bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐speed TDM photonic switching system
Authors: Murakami Koso , Shimoe Toshio , Kuroyanagi Satoshi , Rokugawa Hiroyuki , Seino Minoru , Mekada Naoyuki , Odagawa Tetsufumi 
Published: July 2007

AbstractPhotonic 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

AbstractThe 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

AbstractAs 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

AbstractIn 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

AbstractThis 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

AbstractThe 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

AbstractAntenna 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

AbstractThe 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

AbstractIn 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

AbstractThis 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

AbstractIn 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

AbstractThe 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

AbstractWith 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

AbstractThis 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.
Analysis of disk‐loaded antenna with matching posts by diakoptic theory
Authors: Endo Kazuo , Arai Hiroyuki , Toki Masahiro 
Published: July 2007

AbstractAs equipment becomes smaller and lighter, the antenna needs to become smaller and planarized. One of the analysis methods for the small antenna with a complex configuration is the Diakoptic (DK) method which is a type of moment method. By means of the DK method, an analysis is carried out for a disk‐loaded monopole antenna (DLA) with matching posts which is a planar antenna suitable for mobile communication. In the analysis, the current distribution on the disk is approximated with a single current distribution function to reduce the computational amount and time. The effectiveness of the analysis is demonstrated by comparing the analysis results for the cases with one and two matching posts with the experimental data.
A polarization modulation (PLM)/optical coherent detection system and its phase noise cancelling effect
Authors: Kuwano Shigeru , Tsukamoto Katsutoshi , Morinaga Norihiko 
Published: July 2007

AbstractIn coherent optical communication systems, the phase noise of the optical source is the dominant factor in limiting the receiving characteristics and its reduction is required. In this paper, a polarization modulationl optical coherent detection system is proposed and theoretical and experimental studies are carried out for this system.First, it is demonstrated that the polarization modulation signal is a differential phase‐modulated optical signal between the two orthogonal polarization components. The fundamental principle for the optical coherent detection system is presented.Next, by taking into account the characteristics of the modulator, a general representation of the polarization modulation optical signals is derived and the inherent characteristics of the present system is shown. Further, for a polarization modulation/optical heterodyne detection system for a long‐distance transmission, the detection and demodulation methods are presented. The phase noise cancellation effect is found as well as the fact that the polarization axis matching between the transmitter and the receiver is not necessary if a circular polarization modulation is used.The bit error rate of the polarization modulation/optical heterodyne detection system is analyzed theoretically. By comparing this system with other coherent optical communication systems, the receiving characteristics are evaluated. Finally, fundamental experiments are carried out for the optical heterodyne detection of the polarization modulation signals and the phase noise cancellation effect of the present system is confirmed.
Assessing extremal dependence of environmental spatial fields
Authors: Bel L. , Bacro J. N. , Lantuéjoul Ch. 
Published: July 2007

AbstractSpatial environmental processes often exhibit dependence in their large values. In order to model such processes, their dependence properties must be characterized and quantified. In this paper, the performances of several estimators of the extremal coefficient are tested and compared using simulations of various spatial models. Two case studies (annual temperatures in France and precipitations in the French province Burgundy) are also presented. Copyright © 2007 John Wiley & Sons, Ltd.
Approximation methods for reliability‐based design optimization problems
Authors: Kaymaz Irfan 
Published: July 2007

AbstractDeterministic optimum designs are obtained without considering of uncertainties related to the problem parameters such as material parameters (yield stress, allowable stresses, moment capacities, etc.), external loadings, manufacturing errors, tolerances, cost functions, which could lead to unreliable designs, therefore several methods have been developed to treat uncertainties in engineering analysis and, more recently, to carry out design optimization with the additional requirement of reliability, which referred to as reliability‐based design optimization. In this paper, two most common approaches for reliability‐based design optimization are reviewed, one of which is reliability‐index based approach and the other performancemeasure approach. Although both approaches can be used to evaluate the probabilistic constraint, their use can be prohibitive when the associated function evaluation required by the probabilistic constraint is expensive, especially for real engineering problems. Therefore, an adaptive response surface method is proposed by which the probabilistic constraint is replaced with a simple polynomial function, thus the computational time can be reduced significantly as presented in the example given in this paper. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)