bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallel‐running of two ladder‐type microwave multiple‐device oscillators
Authors: Fukui Kiyoshi , Nogi Shigeji , Wang Ming
Published: July 2007

The steady‐state operation and the stability of the parallel operation of two multiple‐device oscillators are studied when the coupling is small. The oscillators are of the form made of device mounts arranged along the propagation direction in the waveguide cavity or, in general, the form with the equivalent circuit expressed in terms of an active ladder network. The phase reference planes of both oscillators are chosen at their final stages. The section between these stages is considered as the coupling circuit. Formulas for the system response (locking frequency, phase difference between the element oscillators and amplitude response) are derived for the degree and phase of coupling and degree of mutual detuning. As the number of stages increases in a multiple‐device oscillator with more than two stages, the phase reference planes effectively move toward the interior of the cavity. However, if the effective coupling phase is used, the response can be represented by the theoretical equation identical to the case of parallel running of single‐device oscillators. In the case of the multiple‐device oscillator in which the device mounts are placed near the side walls of the cavity, the external Q decreases with an increasing number of stages and the increase of the locking range is derived from a theory. In the experiment, two multiple‐device oscillators of this type with up to eight stages (16 devices) are used and the theoretical results are confirmed. The output combining efficiency is more than 98 percent.
Constraints of the output‐power‐minimization adaptive array for a broadbanded desired signal
Authors: Takao Kazuaki , Ishizaki Toshio
Published: July 2007

When a broadband desired signal is incident on an adaptive array under output‐power‐minimization with constraints, the sideband components of the desired signal away from the constraints are regarded as the unwanted signal and the frequency characteristics are degraded. The following three constraint methods for broadband desired signals are compared in terms of their output distortion and signal‐to‐interference‐plus‐noise ratio under various conditions. In the higher‐order derivative constraint method, good characteristics are exhibited even if little preliminary knowledge is available on the desired signal. However, too much of its degrees of freedom are spent. In the double‐frequency constraint and the conventional correlation constraint methods, the output distortion increases when the anticipated value of the bandwidth of the desired wave and that of the actually incident wave are different. On the other hand, in the improved correlation constraint method in which the amount of feedback is modified in software, good performance is observed regardless of the bandwidth of the incident wave, and hence is the most desirable choice.
64‐kb/s wideband speech coding algorithm based on bandsplitting and adaptive prediction
Authors: Suzuki Junji , Taka Masahiro
Published: July 2007

The wideband speech signal spectrum is mainly distributed within the low‐frequency band. Subband coding and adaptive predictive coding have been proposed as low‐bit rate speech coding algorithms to take advantage of this property. This paper theoretically clarifies the improvement in signal‐to‐quantization noise ratio when these two bit‐rate reduction techniques are used at the same time and quantitatively analyzes the speech signal spectrum distribution. It also proposes a wideband speech coding algorithm which encodes 7‐kHz‐band speech signals at 64 kb/s, the same encoding bit rate as that of the conventional companding PCM. Through computer simulation the subjective quality is evaluated and the effectiveness of the algorithm is shown.
Steady‐state analysis of nonlinear oscillatory circuits by iterative decomposition method
Authors: Yamamura Kiyotaka , Horiuchi Kazuo
Published: July 2007

Newton's method is well known for finding the fixed point of the Poincaré mapping for steady‐state analysis of nonlinear oscillatory circuits. However, in practice, quadratic convergence of this method is not ensured due to the discretization error of the numrical integration and the errors of the approximate solutions for nonlinear equations which are solved at each time‐step of the numerical integration. This paper proposes a new method for the steady‐state analysis of nonlinear nonautonomous and autonomous systems which takes account of the numerical integration error stated above. In this method, the system of equations which includes a Poincaré mapping is discretized and reexpressed is a system of finite difference equations to which an iterative decomposition method is applied. Although this approach is essentially equivalent to the conventional Newton method based on the Poincaré mapping, it has the advantages that the Jacobian matrix can always be computed exactly for an arbitrary time‐steplength and that the local quadratic convergence of the algorithm is guaranteed. Considering these advantages, this paper also proposes a strategy to improve the computational efficiency of the algorithm in which initially, a large time step is used to find a rough solution which is then used as the starting value in the subsequent Newton iteration. Numerical examples are given to verify the relevant theorems and to show the effectiveness of the proposed algorithm.
Secret sharing system using (k, L, n) threshold scheme
Authors: Yamamoto Hirosuke
Published: July 2007

In the (k, n) threshold scheme, the information X is partitioned and coded into subinformation. If any k subinformation is obtained among n subinformation, the original information X can be recovered completely. However, no information can be obtained at all concerning X from any (k – 1) subinformation. Thus, the (k, n) threshold scheme is suited to the distributed storage or transmission of information. On the other hand, each subinformation requires the same number of bits as the original information X, which is very inefficient from the viewpoint of the coding efficiency. This paper extends the (k, n) threshold scheme and proposes the (k, L, n) threshold scheme. In the proposed scheme, the original information can be recovered completely from any k subinformation, but no information concerning X is obtained at all from any (k – L) subinformation. From any (k – t) subinformation (1 ≤ t ≤ L – 1), the information obtained for X contains the ambiguity of (t/L) H(X). In (k, L, n) scheme, the bit‐length of each subinformation is 1/L of the information X, which is a coding with very high efficiency. This paper presents a construction method for (k, L, n) threshold scheme, together with the discussion of its characteristics.
Broadband power inversion adaptive array
Authors: Inagaki Oki
Published: July 2007

The power inversion adaptive array proposed by Compton differs from other adaptive arrays in that it does not require any information on the desired signal. However, there is a sudden reduction in the ratio of signal to interference and noise (SINR) at the output terminal when the relative bandwidth of the interference signal exceeds 5%. In this paper the elements are arranged in a circular arc and a formula is proposed for microprocessor determination of the element weight from the covariance between the element inputs. It is shown that the decrease in SINR is kept below 3 dB even when the relative bandwidth of the interference is as large as 50%. In Method 1 of the circular arc arrangement an element is placed at the center of the circle and in Type 2 no element is placed at the center. Wideband elimination of the interference can be achieved with the arrival angle orthogonal to the line connecting two arbitrary elements. The element arrangements are studied with a low level of redundancy for this ideal angle of arrival. It is shown that a system without redundancy can be realized with a 4‐element array of Method 2.
A method for overload handling in synchronized multiplex system
Authors: Takase Juhro
Published: July 2007

This paper presents theoretical relations between transmission characteristic and increase of effective binary access channels in existing synchronized digital multiplex communication systems such as FDM and TDM to absorb traffic burst when connected to digital channels whose capacity is larger than their traffic capacity. At BER = 103 in noise‐free transmission and without off‐set of the demodulator, a 10 percent increase of digital channels is obtained by using a discrete amplitude level of 4 (2‐bit alternating binary encoding) and 14 percent increase by the amplitude level of 8 (3‐bit alternating binary encoding). At BER = 10‐4 with transmission S/N of 30 dB and demodulator off‐set of ‐23 dB, the increase of channels is 5 percent both by the amplitude levels of 4 and 8. The case of amplitude level of 4 is most preferable considering the relation between BER and the increase of access channels.
Outer conductor shields and electromagnetic fields around delay–type inductive communication cables
Authors: Okamoto Kunihiko
Published: July 2007

Two kinds of delay‐type inductive communication cables in actual use for mobile communication are shown theoretically and experimentally. They are characterized by two different types of outer electromagnetic fields, that is, convergence type and induction type, according to the shield construction of the outer conductors. The convergence type aims at limiting the communication region by using the wavelength reduction rate in a cable; the induction type aims at generating a relatively strong outer electromagnetic field. Despite the similarity of their appearances, these two kinds of cables are shown to have entirely different usages, characteristics, and mechanisms of generating electromagnetic field. This paper studies the shield effect of the delay‐type line outer conductor, especially the phenomenon of outer electromagnetic field generated by earth return circuit as a result of the imperfect shield effect of outer conductor for longitudinal electric field. This field interferes with the main wave in the case of the convergence‐type cable, and is a dominant main wave in case of the induction‐type cable. These two kinds of cables have already been developed and are now in use.
Properties of the second‐order digital bandpass functions obtained by bilinear transformation
Authors: Matsumoto Naoki
Published: July 2007

This paper describes the properties of the second‐order digital bandpass filter functions which are obtained from the secondorder analog bandpass functions by the bilinear z‐transformation. Taking note of the magnitude and the argument of the poles of the bilinear‐transformed transfer function, we can express the center frequency, the bandwidth and the variable range of the center frequency of the bandpass filter as simple functions of these parameters. In particular, when the poles are complex conjugate, it can be shown that the bandwidth does not change with the argument of the poles if the magnitude of the poles is constant. It seems that in the past the quality factor Q of digital filters has not been investigated fully. In this paper we introduce two definitions of Q from the time and frequency domains, and show that they are numerically equivalent if the ratio of the product of the center frequency and sampling rate to Q is less than a certain value. Finally, we discuss the relation between the pole argument and the filter dynamic range when the second‐order digital bandpass function is realized in direct form.
A traffic forecasting method taking account of outliers
Authors: Saito Hiroshi , Abe Takeo
Published: July 2007

Traffic forecasting is used for circuit dimensioning and income prediction. Traffic forecasting in Japan has been carried out mainly by multiple regression models. However, recently, a traffic forecasting method using the Kalman filter for a state space model was proposed by David and Pack. When such a forecasting method is used, it is necessary to cope with outliers caused by various factors, such as social and/or economic factors, and observation errors. In this paper, because outliers correspond to the outliers of noises in the state space model, an algorithm for detecting and discriminating outliers by considering the noise distributions is developed. A new traffic forecasting method with a state space model including this algorithm is proposed. This method detects and discriminates changes in traffic patterns, and applies the necessary dispositions. The validity of this method is confirmed by applying it to field data.
Rounding error analysis of the triangular lattice and escalator algorithms
Authors: Iiguni Youji , Sakai Hideaki , Tokumaru Hidekatsu
Published: July 2007

This paper deals with the Triangular lattice (TL) and Escalator (ES) algorithms for recursive least squares filtering problems. First, systolic array implementations of these algorithms are compared. Next, analysis of fixed point errors for the normalized TL and ES algorithms are performed and the expressions for the steady state biases in the estimated coefficients are derived. Finally, the total effects of finite wordlength arithmetics on both algorithms are compared through a numerical example.
Methods of stabilization for linear time‐delay systems based on stability margin
Authors: Mori Takehiro
Published: July 2007

Several simple methods are proposed to stabilize a linear time‐delay system with a feedback of the internal variables at two instants: the present and the past by the delay‐time. The methods are derived by virtue of the stability criteria obtained earlier for a linear system with a time‐delay. These criteria imply intuitively that the systems are stable if the stability margin of their simplified systems is greater than the magnitude of the residuals. Some of the four obtained methods include the time‐delay, while others do not. The stabilizability condition can be represented by scalar inequalities which can easily be proven. Once a parameter is found satisfactory for the criterion, the feedback law for the stabilization can easily be formed by using a conventional pole‐assignment method. The results were compared with those obtained earlier based on the same idea. The proposed methods are demonstrated with examples.
Switched‐element spherical array antenna for wide scan angle
Authors: Hori Toshikazu , Terada Noriyoshi , Kagoshima Ken‐Ichi
Published: July 2007

This paper proposes simple switchedelement spherical array antennas with variable phase shifters whose number is the same as that of the simultaneously excited elements. By employing the phase shifters, the total number of array elements can be reduced as to half that of the conventional switched‐element array. This small number of elements makes this antenna smaller in size and lower in cost. To confirm the design concepts, this antenna has been applied to mobile stations for satellite communication systems. Experimental results show the high performance of this antenna, particularly its wide‐angle scanning capability.
Stochastic distributed optimization algorithm
Authors: Fukao Takeshi , Yue Zhao
Published: July 2007

Expect for special cases, the solution of the combinational optimization problem depends greatly on the heuristic approach. Recently, Kirkpatrick et al. proposed with success the “simulated annealing” algorithm based on the analogy to the statistical thermodynamics. The method has already been applied with success to the large‐scale combinational optimization problem, such as partitioning, allocation, and wiring in VLSI design. The algorithm based on the analogy to the physical system may not be considered as an analog approach in the sense that the discrete representation is used. It can provide the parallel and distributed representation of the events in a natural way. Although the present simulated annealing algorithm does not contain such a parallel and distributed representation, those ideas should naturally be introduced. This paper adopts a viewpoint which is more general than the physical model such as the Ising model, and discusses the stochastic algorithm and its distributed representation for the optimization from the viewpoint of the Markov field. Various schemes under such a parallelism, i.e., synchronization and distributed‐lumped analogy to the field are discussed. As an application, the result of distributed formulation and computation for the decomposition problem are presented.
Development of light beam CT system for measurement of ultrasonic wave fields
Authors: Akiyama Iwaki , Nakajima Masato , Waki Hisao , Yuta Shin'Ichi
Published: July 2007

When an ultrasonic wave is irradiated perpendicularly by a coherent light beam, the ultrasonic wave behaves as a phase diffraction grating, and the light is phase‐modulated. Since the degree of modulation of the light is proportional to the line integral value of the sound pressure in the light‐beam path, the sound field can be reconstructed by measuring it in various directions and by applying the CT method. This paper describes a development of the light beam CT system for measuring ultrasonic fields and the obtained results. A system to measure the projection data from various directions was developed, and sound fields produced by various transducers were reconstructed. The results were compared with the experimental data obtained by a hydrophone and the numerically calculated values. The degrading of the quantitativity of this method due to the fact that the ultrasonic wavefront is not really a plane (this is a crucial point in the method), was examined by using a computer simulation. The results show that the errors are negligible in the far‐field region of a plane‐type transducer or in the focal plane of a concave‐type transducer. However, the errors are significant in the rest of the region.
Low‐sidelobe multibeam antennas fed by cluster horns
Authors: Yamada Yoshihide , Kagoshima Kenichi , Kobayashi Takehiko
Published: July 2007

A multibeam antenna fed by cluster horns can reduce sidelobe level, and a design method for determining antenna parameters is described as well as its electrical properties. The horn size and the antenna aperture diameter are determined, and a relation between the horn excitation amplitude distribution and the sidelobe level is discussed. Degradation of sidelobe level is given as a result of errors in horn size, frequency, and excitation amplitude. The received mode analysis method is optimized when horns are displaced from the focal point of the antenna, and the excitation distribution is determined. Finally, results are described of the present method, which is applied to the domestic satellite‐borne multibeam antenna.
Performance evaluation for FCFS‐like group random access protocol on bus networks
Authors: Goto Kunio , Takahashi Yutaka , Hasegawa Toshiharu
Published: July 2007

Performance of bus‐type local area networks using CSMA/CD protocols, such as Ethernet, is known to deteriorate as the ratio of round‐trip propagation time to packet transmission time increases. In this paper, we propose a new FCFS‐like transmission protocol (FCFS‐GRA) in which each successfully transmitted packet includes the information of the number of packets having been successfully transmitted while being backlogged, and each busy terminal controls the timing of its transmission by the information.

A queueing model which represents the bus system using FCFS‐GRA is described, and by solving an embedded Markov chain of simplified system states, throughput and delay are obtained. In more generel cases, throughput and delay distribution are obtained numerically by simulation. The performance of FCFS‐GRA is compared with that of CSMA/CD and it is found that the FCFS‐GRA protocol shows good performance even in the case of a long bus over 10 km.
FSK‐ASK transfer characteristic of the double‐mode oscillator with third harmonic oscillation
Authors: Umeda Hiroyuki , Nakano Takahiko , Shiraga Yoshiaki
Published: July 2007

Numerous detailed studies have been made on the injection locking of the solid‐state microwave oscillator, but there have been few applications of the locked multimode oscillator to the communication system. The double‐mode oscillator with the third harmonic oscillation has the feature that it can easily be locked to the external signal and has two kinds of stable locked steady‐states. When an FSK signal is used as the external signal, the signal is converted into ASK signal, and the oscillator operates as an the FSK‐ASK converter. This paper discusses the fundamental operation of the FSK‐ASK converter with the following contents: (1) For the case where the frequency of the injected signal changes stepwise, the transient locking response of the oscillator is analyzed. It is shown that the upper bound for the FSK modulating frequency (modulation rate), for which the FSK‐ASK conversion can be realized, is determined by the rise‐time and the fall‐time and the fall‐time of the oscillator output; (2) the code‐error rate of the ON‐OFF amplitudes of ASK wave is calculated. It is shown that the signal can be detected with an error rate equal to or less than that of the FSK coherent detection; (3) The power spectrum desnsity and correlation time of ASK wave, as well as the noise suppression by the double‐mode oscillator are derived. Finally, an experimental example is shown for the typical basic characteristics, indicating the validity of the theory.
Optimal design problems of highly reliable systems and their solution methods by surrogate constraints algorithm
Authors: Hikita Mitsunori , Nakagawa Yuji , Nakashima Kyoichi , Yamato Kazuharu
Published: July 2007

This paper presents a solution method for the reliability optimization problem of systems which is formulated as a mixed‐integer nonlinear programming problem with multiple constraints. The system structure is series, series‐parallel, or complex. In the solution method, the optimal solution is obtained by solving the surrogate dual problem. Surrogate problems with only one constraint which appear in the optimization process are solved by a technique using dynamic programming. Some computational experiences are shown along with comparison with other approaches.
A synthesis of low‐sensitivity digital filters using t‐casade connection
Authors: Watanabe Eiji , Murakoshi Nobuo , Nishihara Akinori
Published: July 2007

When we realize a digital filter, a low‐sensitivity structure is desired to produce less degradation of characteristics in finite word length. In addition, for the fast operation, a structure that can be parallelized or pipelined is preferable. The low‐sensitivity digital filter, a wave digital filter proposed by Fettweis, is well known. Taking into consideration the fore‐mentioned, we propose synthesis of a digital filter that will permit pipeline processing and possess low‐sensitivity as in a wave digital filter. First we show that a circuit structure usingT‐cascade connection of basic sections allows pipeline processing; we then derive a method for synthesis of a digital filter having this form of structure from a given transfer function inz‐domain. Then in the proposed method we demonstrate synthesis of not only IIR filters but also FIR filters in a unified fashion. A realization of basic sections used in circuit synthesis is shown and the effectiveness of our synthesis method is verified by examples.
An adaptive digital filter using a system of orthogonal functions
Authors: Kobayashi Masaki , Itoh Yosio
Published: July 2007

The FIR adaptive digital filter has been applied widely to the echo canceller, automatic equalizer, and the noise canceller. For the viewpoint of the realizable transfer function, the FIR filter can be regarded as an adaptive digital filter which adjusts the zeros of the transfer function under the strong constraint that the poles of the transfer function can exist only at the origin of z‐plane. This paper proposes an adaptive digital filter, which can adjust independently all adaptive parameters specifying the zeros, with the poles of the transfer function being placed at arbitrary positions within the unit circle of z‐plane. First, a system of orthogonal functions is described which can realize the poles of the transfer function at arbitrary positions within the unit circle of z‐plane. The adaptive digital filter utilizing this system of orthogonal functions is discussed. Finally, the effectiveness in convergence is demonstrated by computer simulation.
Low‐sensitivity realization of linear‐phase FIR digital filters using cascade form
Authors: Honma Hitoshi , Mori Yukio , Sagawa Masahiko
Published: July 2007

It is important from the viewpoint of economy to realize the digital filter with as little hardware complexity as possible. On the other hand, the theory of low‐sensitivity FIR filter is not advanced, compared with that of the IIR filter. From the viewpoint of minimizing the coefficient word‐length, an investigation of this problem is required. With this as background, this paper aims at the reduction of the coefficient wordlength of the multiplier, and proposes the cascade construction of the FIR filter. First, using the coefficient sensitivity, an evaluation function is defined and used to evaluate the degradation of response due to the coefficient quantization. Then the relation between the locations of zeros and the value of the evaluation function is discussed. It is pointed out that the zeros with relatively remote locations reduce the response degradation. A systematic construction of the low‐sensitivity structure is described, considering the relation between the location of zeros and the evaluation function. Finally, to show its effectiveness, several examples are handled by the proposed method.
Optimum primary radiator tilt angle of a shaped offset dual reflector antenna
Authors: Karikomi Masahiro , Kagoshima Kenichi
Published: July 2007

When we shape reflector surfaces of an offset dual reflector antenna for a given desired aperture distribution, we create a phenomenon in which the direction of the reflected ray by the shaped surfaces and an assumed direction of radiation by geometric optics do not coincide. Hence, the characteristics of cross‐polarized waves are degraded. If we shape the surfaces at a tilt angle of the main dish with respect to the direction of the main radiation pattern, we found that the directional errors become extremely small between the direction of the actually reflected ray and that of the assumed direction of radiation by geometric optics for an optimum tilt angle. At this tilt angle, we can shape the reflector surfaces satisfying almost all of the conditions imposed by geometric optics. When we shape the surfaces at the optimum tilt angle, we obtain continuous surfaces which generate a desired axisymmetric aperture distribution along the radial direction. We can design an offset dual reflector antenna with low sidelobes and favorable characteristics for cross‐polarized waves.

Based on this theory, we built an experimental offset Gregorian‐type antenna with aperture diameter of about 50 λ. Measured results revealed excellent characteristics for cross‐polarized waves and those for sidelobes. Thus, we confirmed the validity of the theory of shaping reflector surfaces.
Improvement of picture quality and coding efficiency using discrete cosine transform
Authors: Izawa Yuuji , Takizawa Masaaki
Published: July 2007

In the applications of still picture coding such as image data base, the progressive coding is effective in reducing the retrieval time and the transmission cost. For the block coding based on the discrete‐cosine transform (DCT), a study has been made on the progressive and successive transmission from dc to higher‐order ac components. In this scheme, the major cause of the picture quality degradation is the block distortion produced at the initial stage.

This paper proposes two methods to reduce the block distortion where the lower‐order ac coefficients are determined from the dc coefficients transmitted at the first stage and applied the inverse‐DCT. The first method is to determine the lower‐order ac coefficients so that pixel values are smoothly connected at some points on the block boundary. The second method is based on the application of the interpolation filter utilizing the property of DCT. Furthermore, it is shown that by transmitting the difference between the DCT coefficients to be transmitted and the coefficients generated by the proposed method, the coding efficiency can be improved by 5 to 8 percent.
Comparison of traffic characteristics of gos control methods for a trunk group carrying multislot calls
Authors: Oda Toshikane , Fukuoka Hiroyuki , Watanabe Yu
Published: July 2007

In multislot circuit‐switched networks, it is necessary to apply a GOS control method to trunk groups to improve network utilization and to protect services against overload. As a GOS control method for multislot networks, this paper considers a trunk reservation method, split high‐usage group method, split final‐group method and virtual circuit method, which have also been studied for telephone networks. They are compared then by evaluating their blocking performance and peakedness of overflow and carried traffic involved. Based on numerical examples, it is shown that although the trunk reservation method is superior with respect to trunk utilization, there are some cases where the other methods are advantageous with respect to the ability to withstand overload and peakedness of traffic.
Composition of robust error control scheme using adaptive coding and its effect on data communication
Authors: Sato Takuro , Kawabe Manabu , Kato Toshio , Fukasawa Atsushi
Published: July 2007

This paper describes a robust error control scheme used for propagation paths especially involving a long time‐frame burst error as in mobile radio communication and its effect on actual data communication channels. This is an adaptive error control scheme based on forward error correction code and composed adaptively of plural coding modes.

Here, the BCH code is used as a block code, the diffused code is used as a convolutional code, and 3–5 majority logic is used as a majority voting code. The optimum coding mode is selected automatically according to the status of data transmission channels composed of a radio transmission span and telephone cable transmission lines. Cyclic code is used as an error detection method to evaluate channel status.

Under practical transmission circumstances, extremely high throughput efficiency of more than 70 percent is realized for 4800 bit/s data for transmission over the cellular network in Britain. This scheme has been presented at CCITT SG XVII as a standard scheme candidate.
Evaluation of token ring characteristics containing subnetworks of CSMA/CD‐LAN
Authors: Satoyoshi Tsutomu , Takahara Mikio
Published: July 2007

As the local area network (LAN) becomes popular, LAN systems which cover wider areas and which resolve traffic concentration in the system are going to be needed. This paper analyzes a system which consists of a token ring LAN as the main network to which some CSMA/CD‐LANs are connected with bridges. Such a system is called the “compound LAN system” in this paper. The optimum condition of this system due to the performance evaluation of the compound LAN system is shown by comparison with the throughput of each LAN. The results of analysis are confirmed by computer simulations. Moreover, the optimized scheme condition is confirmed by using the power function evaluation for the system.
Detection of multipath signal by cross‐channe‐interference measurement
Authors: Zhou Hong , Yoshida Susumu , Ikegami Fumio
Published: July 2007

In a multipath fading channel, the arrival time delay difference of multipath signals gives rise to an asymmetric transfer function of the channel, thereby causing cross‐channel‐interference (CCI) between in‐phase and quadrature channel components of a transmitted signal. This paper proposes the use of CCI for detecting multipath signals and roughly estimating multipath delay spread in a digital mobile communication environment.

First, the relation between CCI and multipath signal delay time is analyzed under the assumption of static two‐ to three‐ray multipath signals, taking BPSK and QPSK as examples.

Next, taking BPSK as an example, the existence of a close relation between CCI and delay time difference or between CCI and delay spread under quasi‐static and Rayleigh fading multipath signal conditions is shown by theoretical analysis and computer simulation. The correspondence between CCI and bit error rate (BER) performance also is studied by computer simulation, and good agreement is found.

Finally, the relations obtained were confirmed by laboratory measurements. Accordingly, multipath signal can be detected from CCI. Moreover, rough estimation of delay spread and variation characteristic of BER can be obtained from CCI. Thus, CCI can be used as an effective piece of information for evaluating transmission quality in digital mobile communication.
Relation between spacing and receiving efficiency of finite rectenna array
Authors: Otsuka Masataka , Omuro Norihiko , Kakizaki Kenichi , Saitoh Seiji , Kuroda Michiko , Horiuchi Kazuo , Soejima Teruzane
Published: July 2007

In the rectenna array used for rectification of the microwaves received on the ground in the solar power satellite system, it is required that the rectenna elements have a high dc power conversion efficiency and that the element spacing is optimized so that the arriving microwave power is received efficiently and the number of elements can be reduced. In this paper, a microwave rectifier is fabricated in an integrated form with a microstrip line on a teflon substrate. A circular microstrip patch antenna is used. A high rectification efficiency, 66.7 percent is obtained at a microwave input of 750 mW and 75.7 percent for input of 500 mW.

With this rectenna element, a 7 × 7 lattice array is formed and the variation of the receiving efficiency (the ratio of the power converted to dc to the input microwave power) is measured by varying the element spacing. On the other hand, the receiving efficiency is calculated for a given element spacing of this rectenna array from the circuit equation of the antenna system by deriving the mutual coupling between the elements. The relationship between the element spacing of a finite array and the receiving efficiency is obtained both experimentally and theoretically. This computation method is extended to the case with many elements so that the change of the receiving efficiency is investigated.
Wave impedance in the near field around the fundamental electromagnetic radiating elements
Authors: Yamaguchi Takashi , Okumura Yoshihisa , Amemiya Yoshifumi
Published: July 2007

Standards for electromagnetic protection taking into account human health have been established in a number of countries. Most of the present standards are expressed in terms of the intensities of electric and magnetic fields or the power density of the irradiating electromagnetic field. Usually, for conversion among these quantities, the relationship in the electromagnetic field at a distance far away (far field, plane wave) is used. However, near the electromagnetic source where the electromagnetic wave is the strongest, the relationship among the forementioned quantities varies depending on the location of the observation point or the type of the source. Therefore, there are recommendations to reconsider the standard values.

The purpose of this paper is to provide fundamental references for modeling the electromagnetic sources in various electromagnetic equipment to reconsider the protection standard of the near field, and to develop the electromagnetic shielding theory in the near field. In this paper, the distance characteristics and the spatial distribution of the electromagnetic wave impedance characterizing the nature of the electromagnetic wave are studied near the elementary radiating elements such as the electric dipole, magnetic dipole, half‐wave dipole antenna, small current loop and small helical antenna.
An output‐buffered ATM switch in the multichannel bandwidth allocation environment
Authors: de Zhong Wen , Onozato Yoshikuni
Published: July 2007

It is desirable in the high‐speed broadband communication network to satisfy the high‐level requirements for the communication quality for various communication services while efficiently utilizing the communication network resources. From such a viewpoint, Pattavina proposed a multichannel bandwidth allocation scheme and constructed an input‐buffered multichannel ATM switch based on the forementioned scheme. This paper follows his idea and discusses the construction of a multichannel ATM switch with buffers at both the input and the output, a well as with the buffer only at the output.

A periodic channel assignment algorithm is proposed, aiming at the balanced load allocation among the channels of the same output channel group. The proposed algorithm helps to share efficiently the resources (buffer and channel) of the same output channel group and to realize an economical use of the buffer. The performance evaluation is made for the case where the buffer is provided only on the output side. It is shown as a result that the cell loss probability and the buffer size required to satisfy the specified loss probability are greatly reduced with the increase of the group size. It is shown also that a better throughput‐delay performance is obtained than that of the input‐buffered multichannel ATM switch.
The helical loaded monopole antenna
Authors: Nakamura Kotaro , Nakamura Tetsuo
Published: July 2007

Medium‐wave radio broadcasting in Japan has been disturbed by jamming from neighboring countries. To deal with this problem, consideration should be given to the use of numerous low‐power broadcasting stations, each with a rather narrow service area. A helical loaded monopole antenna is recommended for use in such stations. A field experiment was conducted using a model one‐tenth the size of the actual antenna. The antenna impedance was almost identical to the theoretical and the apparent efficiency was 32 percent at an antenna height of 0.1 wavelength.
Characteristics of CMA adaptive array for selective fading compensation in digital land mobile radio communications
Authors: Ohgane Takeo
Published: July 2007

This paper considers CMA adaptive array for the high‐speed TDMA transmission system using GMSK, which is the most ordinary constant‐envelope modulation system in the digital mobile land communication. A computer simulation is executed for the case where a four‐element adaptive array is applied to cope with the selective fading. CMA is employed as the array control algorithm, which is suited to the compensation of the constant‐envelope modulated signal. Assuming a model with two arriving waves, the convergence and the BER performances of CMA are evaluated. It is shown that the BER is improved greatly up to the limit that no more error can be reduced, compared to the case without an adaptive array. It is seen also that the error rate is improved better when the delay difference between the two arriving waves is large. Thus, the proposed method is shown to be an effective technique to cope with selective fading.
An efficient coding for Bi‐level facsimile images with dynamic arithmetic coding
Authors: Ohsawa Hidefumi , Kato Shigeo , Yasuda Yasuhiko
Published: July 2007

In the conventional coding of the facsimile signal, codes such as modified Huffman (MH) and modified Reed (MMR) codes have been used, where the statistical properties of the image are assumed as known and the image is assumed as stationary. In practice, however, it is not always adequate to represent the probabilistic structure of the image data by a single model. It is desirable to employ a code whose coding parameters can be adjusted according to the variation of the statistical properties. The arithmetic code can realize independently the symbol coding and the probability estimation, and the dynamic modification of the coding parameters is easy.

From such a viewpoint, this paper proposes a new dynamic adaptive coding based on the arithmetic code. In the proposed method, the effective probability of the less probable symbol, which is the coding parameter of the arithmetic symbol, is selected from the values obtained by the approximation using a polynomial sum of the powers of 2. The algorithm of transition in each coding parameter is determined by considering both the static and the dynamic coding characteristics. In addition, a method is presented in which the decision about the stationarity is included, and the convergence from the initial value is improved by controlling the number of transition steps. As a result of simulation, it is seen that the proposed method can reduce the number of bits of the coded output by 27.2 percent on the average, compared to MMR coding.
An input buffer‐type ATM switching system using schedule comparison
Authors: Fan Ruixue , Akiyama Minoru , Tanaka Yoshiaki
Published: July 2007

An input buffer‐type, high‐capacity ATM switching system using schedule comparison is proposed for a high‐speed ATM switching system whose internal link speed is equal to trunk speed. Its throughput, delay, and loss characteristics are evaluated. The schedule of the input buffer to send cells and that of the output to receive cells are compared to decide the timing to send a cell so that there exists only one cell bound for the same output line.

The maximum throughput (outgoing trunk efficiency) is more than 0.9, and the mean delay is less than 10 cell times. Moreover, if a doubled transfer network is used, higher throughput can be achieved and the delay characteristic is almost equal to that with an ideal output buffer type.

A comparison of the proposed scheme with the output buffer‐type system under the same cell loss probability 10−5 reveals that the delay is almost the same and the required buffer size is one‐third. This characteristic holds even if the system size is extended to 4096 lines; hence, a super high‐capacity, high‐speed switching system can be configured with the proposed system.
Parallel processing scheme of the received data based on OSI protocols
Authors: Ishizaka Michihiro , Tsuchida Mitsuru , Ideguchi Tetsuo
Published: July 2007

This paper studies a parallel processing scheme for the OSI protocols in session layer and below to achieve high‐speed processing for the received data. First, technical issues are extended to exploit parallelism based on the layered structure of the OSI reference model. A basic parallel processing model including the distribution function for the received protocol data units (PDUs) and the synchronization mechanism is presented to make each microprocessor assigned to a layer execute the protocol processing for the received data in parallel.

Next, the configuration of the distribution function is discussed with a particular emphasis on reassembling of segmented PDUs. Then a distribution processing scheme is proposed and algorithm is selected from the consideration on the separation processing corresponding to the concatenation of PDUs. Here, the issues are examined relating to execution of the proposed algorithm, such as the prevention of the disorder of the data unit sequence induced by the reassembling process.

Finally, the characteristics of the parallel processing scheme are presented based on the proposed algorithm by comparing the communication performance with that of the ordinary sequential processing scheme by computer simulations.
Design of log‐periodic two‐stacked circular loop antenna
Authors: Korekado Toshikazu , Okuno Kiyoshi , Kurazono Sadao
Published: July 2007

By taking into consideration the high gain characteristics of a circular twin‐loop antenna and by distributing this antenna in a log‐periodic arrangement, an antenna with a wide bandwidth was proposed. Equivalent circuits for the loop part and its transmission line part were established to perform a numerical analysis. After examining its properties, data to design such an antenna were obtained. In particular, the reason why this antenna had a high gain and wide bandwidth through its current distribution was clarified.

Based on the design data of this paper, an antenna was constructed and its performance was measured. As a result, its half‐power bandwidth was about 80 deg for the E‐plane and 45 deg for the H‐plane with a sharp directivity. Over a wide bandwidth of about 360 MHz for the 3‐dB bandwidth, VSWR was less than about 2.2 and the directivity gain was more than about 10 dB. From these data, the validity of the present design method was confirmed. Thus, at present, the proposed antenna is a wideband antenna with a structure that has the highest gain.
Slotted aloha with PCT (power control during transmission) scheme using capture effect
Authors: Mutsuura Kouichi , Okada Hiromi , Tezuka Yoshikazu , Ohtsuki Kazuhiro
Published: July 2007

This paper proposes two new access protocols, wherein the power control during transmission (PCX) scheme attempts improvement of the throughput by capture effect; this scheme is applied to s‐ALOHA. Either method solves the problem of contradiction between the packet transmission time difference required in PCT scheme and the synchronized transmission as the basic requirement in PCT scheme and the synchronized transmission as the basic requirement in s‐ALOHA.

The first protocol is the s‐ALOHA with capture interval (s‐ALOHA/CI), which is concerned with the fixed‐length packet format. A capture interval is provided in the first part of the slot, wherein the transmission time is selected at random to provide the transmission time difference.

The second protocol is s‐ALOHA with tail synchronization (s‐ALOHA/TS), which is concerned with the variable‐length packet format. Utilizing the variable‐length property, the tail of the packet is synchronized to the tail of the slot and the packet is transmitted. Then the packet length difference produces the transmission time difference. It is verified through evaluation by analysis and simulation that the throughput performance of traditional s‐ALOHA is greatly improved in either protocol by the capture effect. Especially, in contrast to the deterioration of the effective throughput of the traditional s‐ALOHA due to the slot loss, it is verified that the performance of s‐ALOHA/TS is better than that of the fixed‐length packet scheme. These high‐performance protocols will serve as a powerful means of realizing the effective operation of VSAT network, etc., with the synchronization function.
A new pulse echo fault location method using waveform pattern matching for paired subscriber cables
Authors: Takeda Kazutoki , Kawashima Makoto , Koga Hiroaki , Hayashi Akira
Published: July 2007

A pulse echo wave tester can locate a fault in paired cables. However, when a paired cable comprises branched cables and different types of wire gage along a length, the pulse echo tester cannot detect faults because of complicated pulse echo waves.

This paper describes a new pulse echo tester which can locate a fault by the correspondence between measured and calculated pulse echo waves in case of such complicated cable structures.

First, we derive a calculation method of pulse echo waves in complicated cable structures. The fault is located by the condition that the difference between measured and calculated pulse echo waves becomes the minimum value. Next, location errors and the distance limitation of a fault location are described considering variations of cable parameters. It is clarified that the distance limitation of a fault location depends mainly on a pulse period. In the experiment, the fault is located in a 2‐km paired cable with a branched cable. As a result of this test, a fault location error is about 10 m.