bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative study on digital noise suppressors for PCM speech
Authors: Yoshiya Kiyosumi 
Published: July 2007

AbstractIn PCM transmission systems a digital, click‐like noise due to bit errors is added to the demodulated speech. In former reports by the author an effective receiver side noise suppression system (SUNDER) was proposed which provides better error detection ratio and output S/N characteristic than other known error detection methods. the characteristics of the system for PCM speech containing background noise and for various binary codes were also published. the present paper considers a comparative study of the SUNDER and other proposed digital noise suppression systems, based on a computer simulation experiment of the output S/N improvement and other related characteristics in the case of PCM speech (8‐bit folded code, μ = 100 logarithmic companding) under the same error conditions. the results have shown that for error rates in the range of 10−5 to 10−2 the output S/N improvement by the SUNDER system is about 18 dB, which is higher by 8 to 9 dB than that by other systems.
Throughput analysis of window data link control procedures
Authors: Inoue Takeshi , Nakanishi Hikaru , Sanada Hidehiko , Tezuka Yoshikazu 
Published: July 2007

AbstractThis paper presents an analysis method for the maximum throughput of the window‐controlled data link under the effect of the propagation delays. the data link is divided into two submodels, and each stochastic process is analyzed independently and the results are integrated. the calculation by this method is simpler than that by the direct analysis, and highly accurate evaluation can be made for comparatively general frame length distributions. It is shown that this approach provides very good approximation, especially for the throughput efficiency ranging from 0.7 to 1.0. the region satisfying certain throughput value is derived and an effective way of selecting the value of window size is presented.
On the computational complexity of an external pin assignment problem
Authors: Kimoto Tsutomu , Tsukiyama Shuji , Shirakawa Isao , Members Regular 
Published: July 2007

AbstractThis paper analyzes the computational complexity of the external pin assignment problem to determine through which external pins the signals are drawn out from a packaging module such that the external pins are arranged on the periphery of the module. the problem is shown to be NP‐complete if there exist preassigned signals (which are to be drawn out through the specified external pins) and sequences of signals such that the signals of each sequence must be drawn out through a set of external pins located consecutively. the complexity of a branch‐and‐bound algorithm for the problem is also analyzed.
Buffer management schemes for a heterogeneous packet switching system
Authors: Takenaka Toyofumi 
Published: July 2007

AbstractIn a heterogeneous packet switching system which handles two kinds of packets with different nonpreemptive transmission priorities and different average lengths, the stationary distributions for the number of packets in the system are analyzed for share and partition buffer management schemes, using Fabens' formulas for the semi‐Markov process. the overflow characteristics are examined by numerical calculations. As a result, it is clarified that in the case of a partition scheme, when the ordinary packet length is fairly longer than that of the other packets, the overflow probability for ordinary packets is smaller than that for the other packets. In the case of a share scheme, the overflow probability for ordinary and priority packets when the ordinary packet length is several times longer than that of the other packets, is smaller than that when both lengths are equal.
All digital phase‐locked loop with nonlinear multilevel quantized phase comparator
Authors: Zheng Nanning , Mori Shinsaku 
Published: July 2007

AbstractThe PLL has assumed an important role and is widely employed in communication systems. In recent years efforts have been directed toward implementation of PLLs by means of digital circuitry and a large number of digital PLLs (DPLLs) have been reported. the binary quantized DPLL has received particular attention. However, in a first‐order PLL, pull‐in performance and operation in the lock mode have conflicting requirements and, in addition, a steadyphase difference is produced when the input signal has a frequency offset, resulting in unfavorable effects on the communication system. In the past, these problems have been resolved by employing a second‐order loop but, due to the resultant complexity of the loop, this causes several problems, including poor transient response and integrator drift. In this paper we present a new DPLL incorporating a nonlinear multilevel quantized phase comparator (with characteristic τ sgn ψ ‐ ψ). By means of its phase comparator characteristic this loop improves the steady‐state phase error and also affords more rapid transient response as well as other features including excellent jitter suppression within the pull‐in range. Performance characteristics of the proposed loop are determined theoretically and are verified by experiment.
Effect of write head saturation on the characteristics of digital magnetic recording
Authors: Nishikawa Masaaki , Kirihara Akio 
Published: July 2007

AbstractAlthough there have been various theories on the effect of the magnetic saturation of a write head on the recording characteristics of a magnetic medium, they include many vague points. to obtain a complete picture of the effects, this paper compares the digital recording characteristics. These have been obtained by changing the starting point of the saturation of a write head over a wide range referring to the saturation point of a magnetic medium (the variation is made utilizing the temperature characteristics of ferrite used for the head). When the head is not saturated, in both the unsaturated region and the highly saturated region of the medium, the recording characteristics of the medium depend greatly on the recording magnetic field strength. This dependency is less in the region between the two regions. In the two regions, if the head is saturated, the variation of the write characteristics due to the write current is restrained after saturation. In the intermediate region, if the pole tip is saturated, the write characteristic is somewhat degraded. If the head is saturated around the intermediate region, the overwrite erase rate is greatly degraded, since this is sensitive to the erase magnetic field strength around the saturation point of the medium.
An algorithm for generation of s‐t acyclic graphs
Authors: Higashiyama Youichi , Ariyoshi Hiromu 
Published: July 2007

AbstractThe problem of finding all s‐t acyclic graphs between two given vertices of a digraph is interesting in relation to the evaluation of the reliability of a communication network. There is already an algorithm which generates all s‐t acyclic digraphs without duplication by opening an arc or a set of arcs one by one starting with a given graph. But the efficiency of that algorithm decreases when the number of cycles in the graph becomes large. This paper proposes an algorithm which generates s‐t acyclic graphs without duplication by combining s‐t paths obtained by a depth‐first search. Compared with the existing algorithms (i) the execution time of this algorithm is not affected much by the number of arc disjoint cycles of the graph; (ii) when the generation is stopped at an arbitrary level i, all the s‐t acyclic graphs composed of paths of length i or less will have been generated. Thus they can be used to approximate the reliability.
Design and characteristics of standard launching fiber for optical loss measurement
Authors: Tokuda Masamitsu , Horiguchi Tsuneo , Ueki Akihide , Oshima Toshio , Tanaka Masao 
Published: July 2007

AbstractWe have studied a standard launching filter, which can realize a field distribution close to the steady‐state modal field in the optical‐loss measurement of graded fibers and can be used as a reference fiber in the splicing‐loss measurement by a back‐scatter method. By using a small‐core fiber with the core radius 30 ‐ 40 μm, which is smaller than that of the fiber to be measured (50 μm), we realized a field distribution close to the steady‐state modal field. It was found that the variation of the excited modal distribution due to a difference in the radiation pattern of the optical source can be reduced by inserting a graded fiber and a step‐index fiber between the source and the small‐core fiber. When a fiber with a standard backscattering coefficient is placed between a small‐core fiber and the fiber to be tested, it becomes possible to apply the splicing‐loss measurement based on the backscattering technique. The optical loss measured by a standard fiber designed for the 1.3‐μm wavelength agreed with the value at the steady‐state modal distribution within ±0.05 dB/km. It was found that the optical loss at 0.85 μm can be measured within ±0.1 dB/km by using the same standard fiber. From these studies, it now becomes possible to measure the optical loss and the splicing loss with high precision.
Arc‐fusion splice of multimode optical fibers using pre‐fusion method
Authors: Miyauchi Mitsuru , Matsumoto Michito 
Published: July 2007

AbstractIn optical fiber splicing, the fusion technique using gas discharge heating is considered a practical method from the viewpoints of operation and reliability. The fusion by which the splicing is made after pre‐shaping by a gas discharge on the optical fiber ends, has excellent features of low loss and stable splices. However, the splicing mechanism and the optimum splicing condition have not yet been analyzed sufficiently. This paper studies splicing conditions such as the pre‐fusion time, optical fiber stuffing length and shape‐up time of the optical fiber splicing by pre‐fusion method from the viewpoint of splicing shape, splice loss and core distortion. The optimum conditions for realizing a low‐loss splice are then determined. As a result, it is clarified that although the pre‐fusion method essentially becomes a mechanism for increasing the splice loss due to core distortion caused by pre‐fusion, there exists an optimum stuffing length for minimizing its effect. It is also shown that for performing stable, low‐loss splicing (even in the case where the condition of the optical fiber end is bad), it is proper to have a pre‐fusion of 0.3 ∼ 0.4 second. A foundation for the design of the splicing apparatus is obtained.
Improvement of signal‐to‐noise ratio in a combination of a linear and a nonlinear amplifier
Authors: Shinriki Masanori , Member Regular 
Published: July 2007

AbstractIn general, when a signal with noise is applied to a nonlinear amplifier, the nonlinearity will suppress either the signal or the noise. This property is utilized in this paper; the input signal is applied to nonlinear and linear amplifiers and an output circuit forms their difference. It is found that such a circuit can markedly improve the signal‐to‐noise (S/N) ratio of an input signal containing strong noise. Simple saturation nonlinearity is produced by an element xν(ν < 1); with ν>1 extension‐type nonlinearity characteristics result. A general type of noise is treated as a narrowband noise with a Weibull amplitude distribution. Analysis shows that when the Weibull coefficient is small, the use of the saturation characteristics of a nonlinear amplifier improves the S/N ratio considerably; when the Weibull coefficient is very large, neither extension‐ or saturation‐nonlinearity shows a marked difference. If the signal is contained in narrow‐band noise of constant amplitude, tests confirm the effectiveness of the theory.
Temperature characteristics of optical fiber cable installed on aerial line
Authors: Matsumoto Michito , Saito Takeo , Hirose Mitsuhide 
Published: July 2007

AbstractWhen an optical cable is installed on an aerial line, it will be affected strongly by the temperature and vibration due to wind. Therefore, it is necessary to grasp these effects quantitatively and establish a design method for the optical cable which will not be controlled by weather conditions. For this reason, we hypothesize a line close to the actual form and construct a 48‐core optical cable using a lashing machine, and then investigate the effects of temperature between ‐20°C and 60°C on the optical cable. The mechanical behaviors of the cable include the following: (1) Relative displacement between the strand and the optical cable accompanies temperature variations. The displacement is approximately 30 mm maximum at the end of a cable 57 m long; (2) Relative displacement between cable sheath and core occurs due to the release of the residual strain during manufacturing. It is 18 mm in the case of a 57 m cable; and (3) About 200 kg thermal stress occurs at the cable end, however, only about 10 kg in the vicinity of the slack. Based on the above experiment, the mechanical behavior of the optical cable is analyzed theoretically by setting up a simple model. It is confirmed that the analytical results agree very well with the experiment results. Variation of optical loss increases at approximately 0.15 dB/km at 60°C and this is about the same change as drum‐wound cable.
Performance of a microwave amplitude limiter using GaAs MESFET
Authors: Komaki Shozo , Kurita Osamu 
Published: July 2007

AbstractThis paper explains the input/output power and AM‐PM conversion characteristics of an amplitude limiter using GaAs MESFET. It is also pointed out that the AM‐PM conversion can be minimized conveniently by adding inductance in parallel to the gate terminal. In this paper the FET equivalent circuit is used for a calculation from which the relationship between the AM‐PM conversion and the gate series resistance, driving source impedance and the added inductance is clarified; the design method for minimizing AM‐PM conversion is established. The measured charactersitics are found to be the same as predicted by theory, and the correctness of the analysis is confirmed.
Non‐stop controlled vertical scanning technique for high‐speed digital facsimile
Authors: Suzuki Ryota 
Published: July 2007

AbstractFor high‐speed facsimile with redundant supression code, the intermittent variable scanning system has traditionally been used, accompanied by the start/stop function for the vertical scanning. However, the system requires a certain settling time in stopping and a limitation is imposed on the speed when the vertical scanning mechanism is heavily loaded. From such a viewpoint, this paper proposes a nonstop vertical scanning system, which realizes a smooth vertical scanning operation without stopping the vertical scanning. In the proposed system, the vertical scanning speed is predetermined in N steps and, by comparing the stored bits in buffer memory and threshold values for the buffer memory, the vertical scanning speed is determined as the same as the previous one or one step faster or slower. By this elaboration, a high‐speed system can be realized even when the load is heavy, at the same time achieving low‐noise operation. In the present system, however, selection of the vertical scanning speed is limited to one of three, which prevents the system from complete follow‐up change in the code information, necessitating a line memory and buffer memory. This paper first describes the design method and control scheme for the vertical scanning speed and then presents the result of calculation and computer simulation for the relation between various parameters and the memory capacity. The effectiveness of the proposed system is verified by an implementation. The memory capacity is evaluated at the same time, comparing the capacities of the two kinds of memories.
An intensity/phase autocorrelator for measurement of an ultrashort optical pulse having frequency variation
Authors: Kurobori Toshio , Cho Yoshio , Kanda Masahiko , Matsuo Yukito 
Published: July 2007

AbstractAn autocorrelator which can provide the intensity and phase correlations of an ultra‐short optical pulse simultaneously is presented. This is accomplished by employing an alternate repetition of fast and slow scans to separate the intensity and phase correlations. The proposed autocorrelator is also equipped with the junction of a real‐time monitor for the rapidity and ease of complex adjustments to optimize the various parameters in a mode‐locked laser. Such autocorrelator is useful for measuring ultrashort optical pulses containing frequency variations.
Image reconstruction of long‐wavelength holograms by maximum entropy method
Authors: Yamamoto Tsuyoshi , Aoki Yoshinao 
Published: July 2007

AbstractApplication of the maximum entropy method to one‐dimensional holographic imaging system is proposed. Image reconstruction usually is performed by the Fourier transform method. In this paper, however, the maximum entropy spectral estimation is used instead of such a transform. In digital processing the DFT algorithm is used instead of the Fourier transform, but it requires the quantization of coordinate system of both object and hologram plane. Such quantization sometimes makes the reconstructed image degrade if the position of the objects is not on the quantized position. To avoid such degradations, using windows or increasing the number of data must be considered. However, information in the hologram data will be lost by using such a window. In contrast to a Fourier transform method, this technique can evaluate the image continuously on the object plane; thus degradation caused by quantization of coordinate does not occur. While image reconstruction by the Fourier transform method is a linear operation, this technique is non‐linear. Therefore, linear superposition property of reconstructed image is not guaranteed. Further, the image is obtained by evaluating an all‐pole filter; thus this technique gives good reconstruction if the objects are pointed. Experimental results using ultrasound are presented. These show that this method gives good images even when little data are used.
Miniaturization of stripline hybrid coupled diode phase and shifter and its wavebanding method
Authors: Matsunaga Makoto , Takeda Fumio 
Published: July 2007

AbstractThis paper describes miniaturization of a hybrid coupled diode phase shifter made of striplines and its widebanding. An impedance transformer setting the phase shift of a single‐bit phase shifter is fabricated with a coupled line with two open ends having a bias blocking capability. This makes the size of the phase shifter about one‐half of the conventional one. It is pointed out that a wideband characteristic of this phase shifter is possible by choosing a large ratio of the even‐mode impedance to the odd‐mode impedance in the coupled line. An S‐band hybrid coupled phase shifter fabricated based on the present design method has a phase error less than 7.4 (RMS value) in the relative bandwidth of 26%, a loss of less than 1.4 dB and a VSWR of less than 1.6.
Probabilistic analysis of a sequential algorithm for finding independent sets
Authors: Kawaguchi Tsuyoshi , Nakano Hideo , Nakanishi Yoshiro 
Published: July 2007

AbstractThis paper uses the constant group average degree model, which is a generalization of the constant average degree model, and evaluates the method of solution given in [1] to determine the independent vertex set. The model is a set of graphs in which there exist edges with probability pij = cicj/cn (c Σmi=1 ci|Vi|/n) independently between two vertices v and w such that v ϵ Vi and w ϵ Vj in the vertex set V = Umi=1Vi. When m = 1 holds as a special case, the model includes the constant average degree model. It is shown first that the stochastic variable BG(n, c) representing the solution by the method of [1] satisfies (1 ‐ ϵ) βG(c)n < BG (n, c) < (1 + ϵ) BG(c)n (pr.), where ϵ = 0 is sufficiently small compared with 1 and BG(c) is a value obtained by solving a recurrence formula. Then it is shown that the stochastic variable BG*(n, c) representing the size of the maximal independent set satisfies BG*(n, c) ≦ (1 + ϵ) αG(c)n (pr.), where αG(c) is a value obtained by solving an equation. The results obtained in this paper are applicable to the constant group average degree model with any |Vi| and ci.
Variable‐hue light‐emitting diode using a single crystal chip
Authors: Shimura Hideo 
Published: July 2007

AbstractMonochromatic light‐emitting diodes of different sizes and colors are widely used as small display devices. However, diodes of different colors for commercial purposes are those having a combination of red light‐emitting pellets and green light‐emitting pellets. Such a combination involves problems of color uniformity and brightness degradation. Therefore, a single pellet which has different uniform colors was proposed several years ago, but it has not yet been marketed due to many technical difficulties. The authors succeeded in making a single pellet with a green light‐emitting part and a red light‐emitting part on both sides of a GaP substrate. By changing the current ratio of the current flowing through the device, different colors were attained. This paper deals with different technical problems associated with device fabrication and the solutions to these problems. Also, electrical and optical properties of the device are discussed.
Evaluation of the exponent function E(R) for channels with intersymbol interference
Authors: Sasano Hiroshi , Kasahara Masao , Namekawa Toshihiko 
Published: July 2007

AbstractThe exponent function E(R), a practical measure, is used to study two kinds of decoders having 2l (l = 1, 2, …) quantization levels in a communication channel with inter‐symbol interference: a decoder which takes account of channel memory, and a decoder which does not. The values of E(R) for the same kind of decoder and an increased number of quantization levels, and for the two different kinds of decoder and the same number of quantization levels, are analytically compared for a channel with intersymbol interference of length 1. It is shown that increasing the number of quantization levels for a given type of detector, or taking account of channel memory with a given number of decoder quantization levels, can decrease the upper limit of the error probability. A comparison of channel capacities is shown to yield similar conclusions. Numerical computations indicate that when a decoder which takes account of intersymbol interference is used, the rate of improvement in the upper limit of the error probability is greater for a higher degree of intersymbol interference, but that further increases in the number of quantization levels produce almost no further improvement in such a situation.
Measurements of millimeter wave reflection coefficients over wide frequency range by using a special T‐junction
Authors: Iwasaki Takashi , Nagatsuka Akio 
Published: July 2007

AbstractMany millimeter‐wave applications make use of their wideband nature. Hence, it is desirable to have a broadband method for measuring fundamental quantities of millimeter‐wave circuits at many frequency points in a short period of time. This paper reports a method for wideband measurement without adjustment. It is an extension of the T‐junction method in which reflection coefficients can be measured with a simple circuit. In the T‐junction method, it is necessary to reposition the movable short at each frequency for measuring a characteristic quantity of the system. This makes wideband measurement difficult. We developed a method that enables wideband measurement by using a special T‐junction in which the width of the E‐plane of the waveguide connecting the load is narrowed. In accordance with the theoretical study, a T‐junction was designed and fabricated. The experiment at 29 ‐ 39 GHz indicated that wideband measurement is possible. The estimated error of the absolute value of the reflection coefficient of the load at 34.0 GHz is less than 0.0064 |Γ| + 0.002 for |Γ| less than 0.3.