characteristics of the acoustic system are reproduced faithfully by signal processing to remove electroacoustic conversion distortion contained in the pulse‐echo signal. The proposed signal processing has the feature that the two contradictory requirements for high resolution and high sensitivity can both be satisfied. Another feature is that the single‐peak impulse characteristics can easily be realized. Problems left to be solved for practical applications are the reduction of the processing noise and the improvement of the processing speed. A possible solution is to utilize effectively the a priori knowledge about the distortion characteristics. This paper presents a basic physical discussion on the convolution model for the pulse‐echo system. Presented also is a clear description of the distortion function. Based on the results, a high‐speed signal‐processing system with on‐line recursive computation is proposed using the least‐square transversal filter in the time domain. The solution to the forementioned problem toward practical application is discussed by examining the computation method for the filter coefficients with smaller processing noise. At the end of this paper, an evaluation experiment is performed for the proposed signal‐processing system, indicating that the reflection characteristics of the acoustic part can be restored with small processing noise and high quality.
Design of world loop networks and effectiveness evaluation of dynamic routing
Authors: Mori Hiromichi
Published: July 2007

Intercontinental optical submarine cables with larger capacities than conventional coaxial cables are now being developed. In accordance with international communication demand evolution and digitalization, worldwide optical submarine cable networks will be constructed. A loop network around the world in an east‐west direction, composed of optical submarine cables is considered to be an international backbone trunk network due to the advantages in simplicity, efficiency and reliability. Since the proposed design method aims at making a macroscopic network planning outline rather than making a detailed network design, the stochastic process of traffic is neglected and the traffic is treated as stationary flow. We present the strategies to evolve the world loop network and the increased traffic demand that reflects the actual international communication traffic trend. In addition to the conventional routing scheme in which mainly direct routes are used, a dynamic routing scheme in which routes composed of up to two tandem links are used is studied, and its effectiveness through network evolution is quantitatively evaluated.
Edge extraction and restoration of noisy image by innovation process in kalman filter
Authors: Kawazoe Yasuhiro
Published: July 2007

Edge detection and restoration methods are considered from noisy images without a priori information about original images. The chi‐square test detects edges from an innovation process when applying the Kalman filter to the first‐order AR model. Image‐extracted edges are the binary image and the thin‐line image. The success of the algorithm depends heavily on the window width for the chi‐square test and the value of the threshold in which the detector operates.

Also, edge information is used for restoring images to remove noise in the background of images using a smoother and to obtain sharp edges in other regions using a sensitive filter. The effect of the approach is illustrated by the simulations.
Study on a self‐routing switch network with mutual control
Authors: Uematsu Hitoshi , Watanabe Ryuichi
Published: July 2007

Recently, the application of self‐routing switches to transport processing nodes such as the digital cross‐connect system and digital switching system is being studied to realize a large‐capacity enhanced transport processing node by distributed control. For this purpose, Shuffle‐Exchange networks, Batcher‐Banyan networks, etc., have been proposed so far. A Shuffle‐Exchange network is minimal in its switch size but is a limited‐availability system. The Batcher‐Banyan network is a full availability system in a sense that the routing is controlled and automatically rearranged in a distributed manner at a switch cell. This paper proposes a new type of packet switching network, which consists of self‐routing switches having mutual switching control for packet headers between a pair of self‐routing switches. All the switch cells are controlled with only one bit of input packet header by the same switching algorithm. The proposed switching network is a nonblocking (fully available) switch having a self‐rearrangeable function similar to the Batcher‐Banyan network and is controlled in a distributed manner within a switch cell. Its performance is compared with those of existing switching networks and its characteristics are shown.
Performance evaluation of processing element in a data‐flow control scheme
Authors: Nogami Shinya
Published: July 2007

This paper describes the behavior of the processing element (PE) generally used in applying the data‐flow control scheme to signal processing equipment in the switching system or in the computer system. A performance evaluation is presented in terms of the characteristics based on the theoretical analysis. It is important in this scheme to evaluate the time until the program execution is completed (program execution time) for the given parallelism of the data‐flow program and the multiplicity of the program (task). As a preliminary to the estimation of the program execution time, this paper evaluates PE as a whole.

First, the matching‐store unit of PE is considered. A simple numerical analysis based on the traffic model is presented and the performance is evaluated. The characteristics such as the mean number of waiting calls and the mean waiting time are calculated. Using those results, the whole PE is modeled as a BCMP‐type queueing network, and the mean cycle time is derived. Finally, the result of numerical calculation and the result of simulation are illustrated. The range of application is described, together with some discussions.
Observation and interpretation of patched structures in the spectra of low‐latitude whistlers
Authors: Ohta Kenji , Eguchi Hiroyuki , Hayakawa Masashi
Published: July 2007

It has been known for a long time that the intensities of the whistlers observed on the ground sometime exhibit frequency dependence through analyses of sonograms. The frequency dependence of the intensities of whistlers observed at low altitudes was examined in detail with the aid of a PCM recorder and FFT analysis. As a result, whistlers were found whose intensity spectra were independent of the frequency spectra of their causative atmospherics. In other words, the changes of the received signal intensities of each whistler with respect to the frequency had patchy patterns. This paper describes various characteristics of patched whistlers. For their interpretation it is proposed that their generation was due to the wave interference by the irregularities of electron densities in the F‐layer ionosphere.
Adapative arq schemes and their performance evaluation under full‐duplex transmission
Authors: Ishibashi Yutaka
Published: July 2007

Adaptive ARQ (automatic repeat request) is an error‐control scheme in data transmission in which the number of successively transmitted data blocks and the data block length are adjusted according to the bit error rate. This scheme performs better in half‐duplex transmission than the conventional selective repeat (SR) and go‐back‐N (GBN) schemes when the bit error rate is either not known or varies with time.

This paper proposes a control procedure for the full‐duplex adaptive ARQ scheme. In this procedure an observation period is defined and the data block length is adjusted dynamically according to the success of the data block transmission in the observation period. The throughput of this scheme is analyzed. The proposed scheme is compared with nine conventional schemes, including SR and GBN, in terms of performance. The results indicate that the performance of the adaptive ARQ scheme is very close to that of the fixed data block scheme in which the optimal data block length is selected statically. It is also shown that the performance of the adaptive ARQ scheme does not degrade as rapidly as in other schemes when the bit error rate increases.
Comparative study on dpll's based on power density spectrum of phase error sequences
Authors: Nakao Mutsuhiko , Yamashita Kazumi
Published: July 2007

Until now, four different types of first‐order digital phase‐locked loop (DPLL) for tracking of clock signal have been reported which are distinguished mainly by a difference in the control circuit. The performance of these digital loops is determined by rms phase error and transient response which are obtained in the reporter's own way established on a basis of Markov theory. However, performance comparison has not yet been made.

In this paper, first, it is proved that phase error sequences of four digital loops are all classified into semi‐Markov sequences (SMS) if time jitter in each cycle of the input signal is an independent random variable with a certain distribution function.

Second, under the condition that time jitter is an independent random variable with Gaussian distribution, the rms phase error and power density spectrum of the phase error sequence are computed for typical values of input variance according to formulas derived for SMS.

Finally, using this curve and equivalent first‐order linear PLL, the rms phase error, loop noise bandwidth and phase amplification factor are obtained; and based on these results, the performance of four digital loops is discussed.
Proposition of observation system by distributed circuit for fast transients due to discharge in electric contact
Authors: Kawamata Kei , Yang Xinwei , Haga Akira , Sato Risaburo
Published: July 2007

In the detailed time domain analysis of high‐speed transient phenomena in connection with discharge of an electric contract viewed as a noise source, an experimental circuit for observation of the phenomena was investigated. It was found that the effect of wiring cannot be neglected and the investigation becomes more difficult in the experiment with a lumped element system if the sampling rate of the waveform observer is high. For this reason, a distributed experimental circuit system suitable for observation of a high‐speed phenomenon was set up and an experiment was carried out with this circuit.

From the results of observation of transient voltage variation in connection with the discharge, it was found that the transient waveform agrees well with the theoretical waveform and a detailed observation is possible even if the sampling rate is 1 GS/s. In this experimental circuit, there is no effect of the interior of the power supply, of the load and of the reactance and interference of wiring and devices. Since the charge is stored in the distributed circuit, it is possible to generate discharge with a supply of a homogeneous electric energy for a given time. Therefore, detailed observations of various phenomena are possible.
Performance improvement of dpll with adaptive binary quantized phase‐frequency comparator
Authors: Nakajima Osamu , Hikawa Hiroomi , Inoue Takashi , Mori Shinsaku
Published: July 2007

PLL's (phase‐locked loops) are playing widely important roles in various fields of communication. In recent years, efforts have been shifted toward implementation of the PLL's by means of digital circuits. There arise various problems which are common to that approach, such as the contradictory relation between the phase‐locking range and the jitter suppression, as well as the steady‐state phase error due to the frequency offset.

This paper attempts to cope with those problems by improving the conventional binary quantized phase comparator which produces only +1 and ‐1 outputs. A new phase‐frequency comparator is proposed which adaptively modifies the phase comparison characteristics according to the frequency error and the input phase jitter, aiming at an improvement of DPLL performance.

The modified comparator improves performance of the loop by increasing its output gain in the pull‐in state, and decreasing the gain in the steady state. When there exists a frequency offset, the cycle slip and the steady‐state phase error are detected, and the output frequency is controlled by adding a constant quantity which reduces the frequency error to the comparator output in the steady state.

By this scheme, the locking range is increased. Theoretical analyses are made for the frequency acquisition, phase acquisition and jitter suppression for the proposed loop. The result of the theoretical calculation is compared with the result of simulation, and it is verified that the proposed loop structure offers a wide locking range and a high jitter suppression, at the same time improving the steady‐state phase error.
A ring cavity antenna of wide beamwidth
Authors: Arai Hiroyuki , Goto Naohisa
Published: July 2007

Mobile telecommunication systems by satellite meet the requirement of antenna radiation pattern of wide beamwidth. The wide beamwidth of the circular microstrip disk antenna is obtained by high dielectric constant substrate. However, the dielectric losses and difficulty in manufacturing are problems for high dielectric constant materials.

Wide beamwidth is obtained also using the antenna with an electrically small magnetic current loop.

This paper presents the ring cavity antenna without dielectric materials. It also has electrically small magnetic current loop. Antenna characteristics calculated by the cavity model showed that the ring cavity antenna has wide beamwidth. Theoretical values are verified also by the measured radiation pattern and the input impedance.
Performance analysis of improved stutter go‐back‐n arq scheme
Authors: Komatsu Masaharu , Hayashida Yukuo
Published: July 2007

In the stutter go‐back‐N ARQ scheme proposed by Towsley, a packet is transmitted by sending its copies in idle slots. Thus, it can achieve very small packet delay at light‐offered traffic load, but the maximum throughput is small.

The stutter go‐back‐N scheme is improved by sending a multiple copy of a negatively acknowledged packet at retransmission time. The improved scheme is analyzed, and average packet delay, maximum throughput, and so on, are derived. Furthermore, from numerical examples, it is shown that the improved scheme can achieve higher throughput and smaller average packet delay than the basic go‐back‐N and the original stutter go‐back‐N schemes.
V dipole antenna with multiple stub loading
Authors: Nakamura Takashi , Fushimi Hideki , Yokokawa Senji
Published: July 2007

A V dipole antenna with multiple stub loading is proposed as a traveling wave antenna with a wide bandwidth in both the gain and input impedance. It is considered that the present antenna is essentially a tapered transmission line loaded with open stubs. Then the operating principle is studied by reducing the structure to an equivalent nonuniform transmission line. It is found from the relationship between the equivalent distributed parameters and the stub that the dipole‐type stub array with its stub length reduced gradually from a half wavelength to a quarter wavelength is a basic structure for the broadband nature by the decaying traveling wave. Based on this concept, an actual stub‐loaded V dipole antenna was characterized numerically.

It is demonstrated that uniform characteristics of an input admittance of 5 mS, a gain of 8 dB and a front‐to‐back ratio of 10 dB are obtained over ±30 percent around the center frequency in the case of a V dipole with an included angle of 30°. This antenna was fabricated and the validity of the present theory was confirmed because the theoretical and experimental results agreed well.
Optimization of error probability in quantum control communication processes
Authors: Ohya Masanori , Suyari Hiroki
Published: July 2007

Rigorous study of optical communication processes has become interesting since around 1970. Especially, quantum information theory has been developed in both mathematics and engineering. In this paper, by controlling the energy associated with a quantum input state, we obtain an optimal solution (optimal state, optical modulation, etc.) giving the minimum value to the error probability in the attenuation optical communication process. For instance, we find some relations between the energy constraint of the input state and the optimal error probabilities in each modulation.
Characteristics improvement by synthesizing nonaxisymmetrical aperture distribution
Authors: Karikomi Masahiro , Yamada Yoshihide
Published: July 2007

Improvement of the radiation characteristics by the “nonaxisymmetrical aperture field distribution” is described. The aperture distributions in the horizontal and vertical planes are designed to be a low‐sidelobe type and a high‐efficiency type, respectively. As a measure of the degree of nonaxisymmetry, the ratio of the edge levels in the vertical and horizontal planes is introduced. The dependences of the degrees of improvement of the aperture efficiency and the wide angle radiation pattern upon the edge level ratio were studied and the amount of improvement was presented quantitatively.

For example, the wide angle radiation level was reduced by about 15 dB by nonaxisymmetric aperture distribution with the aperture efficiency kept constant. On the other hand, if the wide angle levels were kept constant, the aperture efficiency was improved by about 0.4 dB with nonaxisymmetric distribution. In the case of an offset antenna, sidelobe levels in the wide‐angle region were increased from the numerical results with the aperture field method by the effect of the edge diffraction.

The increase is shown to be less than 3 dB in the case of an offset angle of 60°. Moreover, the wide‐angle directivity can be improved in a certain region centered on the plane in which the attempt was made to achieve a low sidelobe level by means of a nonaxlsymmetric distribution. Possibilities and examples of widening or reducing this region and furthermore shifting it to the surface other than the horizontal one were described.
Performance analysis of wide zone AVI systems
Authors: Mukumoto Kaiji , Fukuda Akira
Published: July 2007

The wide zone AVI system is an automatic vehicle identification system that can cope with more than one vehicle in the detection zone. Such a system includes a possibility of identification failure by the collision of ID packets, in addition to the ordinary transmission failure. A method to remedy this is to transmit the ID packet several times. This paper considers two methods of transmitting the ID packet from each vehicle. In the first, the packet transmission interval follows an exponential distribution, and in the second, a specified number of transmissions are made at random points which are distributed uniformly during the zone pass period.

Using approximate analyses of the identification failure probability, the effects of the design parameters on the system performance are examined for each method. As a result, it is shown that the constant number transmission method has a better performance than the exponential transmission interval method, in terms of the probability of identification success, the number of ID packet transmissions, and other aspects.
Error performance of triangular‐shaped signal set
Authors: Oshita Shinjiro , Yamazato Takaya
Published: July 2007

The error performance of an amplitudephase shift keying system with triangularshaped signal set (TSSS) is discussed. Expressions for the probability of error performance of this scheme are derived for the case of 64, 128, 256, 512, 1024 states and compared to QAM and modified QAM (MQAM) for the same number of states. It is shown that this signal set outperforms both QAM and MQAM in the presence of an additive Gaussian noise channel.

The performance improvement is attributed to the larger decision region obtained for each state in the signal constellation, as compared to QAM and MQAM. Degradation due to the phase error is also discussed in detail.
High‐speed TDM photonic switching system
Authors: Murakami Koso , Shimoe Toshio , Kuroyanagi Satoshi , Rokugawa Hiroyuki , Seino Minoru , Mekada Naoyuki , Odagawa Tetsufumi
Published: July 2007

Photonic switching, a technique for switching optical information from an optical fiber transmission line without optical‐to‐electrical and electrical‐to‐optical conversion, is currently under intense study. Large‐scale and economical optical fiber transmission lines have been realized based on TDM. Therefore, TDM photonic switching is the key technology for the development of high‐speed and large‐scale switching devices when matching with transmission lines is considered. However, no satisfactory system or devices have developed.

This paper examines the structure of space and time switches, which are channel structure elements of a TDM photonic switching system. An optical matrix switch structure is proposed that is the optimum space switch for high‐speed and large‐scale systems. It is shown that such a time switch can now be constructed. Also, a TDM photonic switching system was constructed that combines the optical switch and an optical bistability semiconductor laser. This system operates at 512 Mbit/s.
Contoured‐beam antenna using shaped offset‐fed dual‐reflectors for broadcasting satellites
Authors: Shogen Kazuyoshi , Ohmaru Kenji
Published: July 2007

The antenna for broadcasting satellites succeeding the BS‐3 can utilize larger antennas than before and there is a very strong desire to improve the capability of precise beam shaping. To develop an antenna which meets this requirement, the reflector shaping technique has been investigated for a system which consists of two reflectors and one horn, and where reflectors can be shaped to provide easy and precise beam shaping.

To determine the aperture distribution of the main reflector for the desired radiation pattern, imaginary multihorns are used, and the position and power of each horn is adjusted. Then one horn is placed at the feed point and the subreflector is shaped keeping in mind the amplitude distribution given by imaginary multihorns. Afterward, the main reflector is adjusted taking into consideration the phase distribution.

Using this two‐step reflector shaping technique, dual‐reflector antennas with the main reflector having a diameter of 2.8 m were designed at a frequency of 12 GHz. As a result, a radiation pattern of good shape was obtained which covers all the four main islands of Japan at ‐2 dB (relative value), Okinawa at ‐4 dB and Ogasa‐wara Islands at ‐14 dB. To check the validity of this technique, a scale model of approximately one‐half size was fabricated and measurements were made at 22.75 GHz. The calculated values are shown to agree with the measured values.
Adaptive equalization of selective fading channel based on AR‐model of channel‐impulse‐response fluctuation
Authors: Ara Youjirou , Ogiwara Haruo
Published: July 2007

As an adaptive equalization method for multipath fading in a high‐speed mobile communication at 100 kbit/s or more, a decision feedback equalization method with a Kalman filter is proposed based on the time‐variant model of the impulse response variation of the transmission path. In this paper, by means of this equalization method, the autoregressive (AR) model of the variation is derived from the measured values of the impulse response variations. The result of simulation of the equalization is described.

First, a method is explained to derive an AR model to be set in the equalizer from a set of measured data of the impulse response. Next, the results of simulation are presented for the case in which the variation characteristics of the transmission path and the equalizer model correspond to each other. It is shown that the results have the error rate almost equal to the case of uniform fading without a delayed wave and are better than those from the LMS method. Further, since the variation of the transmission path is slower than the transmission speed, a model is introduced in which the pole of the AR model is approximated by 1. It is shown that the variation of the transmission path in a wide region can be equalized without significant degradation even if the equalizer model is fixed.
Planar four‐direction antenna for antenna pattern diversity reception
Authors: Arai Hiroyuki , Teramoto Hiroyuki , Toki Masahiro
Published: July 2007

In digital mobile communication, the directional diversity method is useful against fading. In this method, the antennas are switched successively to the antenna directed toward the arrival of the desired signal.

In this paper, a four‐directional switching antenna is proposed for the directional diversity. The proposed planar antenna consists of a sectoral patch antenna and 3‐dB hybrids. By means of the cavity model, the eigenvalue, radiation pattern and mutual coupling between the elements are calculated for this antenna.

It is shown theoretically that this antenna has the necessary characteristics of a four‐direction antenna. The radiation pattern and the mutual coupling between the elements were measured for the antenna fabricated on a dielectric substrate to confirm the validity of the computation.
Framing system using error checking information
Authors: Sato Naoshi
Published: July 2007

This paper discusses a framing system which uses error checking information obtained by a CRC or parity check. Theoretical analysis with a signal flow graph clarifies that the system is effective in extending the misframe interval, in reducing the refraining time, and in decreasing the quasi‐reframing probability. The system is also found to increase the rehunting probability due to bit errors which occur during the reframe check process.

Taking the forementioned advantages and disadvantage into consideration, this paper assesses the framing performance of the system using the ratio of blocks including burst errors due to the out‐of‐frame and shows that the system is effective in improving that ratio.
Double‐stage phase‐diversity (DSPD) scheme for coherent optical fiber communications—optical circuit imbalance and its compensation
Authors: Yamashita Shinji , Okoshi Takanori
Published: July 2007

The double‐stage phase‐diversity (DSPD) scheme we have proposed features a phase‐diversity‐type optical homodyne detection followed by a phase‐diversity‐type electrical frequency up‐conversion, giving a heterodyne‐like intermediate frequency (IF) signal. It has the advantages of both heterodyning and homodyning. In this paper, we first calculate the sensitivity penalty due to the optical circuit (hybrid) imbalance in a DSPD receiver. It is shown that the penalty is as small as that in a conventional phase‐diversity receiver and that the optical circuit requirement is not severe.

The DSPD experiment with an adjustable imbalance is then performed to confirm the theory; experimental results are in good agreement with the theory. Finally, the possibility of compensation of the optical imbalance at the electronic stage of the receiver is shown.
Analysis of correlation characteristics of antenna diversity in land mobile radio environments
Authors: Taga Tokio
Published: July 2007

Antenna diversity reception can significantly alleviate fading with a relatively simple configuration. Hence, this technique will be indispensable in future portable radio systems. In the antenna diversity system installed in a portable transceiver, degradation of the diversity effect due to artificial variation of the radiation pattern (polarization characteristics) is expected. To design an effective diversity branch which reduces degradation by such variations, it is necessary to carry out an analysis of characteristics of the diversity branch in which the arrivals of both the co‐polarization and cross polarization are taken into account.

This paper presents a theoretical analysis method for the antenna diversity correlation characteristics which takes into account the statistical incident wave distributions of both the co‐polarization and cross polarization. In addition, a theoretical study is carried out on the correlation between the cross dipole antenna branches, constituting a polarization diversity antenna. The theoretical analysis reveals that the correlation characteristics of the diversity branches depend strongly not only on the antenna directivity but also on the incident wave characteristics and that the correlation between the diversity branches becomes almost zero regardless of the antenna pattern variation and the incident wave characteristics if the cross‐polarization power ratio (XPR) is ‐1.5 dB. Further, the validity of the present analysis is confirmed through 900‐MHz band experiments in a metropolitan area.
A unified prediction method for space diversity improvement in received power on microwave links
Authors: Hosoya Yoshio
Published: July 2007

The space diversity technique is used widely to improve propagation impairment on line‐of‐sight microwave links. Although prediction methods for the space diversity improvement in received power were proposed by Makino and Morita, Vigants, Boithias and Battesti, and Boithias, Battesti, and Rooryck, the predicted results were quite different among all these methods.

To investigate this point, a data bank was constructed. This data bank consists of 27 data from Japan, the United States, Italy, France, FRG, Sweden, and Finland. Some theoretical investigations also were conducted.

Based on the investigations, it was clarified that the cause of the difference in predicted results was a regional dependence of the long‐term variation in the short‐term average of the received power. This regional dependence is included effectively in the Rayleigh fading occurrence factor. A unified prediction method, which was derived by a multiple linear regression and included the Rayleigh fading occurrence factor as a new parameter, was proposed. Based on the testing by the data bank, the proposed method was proved to be more accurate than the existing methods.
Wrapback reconfiguration mechanism of a counter‐rotating dual token ring
Authors: Nakayashiki Susumu , Kashio Jiro , Harakawa Takeshi , Wada Hiroyuki
Published: July 2007

In the distributed‐control ring LAN (local area networks), a reconfiguration control is required to cope with the independent asynchronous failure detection in the stations. This paper proposes a wrapback reconfiguration mechanism in the dual‐token ring LAN with a parallel dual structure of distributed‐control token‐ring LAN. Here, the ring is wrapped back automatically by the distributed‐control of the stations when a fault is detected in the communication function in the physical layer or MAC (medium access control) layer. Each station connected by the dual ring determines its operation based only on the state of the two input links. When an abnormality is detected in a link, a failure‐detecting beacon is transmitted and the failure domain is located by the reception priority competition control, where the transmission is stopped by receiving the beacon.

The stations adjacent to the failure domain artificially generate a fault in the output link paired to the failure link, so that the station to wrap back the ring at both sides of the failure link‐pair can be located by the same procedure as for the localization of the failure domain. In parallel to the ring wrapback, the active monitor is established, which is needed in the initialization of the ring. Each station discriminates between the current link and standby link, and the ring wrapback by the failure of the standby link is avoided. Applying the international standard (IEEE 802.5) to the token‐ring LAN, the failure recovery time is evaluated. The effectiveness of the proposed reconfiguration mechanism has already been verified by an experiment using the actual equipment.
Suppression of field leakage through aperture of metal enclosure by high‐permeability sheet
Authors: Hatakeyama Ken‐Ichi , Sawado Eikichi
Published: July 2007

This paper proposes a method of enhancing the electromagnetic shielding effect of metal enclosures with apertures. These enclosures are regarded here as waveguides working below the cutoff frequency. To increase the shielding effect, a magnetic fiber sheet is attached inside them.

Theoretical analyses of electromagnetic fields in a waveguide are made with respect to the two cases where the sheet is attached to an E‐plane or an H‐plane of the waveguide, and the relations between the directions of the fibers forming the sheet and their shielding effect are derived.

Experiments are made with an amorphous‐fiber sheet and the results are compared with the theoretical analyses. As a result, it is confirmed that when the sheet is attached in particular directions, its surface has the characteristic of the open wall.

It is possible to increase the shielding effect only when the sheet is attached to the E‐plane and its surface is regarded as having the characteristic of the open wall. It is necessary that the fibers of the attached sheet be parallel to the aperture of the waveguide. This conclusion is significant in the practical application of this method. One of the merits of this method is that the open wall can be obtained over a wide frequency range.
Influence of laser diode phase noise on optical heterodyne spatial tracking systems
Authors: Goto Koji , Araki Ken'Ichi , Yasukawa Koji
Published: July 2007

In optical intersatellite communication, a high‐precision antenna directivity is required for stable communication with a sharp optical beam. The antenna directive accuracy is affected strongly by the performance of the spatial tracking system which constantly tracks the direction of arrival of the optical beam sent by the sending satellite. The tracking system using an optical heterodyne detection to detect the angle of arrival of the optical beam has an advantage over the direct detection system in that its sensitivity is high and it is tolerant to the background light.

Recently, a number of systems using laser diodes as the source have been studied extensively. Although the detection efficiency has been studied in the case where the effect of the electrical noise in the tracking signal detection circuit and the electric field distributions of the signal light and the local oscillator light are taken into account, no study has been carried out on the effect of the phase noise of the laser diode (LD) on the tracking characteristics.

In this paper, the electric characteristics are studied for the tracking signal detection circuit using the optical heterodyne/square detection. The effect of the spectral spread by the phase noise of the LD on the spatial tracking system is studied. The relationship is found between the spectral width of the intermediate frequency signal and the bandwidth of the intermediate frequency bandpass filter which minimizes the effect of the phase noise of the LD. Further, the characteristics are compared with those of the system using the direct detection method.
Design and performance of optical multifiber connector transfer splicing mechanism
Authors: Kobayashi Hideo , Shimizu Masatoshi , Watanabe Ichiro
Published: July 2007

The optical fiber cable transfer splicing mechanism by which existing fibers are transferred to new ones are considered and their dynamic characteristics are analyzed theoretically and verified experimentally.

This paper describes the mechanical model of the horizontal and vertical movements of the ferrule in the transfer action and investigates its vibration characteristics. The vibration settling time is calculated and structural designs in realizing short‐time transfers are described.

It is shown that the previous movements of the guide pin inside the existing ferrule are effective in reducing the transfer time. The rapid transfer time of about 20 ms is shown to be achievable.

Finally, using the manufactured transfer splicing mechanism, realization of 18 to 22 ms transfer time is verified experimentally. As to the reliability, it is indicated that the average splicing loss of 1500 splicing experiments is only 0.34 dB which shows satisfactorily good results.
Single‐mode optical fiber connectors for optical accessing
Authors: Shimizu Masatoshi , Kobayashi Hideo
Published: July 2007

With a view to improving the core illumination technique to confirm the optical fiber core in construction and maintenance, a structural design is presented for a single‐mode optical connector with an optical accessing function that enables monitoring the illumination signal and with a capability of injecting the illumination signal externally. In this paper, an optical waveguide is placed from the single‐mode optical fiber tip to contact with the latter. The other end of the optical waveguide is removed from the container.

Next, the relationship between the connecting loss of the proposed connector and the monitoring efficiency, the one between the index of refraction of the UV epoxy for connecting the optical waveguide and the monitoring efficiency, and that between the connecting loss and the injection efficiency are studied so that the structural design of the present connector is established. Further, an optical connector was fabricated for trial. When the sum of the monitoring efficiency and the injection efficiency is −75.6 dB for the optical source wavelength of λ = 1.3 μm and is −80.8 dB for λ = 1.55 μm. Since the minimum receiving level of the receiver is −90 dBm and the maximum output power of the source is +10 dBm, it is confirmed that the illuminating signal light can be injection detected at an arbitrary connecting point.
Fault location for balanced pair cable by input‐admittance measurement
Authors: Mochizuki Satoshi , Hayashi Akira , Koga Hiroaki
Published: July 2007

This paper proposes a method to detect a fault location in a faulty paired cable consisting of branching cables and different gauge wires along a length. Calculating an input‐admittance of a faulty pair cable involves consideration of cable length, cable secondary constants, branching conditions, and a fault location. Under this principle, a measured input‐admittance can be indicated by fault location if cable length, cable secondary constants, and branching conditions are known. In addition, when a calculated input‐admittance agrees with a measured input‐admittance, the fault can be located. However, a location error appears because actual cable secondary constants are slightly different from those cable secondary constants that, are calculated.

This paper also describes the location errors caused by secondary constants differences.

Furthermore, two improvement methods for location errors have been developed. One method applies the difference between input‐admittances before and after fault. The other method refers a measured input‐admittance of a fault‐free cable to that of a faulty cable. As results, fault location errors in an open fault (a breakdown of wires) and an insulation degradation fault were significantly decreased.