bluuebunny/crossref_metadata_2025 huggingface dataset:
Unified analysis of sound field involving the driving system in time domain
Authors: Takagi Akira , Yoshida Norinobu , Fukai Ichiro
Published: July 2007

Recently, it has become important, with the development of electroacoustic devices, to provide a systematic analysis of the electrical circuit, the electromechanical transducer part and sound field, taking their interactions into consideration. When the boundary condition of the sound field or the shape of the scattering object is complicated, numerical computation is more effective, especially when the analysis of time variation is required. This paper presents a numerical method of computation for the electrical circuit, transducer part and sound field, in which the entire system is represented by an electrical equivalent circuit. A formulation is made of the wave propagation and circuit element characteristics by Bergeron's method, with the time‐axis analyzed by the node equation. As a result, it became possible to analyze the entire system by electrical circuit analysis, clearly indicating the interactions among various parts. The method is based on the time‐response analysis, and the response to the pulse wave, for example, can be calculated on the time axis. As examples, some basic problems with sinusoidal input in two‐ and three‐dimensional space are analyzed, and the results are compared with those of theoretical analysis. A computation is also made for the case where the voltage and current at the transducer input are affected by the reflected wave of the sound field through the vibrating membrane, indicating the feature of the proposed method where the interactions in the system can clearly be demonstrated.
Automatic rounding error estimation and its applications. Solution of linear equations, Newton's and Mcauley's methods
Authors: Kinoshita Eisuke , Kosako Hideo , Kojima Yoshiaki
Published: July 2007

Numerical computations are usually performed by floating arithmetic. Since the operations are performed by a finite number of digits, inevitably a rounding error is produced which is difficult mathematically to handle. This is because associative and distributive laws do not in general apply to the rounding operation. This paper describes a method which estimates the rounding error without using an analytical method. The number is represented by describing simultaneously the approximate value and the error. In parallel to the result of operation, the rounding error produced in that operation is determined and then summed for each operation. When a series of operations is completed, the range of existence for the result can be determined from the result of computation and the sum of errors. From the viewpoint that an unreliable number should not be given as output, the upper and lower limits of the range of existence for the result are given as output, indicating the extent to which the result of computation can be relied upon. It is shown that the proposed method is applicable to the sweeping‐out method, Gauss‐Seidel's method, Newton's method, and McAuley's method.
Absorbing rubber sheet mixed with carbon for X‐band marine radar frequencies
Authors: Shimizu Yasutaka , Nishikata Atsuhiro , Suzuki Shoichi
Published: July 2007

The conventional rubber radio wave absorber consisting of a rubber sheet mixed with ferrite is quite heavy. In order to reduce its weight the authors use chloroprene rubber with carbon added. The dielectric constants are measured using such absorbers with various kinds of carbon. Anisotropy generated in the dielectric constant during rolling is also investigated. Based on these data a radio wave absorber is designed and fabricated for X‐band marine radar (9.4 GHz). The practical utility of this radio wave absorber is confirmed. The present absorber has half the weight of the ferrite‐rubber absorber and hence is useful for covering large bridge structures.
Phenomenon of synchronization in a multimode oscillator with rational ratio frequencies
Authors: Kuramitsu Masami , Takase Fuyuto , Nitta Hiroyuki
Published: July 2007

This paper describes the synchronous oscillation in a multimode oscillator composed of an active element and several resonators with rational ratio frequencies. Using the concept of the averaged potential we proposed previously, we show that the ideal waveform minimizing the loss of the active element is generally the square wave or the stair‐step wave switching the minimal voltages of the active element voltage potential. Then, we can predict that the system has rational frequencies, the approximate square waves composed of these frequency components are excited stably by the synchronization. This synchronization phenomenon is confirmed by the simulation. An efficient algorithm for obtaining all of the stable synchronous oscillations is presented. The algorithm is performed by expressing all the synchronous oscillation waveforms by symbol trains according to their peculiar waveforms and calculating the initial values from the symbol trains. This method is applied successfully to the simulation of the oscillator where the active element is expressed by the cubic‐ or fifth‐power nonlinearity.
Traffic analysis of TSTST time division speech paths
Authors: Akiyama Minoru , Tanaka Yoshiaki , Seguel Julio , Fukushima Hideaki
Published: July 2007

This paper describes the traffic analysis of TSTST type building block speech paths. The main component of this configuration is the switch module. It consists of a small‐sized T‐switch and part of an S‐switch. TSTST configuration is used to make a large capacity switching system with these switch modules. Conventionally, TST configuration was used mainly for speech paths. However, the number of stages must be increased in order to make a large capacity switching system using switch networks with small channel multiplicity. The traffic handling characteristics of TSTST are almost the same as those of TST with the same size T‐switch and the same total number of channels, and this configuration can be applied to a wide range of speech path sizes. Furthermore, flexibility and reliability can be improved by adding alternative links to the fundamental TSTST configuration, and thereby link efficiency can be improved by a few percent compared with the configuration without alternative links.
Stable power‐combining mode operation of a cylindrical cavity multiple‐device oscillator
Authors: Fukui Kiyoshi , Nogi Shigeji , Sato Toru
Published: July 2007

Presented in this paper is a discussion of the output power combining capability and the stable operation of the desired mode in a cylindrical cavity multiple‐device oscillator, in which several devices are placed inside a cylindrical cavity to combine the output of all devices by way of coupling with the TM020 mode of the cavity. A lumped element equivalent circuit is first derived that has the fundamental characteristic of the oscillator structure. From the modal analysis based on this equivalent circuit, it is found that the oscillation output as the sum of the available powers of individual devices can be obtained in principle at TM010 and TM020 modes. It is also noted that the TM020 mode cannot be a stable mode when it is chosen as the desired mode and the TMm10 mode (m ≧ 1) is generated as a stable rotational or standing wave mode. Then we discuss the method of loading the resistor for suppressing unwanted modes in which only the desired output combining mode is stable. Finally, an eight‐device oscillator with a simple structure fabricated for trial is used in experiments of power combining and unwanted mode suppression and the results of the analysis of the modal analysis are qualitatively confirmed.
Scattering of a plane electromagnetic wave by the discontinuity of impedance planes
Authors: Kage Yoshio , Aoki Kazuo , Yoshidomi Kuniaki
Published: July 2007

A method often used for analyzing the problem of scattering by a lossy dielectric slab is an approximate one in which the dielectric slab is replaced with an impedance plane with an infinitesimal thickness. We analyzed rigorously the problem of scattering from the discontinuity between two dielectric slabs by means of the Wiener‐Hopf method. The numerical calculations in such a method is quite complicated. If this problem can be replaced with that of two impedance planes, the analysis and computation can be simplified significantly.

In this paper, the scattered field of the E wave by the discontinuity of two impedance planes is analyzed by the Wiener‐Hopf technique. The results are compared with the rigorous solution of the scattered E wave by the discontinuity of two dielectric slabs. From the numerical results of the two problems, it is found that the scattering patterns agree well if the slabs are lossy (σ/ω ⩾ 1.0) and the thickness is more than the skin depth. It is also found that the magnitude of the scattered wave almost agrees if the thickness is about one wavelength. Hence, if the slab thickness is more than a certain value for the E wave with the electric field component normal to the incident plane, the impedance plane approximation is effective for the lossy dielectric slab problem.
Minimum round‐off noise realizations of separable‐denominator two‐dimensional digital filters
Authors: Kawamata Masayuki , Higuchi Tatsuo
Published: July 2007

In real‐time two‐dimensional digital filters using a special‐purpose processor with fixed‐point arithmetic, the word length should be as small as possible to realize the desired processing accuracy. A digital filter which is affected least by quantization should be used. From such a viewpoint, this paper aims at the synthesis of the two‐dimensional digital filter structure with the separable denominator and with the minimum round‐off error. As the first step, the two‐dimensional digital filter with the separable denominator is represented by the local state‐space model. The result of analysis for the round‐off error already made by the authors is outlined. Based on these results, the synthesis of the structure with the minimum round‐off noise is formulated by equivalent transformation. A method of synthesis is presented. The two‐dimensional digital filter with the separable denominator and with the minimum roundoff noise, which is obtained by the synthesis method in this paper, is shown to be of a structure which does not produce an overflow oscillation for zero input. Finally, the effectiveness of the proposed method is shown by a numerical example.
Performance of a coded 8PSK modem with a viterbi decoder using simplified metric calculation
Authors: Miyake Makoto , Fujino Tadashi , Umeda Yoshiaki , Yamazaki Eizo , Fujiwara Ken‐Ichi
Published: July 2007

Recently, there has been increased interest in coded octal phase‐shift keying (8PSK) modulation for satellite communications, in which convolutional encoding and Viterbi decoding are combined with 8PSK modulation and demodulation. The problem in this paper is how to simplify the process of metric calculation in a Viterbi decoder and realize reduced hardware complexity and increased operating speed of a coded 8PSK modem. An analytical expression is introduced for the performance of a coded 8PSK model with such a simplified Viterbi decoder. The expression is then applied to a typical coded 8PSK modem employing the Ungerboeck code of rate 2/3 and with constraint length ν=2. Effects of simplifications in the Viterbi decoder on the bit error rate (BER) performance of the model have been evaluated. Results in this paper would be useful in the design of future coded PSK modems, since it enables a designer to assess the tradeoffs involved in the simplifications and to realize modems with reduced hardware complexity for highspeed applications.
A proposal for searching for electromagnetic wave sources by using a synthetic aperture technique
Authors: Kikuchi Jun‐Ichi , Sato Motoyuki , Nagasawa Yoji , Sato Risaburo
Published: July 2007

Unwanted electromagnetic waves radiated from equipment making use of electromagnetic energy create numerous societal problems. The prevention of these problems has been studied extensively. In this paper, a method for estimating the location of the unwanted electromagnetic waves is studied. Since it is difficult to make the antenna aperture large especailly at low frequencies, a search for electromagnetic wave source via a synthetic aperture technique is proposed. In the estimated electromagnetic source distribution by this method, images similar to the antenna sidelobes appear. It is demonstrated by computer simulation that the images can be suppressed by use of the synthetic aperture method with subarrays or use of Mill's cross method. Discrepancies between the true source location and the estimated location have been found in regard to the synthetic aperture length and the geometrical relationship with respect to the aperture center. It has been found that the antenna configuration with the synthetic aperture length of 10 λ can estimate an electromagnetic wave source within 10 λ square with accuracy of less than 1/4 λ square. Therefore this method is sufficiently practical if the location of the source is restricted somewhat.
Finite–element analysis of discontinuities in a dielectric slab waveguide
Authors: Hirayama Koichi , Koshiba Masanori , Suzuki Michio
Published: July 2007

For discontinuity problems in a dielectric waveguide, a method for analysis is proposed in which a finite element technique and an analytical solution are combined. A systematic formulation is carried out for both the TE and TM modes. A hypothetical wall is provided in the region outside the waveguide so that the open region waveguide is treated as a closed system. In such a closed system, the mode spectrum becomes discrete and the analysis is simplified. However, the location of the hypothetical wall needs to be chosen carefully. The solution changes violently near the cutoff point of a higher order mode. In the present method, the location of the cutoff points of the higher order modes is calculated beforehand and the hypothetical wall is placed near the midpoint of the two adjacent cutoff points. If the hypothetical wall is placed at such locations, the solution depends much less on the locations. Hence, even if the hypothetical wall is located relatively close to the waveguide, the approximate solution is accurate. In order to demonstrate the fact that the present method can be easily applied to an arbitrary discontinuity, a complicated discontinuous structure such as the core deformation at the splicing point of fibers has been treated. The analytical results have been shown for the scattering characteristics of the TE and TM modes at such junctions.
General expressions for the numbers of spanning trees in interative graphs classified by contact patterns of cells
Authors: Sato Kimio , Onodera Rikio
Published: July 2007

This paper presents a general formula for the number of spanning trees in an iterative graph. This graph is obtained by connecting k m‐cycles Cm and k n‐complete graphs Kn by branch‐contact or by point‐contact into ladder, prism, wheel, step, sector or mill‐wheel types, and 2 × k of them into a lattice type, respectively. A conventional method using a determinant with k, m and n as parameters is used to determine the number of trees in these iterative graphs. In this method there are many cases where the expansion of the determinant is not easy. Thus as an alternative method for such cases we introduce for the first time an electrical network calculation method for driving point resistance conductance in a unit resistance network whose interconnection structure is represented by a graph. In addition, we introduce a series parallel partition method of branches of a graph, so that the derivation of a general formula for the number of trees in an iterative graph is simplified. Then for individual iterative graphs, we show concrete examples and the results of the determination method obtained by mixing the above‐mentioned three methods appropriately.
Markov chain analysis of a single‐stage transfer‐type automated manufacturing system—two‐machine parallel system
Authors: Nakamura Takashi , Ohuchi Azuma , Kaji Ikuo
Published: July 2007

From a microscopic viewpoint in consideration of the loading control of work‐pieces and the machine layout, the dynamic behavior of a single‐stage transfer‐type automated manufacturing system with two same‐type machine tools placed in parallel at both sides of a loop conveyor is modeled and analyzed. The processing time obeys a general distribution and to avoid the collision, workpieces are assigned at random to moving slots at regular intervals on the conveyor. The state is defined on the basis of the physical states of the two machines at the arrival epoch of each slot and the system behavior is formulated as a Markov chain. Performance measures such as production rate and inflow rate are obtained by finding the equilibrium state probabilities. Especially, in case of exponential processing time distribution, their explicit expressions are derived. Numerical examples are shown and the difference between the two‐machine parallel system and the two‐machine series system [5] is discussed. Moreover, the production rates for the cases of normally distributed processing time and fixed processing time are calculated numerically and then the validity of the analysis results under the exponential assumption is discussed.
Loss reduction of the magnetostatic forward volume wave delay line using the YIG film
Authors: Tsutsumi Makoto , Tanaka Katsuyuki , Kumagai Nobuaki
Published: July 2007

This paper describes from the experimental viewpoint the group delay characteristics, particularly, loss characteristic (both propagation loss and transducer conversion loss) of the magnetostatic forward volume wave in a YIG film nonuniformly magnetized with a conical pole piece. The maximum time delay of 3 m̈s has been observed at 4 GHz and the propagation loss has been found to be 15 dB/m̈s. It has been found that the delay time minimizing the loss increases with the degree of nonuniformity of the magnetic field. A theoretical study has been made for the experimental results. It is assumed that a lens‐like medium is formed in a YIG film by means of the nonuniform magnetic field. From the lens theory, the focal length for the magnetostatic wave beam has been obtained and the focal length is estimated as a function of the delay and the degree of nonuniformity of the magnetic field. It is concluded that the focal point of the magnetostatic wave beam is formed on the receiving transducer if the loss is minimum, and that the loss is related mainly to the conversion loss.
A method using a trial function with unknowns to solve approximately fredholm integral equations of the first kind
Authors: Kurosu Takashi
Published: July 2007

This paper discusses the approximate solution of Fredholm's integral equation of the first kind, using the trial function containing unknown parameters. The unknown parameters are determined from the observed data and the estimated values using the least‐square method. The method is applied to the remote sensing problem, where the method can be applied without a priori knowledge about the true solution, even if few observed data are available to estimate the correct change of the physical variable (true solution). A method is demonstrated which can examine the adequateness of the chosen trial function. Discussions are made for the accuracy of the approximate solution and the error of the physical variable which is estimated from the approximate solution.
Both E‐ and H‐plane converging lens applicator for deep and localized microwave hyperthermia
Authors: Nikawa Yoshio , Moris Shinsaku , Katsumata Tohru , Kikuchi Makoto
Published: July 2007

In hyperthermia which has recently been considered as a promising cancer therapy, heating of tissue is produced by dielectric heating by microwave energy. On the other hand, owing to the substantial attenuation of electromagnetic waves within a biological body, it is not possible to heat a cancer located deep inside the body. The authors have proposed an antenna (applicator) for electromagnetic irradiation of the biological body with a converging effect in the magnetic field plane (H‐plane). In this paper, a new applicator is proposed which has a converging effect in the electric field plane (E‐plane) in addition to the previous effect in the H‐plane. Such an E‐ and H‐plane converging lens applicator has been fabricated. In addition to the theoretical analysis, a heating experiment has been performed for a phantom model of human muscle. The theoretical and experimental results agree well. If a surface cooling device is added in the applicator, the depth of the maximum temperature point is found to be more than twice that of the conventional waveguide with an identical aperture size. A similar theory has been used at 2450 MHz in the simulation of heating of a biological model considering the presence of cancer. Although the skin depth of the muscle layer at this frequency is 17 mm, the range of heating in the hyperthermia reached more than 30 mm (about twice the surface skin depth), indicating the effectiveness of the applicator developed here.
Adaptive vector quantization of picture signals in discrete cosine transform domain
Authors: Aizawa Kiyoharu , Harashima Hiroshi , Miyakawas Hiroshi
Published: July 2007

This paper proposes the adaptive discrete cosine transform coding with vector quantization (adaptive DCT‐VQ), as a highly efficient coding for the picture signal. In the proposed method, the vector quantization is performed by applying the discrete cosine transform to the picture subblock and partitioning the transformed domain into several vectors. By regarding the transformed domain as more than one vector, the complexity in the coding is reduced. Each vector quantizer is designed according to the standard probability distribution of the cosine transform coefficient, and the universality of the vector quantizer is realized. The mode‐selecting type adaptive control is introduced, to effect the adaptive control of the coding parameters according to the local property of the picture. To cope with the large bit allocation resulting from the adaptive control, each vector quantizer has two‐stage structure thereby reducing the coding complexity. As a result of the performance evaluation by simulation, it was verified that the proposed coding method has a higher performance than the conventional adaptive cosine transform coding and has much less complexity than the vector quantization in the original space domain.
Analysis of a heuristic algorithm for planar assignment problem
Authors: Yamada Shoichiro , Harashima Katsumi , Kasai Tamotsu
Published: July 2007

This paper describes a theoretical analysis of the heuristic algorithm for the efficient solution of (the linear) assignment problem defined on a plane. The evaluation function, or assignment cost, in the assignment problem discussed in this paper is defined as the square‐sum of Euclidean distances between points included in the two point sets. A heuristic assignment algorithm, based on a vertical or horizontal partitioning of the given plane, is presented. Then the average‐case analysis is performed for the algorithm, assuming that the points are distributed uniformly on the unit square plane. Letting the size of the point set be n, the number of partitioned stages in the algorithm be hm and the average assignment cost for n → ∞ be Ǐ, it is seen as a result of analysis that the rate of increase of Ǐ in regard to n decreases monotonously with the increase of hm. It is also seen that when hm is maximum, Ǐ is (1/4) log2. n. The result of theoretical analysis is compared with the result of experiment.
Synthesis of active R allpass networks
Authors: Okine Mitsuo
Published: July 2007

Many reports have been made on the synthesis of active R filters which operate in the high‐frequency band using general‐purpose operational amplifiers. Most of these reports were on low‐pass and band‐pass filters. A solution to the problem of obtaining a transfer function whose nominator and denominator polynomials are of the same order as the degree of s similar to other filter functions, that is, high‐pass and allpass filters, still has not been reported. Hence, this paper considers allpass functions which are especially useful in proposing active R networks which are very simple and can be synthesized in an easily designed construction. Three kinds of circuit synthesis methods are presented. Since in networks of this kind, as is well known, the internal signal level generally is higher than the output level, e.g., similar to bandpass filters, it was important to suppress it. Using a concrete example, we show that one of the three kinds of proposed networks is improved considerably with respect to this point compared with other networks. Moreover, we make a detailed concrete examination of networks for (1) the center frequency realizable, (2) the design in the event that GB products of operational amplifiers are all different, (3) influence by the secondary pole on the amplitude and phase characteristics, and (4) the temperature characteristic.
A realization of high‐frequency active RC bandpass filters using voltage followers
Authors: Takagi Shigetaka , Fujiis Nobuo
Published: July 2007

Using voltage followers as active elements in the synthesis of active RC immittances, no impedances could be realized which become zero at dc and no admittances which become infinite with the 2nd order or more at infinite frequencies. A realization method which simulates arbitrary LC filters impedance‐scaled by (1 ρ/s) has been proposed by the authors. This paper presents a realization of high‐frequency active RC bandpass filters simulating impedance‐scaled LC filters by using voltage followers and a passive RC circuit. The frequency characteristics of the simulated filters are damaged mainly by the input capacitances of voltage followers. The effect of the input capacitors is compensated by simulating a circuit consisting of L, C, and ‐R. A transformation of resistively doubly terminated LC bandpass filters is also shown to apply this compensation. Sensitivity analysis and experimental results confirm the effectiveness of the proposed realization method.
Accurate numerical analysis of inductive windows in a rectangular waveguide by singular integral equations
Authors: Matsushima Akira , Itakuras Tokuya
Published: July 2007

Accurate numerical techniques using singular integral equations are presented for the scattering problem of electromagnetic waves at discontinuities of waveguides. We take the case of inductive windows made of perfectly conducting strips and derive a set of singular integral equations with the same number of unknowns as the number of windows. In the case of a single window, we extend the quasi‐static analysis in the same way as Lewin's so as to be effective even in the multimode range. Accurate approximate solutions are obtained in closed forms in the frequency range in which at most two modes propagate. For the multiple windows, numerical solutions are obtained by applying Galerkin's procedure directly to a set of singular integral equations because the forementioned analysis becomes increasingly complicated. By this method, we can perform the analysis automatically regardless of the number of windows. Also, unlike the numerical solution using conventional integral equations, relative convergence can be avoided. The error analysis is made by comparing the numerical results with exact solutions and experimental values. As a result, it is proved that the accurate solutions are obtained by these methods even if small‐sized simultaneous linear equations are solved.
Radius and diameter with respect to edges in a nondirected graph, and upper and lower bounds for the diameter
Authors: Sengoku Masakazu , Kobayashi Kazuhito , Shinoda Shoji
Published: July 2007

The radius and diameter of an undirected graph G are well known as basic concepts of graphs. It is known that an inequality r(G) ≤ 2r(G) holds for the radius r(G) and diameter d(G). This exhibits the upper and lower bounds for the diameter, and these bounds are known to be optimal. The radius and diameter of graphs are the quantities defined by the distance between vertices. On the other hand, edges are also important elements as well as vertices in graphs. However, the radius and diameter with respect to edges have not been considered very much. This paper proposes an idea concerning the radius and diameter of graphs defined with respect to edges. In other words, a quantity is defined corresponding to the distance between edges by the minimum length of a tieset containing the two edges simultaneously. Then it is shown that the quantity is a quasi‐distance satisfying the triangular inequalities. Concepts of the radius and diameter are introduced as well as in the case of vertices. Further, an inequality revealing the upper and lower bounds with respect to edges is derived and it is shown that the upper and lower bounds are optimal. Finally, it is described that similar results are obtained concerning the upper and lower bounds of the diameter when the quasi‐distance between edges is defined using cutsets.
Optimized equivalent‐weight budget design of communication satellite in multibeam mobile satellite communication system
Authors: Hagiwara Eiji , Yasuda Yoshiyuki , Mishima Hiraku
Published: July 2007

Optimization of system design parameters, such as onboard antenna diameter, number of beams, and number of onboard transponders, is of great importance to decide system capacity of subscribers in a multi‐beam mobile satellite communication system.

This paper describes an optimization method of important system design parameters to maximize system capacity of subscribers under limited weight budget and dissipation power of satellite mission and limited service area.

First, the concept of aquivalent weight, which is defined by a linear combination of weight and dissipation power of satellite mission is proposed. Next, the optimization of above design parameters, giving the maximum system capacity of subscribers, is made under the constant equivalent weight of the total satellite mission.

As a result, it is found that the optimized conditions are simply expressed and universal.
Computational accuracy in determining the sign of an algebraic quantity
Authors: Yoshida Kiyonori
Published: July 2007

This paper considers the computational accuracy when performing a numerical computation of an algebraic quantity to determine the sign. For an algebraic function α({di}) of data {di} we introduce the (n, m, l) degree to discuss a method for its estimation. It is shown that when data {di} are given in fixed decimal point form with finite figures, we can correctly determine the sign of the value of α with approximately m times more figures.
Time complexity of gate assignment problem in one‐dimensional array
Authors: Fujii Takashi , Kikuno Tohru , Yoshidas Noriyoshi , Horikawa Hideya
Published: July 2007

In the one‐dimensional array approach, a logic circuit is realized by arranging NAND (NOR) gates in a one‐dimensional array and interconnecting them. The horizontal length of the resultant layout of the logic circuit is determined uniquely by the number of given gates, while the vertical length varies depending on the order of assignment of gates. Thus, to minimize the area required, we must find a one‐dimensional assignment of gates so as to minimize the vertical length. This optimization problem (called problem G) has been formulated as a graph problem and has already been proved to be NP‐hard.

In this paper, a restricted problem (called the problem R) is introduced anew wherein a connection of each net is restricted to be between two gates. The problem R plays an important role in developing a heuristic algorithm for the problem G. As for the time complexity, we show that the problem R is also NP‐hard.
Time series analyses of 1/f noise with its unbounded invariant density
Authors: Kohda Tohru , Murao Kenji
Published: July 2007

The time‐series analysis (called indirect method) based on the Perron‐Frobenius operator is well known as a theoretical method which can determine the statistics for various chaos in one‐dimensional distance dynamical systems without determining the trajectory. However, it is rare that a strict solution for the statistic can be determined explicitly and consequently, the indirect method is not practical at present. To remedy this situation, previously we proposed an indirect method based on Galerkin's approximation to the operator, and verified its usefulness. However, the method was not effective for the intermittent chaos with 1/f power spectrum. This paper extends the indirect method using Galerkin's method by introducing the singular function in the approximation to the unbounded invariant density. As a result, the power spectrum is obtained which agrees fairly well with the data calculated directly from the trajectory over a wide frequency range. An interesting result was obtained by the recent study wherein the spectrum of the intermittent chaos has the form of 1/fδ in the limit of zero frequency, where the exponent δ is related explicitly to the nonlinearity of the one‐dimensional discrete dynamical system. However, the forementioned result refers only to the spectrum of the chaos in the limit. By contrast, the proposed method can serve as a practical method to estimate the power spectrum of 1/f noise over a wide range.
Design of digital signal processing quadrature modulator for digital fm and analog FM signals
Authors: Yamao Yasushi
Published: July 2007

In the field of mobile communication, the transmission of picture and data signals in addition to conventional speech transmission requires modulators that are suitable to both analog and digital FM. In the present paper such a quadrature modulator is proposed which provides stable transmission characteristics by digital signal processing (DSP) techniques. The analysis is mainly aimed at additional noise effects due to the digital generation of analog FM signals.

The relations between the sampling frequency used in the D‐A conversion of analog speech signals and the sideband noises accompanying modulation are developed. The relations are given between the number of bits used for quantization in the A‐D conversion and the baseband signal/noise ratio in the case of FM or PM reception of the analog FM wave generated by the proposed modulator.

Based on the results of this analysis, a modulator design method providing sufficiently high noise suppression is presented in a flowchart form. The results of measurement of a quadrature modulator realized by the proposed method are shown to agree well with the results of analysis. The agreement demonstrates that the required modulator characteristics can be obtained without tuning.
Data compression and statistical inference
Authors: Amari Shun‐Ichi
Published: July 2007

When mutually correlated data are observed at two different places, it may happen that data are compressed independently, losing the correlational information as a whole. Such cases are observed frequently in economical and environmental data. When the compressed data (statistics) are combined to perform a statistical inference concerning the probability structure governing the two observations, the loss of the statistical information due to the independent data compression should be noted. In other words, a problem arises of estimating Fisher information lost by the independent data compression in the sense of Shannon information at the two sites. It is another problem to determine the best ways of data compression and estimation. This paper introduced anew the notion of mutual Fisher information, and answers those questions by a new theory, combining the information and the statistical theories. The usefulness of the information geometry, which works on the geometrical structure of the probability space, is also indicated through the discussion.
Accurate analysis of δv/v surface acoustic waveguides on a piezoelectric anisotropic substrate
Authors: Yamada Akira , Shimizu Hiroshi
Published: July 2007

This paper presents an accurate analysis for the Δv/v surface acoustic waveguide, which is generally applicable to the anisotropic substrate. This is a three‐dimensional boundary‐value problem in the anisotropic semiinfinite piezeoelectric medium, and includes a number of difficult points for analysis. There are two contradictory requirements for the analysis: (1) flexibility in the object of analysis; and (2) a simple program for numerical computation and small computational complexity. There has not been presented a method which satisfies both these requirements. The method presented in this paper is highly practical, providing a reasonable compromise between the two. The method is as follows. The boundary condition on the substrate surface of the guide is replaced by an integral equation using Green's function. The resulting equation is converted into a matrix equation by partitioning the boundary into elements for discrete representation. Then the eigenfrequency of the guide is determined by solving the equation numerically. The usefulness of the proposed method is demonstrated by the result of numerical calculation for the dispersion characteristics and the field distribution of the guided mode.
A consideration for the interpolation problem with first‐and second‐order information
Authors: Suzuki Masakiyo , Nagai Nobuo , Miki Nobuhiro
Published: July 2007

A wave digital filter (WDF) is a low‐sensitivity digital filter which simulates lossless analog circuits. A lattice‐type digital filter (AR lattice filter), which is used in digital signal processing, is a WDF equivalent to a cascade of unit elements (u.e.). As the generalization of this relation, a WDF realizing a modeling filter for an ARMA process has been obtained and the network theory with WDF's has been applied to the digital signal processing. The conventional WDF's, except for the AR lattice filter, are constructed by using the transfer functions to be realized. In this paper, unlike the conventional network synthesis, we propose a synthesis method. In this method, a network approximating a modeling filter for a stationary stochastic process is synthesized recursively using a finite number of data of the autocorrelation coefficients (second‐order information) and the impulse response of the modeling filter (first‐order information). A lattice‐type digital filter is derived realizing an approximation of the transfer function. The approximation is one in which first‐ and second‐order information matches the forementioned data. Also, modified least square approximations due to Kalman and Mullis can be realized by this lattice‐type digital filter. This lattice‐type digital filter is a kind of WDF and the relationship between the global stability and the local stability is clear.
Loop antenna with a branch wire for circular polarization
Authors: Nakamura Takashi , Yokokawa Senji
Published: July 2007

This paper reports on the analysis and design of a circularly polarized antenna consisting of a loop antenna with a branch wire of an appropriate length. The idea for developing this antenna derives from the fact that the branch wire has a characteristic as a transmission line coupled with a loop conductor. The present structure is a simple single‐feed antenna operating equivalently as a two‐point feed‐loop antenna. The current distribution in the antenna is decomposed to the balanced and unbalanced modes for which the equivalent circuit and equivalent loop antenna have been derived. The condition for circular polarization has been obtained from the equivalent loop antenna. Based on this condition, a circularly polarized antenna has been designed and various characteristics such as the axial ratio have been obtained. From these characteristics it is found that a structure exists for which the axial ratio can be made much more broadband than other antennas with the length of about one wavelength. The validity of the theory has been confirmed by experiments.
Matrix–fraction descriptions and the Mcmillan form of a transfer function meromorphic in the unit disk
Authors: Inouye Yujiro , Kato Koichi
Published: July 2007

This paper considers discrete‐time systems with matrix‐valued transfer functions, each entry of which is a mermorphic function in the unit disk. Making use of Helmer's result [11], the McMillan form is proposed for a meromorphic transfer function G(z). It is shown that all the numerators of right or left irreducible matrix‐fraction descriptions of G(z) possess the same invariant factors up to multiplication by invertible factors. Also, it is shown that all the denominators possess the same invariant factors except unity invariant factors up to multiplication by invertible factors.
Synthesis of three–dimensional separable–denominator digital filters with minimum roundoff noise
Authors: Hinamoto Takao , Hamanaka Takashi , Maekawa Sadao
Published: July 2007

A roundoff noise analysis is presented for three‐dimensional (3‐D) local state‐space digital filters with separable denominator. It is clarified that the output‐noise power and the signal scaling condition are closely related to three, and three positive‐definite matrices, respectively. A procedure is also developed for the synthesis of an optimal 3‐D local state‐space digital filter with separable denominator which minimizes the output‐noise due to roundoff subject to a scaling condition on the state variables. The optimal state‐space realization can be obtained through the 3‐D similarity transformation by individually solving three 1‐D optimization problems.
Characteristics of antenna pattern diversity branches in urban mobile radio
Authors: Ikegami Fumio , Takeuchi Tsutomu , Yoshida Susumu
Published: July 2007

The performance of mobile communication is greatly degraded by the multipath fading which is a large problem in future digital mobile communication. We made a detailed analysis of the urban propagation characteristics and found that use of a directive antenna in a mobile station reduces the fading by the effect of antenna pattern itself. We suggested that excellent diversity branches can be realized by combining more than one directive antenna. This paper discusses first the basic condition for the antenna pattern diversity branches. Correlation characteristics are examined by measurement of 2‐ and 4‐branches. The reduction of the fading is estimated by computer simulation based on the measured data. It is shown as a result that a 4‐branch antenna pattern diversity system has excellent characteristics compared with the space diversity system composed of omnidirectional antennas.
Reduction method of pointing error of El/AZ mount for maritime satellite communications
Authors: Shiokawa Takayasu , Karasawa Yoshio , Yuki Hironori
Published: July 2007

Development of small marine antennas has a very important role in the maritime satellite communications with small ships, especially for Japan which has a relatively large number of small fisherboats. As the satellites become larger in size in the future, the shipborne antennas will tend to become smaller. We propose a control method for the antenna mount against ship motions to assure pointing the communication satellite. The two‐axis EL/AZ mount has a light weight and a small size, which gives rise to a large pointing error when the satellite is near the zenith or when the AZ axis is near the control limit for avoiding twisting the cables. We have developed an algorithm to reduce the pointing errors within the pitching amplitudes of the ship. The principle and the experimental results of this system are described.
Propagation characteristics of electromagnetic waves in groove guides
Authors: Yamaguchi Yoshio , Ohtaki Yukio , Abe Takeo
Published: July 2007

In mobile telecommunications in urban areas, a very small zone system within a few kilometers is adopted to meet an increasing demand. Hence, wave propagation must be investigated in such a situation where transmission and receiving antennas are located lower than buildings. Wave propagation has been studied in a groove structure which simulates a road surrounded by tall buildings to geometrical optics approximation. The result was compared to the microwave simulation experiment with dipole and rectangular horn antennas. Theoretical predictions agreed with observations. At higher frequencies, the wave attenuation became smaller, where the wavelength is much smaller than the groove dimensions and the groove or a road works as a waveguide.
Modeling by MDL criterion for adaptive data compression
Authors: Yokoo Hidetoshi
Published: July 2007

This paper proposes a high‐performance noiseless data compression model which can compress strings generated by a binary Markov information source without prior knowledge of the source. The adaptive expression of the existing universal codes is described by a model with separated sampler and encoder, and the learning structure of each code and the encoding process are described. Through such a discussion, the intuitive reasons are clarified as to why the codes, despite their asymptotic optimality, do not compress well at the start, pointing out room for improvement. Then, the MDL criterion is introduced into each encoder, to improve the performance, while keeping the sampler fixed. The MDL criterion is an estimation for the minimum code length, including the representation cost of the parameters. Based on this criterion, the Markov order which is to be assumed for each symbol is adaptively determined. Since the same determination can be made at the time of decoding, the unique decodability is guaranteed. In the second half of this paper, more detailed techniques are discussed, and a remarkable improvement is demonstrated by a computer simulation. It is also shown that the sampler of the proposed universal code is of a high‐performance, realizing two kinds of encoders.
A design method of fir filters suitable for SAW filters
Authors: Fushimi Shigeo , Morimoto Mikio
Published: July 2007

The surface acoustic wave (SAW) filter is usually designed as a finite‐impulse response (FIR) filter. The SAW filter, which faithfully realizes the arbitrarily specified amplitude and group‐delay characteristics, has been designed using linear programming, nonlinear programming and other techniques. In such design methods, the coefficients of the FIR filter are approximated iteratively. Consequently, a long computation time is required for a higher‐order FIR filter, and convergence is also a problem. This paper presents a design method which can realize a higher‐order FIR filter with arbitrary amplitude and group‐delay characteristics without using an iterative approximation. The design procedure is as follows: (a) the method by McClellan et al. is combined with the discrete‐Fourier transform (DFT) method, and the FIR filter with arbitrarily specified amplitude characteristics is designed; (b) for the group‐delay characteristics which are specified arbitrarily a cosine expansion is formed. By applying Bessel function, the FIR filter with the arbitrarily specified group‐delay characteristics is designed; (c) the two results are convolved and truncated to reach the required FIR filter. The design algorithm and example are presented. An SAW filter was constructed for the video signal extraction using an LiTaO3 substrate. The frequency characteristics and the electrode structure of the experimental filter are described.