bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarization and transmission characteristics of a symmetrically‐loaded single‐mode optical fiber and a proposed polarization‐maintaining fiber holder
Authors: Kusano Kiyonobu
Published: July 2007

It is shown that when an external force is impressed on a single‐mode optical fiber to produce an axially symmetrical internal stress there is no coupling between left‐and right‐circularly polarized waves propagating in the fiber. It is also shown that the external force only affects the propagation constant, especially the phase constant, and its effect is equal for each circularly polarized wave. Based on those results the external force is shown to have no effect on the polarization characteristics of the fiber. The reflection for each propagation, mode affected by the external force is discussed, and the effect appears to be negligible. Finally, as a polarization‐maintaining method it is proposed that optical fiber holders that create these stresses be used—such as chuck‐ or shrink‐fit‐types.
Application of plastic substrate for laser beam memory
Authors: Takeshima Mikio , Okada Takeshi
Published: July 2007

This paper reports a technique for making the plastic substrate for a light beam memory that exhibits excellent flatness, an annealing technique for improvement of surface deflection, as well as a projection technique for making good groove patterns. PMMA and PC materials were used for the substrate. These substrates were prepared by two methods: cell cast and injection molding. To improve the surface deflection and heat resistance of the substrate, we tested the press annealing and spin annealing techniques. It is observed that spin annealing is suitable because damage of the tracking groove can be avoided. As far as the thermal reliability and long‐term stability are concerned, PMMA and PC are good candidates for the light beam memory. Tracking grooves were formed on the substrate, using a stamper with the injection technique. Good groove patterns were obtained on both PMMA and PC substrates.
Phase compensation film for planar optical devices
Authors: Shirasaki Masataka , Daido Yoshimasa , Asama Kunihiko
Published: July 2007

Optical circuit elements, including isolators, circulators and switches are important components of optical communication systems. Operation voltage and magnetic field of these elements can be reduced by using thin planar type optical crystals for polarization converters. However, in a planar wave guide structure, it is necessary to match the phase velocities of TE and TM modes to prevent the degradation of polarization conversion efficiency. This paper proposes a method to compensate the phase differences by applying optical interference films on the device surface; the optical characteristics of these phase compensation films also are examined. The model assumed herein is a 45° Faraday rotator made with rare‐earth iron garnet (which is magneto‐optical crystal). The phase compensation film is assumed to be a three‐layered structure with silicon dioxide and hydro‐genated amorphous silicon. The wave guide characteristics and polarization conversion characteristics have been analyzed and compared with a single clad layer without phase compensation films. The results show that phase compensation film reduces both the phase difference and the Goos‐Hänschen shift, and effectively reduces cross talk in switches.
A method for kernel separation in the multidimensional discrete fourier transforms
Authors: Morikawa Yoshitaka , Kaneda Masahiro , Hamada Hiroshi
Published: July 2007

This paper presents a general kernel separation algorithm applicable to the multidimensional discrete Fourier transforms (DFT). We first extend the formulation of the 2‐dimensional DFT using the periodic lattice point generation vector system and the sampling lattice point generation vector system proposed by Morikawa et al. to the multidimensional DFT and then show that the kernel separation reduces to diagonalization of integer matrix which connects these two matrix systems. After proposing a diagonalization procedure, we apply it to the DFT of the 2‐ and 3‐dimensional signals sampled on the hexagonal and body‐centered cubic lattices. The procedure permits efficient sampling and increased computational efficiency.
Effects of satellite transponder nonlinearities on spread spectrum satellite communication systems
Authors: Katayama Masaaki , Morinaga Norihiko , Namekawa Toshihiko
Published: July 2007

Correlation analysis using the autocorrelation function is applied to assess the effects of satellite transponder non‐linearities on multiple access SS (spread‐spectrum) signals when SS techniques are applied to satellite communication systems. Both AM/PM conversion and AM/AM conversion nonlinearities are employed in our model (parameters k and L). The model can represent various kinds of nonlinearities by choosing the pair of parameters (k, L) and can discuss the effects of AM/AM and AM/PM conversions on SS signals synthetically and individually. The same analysis is then applied to SCPC (single channel per career) signals for comparison. It is shown that AM/PM conversion degrades the output DUR's of both SS and SCPC systems as severely as does AM/AM conversion. The difference between the characteristics of under linear and nonlinear systems is as large for SS signals as for SCPC signals. Direct sequence SS signals are assumed and the DU (Desire/Undesire) ratio at baseband signal demodulation is adopted as an evaluation criterion.
Determination of optimum structure in coated optical fibers and units
Authors: Ishihara Koushi , Mochizukis Satoshi , Nakatani Nobuo , Uchida Naoya , Fukutomis Hideo
Published: July 2007

The losses of optical fibers may increase during cabling or installation. Such a loss increase may be understood to be due to an exertion of unnecessary external forces on the optical fibers during the above processes because of improper fiber structure. This paper describes the result of the finite element analysis for the stresses applied in cross‐sectional direction upon the core fiber and the unit. It is expected that the degradation of transmission characteristics will be prevented if the stress less than an external force is applied to the fiber cores and unit. As for fiber cores, the 3‐layer cores having buffer layer are considered and then the optimum fiber diameter, buffer layer thickness, etc., are studied. In regards to the unit structure, the test is made for the unit in which a steel wire is located at the center, 6 or 10 core fibers are wound and a binder is applied. Using the above samples, the optimum binder wrapping thickness against the side‐wall pressure and the preferable relation between core fiber diameter and unit diameter are investigated. The core fibers and 6‐core unit are manufactured experimentally and the test is carried out to obtain the relation between the side‐wall pressure and transmission losses. The result shows excellent agreement with theoretical analysis. Thus, we use such a design method to minimize the losses of an optical cable.
A hardware neuron model as a component of the neural network
Authors: Koga Kazutoshi , Hoshimiya Nozomu , Matsuos Tadayuki
Published: July 2007

In the nervous system there are two kinds of information processing: intra‐cellular analog operation and digital transmission between cells. These properties are considered to be indispensable in the construction of a large‐scale parallel information processing system having reasonable redundancy and which incorporates a number of spreading spatial and temporal patterns. As a simplified model having these two processing capabilities we propose a hardware neuron model using a voltage‐controlled oscillator IC. The model characteristics are easily controlled and it can supply a number of models as components of the hardware neural network. The fundamental characteristics for neural operation between multichannel asynchronous inputs are investigated with the model. It is shown that the mean impulse frequencies of the asynchronous inputs are linearly added or subtracted at the model despite the non‐linear property characterized by threshold in the output pulse generation. The characteristics of a backward lateral inhibition connection are also investigated for input pulse sequences. It has an input excitation frequency threshold and shows variable gain or hysteresis characteristics, depending on whether the weighting coefficients of the inhibition inputs are large or small. The model can be connected directly to a microprocessor and can process spatial analog information without an A‐D converter. These characteristics suggest that the model can be used as functional elements in the pre‐processing network of an information processing system for spatial patterns.
Design for nonresonant type microstrip line slot array antenna
Authors: Nakaoka Kaijiro , Shimizu Tadashi , Itohs Kiyohiko
Published: July 2007

There are two versions of the microstrip line slot array antenna: resonant array and nonresonant array according to its termination. Because microstrip loss is much larger than waveguide loss, a design method for the waveguide array is not applicable to the microstrip array. This paper proposes a new design method that utilizes nonlinear optimization and reduces the total loss; it is compared with a conventional design method. Two 2‐array antennas with 64 elements were manufactured with new and old design methods. The antenna designed by a new method showed predicted properties.
A new variable directional coupler using n‐insb thin films
Authors: Tanaka Ikuo , Isai Masaaki , Ohshitas Masahide
Published: July 2007

A microwave directional coupler is reported whose coupling can be varied with externally applied magnetic field without any mechanically moving parts. Variable coupling is achieved by using evaporated n‐type InSb films. A simple, single‐hole coupler is discussed first with regard to its performance, e.g., coupling, variation in coupling, VSWR and insertion loss in mm‐wave region. These quantities are related to the properties of the thin film, in particular, to magnetoresistance of InSb. Second, an improved variable directional coupler using InSb‐Sn‐Ag films, and which has an insertion loss and VSWR less magnetic‐field‐dependent, is introduced and discussed. In the improved coupler, the coupling varies from 19.3 dB to 42.4 dB at 33.8 GHz as the magnetic field is varied from 0 to 10 kGs. The insertion loss and VSWR are 1.18 dB and 1.27, and the directivity is in excess of 19.8 dB. Over the frequency range of 33.8 ± 1.0 GHz, the 2‐hole coupler shows a directivity higher than 14.0 dB, insertion loss lower than 1.23 dB, and VSWR less than 1.33.
Liquid phase epitaxial growth of high resistivity gaas layers by impurity doping
Authors: Kojima Kiyoaki , Hasegawa Hideki
Published: July 2007

Using Fe and Cr, we fabricated high‐resistivity epitaxial GaAs layers. We performed theoretical and experimental studies on the conditions necessary for the growth of high‐resistivity GaAs layers and the electrical behavior of the dopants. Fe doping gives resistivities greater than 104ωcm with good surface homogeneity under moderate growth conditions. We performed theoretical calculations and experiments on the temperature dependence of the resistivity and detected traps using photocapacitance measurements and DLTS. Fe forms a deep acceptor level at 0.47 eV above the valence band in the LPE layers. Cr also gave high resistivities but conditions for growth were much more severe with reduced reproducibility. Cr‐doped layers had a complicated temperature dependence which could not be explained as being due to a single‐Cr deep‐acceptor level.
Analysis of time series signals of wave fields using state vectors
Authors: Aoki Yoshinao , Yamamoto Tsuyoshi , Onda Kunio
Published: July 2007

This paper proposes a method of analysis of time seriesignals of wave fields by state vectors with regard to complex variablez and discrete time variable. The scalar product of these state vectors, the condition of completeness and operators acting on states are defined and basic equations arqderived. The z‐transformation and the convolution theorem are discussed. The present method is applied to the signal analysis by digital filters wherein the signals in the spatial coordinate of wave fields are converted to the time series signals. Two digital filters are introduced to perform Fresnel transform to express the wave propagation in the Fresnel zone. In this analysis, the filter must have characteristics of propagator transform. Further, amethod of reconstructing images as filter outputs is discussed; the hologram signal is converted to the time s eries signals and input to the filter which performs the Fresnel transformation. The result of image reconstruction by this method is compared with the result obtained by the conventional numerical image reconstruction method.
Motion compensated prediction for inter‐frame coding systems
Authors: Ninomiya Yuichi , Ohtsuka Yoshimichi
Published: July 2007

An interframe coding system is most promising when a high coding rate is required. However, it is disadvantageous in that the coding rate for the moving picture is not very high. To eliminate this disadvantage, it is effective to compensate for motion displacement. To do this, we propose a method whereby an image is segmented into many blocks. Each block which contains many motion‐displaced pixels compared with that of the previous frame, is selected. A motion vector is considered as a shift vector contained in correlated blocks which is detected by calculating the correlation between the preceding frame and the current frame for each block. A simple application of this idea to interframe coding requires a vast amount of calculation, and the realization of the above real‐time operation device is difficult. This problem is solved by using a system which modifies sequentially the detected motion displacement in the preceding field, and an experimental device for a motion compensated prediction system is built to test its performance. As a result of an experiment on an actual broadcasted moving image, it has been shown that the amount of the active picture elements of the proposed method has been reduced to about 50 ‐ 60% of that of the simple frame‐to‐frame prediction method, and the average log prediction error has been decreased to about 50%.
A method of calculating transmission signal values for chrominance components in a color imaging system
Authors: Fujio Takashi
Published: July 2007

When the information of a color imaging system is efficiently stored or transmitted, it is desirable that the image information which is decomposed into three primaries is transformed for transmitting primaries and its signal is processed and transmitted so that it is compatible with the visual and channel properties. In color imaging systems (color TV's), R, G, B, primaries are transformed into a luminance signal and chrominance signal while allocating the bandwidth and the value of the transmission signal to them for broadcasting. In this paper, when the three primary signals to be transmitted consist of a luminance and two chrominance components, we propose a method to quantitatively deal with these transmission signal values, an experiment, and the results of observation. In addition, we describe the results of an examination of how to allocate signal values for multiplexing the primary signals based on the above observation. Also, we examine what property and performance the standard color TV signals possess for various transmission systems. The above discussion is effectively applicable to the selection of the transmission primaries or the form of the transmission system for new color imaging systems of the future.
Start‐up transient responses of a DC‐DC converter
Authors: Nabeshima Takashi , Harada Koosuke
Published: July 2007

Small‐size high‐efficiency DC‐DC converters have been used widely as power sources of various electronic devices. However, because of their large start‐up inrush current and high overshoot of the output voltage, the reliability of the power source and the device is low. In this paper, the generation mechanism of the large inrush current and high overshoot of the output voltage is investigated for the buck‐type DC‐DC converter. It is found that in the converter without feedback circuit, the maximum inrush current is proportional to the product of the switching transistor's ontime ratio and the input voltage. In the converter with the feedback circuit, three types of different operating modes appear depending on the magnitude of the feedback constant. The large inrush current and high overshoot of the output voltage can be suppressed sufficiently by adding a simple integrator to the pulsewidth control circuit.
Decoding of triple and quadruple error‐correcting BCH codes by direct solving of error‐locator polynomials
Authors: Okano Hirokazu
Published: July 2007

The error‐correcting codes have been used extensively to increase the reliability of digital systems in data communication. However, with increasing error‐correcting capability, the complexity of decoders also increases. At present, only one‐bit and two‐bit error‐correcting codes are used. This paper proposes a decoding algorithm for triple and quadruple error‐correcting BCH codes. In decoding the BCH codes, the error‐locator polynomials must be solved by Chien's algorithm. In his method, however, with increasing code length, the decoder becomes complicated and the efficiency deteriorates. In the method proposed in this paper, the fourth‐or lower‐order equations are reduced to the quadratic equation and, therefore, the efficiency is good. This method is also independent of the code length. Its function and efficiency are confirmed by simulation using microcomputer. The present decoding algorithm enables one to realize an efficient decoder with hardware construction using the ROM.
Design of uniform electric field exposure system for biological experiments
Authors: Kobayashi Tetsuo , Matsumoto Goro , Nishiyama Fumihiko , Nakamura Hiroshi
Published: July 2007

In recent years, an interaction between electromagnetic environment and the living body has attracted researchers' attention. The authors have studied the effect of low‐frequency (50, 60 Hz and dc) electric field on the living body and constructed the electric field exposure system. In the conventional exposure system, animals are exposed to electric field between parallel plate electrodes in an insulated cage. However, the electric field inside the cage has not been investigated in detail. In this paper, the electric field intensity and the field uniformity inside the cage are analyzed. Based on the analysis result, a new exposure system is designed. The electric field distribution inside the cage is analyzed by the finite‐difference method. The field uniformity is more than 84%. The measured value agrees with the calculated value. The new system is simple in structure, can readily be constructed and is reliable for a long time.
Shielded TM010dielectric rod resonator
Authors: Kobayashi Yoshio , Kojima Katsuto , Yoshida Shinichiro
Published: July 2007

The resonant characteristics of the shielded TM010dielectric rod resonator are analyzed and its design method is proposed. The resonant frequencies and the no‐load Q value are calculated and their dependence on the specific permittivity and dimension ratio is clarified. Then with a constant ratio of the frequencies of the TM010mode to higher modes, the optimum dimension for the maximum no‐load Q value is determined. The temperature characteristics of the resonator are improved by inserting the conductor to both ends of the rod. The effectiveness of the design method is confirmed by the experiment. The resonator advantages are such that higher modes do not appear in the frequency band over more than one octave, and the no‐load Q‐value is high.
A study on structural identifiability of compartmental systems
Authors: Okano Shigetoshi , Maeda Hajime , Kusuoka Hideo , Kodama Shinzo
Published: July 2007

This paper considers relationships between structural identifiability of compartmental systems and the interconnections of their compartments. First, structural identifiability is defined in such a way that the definition is practically significant and in addition, the interconnection structure of a system well is represented. Then an algebraic condition equivalent to this definition is derived. Based on this, necessary conditions are derived for classes of compartmental systems to be structurally identifiable in terms of interconnection graphs of compartments. A numerical procedure for examining the structural identifiability is given. The results of the application of this procedure to 3‐ and 4‐compartment systems show that the necessary conditions are also sufficient conditions. Finally, several conjectures based on the results of numerical computations are given.
Analysts of anisotropic single‐mode fibers
Authors: Kusano Kiyonobu , Nishida Shigeo
Published: July 2007

The surface wave propagation characteristics of several isotropic single‐mode fibers are analyzed by applying the mode‐coupling theorem to left‐handed and right‐handed circularly polarized waves. In the gyrotropic fiber or unidirectional fiber, both polarized waves become eigenmodes and Faraday rotation occurs at linearly polarized wave incidence due to the difference in propagation constants. The rotation angle in the fiber in which the core and clad have the same anisotropy is identical to the rotation angle of a plane wave propagating in infinite gyrotropic media. The 45° Faraday rotator may be constructed by these fibers with sufficiently practical length.
Polarization properties of optical waves in a twisted elliptical fiber
Authors: Kosano Kiyonobu , Nishida Shigeo
Published: July 2007

When an isotropic optical fiber is twisted, its permittivity becomes anisotropic. In case of a circular fiber, the polarization plane rotates because propagation constants of left‐handed and right‐handed circularly polarized waves are different. In case of an elliptic fiber, the left‐handed and right‐handed circularly polarized waves couple with each other and its polarization characteristics are complicated. The polarization characteristics of the fiber with small twist can be approximated to those of the elliptical fiber and approach those of the circular fiber as the twist angle increases. The effect of the cross‐sectional deformation on the polarization characteristics may be eliminated by applying a large twist on the fiber. The polarization characteristic curves have 90° periodicity with regard to the incident polarization angle. The circularly polarized wave is generated at some incident polarization angle when the ellipticity and twist angle are optimum. These findings coincide with the experimental results.
Amplication characteristics of injection‐locked oscillator having an opposite phase self‐injection circuit
Authors: Iida Yukio , Morita Masanobu
Published: July 2007

This paper deals with an injection‐looking amplifier with opposite phase self‐injection circuit to which a part of the microwave oscillation output is injected by reflection with proper time delay and opposite phase to the oscillator. The amplifier characteristics are compared with those of the non‐self‐injection case under the oscillator load coupling state which gives maximum amplifier output. First, the optimum delay time of the opposite phase self‐injection circuit for different input and self‐injection conditions is obtained together with the static and phase responses, from which necessary basic data for self‐injection circuit construction are obtained. Next, one of the self‐injection circuits is shown and the characteristics of the amplifier with self‐injection circuit are investigated. Finally, the amplifier is tested and the phase response as a principal characteristic is investigated experimentally. Results show that the amplifier has fast phase response when the comparison is made under maximum output condition.
An interface boundary decision technique in laplace‐poisson domain problems‐a finite element analysis of junction FET
Authors: Kagawa Yukio , Murai Tadakuni , Matsumoto Osamu
Published: July 2007

In treatment of problems of domains governed by either Laplace or Poisson type partial differential equations, such as in field‐effect semiconductor devices, an important problem in practice is the determination of the boundary between the two domains. This paper presents a method using the finite‐element approach to determine the Laplace‐Poisson domain boundary. This method gives the solutions to the shape determination problems with high‐order nonlinearity by adding a modification quantity in applying the sensitivity analysis for given initial boundary shape. Thus, it has the advantages of clear mathematical structure and convenience in applications. As a concrete application example, the two‐dimensional junction FET is taken. Problems involving determination of the depletion layer (Poisson domain) and the current path (Laplace domain) are investigated. Results show that the boundary determination method presented here yields such FET characteristics as the field distribution, substrate effect and the pinch‐off voltage and useful knowledge for design is obtained.
Electron injection parameters and memory characteristics of MNOS devices
Authors: Ohnishi Kazunori , Ushirokawa Akio , Befu Makio
Published: July 2007

The charge injection mechanism of MNOS memory devices is analyzed in terms of the effective electron occupation function fT(t) of N‐O interface traps, and the flat‐band voltage (VFB) shift is derived as a function of pulse voltage and pulsewidth. The N‐O interface trap density NT is determined from the charge injection parameters (vO, r, n). According to the measurement using an automatic VFB measurement device, NT is 1 ‐ 3.6 × 1016 m−2. The parameter vO relating to tunneling in the absence of the applied voltage is dependent on Nss; 3 × 10−9 s−1 for samples with large Nss and 1.4 × 10−12‐1 × 10−18 s−1 for samples with small Nss. The calculated results of the pulse voltage and pulsewidth characteristics using these values agree with the measured results. The present analysis method is applicable for samples with different permittivity, film thickness and fabricating conditions as long as the nitrided film current can be ignored.
A receiver system with a pitch synchronized interpolator
Authors: Murakami Hideo , Irie Kazunari
Published: July 2007

In mobile communications (e.g., vehicular telephony) instantaneous interruption is caused by rapid fading while passing through a downtown area where buildings are dense. The interference caused by this fading markedly deteriorates the quality of communication. To improve the quality of communication, the authors propose a method called pitch synchronized interpolation which interpolates the transient signal by employing the time intervals between speech signals. This paper deals with a receiver system which incorporates this pitch synchronized interpolator. In the pitch synchronized detection or interpolation process of this system, the received speech signal, after undergoing A/D conversion, is fed to a sequential delay memory. This delay memory speech signal is processed by a digital signal processor. Various methods and parameters used here are discussed (e.g., the pitch period detecting method, the frequency of execution of pitch period detection, coding methods, maximum interpolation time, the damping coefficient for damping the interpolation output level to zero when the interruption period exceeds the interpolation time and the design parameters for the speech specimen period). Further, the necessary condition for these parameters are clearly defined. Also, based on the studies of these parameters, a prototype model of pitch synchronized interpolator is designed and fabricated with a reduced pitch period detection cycle of 4 ms and the desired decrease in interruption noise is confirmed.
A method of successive problem decomposition based on an algebraic structure of a problem
Authors: Niizuma Seizaburo
Published: July 2007

The author has recently proposed a method which, given information concerning the relation between the difference of states and the means to be adopted, constructs the quotient problem based on that information and decomposes the given problem into a sequence of subproblems using the solution of the quotient problem. This paper proposes a successive problem decomposition method which, by repeating the decomposition procedures, decomposes the given problem into a sequence of subproblems that is the simplest in the sense that there exists only one difference between the initial state and the goal. A sufficient condition is presented for such a decomposition to be executed. Given a sequence of differences D, the decomposition procedure is represented by an AND/OR sub‐problem tree T(D) and a sufficient condition is sought for T(D) to contain a solvable tree. When T(D) contains a solvable tree, it is possible for the proposed successive problem decomposition to decompose the given problem into a sequence of simplest subproblems.
Trunk division methods in the channel routing style
Authors: Asano Tetsuo
Published: July 2007

In the layout design of building block LSI's wires are placed in the region between a pair of columns of cells. Usually, lines parallel to columns of cells (trunk) and lines perpendicular to them (branch) are placed in different layers and they are connected by throughholes. In the channel routing method we note first that the ordering of trunks is restricted if branches of different nets should not intersect each other. Then we represent this restriction with a digraph called a constraint graph. Using this graph we determine the order of placements of trunks. When there are directed circuits in a constraint graph we must destroy them by partitioning trunks.

In this paper we modify the definition of constraint graph so that transformations on a constraint graph due to a partition of trunks become easy. To be more specific, information on terminals also will be incorporated in a constraint graph thereby limiting the extent of a transformation due to a partition of trunks. In addition, the trunk division method proposed earlier is redefined considering multiple divisions; conditions for each partition method to be effective in removing conflicting constraints are examined.
Composition and analysis of a new waveguide resonator filter with dielectric loading
Authors: Fukasawa Atsushi
Published: July 2007

This paper proposes and analyzes a new waveguide resonator filter for comparatively low microwave frequency use. It describes a practical example for its application. The new waveguide structure consists of thin center conductors embedded in cylindrical dielectric rods in contact with conducting parallel plates. This structure can be viewed as a dielectric‐filled coaxial cable provided its external cylindrical conductor extends to a parallel plate. By using the relaxation method calculations are conducted under the assumption of pure TEM fields. The calculated impedance, line coupling, effective dielectric constant and circuit Q are found to be in good agreement with experiment.

In order to investigate the higher‐order mode of the filter using this guided structure, the lowest higher‐order is assumed to be the TM01 mode and the effect of the conducting plate is excluded; the wave‐numbers are calculated and compared with experiment. The Q of the 1/4‐wavelength resonator using this guide is higher than that of the dielectric‐filled coaxial line resonator and, without using the interdigital arrangement, couplings between resonators can nonetheless be realized. In the example of the 850‐MHz band filter, it is clear that this waveguide can be used to realize miniaturized, light‐weight, inexpensive and high‐performance filters.
Minimum feedback arc sets of directed star polygons
Authors: Ariyoshi Hiromu , Higashiyama Youichi
Published: July 2007

Graph theoretic algorithms often are evaluated by their behaviors on random graphs. This paper attempts to find graphs which can be used to evaluate heuristic algorithms for the minimum feedback are set problem. For these graphs the following properties are required: (i) ease in generating, (ii) their minimum feedback are sets are known. Here we consider directed star polygons (DSP). First, we show that a DSP can be represented by a set of integers (symbols) indicating the number of its vertices and its interconnection structure. Then we discuss transformations of symbols, equivalent symbols, connectivities and a method of obtaining an equivalent class of DSP. Also, we discuss the relationships between symbols of DSP and its feedback are sets. In the case of degree equal to 4, the problem of finding a minimum feedback are set and its density is equivalent to that of finding the maximum number of are disjoint cycles or a symbol the sum of whose elements is the smallest.
Two types of speech compression systems using inverse filter codebook
Authors: Matsuyama Yasuo
Published: July 2007

Two types of speech compression systems which use a set of precalculated inverse filters (the inverse filter codebook) are studied. The information theoretic ideas of universal coding and block quantization motivated the use of the inverse filter code‐book. The first system finds the indices of the best matching inverse filter, the gain and the pitch interval for each frame of the input speech signal. In this case, a system operating at 800 bit/s for speech sampled at 8 kHz is adopted as the basic system. The second system is a waveform encoder which uses the inverse filter code‐book and tree searching. The system uses a single tree search, which is an improved version of the parallel tree search presented by the author, and a system of 8,875 bit/s is adopted as the basic device. Application of the inverse filter codebook is effective in achieving rate reduction and/or decreasing the system complexity.

The first system falls into the class of vocoders and the second is a waveform encoder. The data rates of the two differ considerably, yet both types of systems are necessary. An example explaining this fact is also given in the text.
Scattering of a plane electromagnetic wave by a thick lossy dielectric slab
Authors: Aoki Kazuo , Uchida Kazunori
Published: July 2007

Scattering of a plane wave (E wave) by a thick lossy semiinfinite dielectric slab with conductivity σ is evaluated by Fourier transform. The formal solution of the scattered field is derived by the Wiener‐Hopf method. The result is applicable to the cases of lossless media (σ = 0) and perfect conductors (σ → ∞). The scattered far field is evaluated by the saddle point method. The integral along the branch‐cut in the formal solution is evaluated numerically and the effects of the medium loss, slab thickness, and the incident angle on the scattered far field are examined.
Soft error in MOS dynamic RAM
Authors: Yoshihara Tsutomu , Takano Satoshi , Nakano Takao
Published: July 2007

As the degree of integration increases and the power supply voltages decrease in MOS dynamic RAM's, soft errors become increasingly important and need to be studied from the points of view of circuit, process and device technology. In this paper, analytical and experimental studies are conducted on the soft errors of 64‐Kbit dynamic RAM's. First, the relation between the device parameters and the critical charge is examined. If the charge distribution collected in the silicon substrate is Gaussian, the soft error rate is expressed as a complementary error function of the critical charge and agrees well with the experimental results conducted by the use of 241 Am. To improve the soft error, we studied the use of Hi‐C cell structures for increased critical charges and reduced charge collection area by employing polysilicon bit lines and boosted word lines before operation of the sense amplifier. Compared with conventional structures, the critical charge is increased 1.8 times and the collection area reduced to less than half. As a result, the soft error is improved by 700 times and the chip itself is less susceptible to soft error.
Evaluation of pattern registration accuracy in X‐ray lithography
Authors: Okabe Masahiro , Furukawa Yasuo , Inagaki Takefumi
Published: July 2007

In the conventional X‐ray lithographic system using the proximity printing technique by a divergent X‐ray from a point source, it is difficult to analyze the mismatch of overlapping patterns. In this paper, a statistical technique for analyzing and evaluating the performance of a mask aligner and pattern configuration accuracy of masks is proposed. When this technique is applied to an X‐ray lithographic system, the accuracy of the aligner increases to about 0.1 ym (2α) and the distortion of the silicon‐polyimide complex mask becomes about 0.2 ym (2α).
Temperature dependence of SAW dispersive delay lines
Authors: Shimizu Yasutaka , Nakata Taku , Yamamoto Yasushi
Published: July 2007

The SAW dispersive delay line is used extensively for signal processing, such as pulse compressor and spread spectrum system. In the filter and delay line using the ordinary interdigital transducer, the temperature coefficients of the delay time, phase and frequency are identical and depend on the substrate material. In this paper, we discuss the SAW dispersive delay line whose temperature coefficients of the delay time, phase and frequency are dependent on the substrate material and the frequency‐dispersive characteristics. The temperature characteristics can be improved by optimizing the dispersion characteristics. The zero temperature coefficient can be realized even if the substrate temperature coefficient is impractical. The design of the dispersive delay line is proposed with consideration of the temperature characteristics.
Quality improvement of synthesized speech in noisy speech analysis‐synthesis processing
Authors: Nagabuchi Hiromi , Kobayashi Tsutomu
Published: July 2007

Speech analysis‐synthesis is an effective method for low bit‐rate speech coding. However, it has been pointed out that system performance degrades as noise is added to the input speech. In this paper, we describe a method of improving the quality of noise‐de‐graded synthesized speech by using noise reduction methods which are based on the previously proposed comb filtering in the frequency region for the case that the noisy speech signal is processed by the PARCOR analysis‐synthesis method.

Quality degradation of synthesized speech due to additive noise is caused mainly by an increase in spectral distortion. In the speech analysis method proposed in this paper, the basic frequency (pitch) of the speech is stably extracted from noisy speech and spectral distortion is eliminated by obtaining the spectral envelope parameter after reducing the noise from the input speech based on this pitch information. Furthermore, the proposed method prevents degradation of the quality of the synthesized speech by using the extracted pitch as the pitch parameter of the analysis‐synthesis system. As a result of auditory experiments, it is shown that the subjective speech quality and intelligibility of the synthesized speech are improved by the proposed method. In addition, we obtain some clues to the configuration of a speech analysis‐synthesis system which is resistant to additive noise.
Synthesis of circular polarization with nonresonant slots in the narrow wall of a rectangular waveguide
Authors: Seki Hajime , Goto Naohisa
Published: July 2007

For a planar array antenna consisting of stacked slotted waveguides a circular polarization created by a slot pair on the narrow wall is proposed. The pair configuration satisfying the circular polarization condition is theoretically determined. It is necessary to accurately obtain the mutual coupling between slots. A formulation for the coupling is given as a boundary value problem. We first derive simultaneous integral equations for the aperture electric field in each slot. Next, solving these equations numerically, we find the effect of mutual coupling quantitatively. In the formulation process, the wall thickness of the waveguide is considered, unlike other analyses, which neglect the thickness. It is found that the effect of finitely thick walls is not negligible. To confirm the validity of the pair arrangement determined by the present analysis, experiments are performed with WRJ 3 waveguides for the S band and an almost perfect circular polarization of axial ratio 0.98 (−0.2 dB) is obtained.
Propagation characteristics of the dominant mode in tunnels with elliptical cross section
Authors: Yamaguchi Yoshio , Abe Takeo , Shimizu Tomio
Published: July 2007

This paper seeks to obtain basic knowledge of the wave propagation characteristics for radio communication in tunnels or subways. The problem of a hollow cylinder surrounded by a lossy medium is modeled and the propagation characteristics of the dominant mode, which is most important in practice, are rigorously obtained. For a medium of elliptical cross section with high conductivity, the propagation characteristics can be calculated by a perturbation method, whereas for those media with low conductivity, such as concrete and rock, this method fails. Herein the governing characteristic equation for the propagation constant is derived and the constant is calculated numerically.

Since the elliptical cross section has two symmetric axes, there exist odd and even dominant modes. It is shown numerically that in the hollow elliptical cylinder in an actual tunnel, the two attenuation constants for the two modes decrease with frequency and that the odd mode attenuation is less than that of the even mode. The attenuation is also investigated with respect to the medium constants and is found to be dependent more on the dielectric constant than conductivity. Also, measurement of attenuation according to the modeled experiment is found to be in good agreement with the analytical results.
Analysis of a class of free electron laser using a periodic static magnetic field
Authors: Shiozawa Toshiyuki
Published: July 2007

With the aid of coupled mode theory, this paper clarifies quantitatively the oscillation mechanism of the free electron laser in the submillimeter and far infrared wave region which is composed of a relativistic electron beam and periodic static magnetic field. First, on the basis of Maxwell's equations, the relativistic equation of motion for the electron and the equation of continuity for electrons, the coupled mode equations are derived which couple the electromagnetic wave mode (positive‐energy wave) and electron plasma wave mode (negative‐energy wave) propagated along a relativistic electron beam. Also, the spatial growth rate for these wave modes is obtained from these equations. Next, the energy relations for the electromagnetic and electron plasma wave modes are formulated, together with the discussion on the mechanism for energy exchange between these two modes. Finally, this paper considers the saturation in the laser output produced by trapped electrons in the electron plasma wave, and the efficiency of energy transfer from the kinetic energy of the electron beam to the laser output.
The partial realization theory of finite size two‐dimensional arrays
Authors: Matsuo Tsuyoshi , Hasegawa Yasumichi , Okada Yoshikuni
Published: July 2007

The authors have already proposed the realization problem for (infinite) figures (arrays) as an application of realization theory for nonlinear systems, and the array realization theorem was obtained by commutative linear representation system. A discussion was also made of the relation between the infinite array and the finite‐dimensional commutative linear representation system. This paper discusses the partial realization problem for finite arrays. The notion of natural partial realization system is introduced for a finite array and the following properties are shown.

For any arbitrary given finite array, there exists a minimum‐dimensional commutative linear representation system that partially realizes it.

The necessary and sufficient condition for the natural partial realization system to exist for a finite array is derived in terms of the condition for the rank of the bounded Hankel matrix of the finite array.

The necessary and sufficient condition for the minimum‐dimensional partial realization system to be unique except for the isomorphism is that there exists a natural partial realization system for the finite array. The proposed theory for partial realization of a finite array will be applicable to the theory for the communication of pattern information.
Two new solutions in cylindrical coordinates of electromagnetic fields of axially traveling waves and some applications
Authors: Shimizu Tatsuaki
Published: July 2007

A new method of solving Maxwell's equations is introduced for electromagnetic waves propagating in the steady state along the z axis of a cylindrical coordinate system (r, θ, z) in free space. We solve the wave equation for the electric field E completely for two degrees of freedom and find two methods for obtaining the magnetic field by rotE. Considering completeness of the solution, the electromagnetic fields are classified and summarized in two tables. As an application example, we study complete guided modes of a clad optical fiber. It is found that the electric field preferred boundary conditions of a circular dielectric structure, complete guidance of singular (cutoff) modes with angular index m ≧ 3 and analytical expressions physicially accurate of linearly polarized remote‐cutoff HEIn modes.

In one of the two new methods, the wave equation for Ez is solved first. Next, from the Er equation, Eθ is eliminated in divE = 0 and variable coefficient linear partial differential equations for unknown Er with inhomogeneous term Ez are derived. After these equations are solved for Er in both homogeneous and inhomogeneous cases, Eθ derived from divE = 0 is evaluated by using the Eθ equation. In another method, we derive simultaneous angular equations from the Er and Eθ wave equations. After solving these, we evaluate Ez derived from divE = 0.
Notes on addition over a finite field using an addition table
Authors: Sugimura Tatsuo , Kasahara Masao , Namekawa Toshihiko
Published: July 2007

Arithmetic operations on a finite field are now often used in error control or digital signal processing and there is need for a more practical method for carrying out these operations. A detailed discussion is given of the arithmetic operations, with the elements of finite field represented as powers. In other words, the addition table which can be constructed is of the order of 1/(2 · m) of the Zech logarithmic table. A detailed discussion is given of its construction algorithm, and a practical arithmetic operation algorithm using the table is presented. The size of the addition table is estimated and a storage scheme is considered for the addition table over a finite field with index 2. It is also shown that the addition table is easily set up on a computer.