bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polarization diversity receivers using error‐control codes for heterodyne detection lightwave transmission systems
Authors: Yamaguchi Haruo 
Published: July 2007

AbstractIn a coherent optical fiber communication with a single‐mode fiber and an optical heterodyne detection for improved receiver sensitivity, degradations of the receiving sensitivity due to fluctuation of the polarization condition of the received light are a problem. As a possible solution to this problem, this paper proposes a polarization diversity system with an error‐detecting code or an error‐correcting code. Its characteristics are analyzed and optimum design values are obtained.When a parity‐check code with the code length N is used as an error‐detecting code, N =32 presents an optimum design. In comparison to a reference system in which an ideal polarization matching occurs and a conventional binary code is used, the SNR degradation is about 0.7 dB. In the enhanced reference system in which a single error‐correcting/double error‐detecting Hamming code (enhanced Hamming code) with a code length of N is used, N =256 provides an optimum design. Compared to the reference system, the SNR is improved by about 2.1 dB. In the present system using an enhanced Hamming code, N =64 is an optimum design and the SNR is improved by about 1.1 dB in comparison to the reference system, but is degraded by about 1.0 dB in comparison with the enhanced reference system.
Data compression of gray‐scale images by level plane coding
Authors: Associate Yuji Sato, , Takahashi Kenichi , Ohta Masamitsu 
Published: July 2007

AbstractThis paper proposes a single compression coding method of gray‐scale images for applications as image retrieval, etc. With this method, the psychological burden on the observer is lightened by transmitting first the approximation of the image and adding the details later. At the final stage, the exact replica of an original image can be obtained with a high compression ratio. In the coding, the image is separated first into two groups: upper bit planes relating to the most significant n bits and lower bit planes relating to the remaining bits. The pixels within the upper bit planes are encoded by subsampling and level plane coding. Subsequently, a compression coding of the pixels not yet transmitted is performed by level plane coding of the difference between the actual values and the interpolated values derived from the pixels already transmitted. Following the transmission of the upper bit plane pixels, the remaining planes of the image are transmitted bit‐by‐bit. To investigate the characteristics of the proposed method, computer simulations are performed by using standard SIDBA pictures. The performance of the proposed method and four other compression coding methods for grayscale images are compared. It is shown that this method achieves almost the same entropy as those of the high‐efficiency coding method; the achieved average entropy is 5.21 bits/pixel.
Pulse compression filter for ultrasonotomography utilizing L(0,3) mode of the elastic wave in a fused quartz rod
Authors: Kiryu Syogo , Moriya Tadashi , Yoshizawa Masasumi , Fuse Tadashi 
Published: July 2007

AbstractTo introduce the pulse compression technique into ultrasonotomography, a pulse compression filter with a large delay time difference of 100 μs at a bandwidth of 1 to 2 MHz is needed. In this paper, it is clarified that a pulse compression filter with the forementioned capacity is realized by utilizing the L (0, 3) mode of elastic waves propagating in a fused quartz rod approximately 1 mm in diameter and 1 to 2 m in length. In using the L (0, 3) mode, the L (0, 2) mode causes deterioration in the S/N ratio after pulse compression because it is an unwanted spurious vibration. Therefore, the unwanted signal caused by the L (0, 2) mode is eliminated by the difference in vibration patterns between the L (0, 2) mode and the L (0, 3) mode. In addition, a pulse compression ratio of 100 with ‐32 dB sidelobe level has been obtained in a pulse compression system using the filter proposed herein.
Optimization of frequency assignment for reduction of cochannel interference
Authors: Mizuike Takeshi , Ito Yasuhiko 
Published: July 2007

AbstractThis paper describes the method of optimization of frequency assignment in satellite communication, aiming at reducing cochannel interference. The method is based on the formulation of the assignment problem, so‐called mathematical programming, and is widely applicable. The basic model is defined, and is composed of a pair of systems sharing the same frequency band. A discrete frequency assignment is made with the small segment as the unit, which is obtained by equi‐partitioning the common channel, and the model is formulated as an assignment problem. The lexicographical minimization is employed as the criterion of optimization, by which the interference is reduced for all carriers. A method is presented in which the optimum solution is obtained by the numerical conversion of the cost matrix and the Hungarian method for the assignment problem. To determine efficiently the optimum assignment for carriers with various bandwidths, an algorithm is presented which is based on the branch‐and‐bound method used frequently in the mathematical programming. By this method, the solution can be determined with a small amount of computation for a problem of practical size. Examples are shown which are the assignment of FM carriers by the basic model and the optimum frequency assignment for eight satellites. As a result, it is shown that the frequency assignment can be determined with sufficient accuracy, and the interference is reduced drastically by sufficiently fine segmentation.
Numerical analysis of the microstrip printed dipoles
Authors: Kominami Masanobu , Rokushima Katsu 
Published: July 2007

AbstractThe moment method in the Fourier‐transformed domain has been used widely as a rigorous numerical method for analysis of patch antennas, microstrip lines, finlines and planar circuit structures. In this paper, this method has been applied to a planar printed dipole on the grounded dielectric substrate. The integrand in Sommerfeld‐type integrals with a slow convergence rate has been modified by means of an effective dielectric constant determined from the asymptotic values for large spectral components so that the convergence can be improved significantly. The method of computing the matrix elements in the moment method, evaluation of the effective radius of a planar dipole and separation of the radiated power and the surface wave power are discussed. Finally, the validity of the method is confirmed by comparison with measured data. In addition, the effect of the substrate thickness on the antenna performance is discussed.
Consideration on tap‐length of acoustic echo canceller
Authors: Furukawa Isao , Yasukawa Hiroshi , Shimada Shoji 
Published: July 2007

AbstractThis paper discusses the optimum taplength of the FIR acoustic echo canceller. The learning identification algorithm is employed in the estimation of the echo path. For the case where the tap‐length of the echo canceller and the impulse response of the echo path are given, a theoretical expression is derived for the echo return loss enhancement. The validity of the expression was verified by computer simulation. Then assuming the case where the power envelope of the impulse response of the echo path exhibits an exponential decay, the approximate expression is derived for the echo return loss enhancement with the tap‐length of the echo canceller as the parameter. It is shown that the calculation by the approximate expression agrees well with the theoretical value as well as the result by computer simulation. The optimum tap‐length is determined by the approximate expression for the required echo return loss enhancement. The effect of the near‐end noise of the echo path was analyzed also.
Encoding of still pictures with successive clustering and predictive vector quantization
Authors: Shinohara Katsuyuki , Minami Toshi 
Published: July 2007

AbstractThis paper describes the predictive quantization of still pictures using the newly developed clustering with faster convergence than L.B.G. algorithm. In the proposed scheme, the input vector is separated into the average density and the deviation from the average (average density separated vector). Then the latter is quantized predictively using two code books of category 1 and category 2. Examining the utilization frequency of the codeword, the coding efficiency is improved by suppressing the redundancy. The code book of category 1 is designed using 256 codewords and successive clustering. Letting [] be the codeword used in the quantization of the immediately preceding input vector, the code book of category 2 is composed of the set J([]) with high probability to be used in the next quantization. It is predicted that the input data following the codeword [] is quantized by an element of J([]), and encoding is performed by the index attached to that element. The number of elements in J([]) is 4 to 32 including the control code, which is less than that of the code book 1, realizing an improvement in the coding efficiency. If the codeword to be encoded is not found in J([]), the code book 1 is used. The codewords in code book of category 1 are arranged in the order of their variances, which reduces the retrieval time in the code book to one‐ninth to one‐sixth the total retrieval time. Using the proposed scheme and seven still pictures with 256 × 240 pixels and 256 gray scales as the training sequence, eleven pictures including the forementioned seven were encoded. The result revealed that 0.8 to 0.5 bits/pixel is required and the signal‐to‐noise ratio is 30 to 36 dB, indicating the excellent performance of the proposed scheme.
Fault and robust detection of error of a system with intermittent faults
Authors: Sugasawa Yoshio , Seya Koichiro 
Published: July 2007

AbstractThis paper discusses the intermittent fault of a system and the robust detection of fault, and introduces a model interpretation by Petri net. An intermittent fault is produced in an intermittent period, and the detection of such a fault is considered very complex. In this paper, the intermittent faults are divided into benign faults and active faults. The model with the following two properties is considered for robust detection of the faults: (1) the fault is detected while the system is in the active fault; (2) the system shifts from the active fault to the error state where the fault is detected, or to a failure. The model is interpreted via Petri net. The Markov regeneration process is applied considering the time instant of firing for the transition. The limiting probability is determined for the system to start from the normal condition until the fault is detected or the system enters in a failure. Finally, using numerical examples, the stochastic process is demonstrated by introducing numerical values for the case where the fault is detected by the robust detection or the error state shifts to a failure.
Evaluation method of propagated optical wave for coherent optical transmission
Authors: Higashi Tsunehito , Tsubokawa Makoto , Shibata Nori , Seikai Shigeyuki 
Published: July 2007

AbstractIn coherent optical transmission systems using heterodyne detection for long‐distance and high bit rate transmission, the quality coefficient (product of polarization coefficient and degree of coherence) was introduced to evaluate the propagated optical signal (POS). Relating this coefficient to the bit error rate in the ASK, FSK, and PSK optical transmission methods, the minimum received optical power needed to realize the coherent optical transmission system has been obtained as a function of the quality coefficient and the transmission bit rate. Next, analyzing the phase difference between the POS and local optical signal (LOS) caused by the length of the optical fiber, the chromatic dispersion, and the thermal characteristic of the optical fiber, it was found that the thermal characteristic of the optical fiber is an important factor in determining the degradation of coherence. Additionally, considering the allowable quality coefficient and the degree of coherence in the presence of thermal variation, the range of the polarization state, which the POS must satisfy, has been clarified. For example, when using a light source with a relative spectral width of f/f= 10‐9 and an optical fiber with length of 300 km, the FSK and PSK transmission with a bit error rate less than 10‐9 at 1 Gb/s is carried out under the temperature variation of 40°C; the polarization state which the POS should satisfy is that {degree of polarization × cos(2 × azimuth)} °0.69. The polarization state should be controlled to stay in this range. Actually, the condition that {polarization degree × cos(2 × azimuth)} =1 represents the limit of the transmission distance.
Perception of motion in successively displayed pattern stimuli
Authors: Shimodaira Yoshifumi , Hiwatashi Kenji 
Published: July 2007

AbstractMotion perception in human vision was measured psychophysically for successively displayed rectangular patterns on CRT when a subject's eyes were fixed and moved. The stimulus patterns were displayed discretely in various temporal and spatial intervals.Results show that the motion perception is completely the same as the real movement when temporal and spatial intervals of stimuli are short and that this spatio‐temporal region is expanded in the direction of increasing spatial intervals when the subject's eyes pursue the pattern.Further, it was found that the fore‐described region is very different from that of the optimal condition of β movement, which also was measured in this study.
Convergence of stochastic relaxation process
Authors: Ejima Toshiaki 
Published: July 2007

AbstractThis paper discusses the convergence of the stochastic relaxation process. The principle of the stochastic relaxation process is to assign stochastic vectors to the objects, innovate the vectors so that they are better matched to the neighborhood states and, finally, eliminate the ambiguity of all the objects. However, there still exist several points concerning the convergence, i.e., whether or not the process approaches the state without ambiguity, by iterating the innovation of the stochastic vectors. In the past, the variational method and linear programming have been used in the discussion of the convergence of the stochastic relaxation process. However, they are based on the specified matching function and cannot be considered as general. This paper introduces the Lyapunov function which is applied widely to the analysis of the stability of system, and evaluates quantitatively the convergence of the stochastic relaxation process. By introducing the Lyapunov function for the analysis of convergence, the following properties are realized.(1) The convergence is analyzed independently of the form of the matching function(2) it is possible to evaluate the global convergence.
Digital signal processing method in inductive radio system using three‐conductor transmission line for detecting linear synchronous motor vehicle position
Authors: Hatta Tohru , Kusakabe Takashi , Asai Takahiro 
Published: July 2007

AbstractA digital signal processing method is proposed for the detection of linear synchronous motor vehicle position via an inductive radio system using a three‐phase, three‐conductor transmission line. The method used to detect the position of vehicles within a fixed periodic range is not based on the information related to the phase of induced voltages between neighboring conductors of the transmission line, but only on the amplitude information. This digital signal processing method, which is extremely suitable to centralized processing of the position signal, transmits the induced line‐to‐line voltages of the induction line over communication cables to a remote substation equipped with a digital computer. In this paper a quantitative study is also made of the position detection error due to space harmonic components that are present in the induced voltages, and on the error due to crosstalk generated along the transmission line between positive and negative phase sequence voltage components, respectively. With regard to these errors, it is demonstrated that the performance is neither superior nor inferior to the “direct signal processing method” (requiring both amplitude and phase information between the lines) published earlier.
Electromagnetic noise from an automobile and the flow of noise currents on automobile body surface
Authors: Nagasawa Yoji , Fujiwara Toshiharu , Ujiie Hiroshi 
Published: July 2007

AbstractWith the widespread use of various electrical applicances in daily life, there has been an increase in unnecessary radiated electromagnetic waves influencing many spheres of social life. In addition to the radiation of unnecessary electromagnetic waves by electrical machinery, considerable noise arises from ignition systems of internal combustion engines. We assumed that the sources of electromagnetic waves were always due to the flow of radio wave currents. As an example of internal combustion engines, this paper uses an automobile engine. Also, a surface current detector was used for the generated noise currents (in the 300‐MHz band). By means of measurements over the body of an automobile (sedan type), the relationship between the noise currents and the radiated noise waves was examined. The automobile body receives various electromagnetic waves which exist in space, especially TV waves, and that flow as high‐frequency currents all over the automobile body. Naturally the reradiation if these waves is considered. On the other hand, a large amount of noise currents of the engine system flows on the bonnet near the fender part. It was observed especially that the noise currents tended to flow from the top of the ignition coil inside the engine housing. However, no noise currents were observed on the car door, roof and trunk. Based on these measurements of the radio noises actually radiated, it can be inferred that it is possible to reduce the electromagnetic radiation if the noise currents which are flowing in the bonnet and the fender part are eliminated.
Analysis of self‐exciting oscillation in nonlinear system with hysteresis characteristics
Authors: Okumura Kohshi , Matsuo Tetsushi , Kishima Akira 
Published: July 2007

AbstractThis paper presents a method of numerical analysis by the multiple input describing function for the self‐excited oscillation in a nonlinear system with hysteresis. In the traditional analysis by the describing function, the describing function for the hysteresis is determined in an analytic form, and a very complex calculation is required to perform a highly accurate analysis including the harmonic components of the self‐excited oscillation. Consequently, in practice, it has been impossible to determine analytically the describing function for the multiple input. Furthermore, the calculation is impossible for the describing function, where the hysteresis characteristics contain a minor loop. From such a viewpoint, this paper proposes a method and algorithm for the analysis of self‐excited oscillation. In the proposed method, the describing function is determined numerically by the digital simulation of the hysteresis, and the discrete Fourier transform and its inverse are applied to the result. By this method, the describing function can be determined numerically even for the cases of multiple input and the case with a minor loop. Thus, the self‐excited oscillation can be analyzed considering the harmonic components and the multiple mode. As an example, the self‐excited oscillation of the nonlinear system is analyzed for the case where the linear part is represented by a second‐order transfer function or by a sum of such functions.
A prediction method for cross‐polarization discrimination on line‐of‐sight radio links with strong surface reflections
Authors: Sasaki Osamu , Hosoya Yoshio , Yoshikawa Makoto 
Published: July 2007

AbstractThis paper proposes a prediction method for cross‐polarization discrimination (XPD) during multipath fading on line‐of‐sight propagation paths that encounter strong surface‐reflected waves. This prediction method is required for the design of radio‐relay systems.First, the so‐called C parameter has been used widely to predict XPD but without any clear physical explanation. It is equivalent to the mean‐squared value of the cross‐polar component of received power during deep fading, when the fade depth is 10 dB or larger, if the cross‐polar component is normalized to the co‐polar component of the received power during normal (i.e., nonfading) conditions.A two‐ray interference and direct‐wave depression (i.e., mean‐value depression) model was developed. This model predicts the value of the C parameter by using such propagation path conditions as the separation angle between the direct and reflected waves and antenna directivity pattern.Finally, this prediction method was found to be fairly accurate by comparison of predicted values with XPD data, obtained from propagation paths with strongly reflected waves.
A highly stabilized fet oscillator for ku‐band receiver
Authors: Shinkawa Keiro , Noda Masaki 
Published: July 2007

AbstractThe utilization of Ku‐band satellite broadcasting and satellite communication is progressing. A high stability of oscillation frequency is required for local oscillators of receiver converters used in such communication. Therefore, analytical and experimental examinations have been carried out for the oscillation principle and the stabilizing method for oscillators using a common drain GaAs FET without an external feedback circuit and a very high‐Q dielectric oscillator.First, the output admittance of the common drain FET oscillator is calculated using GaAs FET small‐signal parameters to clarify the oscillation principle. Next, the oscillation frequency characteristics are analyzed and it has been shown that it is necessary to reduce the variation of oscillator output susceptance with the applied voltage to stabilize the oscillation frequency. The addition of a capacitive admittance to the oscillator source output is effective for this purpose.In an oscillator with a 0.02 S capacitive stub formed at the source output, oscillation frequency of 10.678 GHz, temperature variation of less than 600 kHz (‐20°C ∼ +60°C), and phase noise of ‐95 dBc/Hz (offset frequency: °10 kHz) have been obtained.
Delay performances of a continuous arq system with copy‐transmissions
Authors: Hayashida Yukuo , Fujii Shumji , Tezuka Yoshikazu 
Published: July 2007

AbstractThe characteristics of packet transmission delay in a continuous ARQ (Go‐Back‐N type) system are analyzed here. The copies of each packet stored in the buffer are sent to reduce the delay. The optimum copy size minimizing the delay depends not only on packet error probability and round‐trip propagation delay but also on offered traffic intensity. It is possible to reduce the delay by transmitting many copies and using the residual transmission capacity when offered traffic is light. On the contrary, when offered traffic is heavy, transmission of few copies is preferable in consideration of the number of lost copies for a successful transmission. Finally, considering that packet error probability may be reduced in some practical situations, the relation among packet error probability, propagation delay and traffic density where the optimum copy size changes from 1 to 2 is derived.