bluuebunny/crossref_metadata_2025 huggingface dataset:
A method of coding for correlative transmission systems and its application to a continuous phase modulation system
Authors: Yamada Takahiro , Harashima Hiroshi , Miyakawa Hiroshi
Published: July 2007

To transmit data reliably over band‐limited channels, several correlation digital transmission techniques such as continuous phase FSK, and partial response signaling have been developed. The reliability of correlative transmission systems can further be enhanced by utilizing the error correcting codes. However, it is very important to select a coding scheme that is suitable for a given transmission system. This paper proposes an encoding scheme using block code to improve the performance of certain correlative transmission systems whose transmitters' states can be represented by a simple shift register. The Viterbi algorithm is used in the decoding. The detection of symbols and the soft decision for the decoding of the proposed scheme are combined into a single process. The performance of the proposed method is demonstrated through its application to a duobinary FSK system with modulation index h = 0.5. The results indicate that the proposed scheme outperforms the MSK scheme in both the power spectral distribution and the error rate.
The design and radiation characteristics of dielectric‐loaded H‐plane cosecant‐square‐beam horn antenna
Authors: Sha Kokusho , Sato Kiyomi , Suzuki Michiya , Adachi Saburo
Published: July 2007

An H‐plane cosecant‐square‐beam horn antenna with a non‐planar aperture is described. A dielectric material is inserted into the horn and the aperture surface design is based on geometrical optics. The E‐plane pattern is easily controlled by changing the E‐plane aperture length. Nine antennas with various H‐ and E‐plane lengths are examined with respect to variations of several characteristics as a function of aperture length. A compact wide‐band H‐plane cosecant‐square‐beam horn with good characteristics was realized with an aperture angle of 60 degrees and an H‐plane aperture length of about 10 wavelengths. By changing the E‐plane aperture length the E‐plane pattern can be varied without degrading the cosecant characteristics in the H‐plane. In the tests the E‐plane half‐width was varied from about 44o to 72o by appropriate setting of the parameters. Hence the antenna can easily be designed in conformity with the service area and should therefore be useful for SHF broadcast and multiplex communications base stations. Further, in conjunction with an E‐plane cosecant‐beam horn antenna, both horizontal and vertical polarizations can be used in contiguous service areas to provide efficient use of the frequency spectrum.
Pattern separability of an analog threshold neuron model
Authors: Member Hisashi Mizuno, Regular
Published: July 2007

In the learning of a neural network model, the excitatory and inhibitory synapses and the threshold are modified. There is little discussion, however, as to what function the neural model can realize in the pattern separation when the synapses or the threshold is modifiable. This paper considers the analog‐threshold neuron model, and discusses the pattern separation performance of the neuron when excitatory synapse, inhibitory synapse and threshold are modifiable. As a result of the discussion, it is shown that the pattern‐separating function of the neuron is maximized when the excitatory and inhibitory synapses as well as the threshold are modifiable. Then a learning system is proposed where the excitatory and inhibitory synapses as well as the threshold are simultaneously modifiable. A model with the proposed learning scheme is analyzed. Finally, it is shown by computer simulation that the proposed model operates as the analysis predicts.
An associative memory model based on adaptive feature‐detecting cells
Authors: Ikeda Nobuhiko , Torioka Toyoshi
Published: July 2007

This paper extends the function of Amari‐Takeuchi's model by adding an inhibitory cell with nonlinear characteristics to their self‐organizing model of the feature‐detecting cell. The generalized model is shown to separate even patterns in mutually inclusive relation, forming the feature‐detecting cells for each of the patterns. It is shown that when a learning parameter in the model is modified, it can perform classifications under various criteria based on the similarity. Then an associative model based on the feature‐detecting cell is proposed. The model is composed of three subsystems: the feature‐detecting cell formation subsystem to convert in a self‐organizing way the input pattern to the specified feature set; the learning subsystem, which associates in a multiple way two kinds of signals by cross‐correlation; and the decoding learning subsystem, which restores the original pattern from the coded signal. The behavior of the model was examined under a multiple‐associative environment. The model can handle the mutual and self recalls in a unified way, and the memorized patterns associated with the key pattern are recalled successively. The result indicates a role of the feature‐detecting cell in the associative memory. It is also suggested that the model can be a basis for accounting for the high‐level associative function through association of high‐level notions.
Reliability of v‐grove optical fiber mass splice. improvement of splice loss temperature characteristics
Authors: Nagasawa Shinji , Sankawa Izumi
Published: July 2007

With the development of multiple optical cable and its high‐density assembly technology, the need for establishment of a technology for the mass splice of optical fibers has become urgent. Although the V‐groove mass splice method has been investigated, it has a special problem in terms of reliability because of the splice loss change with temperature. This paper proposes to determine the mechanism of change of the splice loss in order to solve this problem. The investigation has been carried out with the V‐groove mass splice which has been considered to be an important component for the mass splice of a high‐density ribbon fiber, and by examining in detail the splice‐loss temperature characteristic experimentally. The main cause of the variation of the splice loss has been found to be the change of the distance between the ends of two fibers due to the temperature change of the dimensions of the V‐grooved substrate. Although there is a slight effect due to the change of dimensions of the adhesive, it is useful to: 1) employ a material for the V‐grooved substrate which can form the substrate precisely and at the same time has a low thermal‐pansion rate; 2) to minimize the irregularity of the cut‐end surface of the fibers; and 3) to use an adhesive having a low thermal expansion rate. It has been found that even with the maximum initial cut‐end distance of 40 μm, the variation of the splice loss can be reduced to less than 0.05 dB against a temperature change between ‐30°C and +60°C by choosing the thermal expansion rate of the substrate to less than 3.3 × 10‐6/°C. This has been confirmed by the experiments with a prototype splicer using a ceramic V‐grooved substrate and epoxy‐based adhesive.
A new approach to time series analyses of chaotic orbits in one‐dimensional maps
Authors: Murao Kenji , Kohda Tohru
Published: July 2007

The one‐dimensional map is the simplest system in which there can be produced a random orbit called chaos. In the theoretical discussion of chaos, it is important to examine statistics and statistical properties of the chaotic orbit. In general, however, it is difficult, except for some special one‐dimensional maps, to examine analytically the statistics. This paper proposes a new method of time‐series analysis in order to obtain approximately the various kinds of statistics of the chaotic orbit, such as invariant density, autocorrelation function, power spectrum, and K‐S entropy. The essential idea of the proposed method is to replace the integral operator by the finite‐dimensional constant matrix ∼P, which is the finite‐element approximation to the integral operator. The approximate expressions for the statistics are given explicitly by the eigenvalues and eigenvectors of ∼P. Applying the proposed method to several mixing one‐dimensional maps and determining their statistics, it is concluded that the proposed method is useful in the time‐series analysis of the chaos in the mixing one‐dimensional map.
Long‐term reliability assurance for arc‐fusion spliced fiber
Authors: Matsumoto Michito , Haibara Tadashi , Katsuyama Yutaka , Tokuda Masamitsu , Members Tadatoshi Tanifuji, Regular , Member Mitsuru Miyauchi, Regular
Published: July 2007

The technology of low‐loss splicing for optical fibers is well established, but the long‐term reliability assurance of splices has not been studied sufficiently. With the wide introduction of optical cables much effort is being devoted to improve the reliability of arc‐fusion splicing and to estimate its lifetime. In this paper, improvement of the reliability of arc‐fusion splices by proof test is studied theoretically as well as experimentally and optimum conditions to assure long‐term reliability are established. As a result: (1) proof test theory can be applied to the arc‐fusion splice and it is possible to estimate the lifetime by knowing the values of parameters n and m; (2) the effect of proof testing is greatly dependent on proof stress as compared to proof time; (3) it is shown that the 20‐year failure probability can be suppressed below 10‐5 by applying proof stress of 0.15 GPa to the spliced fiber before being reinforced by the heat‐shrinkable tube method.
Movement perception of the chromaticness channel
Authors: Member Haruo Sakata, Regular
Published: July 2007

Pattern movement perception was investigated for the chromaticness channel with a random pattern consisting of two different colors, and the following results have been obtained.

(1) With an isoluminant chrominance pattern, the movement was not perceived, but it was perceived when luminance difference was given to it.

(2) Luminance difference needed for perception of pattern movement was larger for the (r‐g) channel than the (y‐b) channel; there is a component in the (r‐g) channel which works inphase with r and counter‐phase with g.

(3) An intermittent movement chrominance pattern was masked by a continuous movement brightness pattern.

A model is proposed which can explain the mechanism of perception of pattern movement.
Parallel‐pathway at periphery by spatio‐temporal frequency response
Authors: Member Haruo Sakata, Regular
Published: July 2007

This paper presents the result of measurement of the spatio‐temporal frequency response at the periphery (9 deg. from the fovea) on the retina. It is concluded from the following two points that the transmission characteristics of the peripheral vision are composed of a parallel combination of the temporal‐dominant system and the spatio‐dominant system. (1) Drawing equisensitivity curves on the temporal‐spatial frequency plane, the locus at high frequency is not a circle with the low‐frequency point as the center, but is approximately a straight‐line connecting the two axes. (2) There is a dip in the sensitivity near spatial frequency 1.2 cpd and temporal frequency 4.5 Hz. This indicates that the transmission is a combination of two systems (i.e., a spatio‐dominant system and temporal‐dominant system) with a phase difference in the temporal frequency response.
Theoretical analysis of optical fiber mode exciters constructed with alternate concatenation of step‐index and graded‐index fibers
Authors: Koyamada Yahei , Horiguchi Tsuneo , Tokuda Masamitsu , Uchida Naoya
Published: July 2007

Mode exciters which consist of alternate concatenation of step‐index (S) and graded‐index (G) fibers are used widely for the measurement of transmission characteristics (optical loss and baseband frequency response) of multimode fibers. This paper presents a theoretical analysis for the mode exciters based on geometrical ray optics approximation. The mode power distribution controlling effect of the exciters, excited mode power distribution in the test fiber, and accuracy and reproducibility of optical loss measurements are clarified theoretically. It is shown that optical loss measurements under steady‐state distribution can be done by using either SGS or GSG mode exciters which consist of either small core or low NA fibers.
Induced voltages on buried coaxial cable by direct lightning strokes
Authors: Member Toshiharu Nagano, Regular
Published: July 2007

Large numbers of failures occur in coaxial line repeaters which are located in areas subject to high thunderstorm activity. J. Kemp [3] has calculated the voltage induced in coaxial cables which undergo direct lightning strokes, but it has been found that the failure rate that occurs in actual installations may, in some cases, be as great as 100 times the failure rate calculated by Kemp's method. Transient phenomena are generally calculated by means of transforms using Heaviside's operational method, but in the case of transmission lines, because of the need to employ approximations, very significant errors can be introduced. In particular, many of the buried cables installed in recent years have metallic sheaths which are insulated from the earth and it has become necessary to take this fact into account to arrive at accurate results.

Using line constants which take into account the skin effect, the induced voltage is here determined by numerical computation of the inverse Laplace transform and from this the failure rate is computed. The results are in almost perfect agreement with actual conditions. In addition, comparing the results obtained by this method with those obtained by the conventional method, we see that when the metallic sheath is insulated from earth the induced voltage becomes large because the lightning wave flowing into the metallic sheath is not attenuated very much and a high excitation voltage is therefore distributed over a long distance. Since this method permits quite complicated computations, it is expected that its application will facilitate development of suitable lightning protection methods.
An efficient algorithm for computing steady‐state response of nonlinear systems with time‐varying frequency inputs
Authors: Ushida Akio , Kume Tomohiro
Published: July 2007

In the steady‐state response in the nonlinear circuit, a number of frequency components is greatly affected by the amplitude and the frequency components contained in the forced input. In general, when there is only one frequency component as the input, only its harmonic components are produced. However, when it contains more than one frequency, the circuit will produce many frequency components by sum and difference as well as harmonics of the input frequencies. Especially, in the case of an FM input signal, in which the frequency is time‐varying, it is known that the input contains a large number of frequency components, depending on the modulation index. In the analysis of such a nonlinear system containing a large number of frequency components as the input, the solution method in the frequency domain such as harmonic balance, is not effective. This paper discusses the method of solution in the time domain for the nonlinear circuit with time‐varying frequency input. The waveform in the steady‐state response is expanded into Fourier series with periodically time‐varying coefficients, and the initial value is determined which produces the steady‐state response. The method is suited to the analysis of a nonlinear system with two frequency components as the input. In particular, it is seen that the method is especially effective in the analysis of steady‐state response in the nonlinear system with time‐varying frequency input.
A data flow control electronic exchange dataflex‐1
Authors: Yamashita Mikio , Members Minoru Akiyama, Regular
Published: July 2007

The controllers of the majority of existing stored‐program control switching systems employ architecture of Von Neumann. Shortcomings associated with such architecture include high OS overhead in multiprocessing, and difficulties in understanding the relationship between the control structure and the data flow of sequential programming. To overcome these problems this paper proposes a data flow architecture for controlling the switching system and describes the implementation of a prototype DATAFLEX‐1 (data flow exchange‐1). The basic operators of this prototype are implemented to approximate the task macro of the cell processing programs by using seven Z80A microprocessors to provide the necessary functions for intra‐office switching. The self‐documentary feature of the proposed programming technique, the clarity of data flow, the architectural modularity, the expandability of both the control functions and the scale of the proposed scheme are verified.
Power deposition in a block model of man exposed to the near field of a λ/2 dipole antenna
Authors: Uebayashi Shinji , Members Yoshifumi Amemiya, Regular
Published: July 2007

In a previous paper the authors calculated the power absorbed in the head of man holding a portable radio transmitter. It was found that the local absorbed power level exceeded the provisional safety level for ocular damage. For the calculations, however, the head of man was modeled as an isolated lossy sphere, and the effects of the human body and the ground on the absorbed power were not considered. This paper deals with numerical calculations of the absorbed powers in a realistic block model of a man taking into account the effects of the body and the ground. First, some fundamental characteristics are clarified for the calculations using a block model. Second, the absorbed powers in the head of a block model of a man standing on the ground are calculated for both cases when the model is in a plane‐wave field and in the near field of a dipole antenna. The numerical results are compared with those obtained in the previous paper employing the isolated sphere model. It is found from the results that the effects of the body and the ground are less in the near field of an antenna very close to the head than in the field of a plane wave, and that the local specific absorption rate in the eye exceeds the provisional safety level for ocular damage on several cases.
Some design methods for two‐dimensional digital filters with complex coefficients in consideration of linear phase characteristics
Authors: Ichikawa Yaoji , Takahashi Shin‐Ichi , Members Regular
Published: July 2007

In designing a two‐dimensional digital filter with special consideration of the phase characteristics, particularly the group delay characteristics, a very high‐order filter is generally required. This paper extends the coefficients of the filter from real to complex and describes a design technique for comparatively low‐order, two‐dimensional, circularly symmetric filters with consideration of phase characteristics. First, the method of transforming a two‐dimensional input signal into an analytic signal is described and then the design technique of two kinds of complex coefficient filters which use the properties of analytic signals is discussed. In the first kind variable transformation to a 1‐D real coefficient FIR filter is used to obtain a 2‐D FIR filter with complex coefficients. It has the merits of permitting independent setting of the sharpness of cutoff characteristics and circular symmetry. In the other kind of complex coefficient filter a recursive digital filter is obtained by using an all‐pole filter having constant group delay in the passband of the transfer function and having a 2‐D complex coefficient mirror image polynomial. It always has a constant group delay unrelated to the values of the coefficients and the overall group delay is also constant. Moreover, in this paper, design examples based on these methods are given and the validity of our methods is shown.
Scattering of electromagnetic fields by two strips located near a line source
Authors: Nishimoto Masahiko , Aoki Kazuo , Yoshidomi Kuniaki
Published: July 2007

The electromagnetic field scattered by two conducting strips located near a line source is calculated rigorously by using a cylindrical wave expansion. Numerical results are given for radiated far‐fields. As a simple approximate calculation of the present problem, one method similar to the Geometrical Theory of Diffraction (GTD) is also proposed. In this method the scattered field by the strips is approximated by the superposition of those scattered by the conducting half‐planes. It is found from the numerical comparison of the rigorous solution with the approximate one, that both results agree well and that the present approximate method is applicable to the case where the source and the edge are too close for the GTD. The condition of applicability is studied for the present method as applied to a strip grating with finite elements.
Numerical analysis of lock range of a phase‐locked loop with an interfering signal
Authors: Takahashi Yutaka , Kawabe Manabu , Chiba Shin‐Ichi
Published: July 2007

This paper presents a numerical analysis method for the lock range, with respect to the desired signal, of a PLL with two input signals, one being the desired signal and the other an interfering signal. We first consider the phase comparator using a multiplier and determine the model for analysis of the PLL with two unmodulated and noiseless input signals. Next, using harmonic analysis of the nonlinear differential equation derived from this model, we present a method of computing the periodic solution generated by the interfering signal within the PLL. In this numerical computation the detuning of the desired signal is determined as the dc component of the solution, and the stability limits of the periodic solution become the lock range. Finally, we determine the lock range as a function of the amplitude ratio of the desired and interfering signals. Computed examples are presented for appropriate parameters and the results are found to match the experimental data.
90‐degree differential phase shifters using meander‐line networks
Authors: Iwakura Hiroshi , Hamaguchi Masakazu , Sato Risaburo
Published: July 2007

A differential phase shifter uses two all‐pass networks with different electrical lengths and obtains a constant differential phase output from the difference in phase characteristics of the two networks. Since conventional phase shifters basically consist of two‐wire coupling lines and uniform lines, they are relatively large. In this paper, two types of differential phase shifters are proposed to obtain compact circuit geometry by using meander‐line networks. First, meander‐line all‐pass networks are used to construct the phase shifter. Although the differential phase output bandwidth becomes small compared with that of conventional phase shifters, the circuit geometry can be made compact. Next it is shown that the phase shifter consisting of transformers with transformation ratio 2:1 can match the input port and that it can be miniaturized while yielding a similar differential phase output. Within the design band the output ratio of the two networks becomes close to unity and hence the phase shifter can be used as a branching circuit with constant phase difference.
Software configuration of the data‐flow control exchange DATAFLEX‐1
Authors: Akiyama Minoru , Yamashita Mikio , Misu Toshiyuki
Published: July 2007

This paper describes the software configuration of data‐flow control exchange DATAFLEX‐1 which was proposed and fabricated to resolve the software bottleneck problem brought by “von Neumann” style single‐processor centralized control. This experimental machine uses a basic operation element whose size is about that of a task macro and incorporates data‐flow control computer architecture in its execution rule. First, call processing programs are implemented on this machine with seven Z80A microprocessors onboard to realize an intra‐office connection. Then, effective methods on fault detection/ recovery are examined and some principal parts of these processes have been implemented on it.
Automatic equalizer including a decoder of error‐correcting code and its development
Authors: Kohno Ryuji , Imai Hideki , Hatori Mitsutoshi
Published: July 2007

This paper proposes an automatic equalizer containing a decoder for an error‐correcting code. The purpose is the comprehensive compensation of code errors caused by intersymbol interference due to band‐limitation and code errors caused by channel variation and noise. These are major problems in realizing a highly reliable communication. The system is called AEDEC and can reduce the correction error in the tap coefficient innovation due to decision error and the error propagation in a decision‐feedback scheme. Consequently, it can achieve a stable convergence in the channel in an adverse condition where a traditional automatic equalizer cannot lead to a convergence. A control method is proposed for innovation of a tap coefficient and data feedback before the feedback decision based on the decoding reliability. This is estimated in the decoding process of the error‐correcting code leading to the optimum control, and minimizing the effects of undetection or miscorrection of the decoding errors. Furthermore, as an extension of AEDEC, an adaptive canceller is proposed which eliminates the intersymbol interference without emphasizing noise by utilizing AEDEC as a means of preliminary decision. As a result of computer simulation applying algebraic decoding and analog‐weight minimum decoding to recursive (7, 4) Hamming code, it is shown that the proposed schemes can lead to a stable convergence, thereby drastically improving the bit‐error rate.
Multiple access system using linearly independent vectors over a finite field
Authors: Ogiwara Haruo
Published: July 2007

For arbitrary l terminals among n terminals scattered over a space, we prepare a set of n vectors over a finite field among which arbitrary l vectors are linearly independent. Each vector is assigned to each terminal, and messages correspond to elements of a finite field in proper block units. A code‐division multiplex communication system is proposed in which arbitrary 1 terminals can transmit simultaneously to a center station through a common transmission line. Then the terminals synchronously add the products of the message and the vector to a common transmission line over a finite field. This system does not need common control nor collision detection/retransmission processing for channel assignment and has high transmission efficiency. First, this paper discusses the bound of transmission efficiency. Then it is shown that high transmission efficiency can be obtained if the block length k of the message is taken large. Then the relationship of (n, l, k) is clarified for the case where column vectors of parity check matrices of the BCH code and the Reed‐Solomon code are used as the above vectors, and for this case the above set of vectors is made up of products of distinct irreducible polynomials. A specific coding method is given for obtaining high transmission efficiency.
Magnetic circuits of lumped‐element circulator with thin‐type structure
Authors: Takeda Shigeru
Published: July 2007

Lumped‐element types are used most often for circulators and isolators for few tens MHz ∼ 1 GHz applications. In the conventional lumped‐element circulators, size and power handling capability are not very desirable due to two magnets. This paper proposes a new magnetic circuit that uses only one magnet and has a good thermal balance without degrading the electrical characteristics. In this circuit, a microwave garnet is sandwiched between two soft magnetic materials without air gaps. A permanent magnet is contacted on one side while a heat sink is attached on the other side. The structure is thin. First, the theoretical foundation of the present magnetic circuit is described. Then the theoretical and experimental results of the magnetic field distributions are compared. Various experimental results including that for the temperature characteristics as well as the practical test results, are presented for a lumped‐element circulator consisting of the present structure. It is confirmed that with a garnet of given dimensions, the lumped‐element circulator of half the height and more than three times the power handling capability can be realized.
A comparison of adaptive antennas on desired signal arrival angle errors
Authors: Ohmiya Manabu , Ogawa Yasutaka , Itoh Kiyohiko
Published: July 2007

In the Howells‐Applebaum adaptive antenna (H‐A) and the directionally constrained least mean‐squares adaptive antenna (CLMS) their abilities are degraded due to an angular error in the assumed direction of a desired signal. In this paper, several methods of preventing the angular error are compared. One of them is the decrease of the amplifier gain in H‐A, or in the increase of pseudo‐noise in CLMS so that the diagonal elements of the correlation matrix derived from input signal S are equivalently increased. Another is the use of multiple directional constraints in CLMS (multidirectional CLMS) where the number of constrained directions is increased. The effects of these methods are checked by numerical calculations. The evaluation criteria are set so that the angular error is 5 degrees, the upper limit of the dynamic range of the input SNR is. 20 dB, and the lower limit of the output SNR or SINR is 10 dB. Comparison is performed under the condition that the degrees of freedom for the antennas are kept constant. The multiple CLMS is the best way to satisfy the evaluation criteria in a wide range of arrival of interference if interference power is equal to or smaller than the desired signal power. On the other hand, the method for effectively increasing the diagonal elements of the correlation matrix is the best if interference power is larger than the desired signal power. However, when the countermeasure for the angular error suitable for signal environments is chosen from the above two, the choice depends on the evaluation criteria.
Progressive facsimile coding scheme for interactive image communications
Authors: Endoh Toshiaki , Yamazaki Yasuhiro
Published: July 2007

Recent developments have led to increased application of interactive image communications in teleconferencing and video disc systems. Many of these systems have facsimile transceivers as subsets. However, since conventional facsimile devices provide only hard copy, some soft copy display devices are desirable for interactive image communications. This paper proposes a progressive facsimile coding scheme for interactive image communications. This scheme permits rapid browsing of the images and image quality can be improved progressively if required. Simulation and experimental results indicate that the proposed scheme is more efficient than the standard coding scheme for G4 facsimile. Using the progressive coding scheme, the contents of most images can be recognized after 30 to 40% of the total transmission time. The applications of this efficient coding scheme in interactive image communications and the storage and retrieval of images are discussed.
Determination of installation cable size and the ratio of common fibers to total fibers in subscriber optical fiber cable network
Authors: Yamamoto Hideo , Yamamoto Yoshikazu , Matsuura Masaaki
Published: July 2007

To construct an efficient subscriber optical fiber cable network, a highly economical and versatile distribution method is needed. This paper clarifies a technique in which by determining the installation cable size of feeder system and the ratio of common fibers to total fibers, a balance between the service requirement and cost is obtained.

First, gamma distribution, practically used for metal cables, is applied to the demand forecast error distribution and the relation between the number of fibers and the ratio of common fibers to total fibers, which is required to obtain the desired equipment reliability, is clarified. Next, the relation between the cross‐connecting probability is determined and utilizing the ratio of common fibers, the cost function of optical cable system is derived. Here, both the cable installation cost and cross‐connection cost are considered. These two factors are combined and a design method of installation cable size and the ratio of common fibers to total fibers is clarified. This method ensures the desired equipment reliability and is the most economical one. Using this method and assuming all the various costs, it is clarified that for high cross‐connection cost, a cable having a large number of fibers should be installed and the cable network construction having comparatively low ratio of common fibers to total fibers is desirable. When the cross‐connection cost is less, the installation cable having a smaller number of fibers and a higher ratio of common fibers to total fibers is desirable. Moreover, with these results in mind, an economical subscriber optical fiber cable network construction is proposed.
Relations between the possibility of restoration of bandpass‐type band‐limited waves by interpolation and arrangement of sampling points
Authors: Kida Takuro , Kuroda Tohru
Published: July 2007

A study has been conducted on band‐limited waves f(t) of bandpass type, the Fourier spectrum F(ω) of which is identically zero outside an occupied band ωτ < ∥ω∥ < ωτ + ωb. Based on this study, we have obtained the following results: first, when an interpolation of a wave is attempted using a set of even‐numbered samples periodically repeated on both sides of the time axis at a mean distance between samples π/ωb (which in general are arranged ununiformly), the necessary and sufficient condition for said samples to restore a desired band‐limited wave having the same occupied bandwidth is demonstrated; second, a concrete formula of interpolation using a set of the prescribed type that satisfies the necessary and sufficient condition above, is introduced. Then a proof that demonstrates the impossibility that a formula which permits a set of samples of an odd number is periodically repeated at a mean interval of π/ωb to restore any desired band‐limited wave having the prescribed occupied bandwidth on the basis of interpolation unless ωτ or ωb satisfies a special condition. Finally, relations between the possibility of interpolation and combinations of ωτ and ωb for sample positions restricted to a certain extent if the mean interval between sampling points is shorter than π/ωb, is discussed.
Simulation of impedance‐scaled LCR filters with voltage followers
Authors: Takagi Shigetaka , Fujii Nobuo
Published: July 2007

LC simulation by active RC circuits generally requires an equal or a higher number of active elements than the order of the filter. This is one of the main difficulties that delays their practical applications as compared to cascade realizations. This paper proposes a method to simulate impedance‐scaled LCR filters using an equal or a lower number of voltage followers than the number of nodes in the original LCR filter. The influence of the imperfections of the voltage followers is also investigated. As simple examples, a 4th‐order bandpass filter and a 4th‐order lowpass filter are realized. Measurements and sensitivity analysis are performed on the 4th‐order bandpass filter and the results demonstrate the high performances of the method as compared to the other methods.
Interactive decision‐making for multiobjective nonlinear programming problems using fuzzy satisficing regions
Authors: Sakawa Masatoshi , Nango Yuji
Published: July 2007

In this paper, it is assumed that the ambiguous requirement and desired level of the decisionmaker for the objective functions in the multiobjective nonlinear programming problem can be quantified by eliciting the corresponding membership functions interactively. Then the region for the desired solution, called fuzzy satisficing region, is specified for the membership function by a membership value (required membership value) which is the minimum‐required value to be achieved, and another membership value (desired membership value), which should desirably be achieved. For such a fuzzy satisficing region of the decisionmaker, the penalty and the barrier functions are used to maximize the overachievement for the required membership value, and to minimize the underachievement for the desired membership value. In this way, the Pareto‐optimal solution for the specified fuzzy satisficing region is presented to the decisionmaker. The decisionmaker is either satisfied with the achieved Pareto‐optimal solution, or updates, on subjective basis, the required and the desired membership values. By reducing the fuzzy satisficing region in this way, it is possible eventually to derive the solution satisfactory to the decisionmaker from the set of Pareto‐optimal solutions for the given problem, through relatively simple interactive processes. An interactive computer program is constructed based on the proposed method, and an example for the course of interaction is shown for a numerical example.
A method of time‐domain approximation using the transfer function whose attenuation poles are restricted on the imaginary axis
Authors: Kida Takuro , Fukuda Yutaka
Published: July 2007

In the transfer function with zeros restricted on the imaginary axis of S‐plane the phase characteristic is essentially determined by that of the denominator polynomial. As long as the denominator polynomial is a Hurwitz polynomial, the tangent of its phase characteristic, i.e., the ratio of the imaginary part (odd part) to the real part (even part), is a reactance function. This paper proposes a waveform approximation method which approximates the phase tangent of the Fourier transform of the object waveform by a reactance function using an optimization technique. The Hurwitz polynomial, which is the sum of the numerator and denominator of the reactance function, is adopted as the denominator polynomial of the approximate transfer function. The numerator polynomial of the approximate transfer function is derived by adjusting the zeros on the imaginary axis by an optimization technique to approximate the amplitude of the Fourier transform of the object waveform. An evaluation measure in the proposed approximation method is presented, describing its problems and physical implications. It is shown that the proposed method can provide a satisfactory approximation for symmetrical waveforms. For asymmetrical waveforms it is shown that the approximation can be improved by adding a delay time. An appropriate weighting function is proposed for the evaluation measure. Lastly, the proposed method is compared with other methods of approximation.
A practical design of circularly polarized printed array antenna composed of strip dipoles and slots
Authors: Ito Koichi , Kitajima Hiroshi
Published: July 2007

In earlier papers, we proposed a circularly polarized printed array antenna composed of strips and slots (CP‐PASS). We showed that it possessed good properties such as a good axial ratio, a relatively high gain, and had sufficient frequency bandwidths. The purpose of this paper is to obtain a practical design method for CP‐PASS in order to realize a desired radiation pattern or to increase further its antenna gain. First, an equivalent circuit model of a basic element set of CP‐PASS is represented taking into account interelement couplings and a feed line loss. On the basis of the equivalent circuit model, design conditions of circular polarization and input impedance matching are formulated for a normal use of CP‐PASS. Second, satisfying the above conditions, a procedure for determination of an arrangement, dimensions and input impedance of the elements is described to realize desired antenna properties. Numerical examples of CP‐PASS with uniform aperture distributions are shown to clarify its fundamental characteristics. Third, a practical method for determination of the element lengths and coupling gaps is described on the basis of the basic radiating‐element characteristics obtained before. Finally, to demonstrate the validity of the design method presented here, a Chebyshevarray CP‐PASS consisting of four element sets is designed and tested as an example.
Picture coding by an adaptive multistage vector quantization
Authors: Uda Toyokazu , Saito Tsuneo
Published: July 2007

An adaptive multistage vector quantizing system is proposed for highly efficient picture coding method and its coding performances are investigated. This system contains a multistage vector quantizer which means that comparatively large picture blocks are quantized first, then the remaining quantization error is quantized in smaller blocks, gradually refining the resolution at subsequent stages. That is, a rough picture is coded first and finer structures are coded later. Computer simulation studies on several picture samples demonstrate the excellent processing efficiency of the proposed method in comparison with conventional vector quantizers.
Methods for reducing the fresnel reflection in an optical‐fiber connector with index matching material
Authors: Sankawa Izumi , Satake Toshiaki , Kashima Norio , Nagasawa Shinji
Published: July 2007

If there is a discontinuity of the refractive index in optical fibers connected with an optical connector, the light is reflected from this part to the light source, creating a problem in its light transmission characteristic. The main causes of the discontinuity are: (1) the gap between the endfaces of the optical fibers; and (2) the change of the refractive index at the end‐face of the fibers due to their polishing. Solutions to these problems are investigated in this paper, using silica‐based graded index multimode optical fibers. For (l), a refractive‐index matching material is employed, and the method for selecting the central value of the refractive index and the temperature coefficient from the reflected light in the visual‐light wavelength region is investigated. It has been confirmed that the refractive‐index matching material made of silicone resin and chosen by this method can obtain the required reflection loss greater than 40 dB, in each of the transmission wavelengths of 0.85 pm and 1.3 μm, and in the temperature range of −30°C to +60°C. For (2), the relationship between the polishing conditions and the reflected light power was investigated. It has been found that the refractive index of the endface of an optical fiber changes slightly when polished. The conditions of polishing for suppressing this change have been determined, and the property of the polished endface has been clarified.
A study on hybrid switch architecture using hierarchical memory system
Authors: Ishikawa Hiroshi , Kosuge Yasuharu , Miyaho Noriharu
Published: July 2007

On the premise that flexibility in communication is a primary objective for future digital networks providing various services, it is highly desirable to integrate circuit switching (CS) and packet switching (PS) functions into a single switching node. This paper proposes a hybrid switching system where PS and CS switching functions are integrated by making use of a hierarchical memory system in which the CS and PS switching buffers and program buffers reside in the same memory area, and the high‐speed memory in the hierarchy can be accessed both by transmission lines and processors. The design concept which adopts a new architecture necessary to meet the above requirement and the evaluation of its call processing capacity using traffic simulation and theoretical analysis are described.
Comparison of error rate computations on optical communication systems
Authors: Ohta Shinji , Takahara Mikio
Published: July 2007

Error rate is an important factor in evaluation of data transmission over an optical fiber communication system. Accurate amplitude distribution of system noise must be used in the calculation of error rate. Noise in optical fiber systems consists of shot noise, signal dependent multiplicative noise created by avalanche photo diode (APD), and thermal noise. It is quite difficult to obtain an accurate amplitude distribution of the system noise. Therefore, the error rate is usually derived by approximation.

This paper studies the error rate of optical fiber communication system using an integrator‐and‐dump (ID) type receiver. The error rates are computed using four different methods: the exact method based on the exact equation introduced by McIntyre, and three other approximation methods [1]. The results are compared and the adequacies of these methods are discussed.
Linear‐combined multichannel adaptive digital filters
Authors: Fujii Tetsurou , Shimada Shouji
Published: July 2007

The fundamental structure of linear‐combined multichannel adaptive digital filters which can process a multiple‐input single‐output time series, and their tapcoefficient correction algorithms with fast convergence are described. These are fundamental circuits required for multichannel echo‐cancellers, and echo‐cancellers with noise‐cancelling facilities. The structure of linear‐combined multichannel adaptive digital filters using the learning identification (LI) was introduced, and their characteristics were analyzed. Adaptive algorithms using the per‐channel normalization of power were proposed to improve the convergence speed. With a minor increase in the amount of computations, this method is a significant improvement of the convergence speed which, inherently, is degraded by the differences of average powers among channels in a linear‐combined multichannel adaptive filter. For further improvement in the convergence speed, another tap‐coefficient correction equation (the projection method) also was introduced. In the tap‐coefficient equation using the projection algorithms, the convergence speed can also be improved significantly by applying the per‐channel power normalization.
A method of high‐precision frequency detection with FFT
Authors: Tabei Makoto , Ueda Mistuhiro
Published: July 2007

Except for the nonlinear complex method such as MEM, there has not been known a method to determine the frequency with a high accuracy from the short wave train. Generally, it is considered that the frequency resolution in FFT is of the order of the step in the frequency. This paper attempts to derive a correction formula for FFT results by which the frequency, amplitude and phase of the arbitrary input signal with discrete frequencies can be calculated easily and with a high accuracy. The effect of the noise on the accuracy is discussed in the practical measurement condition, and it is shown by theory and numerical experiment for the case of white noise that the accuracy is linearly dependent on the noise ratio.
Estimation formula of vhf/uhf band field strength for mobile communications in suburban area
Authors: Morita Kazuo , Kojima Osamu , Nakano Toshio , Nonmembers Toshimi Haida,
Published: July 2007

In designing a mobile communication system in suburban areas, it is necessary to estimate electric field strengths in open and suburban areas. We measured field strengths in the 150/900‐MHz band in open desert areas and in the 900‐MHz band in suburban areas in the Middle East region, and open and suburban areas in Kumamoto and Okayama prefectures in the 280‐MHz band.

Using these results, this paper discusses the relationship between the median values of the field strengths and distances and their frequency characteristics. As a result, it was found that the average values of measured field strengths at various sites were smaller than the theoretical values of a flat earth model. The field strengths decreased with the squares of distance. This trend agreed generally with the similar relation for the flat earth model.

An empirical equation was derived for the correction factor of the electric field strength which is to be multiplied by the theoretical equation of the flat earth model. Quasi‐theoretical and quasi‐experimental equations were obtained for the estimation of the median values of the field strength of long intervals in the VHF/UHF band for flat open areas and suburban zones. With these equations we can estimate the median values of the field strengths of long intervals in open areas (desert, grassy lands and vegetated regions) and suburban areas with scattered buildings and trees, using frequency, the antenna height of the transmitter and distance as parameters.