bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantization error in differential PCM of laplacian increment inputs
Authors: Hayashi Akira
Published: July 2007

Quantization error is one of the important measures that determine the performance of the differential PCM. This paper investigates the DPCM quantization error characteristic and the exact determination of the stationary error density. The input signal considered is a time‐discrete increment process which is similar to the Wiener sequence, but with Laplacian increments.

A system of equations satisfied by the characteristic function of the prediction error is derived first and the exact formulas are derived for error probability distributions. Using these distributions the meansquared error, the entropy of the quantized outputs, and the probability of granular error are determined. For the obtained optimum quantization step size, it is shown that the granular error exceeds the slope overload error, that the distribution of quantized outputs is nearly geometrical, that the quantization error is almost equal to that of increments for a large number of quantization levels, and that the results agree with rate distortion theory.

The present analysis will be useful to performance analysis of DPCM with stationary non‐Gaussian autoregressive inputs.
All digital phase‐locked loop with a wide locking range
Authors: Hikawa Hiroomi , Zheng Nanning , Moris Shinsaku
Published: July 2007

The phase‐locked loop (PLL) is used widely in communication engineering as one of the key functions. Recently, some attempts have been made to construct a digital circuit for the phase‐locked loop. However, the common problems in those attempts is that there is a trade‐off between the locking range and the output phase jitter. To solve this problem, this paper proposes a new structure for the phase‐locked loop with a wide locking range by combining the frequency control technique. For this purpose, a new digital VCO is constructed, which can vary the central frequency of the system using the programmable divider and the adder. Theoretical analyses are made for the transient behavior from the viewpoints of the locking range, frequency and phase, and the noise characteristics of the loop. The result is compared with the results of experiment and simulation. The theoretical value, experimental value and the result of simulation agreed well, indicating that the phase‐locked loop has a wide locking range.
Unified analysis of ridge‐waveguide slot antenna in three‐dimensional space and time
Authors: Kashiwa Tatsuya , Yoshida Norinobu , Fukais Ichiro
Published: July 2007

Recently, there has been much interest in research and development of a high‐power heating system for nuclear fusion plasma heating. Since these systems deal with high power, there are several problems that are different from those in the sources for communication systems. A structure is proposed which is based on the T‐type ridge waveguide, a simple and sturdy configuration. In these systems, the complex near field due to the three‐dimensional structure including the medium conditions has a significant effect on the characteristics. Especially, in a high‐power system, the effect of higher‐order modes with relatively small power distributions cannot be neglected. Also, transient field distributions strongly affect the characteristics so that the time domain response must be analyzed. This paper applies an analysis technique for the three‐dimensional space and time based on the Bergeron method to the systematic analysis of the radiated near field from the entire system of a T‐type ridge waveguide slot antenna including the waveguide, slot and the heating regions. The power distribution of the field determining the fundamental properties of the heating system is found in terms of the Poynting vector and the fundamental properties of the system are obtained. Specifically, the effect of the dielectric material on the field distribution is found. The cutoff characteristics of the ridge waveguide and the fundamental properties of the slot are studied and their characteristics are investigated.
Reflecting characteristics of lossy anisotropic materials inserted into the rectangular waveguide
Authors: Hashimoto Osamu , Shimizu Yasutaka
Published: July 2007

It is known that a large anisotropy exists in the plane of a rubber sheet composed of rubber mixed with carbon fibers or carbon particles with a subsequent pressing by a roller. This anisotropy can be used for fabrication of microwave absorbers and shielding materials. For this objective it is necessary to measure the complex permittivity tensor of these materials. The standing wave method in a rectangular waveguide has been extended for an application of measurement of tensor materials. The analysis of the reflection coefficient is studied for a short‐circuited waveguide containing an anisotropic lossy material. If this reflection coefficient can be found, a least square method may be applied to the measured data to determine the tensor component. In this paper, for the analysis of hybrid mode propagating in the anisotropic material, a set of generalized transmission equations is used. For each hybrid mode calculated by this method, the mode matching method is applied to find the reflection coefficient. The calculated results by this method are compared with the measured data. It is found that the agreement is excellent even if the direction of the rolling during the fabrication and that of the electric field are different. It is confirmed that the present method can be applied to the measurement of the permittivity tensor.
Centrality functions defined by minimum cuts in a network
Authors: Takeuchi Masashi , Itoh Yutaka
Published: July 2007

It is of interest in graph theory to discuss the degree of centrality of a vertex in a graph or to locate the most central point in the graph representation of systems with network structures such as communication and traffic networks. Various expressions for the centrality of a point in a graph or a network have been considered in association with the above problem and are called centrality functions in general. Most of them are based on the distance between two points, while an expression for the centrality by the gauge between two points in a network is also proposed. Most of the previous centrality functions were defined by distance, whereas in this paper we consider the centrality function defined by the minimum cut separating two points in a network (or the maximum flow between two points). According to this centrality function, the centrality of the point under consideration may happen to be the sum of the maximum flows from the point to every other point in the special case and hence it seems to be significant in estimating traffic networks and reliability with respect to circuit faults in communication networks.
Low‐sensitivity switched‐capacitor integrators
Authors: Ishikawa Masayuki
Published: July 2007

The integrated circuit switched‐capacitor filter (SCF) has the merits that the temperature dependence and the effect of aging are small. To utilize these features, it is important to design the low element‐sensitivity to realize the initial characteristics with a high accuracy. A number of low element‐sensitivity designs have been proposed for SCF's, which concentrate on the ways of combining the SC integrators. This paper aims at the low element‐sensitivity of the whole system, by decreasing the element‐sensitivity of the SC integrators themselves. The low‐sensitivity SC integrators of differential‐input and differential‐output types are proposed. Both types can be easily compensated for the effects of the parasitic capacitance and the number of operational amplifiers can be reduced by multiple uses. The determination of the element values to realize the required integrator coefficient is discussed, and a method is presented to minimize the element‐sensitivity. The leapfrog type low‐pass filter is considered as an example. Compared with the traditional circuits using SC integrators, it is shown by a computer simulation that the element‐sensitivity has been reduced by a factor approximately 1/2, compared with the circuits using traditional SC integrators.
Systolic decoder for reed‐solomon codes
Authors: Kimura Masayuki , Imai Hideki , Dohi Yasunori
Published: July 2007

This paper proposes the systolic decoder for Reed‐Solomon (RS) codes based on systolic algorithms. Three steps of decoding procedures for RS codes can be reduced to simple repetitive algorithms and thus can be realized by one‐dimensional systolic arrays, each operated by simple controls. The decoding system is a cascade connection of these cell arrays in one dimension. In this paper we also design three types of cells building arrays for RS codes on GF(28). Each cell has a size that permits its integration in a one‐chip LSI and we can determine the number of cells according to the error correcting ability for codes.
Decoding error probability of maximum likelihood decoders on intersymbol interference channels
Authors: Sasano Hiroshi , Kasahara Masao , Namekawa Toshihiko
Published: July 2007

Computational complexity in deriving and numerically evaluating the upper bounds of decoding error probability of maximum likelihood decoders with Viterbi algorithm for intersymbol interference channels increases significantly with the length of intersymbol interference. A new upper bound of the decoding error probability is derived for intersymbol interference channels of length 1 and 2. The bound can easily be calculated, and for the intersymbol interference of length 2, the formula is not as complicated compared with the Viterbi‐Omura bound. Numerical results show that the bound is tighter than the Viterbi‐Omura bound by a factor of ten for a wide range of SN ratio. Simulation results show that the new bound is tight when the intersymbol interference is not so large.
Improvement of algorithm using interval analysis for solution of nonlinear circuit equations
Authors: Okumura Kohshi , Kishimas Akira , Saeki Shuichi
Published: July 2007

This paper describes an improvement of the solution by Krawczyk, Moore and Jones (KMJ algorithm) for nonlinear equations based on the interval analysis. When the KMJ algorithm is applied to practical problems such as the determination of the operating point of a multistable electronic circuit, a large computation time is required. The reason for the large computation time is as follows: (i) The existence of the solution is determined using the direct‐replacement type interval extensions of functions, which enlarges the search region for the solutions; (ii) the region partitioning is repeated until a region X is obtained such that K(X) ⊆ X, where K(X) is Krawczyk's interval function and X is the interval region. The situation is demonstrated by an example. As a solution for these problems, the following method is proposed.

(1) The given initial region is partitioned into subregions, and some subregions are excluded from consideration if the solution is judged as nonexistent by the interval extensions of functions; (2) when K(X) ⊆ X, does not apply, the region X is partitioned into XC δ X ‐ (K(X) ∩ X) and XK ∩ K(X) ∩ X, and the KMJ algorithm is applied to XC and XK to examine the existence of the solutions. Finally, as a computation example, the KMJ algorithm with the above two elaborations is applied to the nonlinear circuit equations with two to four variables. It is demonstrated that the computation time can be reduced considerably with the original KMJ algorithm.
Role of formant frequencies and bandwidths in speaker perception
Authors: Kuwabara Hisao , Ohgushis Kengo
Published: July 2007

This paper considers the relation between the vocal tract characteristics under the personality of speech. A pitch synchronous analysis‐synthesis system was constructed in which the formant frequencies and the bandwidths can be modified independently. The speech was synthesized by controlling these parameters in natural speech, and an experiment was made on the discrimination of personalities. As a result, it is seen that the personality is strongly sensitive to the formant frequency shift, especially to the shift of the lower three formants, and it is lost by the uniform shift of 5 percent. On the other hand, the personality is well preserved for the change of formant bandwidth, and is sensitive to the bandwidth change in the fourth‐ and higher‐order for‐mants. In the case of uniform change of the bandwidth, deformation of wider than 5 times or narrower than one‐fifth times completely eliminates the personality.
Ultrasonic cell with IDT's for measurement of liquid acoustic velocity
Authors: Shiokawa Showko , Moriizumi Toyosaka , Kikuchi Tsuneo
Published: July 2007

This paper proposes a measuring system for the small changes of sound velocity, using the leaky surface wave excited by the interdigital transducer (IDT) on a piezoelectric substrate. The ultrasonic cell was fabricated and an experimental investigation was made. It is shown that the sound velocity change of the order of 2 ppm can be measured. When the propagation surface is loaded by a liquid, the elastic surface wave excited by IDT is converted into the leaky surface wave, which excites the ultrasound into the liquid. By constructing the measuring system utilizing this ultrasound excitation in the water, little spurious wave is excited, and a differential measurement can be successfully performed in the present system. The characteristics of the fabricated ultrasonic cell are examined and the measurement limit and accuracy are discussed. As examples, the change of sound velocity in KCL solution by concentration and some other measurements are discussed, indicating the usefulness of the proposed measuring system.
Small‐sized waveguides with periodically loaded posts
Authors: Kim Ki‐Chai , Tokumarus Shinobu
Published: July 2007

To develop a transmission line with a small cross section, a waveguide periodically loaded with posts is proposed. Various characteristics such as phase constants and field distributions are obtained theoretically. The structure is below cutoff if the posts are removed. However, if appropriate external reactances are connected to the posts the wave can be made to propagate. Also, the nature of the wave can be controlled freely from the slow wave to fast wave. In the analysis, the electric fields inside the waveguide are calculated first from the current on the post. Next, the internal impedance seen from the post terminal is obtained. From this impedance and the reactance loaded externally, the determinantal equation for the phase constant is derived. The magnetic field in the waveguide is then computed. As examples, the field distributions are shown for the slow and fast wave cases. The normalized transmission power and the losses with perturbation concepts are evaluated and numerical examples are given. The numerical results are verified experimentally.
A reduction method of tracking errors due to multipath waves in direct sequence spread spectrum systems
Authors: Maruyamatoggle Satoshi , Iwanami Yasunori , Ikedas Tetsuo
Published: July 2007

The speed spectrum (SS) communication is a communication system which has excellent characteristics against noise and is suited to the code‐division multiplex. Numerous applications have recently been considered. The delayed lock loop (DLL) is employed frequently as the tracking circuit for SS communication, where, however, a phase tracking error is produced by multipath waves. This phase error degrades the large processing gain, which is one of the most remarkable features of SS communication. We have attempted to reduce the phase error. Here, it is assumed that the peak of the correlation function of the received wave is fixed as long as the object wave has an amplitude much larger than those of multipath waves. Under such an assumption, a circuit is proposed which aligns DLL to the peak of the correlation function. As a result of the operation experiment for the circuit, it is shown that the phase error due to the multipath wave can be reduced to approximately one‐fifth.
Traffic characteristics of digital pair‐loop network in common usage of channels
Authors: Inoue Yukio , Hirano Junzo
Published: July 2007

An integrated digital pair‐loop network with ring topology of optical fiber cables as a new type of communication systems for interoffice trunk networks in regional service areas is proposed. The pairloop network has a feature in that several switching offices share bidirectional transmission channels, and thus the channels can be utilized in common by several trunk groups of offices belonging to the system. However, if vacant channels are selected arbitrarily and assigned to any calls, blocking probability depends on the office location and a definite grade of service can not be expected. This paper shows that the channel assignment following an algorithm called the channel‐pair selection rule makes it possible for the trunk group to achieve a definite grade of service and improves channel efficiency. It is shown also that analytical results are in good agreement with simulation results.
Design of discrete–time recurrent control systems
Authors: Shinnaka Shinji
Published: July 2007

This paper presents a new method for designing the discrete‐time recurrent control system. Often it is required in the plant control to follow a periodic object trajectory. The recurrent control is one devised for such a plant. It has an attractive property in that the purpose of the control ultimately is achieved with a high accuracy, as long as the control system is stable as a closed‐loop system, even if the plant is not identified accurately. In the previous methods, except for one, it is not easy to ensure the stability, nor has the convergence speed to the object trajectory been sufficient. For the disturbance contaminating the plant, the importance is pointed out of coping with the disturbance, but a design method has not been presented which positively takes the situation into consideration. This paper presents an excellent design method for the highly practical discrete‐time recurrent control system, which is very simple and general, solving simultaneously the problems of stability, convergence and disturbance suppression. The features of the proposed design method are due entirely to the new approach of processing polynomial of the time‐delay operator, which is different from previous approaches.
Coupling coefficients and injection–locking characteristics of microwave oscillators
Authors: Fukumoto Katsumi , Nakajima Masamitsu
Published: July 2007

Injection‐locking phenomena are often studied for the purpose of application to synchronous operation and parallel operation of multiple oscillators. With respect to the coupling of multiple oscillators, synchronization stability, mode control and long‐time effects are problems. In this paper, it is pointed out first that the difference in the locking characteristics at low frequencies and at microwave frequencies is caused by treatment of the incident signal as the voltage and current or as the traveling wave. It is shown that use of the wave concept is more practical and rational in the microwave region. In such cases, the strength of the coupling between oscillators should be considered in two separate aspects: magnitude of the coupling (C ≧ or ≦ 1) between the oscillator and the coupling transmission line, and coupling coefficient r of the oscillator coupling circuit. As a result, it is found that a symmetric coupling with a rather weak coupling factor (r < 1) or, if coupling is strong, an asymmetric coupling is desirable for power combining of Van der Pol oscillators.
Power spectrum, anti–intercept and SN ratio characteristics of direct sequence spread spectrum communication systems using FIR and IIR filters
Authors: Kusaka Hiroji , Nishida Fujio , Simazaki Yoshihito
Published: July 2007

The time series generated from a direct sequence spread spectrum (DS‐SS) signal can be expressed in terms of an auto‐recursive (AR) model. An all‐zero FIR filter (FIRF) and an all‐pole IIR filter (IIRF), which are the inverse to each other, consist of the parameters of the AR model. We propose a spread spectrum communication system using an FIRF on the transmission side and an IIRF on the receiving side as well as a system using an IIRF on the transmission side and an FIRF on the receiving side. The former is called the DS‐SS communication system using FIR‐IIR filters and the latter using IIR‐FIR filters. When the order and the delay time in the delay element (the order and the sampling time interval, respectively, of the AR model of filters are selected properly by the former system, the power spectral density (psd) of the transmission signal can be spread more than that of the DS signal so that the density is lower and the peak value is suppressed. By the latter system, an optimum transmission becomes possible in the sense that the SN ratio is maximum within the main lobe of the psd of the DS signal. Further, the pulse duration time of the rectangular pulse train of the transmitted signal in both systems is transformed to the selected delay time. Since the amplitude of the pulse train changes randomly, both systems have an anti‐intercept property such that interception is almost impossible.
Cyclically orthogonal sequences with low multiplicity of values derived from quadratic residues
Authors: Tanada Yoshihiro
Published: July 2007

Orthogonal cyclic sequences with low multiplicity of values are given for application to spread spectrum communications systems. Two‐, three‐, and five‐valued orthogonal cyclic sequences are obtained by representing real orthogonal cyclic sequences of length N by cosine series possessing phase constant of odd function, or even function with values {0, }, and by relating the phase constant to quadratic residues of N. We use the fact that an extended quadratic residue sequence taking values {0, +1, ‐1} becomes a sequence of odd function satisfying homogeneous equation of discrete sine transform when N is a prime number of the form N =4° ‐ 1 ( is a natural number). When N is a prime number of the form N =4° + 1, the sequence becomes that of even function satisfying a homogeneous equation of discrete cosine transform. Three‐valued orthogonal cyclic sequences are obtained by adding a dc component, to quadratic residue sequences of these odd and even functions. A two‐valued orthogonal cyclic sequence is obtained when a phase constant is given by a quadratic residue sequence of odd function multiplied by a constant. Moreover, when the phase constant is a monomial of odd power and is related to the quadratic residue sequence, a three‐valued orthogonal cyclic sequence is obtained for the prime N =4° ‐ 1, and a five‐valued orthogonal cyclic sequence is obtained for the prime N =4° + 1. Since N sequences obtained by shifting one of those sequences form an orthogonal system, cross‐talk does not occur when these sequences are applied to synchronous spread spectrum multiple access.
DPCM‐PCM hybrid coding and its properties
Authors: Hayashi Akira
Published: July 2007

Differential PCM (DPCM) is a method use to encode analog information sources with greater efficiency than PCM. However, due to its characteristic decoding mechanism, where the decoded signal values depend on previous ones, DPCM is unsuitable for progressive decoding.

This paper proposes a new method, “DPCM‐PCM Hybrid Coding,” which is highly efficient similar to DPCM and also is suitable for progressive decoding.

The principle of the proposed encoding method is described and computer simulation results of its quantization error performance are presented. Finally, the performance of the encoding method proposed herein is compared with that of the conventional DPCM.
Studies on pulse transmission capabilities of a ping‐pong transmission system
Authors: Komiya Ryoichi , Tamaki Norio , Yamano Seiichi
Published: July 2007

This paper describes the design philosophy of a line driver and an automatic line equalizer applied for a 200 kbit/s ping‐pong transmission system using existing metallic pair cables. The semiimpedance matched line driver is appropriate from the viewpoints of transmitted pulse distortion and power consumption. The automatic line equalizer is composed of a frequency domain equalizer as well as a time domain equalizer. The frequency domain equalizer is used to compensate for wide line‐loss variations, while the time domain equalizer is used to compensate for intersymbol interferences due to cable gage changes and bridged taps. The decision feedback equalizer is used as the time domain equalizer. Gain vs. frequency characteristics of the frequency domain equalizer and number of required taps of the decision feedback equalizer are determined to minimize intersymbol interferences due to deviations between automatic line equalizer characteristics and various line characteristics. As a result of the design, the 200 kbit/s ping‐pong transmission system is operative for 99 percent of NTT's existing subscriber cables with 100 percent cable fill.
Polarization diversity receivers using error‐control codes for heterodyne detection lightwave transmission systems
Authors: Yamaguchi Haruo
Published: July 2007

In 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

This 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

To 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

This 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

The 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

This 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

This 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

This 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

In 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

Motion 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

This 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

A 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

With 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

This 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

This 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

The 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

The 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.