bluuebunny/crossref_metadata_2025 huggingface dataset:
Search for electromagnetic wave sources using the maximum entropy method
Authors: Kikuchi Jun'Ichi , Nagasawa Yoji
Published: July 2007

Undesirable electromagnetic waves radiated from various electrical and electronic apparatus recently have become social problems. Research to prevent these effects is in progress in various fields. This paper presents a method of determining the location of electromagnetic wave sources two‐dimensionally. The analysis method is based on the deduction of the power spectrum by applying the maximum entropy method to time‐series information, i.e., the location of electromagnetic‐wave sources in two‐dimension, corresponds to the power spectrum. It is confirmed by computer simulation that the location can be determined with very high accuracy. The relationship between the amount of data measured and the accuracy of location determination, and the relationship between the accuracy of a source‐location detection and the offset of the measuring position, were examined. The number of measurements was found to be almost twice the number of electromagnetic sources, and the detection of the location of a source can have a very high resolution if the measuring position is kept at a high accuracy. The results show that this method is very effective in determining the position of sources, for example, radiated from a system consisting of subsystems.
Structural analysis of t‐invariance of petri nets
Authors: Onaga Kenji , Ge Qi‐Wei
Published: July 2007

This paper studies the t‐invariance of a Petri net by introducing two concepts of the rigidity for its existence and the marked‐graph‐reducibility for its efficient computation. Some characteristics and composition rules of rigidly connected Petri nets are given and an algorithm is designed to determine efficiently t‐invariants of a marked‐graph‐reducible Petri net.
On the multi‐commodity flow problem in certain planar directed networks
Authors: Nagamochi Hiroshi , Ibaraki Toshihide , Hasegawa Toshiharu
Published: July 2007

This paper introduces the concept of capacity balance (CB) to show that multicommodity flow problems for classes CB and CS (capacity semibalanced) directed networks have efficient graph‐theoretic algorithms.

In a wide variety of applications, multicommodity flows are used to represent many important problems. Such applications include the assignment of traffic in roads or communication networks, and routing in VLSI design.

For these networks it is possible to develop polynomial time graph‐theoretic algorithms. It is shown that the integral flow property holds for CB, and class CS networks, which are an extension of CB, are considered. As a special case, this class contains a certain multiterm, multistage production scheduling problem [3]. Its importance in practical applications is shown.
Multifrequency holography on near region using range curvature correction
Authors: Tajiri Katsuhiro , Sakamoto Yuji , Aoki Yoshinao
Published: July 2007

The authors have developed a radar to search an object buried in snow based on multifrequency holography. Multifrequency holography has a deficiency in that the quality of the reconstructed image is degraded. This phenomenon is called the range curvature. This paper proposes a method for correcting this phenomenon to obtain a correct image. The experimental results based on this method are presented. Multifrequency holography is based on the principle similar to that of the synthetic aperture radar. In both multifrequency holography and synthetic aperture radar, the range curvature is a problem. This phenomenon is especially significant in the near region. In this paper, this region is studied and the formula for range‐curvature correction and the simulation for confirmation of this formula, as well as the experiment, are introduced. Two experiments have been carried out with X‐band signals at 8.3 to 9.3 GHz for the object separated from the antenna by about 1 m. One of the experiments used a metal post while another used two metal posts. From these experimental results, it is confirmed that the range‐curvature correction is an effective method.
Almost‐periodic oscillation and generation of chaos in a parametric excitation circuit having an external force
Authors: Kitagawa Takaaki , Tomiyasu Ryuichi , Itoh Makoto
Published: July 2007

This paper considers the generation of almost‐periodic oscillation and chaos which occur in a parametric excitation circuit having an external force, and the region in which they occur.

In a resonance circuit, if one of the reactances is excited with a frequency which is almost twice the resonance, a subharmonic parametric oscillation of one‐half order, i.e., the parametric oscillation for short, is sustained. If an external force with frequency near the resonance is applied to the circuit, the parametric oscillation disappears. The characteristics of this oscillation disappearance are analyzed by using the nonlinearized Mathieu equation with a forcing term which describes this system. For this we assume a solution containing only two harmonic components and apply the method of harmonic balance.

In this paper, using a more detailed investigation of the characteristics of the oscillation disappearance, it is clarified that chaotic phenomena occur in a part of the response curves. Advancing the forementioned method, we obtain a set of four autonomous differential equations. Plotting the solution curve of these equations in the phase plane, we may investigate the behavior of this system. Consequently, it is clarified that under proper condition of circuit parameters, the solution curve tends to a limit cycle or chaos, by only several percent variation of the frequency of the external force. A limit cycle is correlated with an almost‐periodic oscillation. Therefore, the behavior of this system is revealed in more detail.
Radar clutter suppression schemes using multisegment MEM
Authors: Watanabe Hideaki , Azuma Ryuichi
Published: July 2007

This paper proposes a new adaptive suppression scheme for radar clutters. This scheme applies a multisegment MEM which has been known as a means for power spectral analysis and for classification of radar clutters. This adaptive suppression scheme is applied to the multisegment MEM based on the work by Zhang and Haykin who assumed that clutter data in neighboring range rings have a high correlation. Actual clutter data (ground, sea, and weather clutters) collected by an experimental L‐band radar with a low PRF wave were used. A comparison was made of performances based on improvement factors between the new suppression scheme for clutters and the suppression scheme used by Zhang and Haykin. The new processing method is shown to give an improved level by a few decibels for the numerical values of improvement factors. This was confirmed by the detection efficiency of an object signal which was buried in clutters using topological figures. It was clarified that the new suppression scheme for clutter possesses an enhanced capability in detecting the object signal easily compared with the method of Zhang and Haykin.
Design of three‐dimensional separable‐denominator digital filters via singular‐value decomposition
Authors: Hinamoto Takao , Hamanaka Takashi , Maekawa Sadao
Published: July 2007

This paper considers the situation in which the desired three‐dimensional impulse response is represented as a finite series, and discusses the spatial domain design of the three‐dimensional recursive digital filter, which approximates the desired response by a separable‐denominator three‐dimensional local state‐space model. As the first step, a necessary and sufficient condition is derived for the separable‐denominator three‐dimensional local state‐space model to be separately locally controllable and separately locally observable. It is shown that the condition is equivalent to the minimality of three one‐dimensional systems. Then the given three‐dimensional impulse response is represented formally in terms of three one‐dimensional impulse responses, and the coefficients of the separable‐denominator local state‐space model are designed through the singular‐value decomposition of the Hankel matrices. Finally, the validity of the proposed method is verified by a numerical example.
Variable region vector quantization
Authors: Matsuyama Yasuo
Published: July 2007

Generalized algorithms for vector quantization are presented and their convergences are proved. The generalized vector quantization is called variable region vector quantization since the method allows adjusted variable dimensional vectors covering variable subregions of source data.

Algorithm I is the generalization of the LBG algorithm into the variable region case. This is called full‐gain variable region vector quantization. Algorithm II, on the other hand, is the variable region generalization of the gain‐shape type. The formation of each variable subregion is due to the grouping of elements so that the resulting set of variable dimensional super‐vectors has the minimum distortion to a given codebook. Algorithm III considers encoding‐decoding. Algorithm IV gives the suboptimal minimization for the alleviation of computational load.

Methods presented here are applicable to various pattern handling including artificial neural nets. However, data compression terminologies are adopted in this research. All of the foregoing algorithms are introduced without any physical entity to data. Later, the cases of speech and images are discussed using their specific natures. The examples of the region optimization on speech and images are given.
Consideration on parallel type structure of IIR type adaptive algorithm
Authors: Kurosawa Kaoru , Tsujii Shigeo
Published: July 2007

The IIR type adaptive algorithm can be classified by its structure into the series‐parallel type and parallel type. Most of the FIR type adaptive algorithms can be applied to the series‐parallel type. However, this type has the problem that a bias error is produced in the estimated transfer function in the presence of observation noise. On the other hand, while the parallel type is expected to suffer less from observation noise, it may produce oscillation. It is difficult to insure the convergence and only the method by Landau is known. His method, however, necessitates matrix manipulation, which increases the computational complexity. Discussion has not been made on convergence when observation noise is present. This paper shows that the high‐speed least‐mean‐square method can be applied to the parallel type. In this method the computational complexity is small, being proportional to the number of coefficients. The convergences of the proposed method and the least‐mean‐square method applied to the series‐parallel type are analytically compared in the presence of observation noise.
Analysis of a nonpreemptive σ Mi/G/1(σ Ni) system
Authors: Takenaka Toyofumi
Published: July 2007

High‐speed packet switching is a promising technology for multimedia communications in such wide‐band ISDN as speeches, images, and data. In this type of high‐speed packet switching, priority‐transmission technology will be effective, since a different packet‐transmission quality (e.g., transmission delay and loss‐rate) is required for each medium. This paper analyzes a nonpreemptive Mi/G/1( Ni) system which is the basis of the priority transmission system. In addition, n‐priority classes (where n is arbitrary) are treated using models of the Poisson arrival, general service‐time distribution, and individual waiting‐position type, while conventional analyses are limited to two priority classes. To obtain packet loss‐rate and delay characteristics, this paper analyzes mainly the marginal distribution of each priority class. The results of the analysis include an extension of the Cooper‐Gebhardt relationship which formulates the relationship between distributions at an arbitrary moment and after the completion of a service. For the packet loss characteristic and delay‐time characteristic and their approximate calculation methods, the reader is referred to the author's work in [6].
Characteristics and approximation methods of a nonpreemptive σ Mi/G/1(σ Ni) system
Authors: Takenaka Toyofumi , Akaike Takeshi , Takami Kazumasa
Published: July 2007

High‐speed packet switching is a promising method in the wide‐band ISDN system for such multimedia as speeches, images and data. In high‐speed packet switching, conditions (e.g., transmission delay and loss rate) required for the transmission quality of packets are different in each medium. The priority‐packet transmission method will satisfy these conditions. This paper is based on the results of analysis of the non‐preemptive Mi/G/1( Ni) method [6], describes the evaluation of the characteristics of the priority‐transmission system, and proposes their approximation methods. Numerical computation of a three‐priority‐class model was carried out assuming such multimedia as speeches, images and data. The results show that:

It is possible to design the number of buffers independently for each priority‐class

the traffic characteristic of each Priority‐class is not affected significantly by changes of traffic ratio of the class Saving a higher priority than its own.

Two approximation methods are proposed: a method based on an approximation that marginal distribution is independent in ch priority class; and 2 a method using result (2); both methods are evaluated.
Vector correlation detection‐type interference canceller
Authors: Matsue Hideaki
Published: July 2007

The following is a method to eliminate an interference signal. The interference signal is obtained from the source, and the amplitude and the phase of the interference signal is adjusted to the same amplitude and the opposite phase of the interference component, and is added to the received signal. One important problem is how to control automatically the amplitude and the phase of the interference signal. This paper proposes a vector correlation detection‐type interference canceller for the digital system. An orthogonal error signal detector is employed which produces the in‐phase and quadrature error signals. Combining the circuit and the given interference signal, the correlation detection is performed between the two to perform the automatic control of the amplitude and the phase of the interfering signal. In the first part of this paper, the operation principle is described theoretically. Then, the configuration is shown. An experiment was carried out where the desired signal is 16 QAM or 256 QAM, and the interference signal is an FM signal (telephone 3600 ch.). The improvement factor was 26 dB for 16 QAM and 21 dB for 256 QAM. The control response was 50 to 140 ms. The result indicated the validity of the theory and the effectiveness of the proposed canceller.
Harmonic analysis of a capacitor‐filtered rectifier with line impedance
Authors: Kim Duk‐Gyoo , Nakajima Tatsuhito , Masada Eisuke
Published: July 2007

Although the amount of harmonics generated from home electronic equipment such as televisions is small, the number of sets is large and they are used at the same time. Therefore, the harmonics generated from the power supplies of the electronic equipment is a cause of harmonic interference in the power distribution systems [1, 2]. In this paper, the input current of a capacitor‐filtered rectifier used widely as a power supply for electronic equipment is calculated with the impedance of the distribution system taken into consideration. As a result, an accurate expression became possible for the capacitor‐filtered rectifier current which had been treated by means of an approximate equation in the case where a line impedance, particularly inductance, exists [1, 2]. Also, an accurate prediction became possible for the current waveforms and harmonic behaviors according to the variations of the circuit parameters. The results computed as the parameters are varied indicate that the diode current path width, current waveforms and harmonic distributions, are strongly dependent on the inductance variation. The load circuits of a constant‐resistance type and of a constant‐power type were studied. As the inductance is increased, the harmonics are decreased whereas the amplitude and the average power of the fundamental wave are also decreased in the case of a constant resistance load. On the other hand, in the case of a constant power load, the amplitude of the fundamental wave tends to increase as the inductance is increased. When several of the capacitor‐filtered rectifiers are connected in parallel to a power distribution system, the amplitude of the harmonic cannot be evaluated by a linear sum of the harmonic contents of individual rectifiers.
Performance evaluation and optimization of ALOHA scheme with capture effect
Authors: Du Rongping , Nakanishi Hikaru , Tezuka Yoshikazu , Okada Hiromi , Sanada Hidehiko
Published: July 2007

This paper presents an analysis of the frame ALOHA scheme in the multiple‐access broadcasting channel with the capture effect, which has not been taken into consideration in past analysis. First, the transmission‐success rate, together with its expectation and variance, are determined, which indicate the basic performance of the group with various capture rates. The case is discussed where the capture rate is physically limited. Then two optimization problems are considered to maximize the number of terminals with access success. The first approach considers only a particular group, and a necessary condition is derived for the optimization of that group. Second, the performance of the whole system is improved, and the optimum solution is derived for the group assignment from the viewpoint of the capture rate. Finally, a discussion is made based on the numerical example, and it is shown that a higher throughput than in the past is realized in the multiple‐access broadcasting transmission with capture effect. Furthermore, it is shown that a higher performance is realized if all terminals are optimized utilizing the capture effect.
Multichannel CSMA/CD with hybrid load distribution/region distribution scheme
Authors: Ikebata Hiromi , Okada Hiromi
Published: July 2007

A multichannel CSMA/CD scheme has been proposed which aims at utilizing the merits of CSMA/CD, a typical access control scheme in bus‐type LAN, while overcoming the demerits. For this multichannel CSMA/CD scheme, the following three schemes have been proposed: node distribution, region distribution, and load distribution schemes. First, this paper compares and discusses the proposed schemes, especially the load and region distribution schemes. The effective range for each scheme is determined. Then a hybrid load distribution/region distribution scheme is proposed which aims at improving the performance and enlarging the range of applications by dynamically switching between the load distribution and the region distribution schemes, according to the load level of the network.

Discussions and qualitative performance evaluations are presented for the protocol, realizability and reliability of the scheme. It is shown that the load distribution/region distribution scheme in the multichannel CSMA/CD scheme exhibits a very satisfactory performance over the entire range of the load, with excellent reliability and expandability.
An adaptive orthogonal transform coding algorithm for images utilizing classification technique
Authors: Kato Yoichi , Mukawa Naoki , Okubo Sakae
Published: July 2007

An adaptive orthogonal transform coding algorithm utilizing the classification technique is presented. Coding efficiency for natural images can be improved by adjusting coding parameters in accordance with the local property of images. “Classification” is used to categorize small areas of an image into classes based on their characteristics. High coding efficiency results from changing coding parameters adaptively according to the classification index. Classification methods using ac energy, binary pattern and vector quantization index are compared, and the advantage of the classification method with the vector quantization technique is shown. Also, an orthogonal transform coding algorithm with an adaptive variable length coding method is proposed, and its structure and characteristics are described. A coding parameter normalization method to avoid mismatches between input images and coding parameters is also described. Coding experiments show excellent performance of this algorithm, for example, the number of bits for obtaining 40‐dB SNR of monochrome “GIRL” is 0.65 bits/pel, which is 20 percent smaller than conventional methods.
Introduction of interleaving in packet voice communications
Authors: Matsuo Naoki , Yuito Mitsuhiro , Tokunaga Yukio
Published: July 2007

Introduction of an interleaving method in packet voice communications, called packet interleaving, is proposed as a means to reduce speech quality deterioration caused by packet losses.

This interleaving method and methods of substituting for missing samples, are evaluated by subjective tests. The results show that the packet interleaving can reduce speech quality degradation significantly if the values of samples which are missing are replaced with the mean values of their adjacent samples.
Single‐mode fiber transmission using edge‐emitting led for broadband subscriber loops
Authors: Ohtuka Tomoyuki , Yamashita Haruo , Yamaguchi Kazuo , Naitou Hidetoshi , Kondou Ryuichi
Published: July 2007

The edge‐emitting LED, which is less expensive and more reliable than the laser diode, is studied for use in the broadband subscriber loop in combination with a single‐mode fiber. In comparison to the conventional surface‐emitting LED, the present device has a better efficiency in coupling with a single‐mode fiber and has a narrower emission spectrum. In this paper, a method of simple time domain calculation is proposed for the S/N ratio taking into account the wavelength dependence on the dispersion and loss of the fiber, the emission spectrum profile of the edge‐emitting LED, and the pulse response speed. The validity of the computation method and the high‐speed modulation characteristics of the edge‐emitting LED are confirmed through the optical transmission experiment of 600 Mbit/s and 20 km with a simple waveform compensation circuit. Further, the temperature characteristic of the edge‐emitting LED is studied since it is important in the application to a practical system. A method for temperature compensation is investigated. Finally, based on these studies, the maximum transmission distance is studied in which the temperature variations of the optical output, center emission wavelength and the spectral width as well as the device fluctuation are considered. It is shown that the present edge‐emitting LED is capable of an application to broadband ISDN and optical CATV subscriber loops.
Communication protocol for vehicle packet‐communication system using continuously allocated small zones
Authors: Sakai Sei‐Ichirou , Takaba Sadao
Published: July 2007

A new vehicle communication system is proposed to realize an excellent movement control of vehicles on highways. In this system, small communication zones of about 10 m long are allocated continuously along the road, and every vehicle in the zone transmits and receives digital data through the same signal communication channel using the TDM.

In the communication protocol for this system, data packets are divided into small blocks to reduce wasted data to vehicles leaving the zone. A new concept of using information concerning vehicle movement for channel accessing is introduced. When a vehicle leaves a zone, the next zone to which the vehicle arrives is found from this information. Then exclusive trigger pulses are generated in the next zone which effectively receives request signals from the vehicle. Performance of the protocol is analyzed by computer simulation. Reliable connections were achieved without losing high throughputs.
Traffic congestion control based on call density control
Authors: Tokunaga Hiroshi , Kawano Hiromichi
Published: July 2007

As a means to control traffic congestion in the communication system, it is most effective to control the traffic directed toward the congested switch, at the input of the network. From such a viewpoint, a method is employed in which a constant rate of traffic is controlled at the originating switch, according to the state of the switch congestion. However, the congestion recently observed frequently in ticket reservation and in other cases is difficult to be controlled completely by this method. From such a viewpoint, this paper proposes a control method based on the combination of the following two schemes: (1) the call number distribution, where the number of calls which can be processed in the congested switch is allocated individually to the originating switches; and (2) the call density control, where the number of connected calls (output call attempts) per unit time is controlled to within the specified value at the originating switch. The characteristics of the output call attempts at the originating switch are analyzed for the call density control. It is shown that the mean number of output call attempts is close to the ideal, but the variation coefficient of the output call attempts is somewhat large compared with the traditional call gap control. An extended call density control is proposed, where the number of output call attempts is adjusted in each time interval according to the state of connection, and it is shown that the mean number of output call attempts is close to the ideal. By employing the proposed scheme, the normal traffic can be secured, even if the control is started before the congestion arises, and the peak can be reduced when there is a sudden increase in originating calls.
Timing extraction and carrier estimation for PSK signal block demodulation system
Authors: Higashida Yasushi , Hagiwara Masafumi , Nakagawa Masao
Published: July 2007

In recent years, block demodulation systems have been proposed which store blocks of phase‐shift keying (PSK) signal and derive data by batch processing. In such systems the traditional method of realtime demodulation is not considered and block processing is applied after quasicoherent demodulation. Training signals required for traditional methods are not at all needed for this system. Therefore, the data transmission efficiency becomes very high. However, conventional block demodulators have a serious disadvantage–they cannot demodulate the signal without external timing information. This paper proposes a new timing extraction circuit not contained in a conventional block demodulator, which improves greatly practical applicability. Also, a method is proposed for accurate carrier estimation. According to computer simulation results, the permissible noise limit becomes 4 to 5 dB lower in comparison to the conventional method.
Radiation characteristics of cutoff‐waveguide applicators for hyperthermia
Authors: Sen Atsurou , Morita Nagayoshi , Kumagai Nobuaki
Published: July 2007

This paper is a detailed theoretical study of the basic radiation characteristics of a cutoff‐waveguide aperture antenna excited by a post when it is used as a hyperthermia applicator for heating tumors located deep inside the human body. The effect of the wave reflected from the body on the radiation characteristics is considered by an approximate evaluation of the reflected wave from a semi‐infinite lossy medium with electrical constants equivalent to those of a muscle placed in front of the antenna aperture. In the analysis, an equivalent problem is considered in which the aperture is closed by a conductor and unknown magnetic current sources are placed on both sides of this conductor. The integral equation derived from the continuity condition of the tangential magnetic field components at the aperture is solved by Galerkin's method. Extensive numerical data are presented for the relationship of the radiation power and the input impedance to the location of the lossy medium and the dimensions of various parts of the waveguide applicator. It is found that although the radiation power is generally larger if the distance between the lossy medium and the aperture is smaller, for a certain distance the radiation power can be smaller than the case without a lossy medium. It is also found that if the location of the excitation post is distanced somewhat from the aperture, the imaginary part of the input impedance is not affected by the location of the lossy medium.
Service choice behavior modeling of telecommunication users
Authors: Yamamoto Hisao , Inoue Akiya
Published: July 2007

With the open use of the communication activities and the diversified applications of services with various functions, a tendency to utilize the communication network in various ways and for various purposes is observed. There is an increasing need to realize network management based on the prediction technique for the communication activities of the user. This paper proposes a modeling for the choice behavior of communication services by applying the disaggregate behavioral model used in the field of urban engineering as a means of estimating commuter demand. The possibility of application to the communication network management is demonstrated. First, the decision‐making factors to be considered in the model are classified and then the general construction procedure for the model is presented. The qualitative and subjective decision‐making factors are represented numerically using the cardinal scaling based on paired comparisons, and are then used as factors of the model. Assuming a communication service providing 28 kinds of information data concerned with daily life activities, a model construction experiment was made. An examination is made based on actual survey data regarding user intention. It is shown that an excellent performance is obtained in the prediction of service choice, learning based on accumulated data, and the evaluation of service functions. Based on the realized performance, the application of the model to the management and operation of the communication network is discussed.
Application of the boundary‐element method to an infinitely long tunnel
Authors: Sakai Koichi , Koshiba Masanori
Published: July 2007

A hollow waveguide or a tunnel made of a lossy dielectric material such as concrete is presumed. A method of analyzing the wave propagation inside the tunnel by the boundary‐element method is formulated. When the boundary‐element method is applied to an infinitely long tunnel or a tunnel containing a bend or a branch, it is necessary to truncate the tunnel at a finite length. In addition, an analytical matching condition similar to the one for a lossless metal waveguide must be provided at the fictitious boundary. In this paper, a tunnel with a surface impedance approximation as the boundary condition on the lossy dielectric wall (so‐called impedance tunnel) is considered. First, an analytical solution is derived for a uniform impedance tunnel. Next, a method is proposed in which the analytical solution and the boundary‐element method are coupled on the forementioned hypothetical boundary. The algorithm is described in detail. For a straight tunnel, it is confirmed that the results agree well with those by the Fourier integral even when the imaginary part of the relative permittivity is small. Problems of finding electromagnetic fields inside a semi‐infinite tunnel excited by a line current source or an infinitely long tunnel with an aperture are studied. It is pointed out that the present method is extremely useful for a hollow waveguide consisting of a lossy dielectric medium such as concrete. The difference from the case of a lossless metal waveguide is investigated.
Throughput analysis of adaptive ARQ schemes
Authors: Ishibashi Yutaka , Iwabuchi Akira
Published: July 2007

Many ARQ error control schemes have been proposed in data transmission, including go‐back‐N and selective‐repeat schemes. In those schemes, most of the parameters affecting performance, such as the number of continuously transmitted data blocks and the data block length, are fixed. Consequently, the performance may be greatly degraded when there is a time‐variation in the bit‐error rate or when the bit‐error rate is difficult to estimate. This paper proposes a control scheme wherein the number of continuously transmitted data blocks and the data block length are adapted dynamically to the bit‐error rate. The throughput of the proposed scheme is analyzed for go‐back‐N and selective‐repeat schemes using the half‐duplex channel. The evaluations for the go‐back‐N and the selective‐repeat schemes are obtained as special cases of the result of analysis. The effects of various parameters on performance are discussed and the performances of various schemes are compared. The results show that the proposed scheme based on the adaptive control has a performance which is very close to the scheme with a fixed number of continuously transmitted data blocks and fixed data block length, where those parameters are set optimally in a static way.
A study of bit error model on digital subscriber transmission
Authors: Wataya Hideo
Published: July 2007

In digital transmission through a metallic subscriber line, burst bit errors are produced due to impulsive noise and other causes. It is important to investigate the actual properties of those bit errors. This paper presents the result of long‐term measurements using various kinds of cores concerning the bit error gap length in the time‐compression multiplex directional control transmission system. It is shown that the bit error rate can be characterized by three gap length ranges. A model is proposed which can represent accurately the features of those distribution patterns of gap length through a simple formulation. The model is compared with the actual characteristics, and the usefulness of the model is demonstrated. As an application of the model, several evaluation measures for the transmission quality (such as bit error rate and errored seconds) are discussed, and it is shown that a more detailed quality specification than in the past (the evaluation in a short‐term observation for 100 ms, for example) can be realized, based on the estimated distribution.
64 kbit/s video coding equipment using adaptive tree‐search vector quantization
Authors: Watanabe Hiroshi , Hoshino Ryohei , Kuroda Hideo , Hashimoto Hideo
Published: July 2007

This paper proposes a high‐efficiency coding algorithm realization of a 64 kbit/s video coding equipment. A prototype equipment constructed shows a high quality performance for video conferencing and videophones. For high efficiency coding for video conferencing a coding algorithm combined with motion‐compensated interframe prediction and the orthogonal transform coding or vector quantization is usually employed. It is known theoretically that the latter has an excellent characteristic which approaches the rate‐distortion bound. However, another coding system is desired which not only has a high coding efficiency, but a small‐scale hardware and easy control of information generation. This paper proposes an adaptive tree‐search vector quantization in which the size of a code book can be varied according to the local property of an image. The improvement of the coding efficiency due to this idea is demonstrated by a computer simulation compared with a conventional system with a fixed size code book. A 64 kbit/s video‐coding system having the resolution of 384 (horizontal) × 240 (vertical) pixels per frame was constructed. Using the coding system with the proposed algorithm, a temporal resolution of 5 to 7.5 frames/s was obtained, confirming the satisfactory results for practical applications such as video conferencing and videophones.
Performance of the multisampling digital tanlock loop and its extension
Authors: Hagiwara Masafumi , Nakagawa Masao
Published: July 2007

One kind of digital PLL (DPLL), i.e., nonuniform sampling DPLLs, can control the sampling intervals. As a result, they can be used for timing extraction circuits and carrier extraction circuits in PCM and PSK systems, etc. The present authors have already proposed a new nonuniform sampling DPLL, the multisampling digital tanlock loop (MSDTL), which can handle more than two samples in each time period of the input sinusoid. The MSDTL can satisfy the sampling theorem because of the multisampling scheme. Therefore, a system with the MSDTL can easily utilize higher digital signal processing technologies. However, the performances of the MSDTL have not been reported yet. This paper presents detailed analyses of the MSDTL and shows its superior performances. In addition, the range (phase detection characteristic) extended MSDTL (RE‐MSDTL) is proposed.
A coding control algorithm for motion picture coding accomplishing optimal assignment of coding distortion to time and space domains
Authors: Kato Yoichi , Mukawa Naoki , Okubo Sakae
Published: July 2007

In high‐efficient motion picture coding such as systems to compress moving image information below several 100 kbit/s, some visible spatial and temporal distortions are unavoidable. The spatial distortion is perceived by humans as a spatial degradation or noise on the image. On the other hand, the temporal distortion, which is caused by frame dropping, occurs as unnaturalness of motions in the processed image sequence. Here, spatial and temporal distortions are in a trade‐off relationship. Finding the visually best point from this trade‐off is a key feature of good codecs. This paper describes a newly developed coding control algorithm aimed at keeping spatial and temporal distortions in a good balance. In the algorithm, the trade‐off relationship is calculated first from generated information amount vs. the SNR characteristics of the current input frame. Next, an optimal distribution is determined from the viewpoint of human perception. Finally, a coding parameter set is chosen for realizing the distribution and reproduces visually good images. This paper shows the principal of the coding control algorithm and describes an application of the algorithm to an MC‐DCT coding system and simulation results.
Passive telemetry using radar reflectors with controllable reflectivity
Authors: Hasebe Nozomu , Hanabusa Mikio , Kaneita Akihiro , Takahashi Yoshihiro
Published: July 2007

A radar reflector with controllable reflectivity has been proposed by one of the present authors. This reflector is capable of electrically controlling its radar cross section. By using this reflector as a target, information including an identification code at a reflector site can be sent to a radar site by the modulation of reflected echoes. Thus, we can build up a passive telemetry system consisting of radar, the reflectors and a demodulator device.

Since the reflector is a passive device, it does not interfere with other communication systems. Furthermore, the system at the reflector site uses little power because it has no transmitter. Experiments on the ground and on the sea have been conducted successfully.

This paper presents a method of acquiring data in the case of a rotating radar antenna, transmission codes which eliminated the inverting effect of the reflection on the sea, and a type of demodulation process. The evaluated result of this system from outdoor experiments is also presented.

The reflector was put into practical use as a traffic monitoring system and tested over a long period. From the experimental results it was discovered that the demodulation method using automatic threshold selection based on the probability distribution was the most successful. Hence, from the foregoing, we are able to conclude that the system using the radar reflector with controllable reflectivity is useful in passive telemetry.
Characteristics of a planar inverted‐F antenna on a rectangular conducting body
Authors: Sato Kazuo , Matsumoto Kazuhiro , Fujimoto Kyohei , Hirasawa Kazuhiro
Published: July 2007

Characteristics of a planar inverted‐F antenna attached to a rectangular conducting body are analyzed. The rectangular conducting body is modeled by wire grids and the moment method is applied so that the impedance characteristics and the radiation patterns are obtained. They are compared with the measured data. The element values are found for the equivalent circuit using a parallel resonance circuit seen from the feedpoint impedance and the antenna Q is found. The relationship between the relative bandwidth and the variation of the equivalent circuit parameter vs. the dimensions of the rectangular conducting body is investigated. Variations of the current distributions on the body and the radiation pattern are studied.
Experimental studies and improvements on the accuracy of the indoor random field measurement method for obtaining the radiation efficiency of electrically small antennas
Authors: Maeda Tadahiko , Morooka Tasuku
Published: July 2007

The indoor random field measurement (RFM) method is useful for measuring the radiation efficiency of a small built‐in antenna operating in the vicinity of electric gear and the human body. In this paper we report on the first experimental check of the accuracy of the indoor RFM method. We introduce the DDD value as a figure of merit for the measurement site. A new method of using radiowave scatterers is also proposed to improve the accuracy of the measurement. We find that the new indoor RFM method is effective for measuring the radiation efficiency of a small antenna.
Analysis and design methods of planar array antennas with slotted waveguides taking into account mutual coupling
Authors: Konishi Yoshihiko , Mizutamari Hitoshi , Sato Shin‐Ichi , Mano Seiji , Katagi Takashi
Published: July 2007

This paper described analysis and design methods for planar array antennas with slotted waveguides consisting of shunt slots as antenna elements which are cut on the wider surface of a rectangular waveguide. A matrix was shown for the mutual coupling among shunt slots. Also, another matrix was used relating the input and output waves at the array feeder point and the input and output waves between the shunt slots and free space. Through these two matrices the input reflection characteristics and excitation distribution of the array considering the mutual coupling of the total array with the feeder system could easily be obtained. Utilizing the variation of the mutual coupling among the shunt slots when sizes and displacements of the shunt slots from the guide axis were varied to be small, a simple algorithm with fast convergence was presented. Through experimental measurements the validity and effectiveness of the present analysis and design methods were confirmed.
Image restoration for complementary subsampling system
Authors: Tanimoto Masayuki , Yamada Akio
Published: July 2007

When the sampling points of an image are divided into two complementary subsampling points, an image with low resolution is restored from one set of subsampling points, and the image with full resolution can be restored using both sets of subsampling points. In such a complementary subsampling system, either of the two restored images contains aliasing distortion. This paper discusses the restoration of subsampled values, in which the high‐frequency components are lost due to the prefiltering. A method is presented in which the subsampled value is restored by utilizing the other complementary subsampled values, which preserves the highfrequency components as the aliased components. The condition for the restoration by the proposed method is described. Based on the derived properties, a new complementary subsampling system is proposed. This new system can restore without distortion both the image with low resolution and the image with high resolution simultaneously. The usefulness of the method is verified by experiment. The method is useful in the realization of the HDTV system, which contains a high compatibility to the present TV system.
Required accuracy in manufacturing process of three‐wire transmission line used in inductive radio system for detecting linear motor vehicle position
Authors: Hatta Tohru , Kusakabe Takashi , Asai Takahiro
Published: July 2007

The three‐wire transmission lines consisting of square‐wave‐formed line conductors has a structure in which any two of the three line conductors iterate narrow and wide sections at a specified interval along the longitudinal direction. Among those sections, the narrow section has the following problem. If line conductors deviate even a little from their normal positions due to the inaccuracies in the manufacturing process, relatively large unbalances will be produced in the mutual impedances and admittances between them. This leads to the crosstalk between the positive and negative phase sequence components of the signal and consequently to the detection error in the position of the vehicle. We considered the case where the manufacturing inaccuracies distribute at random or uniformly along the longitudinal direction. A quantitative analysis is made for the problem arriving at a guide for the manufacturing accuracy of the transmission line, which is required to ensure the desired accuracy of position detection. It is desirable in the narrow section that the two conductors maintain a distance above a certain value. It is also desirable that the radius of the line conductor be as small as possible, as long as the transmission loss of the line is within the tolerable value. Compared with the transmission line consisting of helically wound conductors, which we have already reported, there will still be a more strict requirement on the manufacturing accuracy on the transmission line consisting of square‐wave‐formed conductors.
Design and characteristics of low‐loss polarization grid
Authors: Kondo Akira , Kagoshima Kenichi
Published: July 2007

Polarization diplexing is possible by means of a grid plate and hence a frequency reuse antenna can be realized. Usually, the characteristics of a grid plate can be evaluated by an analysis based on an equivalent circuit. However, for a practical grid with a support mechanism made of dielectric or honeycomb structures, the reflection level of the unwanted polarization at the time for transmission of the desired wave is larger than the value for the metal grid only and hence the results are different from those by the equivalent circuit analysis. In this paper, the characteristics of the grid with a dielectric support layer are analyzed by means of full‐wave analysis so that the relationship between the thickness of the dielectric support layer and the reflection level of the unwanted polarization is detected. Next, a method is proposed for suppression of this unwanted polarization in a grid with a dielectric support layer. The validity was confirmed by theoretical analysis and experiments. Further, the design method and the numerical results are presented for a low‐loss polarization diplexing grid used in a frequency reuse antenna. It is pointed out that there exists an optimum parameter that minimizes the insertion loss in the operating bandwidth.