bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochromism in evaporated WO3‐MoO3‐V2O5 films
Authors: Sato Susumu , Seino Yosuke
Published: July 2007

Symmetric and asymmetric EC cells are here fabricated using amorphous W03‐Mo03‐V205 films vacuum‐evaporated on substrates prepared in electrolyte of lithium perchlorate and propylene carbonate. Dependences of the reflection spectra of symmetric cells and the transmission spectra of asymmetric cells on the applied voltage was investigated. Almost black displays were obtained with W03‐Mo03 films to which negative voltages were applied (the reduced state) and the contrast ratio was improved compared with films of pure W03 and V205. Reddish displays were obtained with W03‐Mo03 films, and V205‐Mo03 films gave yellow and bluish displays. Addition of Mo03 to 60% W03 ‐ 40% V205 composition has improved EC properties, giving colors between brown and yellow‐green. Possible colors obtained are represented in the CIE (x, y) chromaticity diagram.
Correlated information source coding with a fidelity criterion
Authors: Member Motoaki Ohkubo, Regular
Published: July 2007

This article derives the achievable rate region associated with correlated information sources coding subject to some fidelity criterion. It defines the distortion corresponding to the decoding error in a dual‐channel situation with correlated information sources. Furthermore, an achievable rate region R(d) is derived corresponding to the channel capacity by using a method similar to that used by Slepian in obtaining the upper bound of decoding error rate for random codes.
200 khz pcm timing tank electromechanical filter
Authors: Tomikawa Yoshiro , Konno Masashi , Gounji Takashi , Kasai Yoshihiko
Published: July 2007

This paper describes the design method and experimental results of a timing tank electromechanical filter for low‐speed digital subscriber transmission networks. A composite longitudinal‐mode vibrator consisting of a piezoelectric ceramic sandwiched by consant‐modulus alloy plates is proposed for the filter. This type of vibrator is convenient to weld with its couplers and supporter. The temperature characteristic of the filter can be compensated by the two types of material. It is confirmed that the filter permits electronic characteristics and physical size compatible with LSIs used for PCM apparatus. The resonance frequencies and capacitance ratios of the vibrators and the conditions for suppressing higher‐order or resonance modes are analyzed. 200‐kHz timing tank filters based on the described analysis are fabricated and their characteristics described.
Baseband response characteristics measurement method and measuring equipment for multimode fiber
Authors: Okada Kenji , Members Ikutarou Kobayashi, Regular
Published: July 2007

Problems and solutions for the far end measurement of frequency characteristics of the baseband response of a multimode fiber due to dispersion are presented. Also described is a configuration of the measuring equipment of the baseband response. For the latter, the following are important: (i) removal of the effect of the material dispersion; (ii) stabilization and leveling of the modulation level; (iii) stabilization of the optical output level; and (iv) removal of the effect of the reflected light from the output end and the input end of the fiber. Solutions for these problems are: (i) single‐mode oscillation of the semiconductor laser by reduction of the modulation index; (ii) stabilization and leveling of the modulation level by a negative feedback loop that monitors the modulation level of the backward light of the laser; (iii) stabilization of the optical output by a negative feedback loop that monitors the output level of the backward light of the laser; and (iv) removal of the effect of the reflected light by means of oblique incidence and small input aperture angle. When the baseband characteristic of a fiber a few kilometers long is measured, irregular variations are observed. A solution to this problem is also included.
Effect of compound strategies of error correcting coding, bit interleaving, and diversity combining in mobile radio data transmission
Authors: Member Yoshiya Miyagaki, Regular , Morinaga Norihiko , Members Toshihiko Namekawa, Regular
Published: July 2007

The improvements on bit error rate characteristics due to compounding an error correcting coding, a bit interleaving, and a diversity combining as reliability improvement measures, are evaluated theoretically for mobile radio data transmission affected by the time‐varying fast Rayleigh fading. Although the code, modulation, and decoding are limited to the block code, noncoherent FSK, and hard decision, the time correlation of the fading in a code word is taken into account generally and rigorously in this analysis. On the basis of the calculation results for nine codes, the effect of compound strategies by the degree of bit interleaving, “with or without” diversity, code length, and number of correctable errors, are discussed in detail, and the equivalence among the strategies and the compounding effect is clarified.
Design method of four‐reflector type beam waveguide feeds
Authors: Member Shinichi Betsudan, Regular , Katagi Takahashi , Urasaki Shuji
Published: July 2007

We describe a design method for four‐reflector type beam waveguide feeds composed of a conical horn and four reflectors which are widely used for the first‐stage radiation system of earth station antennas in satellite communication. The relational equation between the design parameters is derived based on beam‐mode expansion and we specify the independent design parameters. We derive the relation between the design parameters and such performance characteristics as spillover loss, cross‐polarization component and frequency. As design criteria (I) we minimize the cross‐polarization component on the condition of maintaining the spillover loss within a tolerable level, and (II) we minimize the spillover loss on the condition of maintaining the cross‐polarization component with a tolerable level. In determining the size of reflectors under prescribed mechanical constraints we establish that the design parameters governing the size of the conical horn and the shape of reflectors can be determined uniquely. Examples of application of this design method are presented to show the effect of the design parameters and to increase the design efficiency.
Hybrid distance and hybrid capacity on networks
Authors: Shibasaki Masashi , Itoh Masaki
Published: July 2007

The distance and the capacity between two vertices in a network are conventionally defined as the shortest path length and the minimum cut capacity between the vertices. In this paper, “hybrid distance” and “hybrid capacity” are proposed as generalized concepts of the shortest path length and the minimum cut capacity, which are defined using the concept of difference decomposition [1] in the matroid theory. These concepts can be measures for evaluating the density or complexity of an edge set between two vertices in a network. It is shown that the hybrid distance satisfies the metric axiom in the same manner as the conventional distance on a network.
A study on satellite circuit assignment and dimensioning methods for a domestic telephone transit network
Authors: Member Kou Miyake, Regular
Published: July 2007

In applying satellite circuits to a large domestic telephone network, it is necessary to study channel assignment and dimensioning methods that take advantage of broadcast communication features. This paper shows that for a large‐scale telephone transit network which has hierarchical structure, in order to absorb traffic fluctuation, it is attractive to apply satellite circuits to high‐usage trunks in combination with terrestrial final trunks, by taking the Japanese telephone toll network as an example. Assuming this network construction, this paper considers three different satellite channel assignment schemes—Pre‐Assignment, Timed Pre‐Assignment, and Demand Assignment–and introduces a circuit capacity dimensionsing method to minimize the total network cost for each assignment. Finally, a comparison of channel capacity and network cost is made among these assignments under some traffic variation patterns. It was found that Timed Pre‐Assignment is the most effective and economical scheme. Demand Assignment is a future technology and its application field is clarified in comparison with other schemes, with the cost increase for realizing Demand Assignment as a parameter.
A study on system fluctuations based on the nondeterministic operator theory
Authors: Horiuchi Kazuo
Published: July 2007

This paper considers the nondeterministic operator G defined on the direct product space of a completely matrizable linear space × and a metric space Y; G is introduced as a projective set G (x, y) ⊂ × for arbitrary × ϵ × and y ϵ Y. Relating to the completely continuous operator f(x) with Y as the range, a fixed‐point theorem is given for the generalized operator equation × ϵ G (x, f(x)). This mathematical theory is applied to the analysis of deviation of the output response when a nondeterministic fluctuation is imposed on the internal structure, internal parameter or input signal of a system. As a result, clear definitions are given for the tolerability and quasitolerability of the system fluctuation, the stability and quasistability of the system, and the tolerability and quasitolerability of the system model and simulation by it. An aspect of the system's sensitivity analysis is also discussed. Of particular importance in this paper is the new proposal of the new concepts of quasitolerability and quasistability, which suggests that these concepts should be utilized more widely the notions of the system and its model by developing the computing abilities.
Arma spectral approximation methods with weighting functions
Authors: Watanabe Hiroshi , Miyanaga Yoshikazu , Miki Nobuhiro , Nagai Nobuo
Published: July 2007

This paper presents an approximation method of the ARMA model using frequency weighting functions that are represented by the ARMA models. The parameters of the approximate ARMA model are calculated with the order update recursion. By selecting the weighting function appropriately, the spectral approximation method weighted the polezero frequency of the original model can be obtained. The relation between the proposed approximation method and the spectral distance measures is also considered. The behavior of the proposed method is illustrated by simulation results.
A maze running router and its wirability for single‐layer printed wiring boards
Authors: Member Takashi Shimamoto, Regular , Sakamoto Akio , Members Akio Ushida, Regular
Published: July 2007

As the integration in electronic equipment progresses, CAD technology becomes more and more necessary. Single‐layer wiring is one of the CAD technologies and some procedures have already been proposed. Primarily, the maze running‐type algorithm is used in them and the shortest path obtained by the algorithm is used for the routing path. In this paper to check the appropriateness of the shortest path selection policy, we present a new maze running‐type algorithm which gives near‐shortest path routes, and compare its wirability with other existing maze methods. One of the features of our algorithm is that if some obstacles exist between two vertices to be connected, a path along the obstacles is found. The path may not be the shortest one, but it becomes easy to implement the succeeding routing since the path along the obstacles preserves the force area as wide as possible. Furthermore, the computation time is shorter than existing maze methods because of a simple stack operation. As a result, the proposed maze running router is expected to give a high wirability with small computation time.
Mic linearizer for satellite communications
Authors: Member Gunkichi Sato, Regular
Published: July 2007

This paper describes the trial production results for two linearizers, one being a compact, lightweight MIC linearizer developed to improve the input‐output nonlinear characteristics of an earth station HPA and the other being a new soft‐limiter linearizer (SL‐LRZ) followed by an amplitude limiter. The symmetric construction of the MIC linearizer is easily implemented with MIC techniques, operates over a wide frequency band and its nonlinearities can be controlled electrically. Also, the transfer characteristics of a TWTA with SL‐LRZ are such that its amplitude response is linear up to saturation, it maintains constant output level beyond saturation and phase shift is not likely to occur. The TWTA with SL‐LRZ can reduce intermodulation products due to nonlinearities of the TWTA in amplification of multiple carriers and can improve transmission performance when a band‐limited PSK signal is amplified at close to saturation. The test‐fabricated SL‐LRZ is sufficiently small and lightweight for on‐board application.
Channel multiplexers for broadcasting satellite transponders in the 12 Ghz band
Authors: Member Toshihiro Nomoto, Regular
Published: July 2007

This paper describes the design and development result of high‐power (over 100 W) channel multiplexers for broadcasting satellite transponders in the 12‐GHz band. The input multiplexer which requires steep attenuation characteristics consists of two light‐pole canonical dual‐mode filters with an orthomode T‐shaped junction suitable for waveguide manifolds. Attenuation at adjacent channel edges AP is 40 dB, insertion loss at channel center A0 is 1.4 dB, and amplitude variation AV = 0.6 dBP‐P. The output multiplexer which requires low insertion loss consists of four‐pole longitudinal dual‐mode filters. To decrease insertion loss, several considerations are applied such as use of the TE113 mode, optimization of coupling apertures and materials of tuning screws. The characteristics of a fabricated four‐channel multiplexer (A = 15 dB, A0 = 0.6 dB, AV = 0.3 dBP‐P) are shown to be unchanged in the thermal test. These multiplexers can satisfy the necessary characteristics required to channel multiplexers for high‐power broadcasting satellite transponders in the 12‐GHz band.
Arrangement of sources in the charge simulation method–the case of e‐wave scattering by one perfectly conducting cylinder of convex cross section shape
Authors: Komiyama Akira
Published: July 2007

The charge simulation method has the following characteristics compared with other approximate methods for the scatteirng problems: (1) Only the zeroth and first‐order Hankel functions are used; (2) no processing of the singularities on the boundary is needed; (3) no numerical integration is necessary. As a result, it is an extremely simple method. However, the arrangements of the sources and contour points are arbitrary and such arrangements affect the accuracy of the approximate solutions. Previously, the source arrangements by the boundary contractions have been used in the charge simulation method. This choice provides good results if the shape of the scatterer is close to a circle or is a circle itself. The accuracy becomes poorer as the shape deviates more from the circle. Also, it is not possible to determine beforehand the arrangement that provides the best result. Hence, the boundary contraction is an important arrangement method. In this paper, arrangement of the sources and contour points is determined by means of the conformal mapping that transforms the boundary to a circle. Numerical calculations have been performed for typical convex shapes. It is found that the charge simulation method based on the present arrangement has the following properties. It exhibits much better accuracy than the arrangement by boundary contraction. The arrangement minimizing the error is found from the conformal mapping. Scatterers with edges on the boundary cannot be analyzed.
Cascade‐connected echo canceller
Authors: Takahashi Kenzo , Members Takashi Sakamoto Regular
Published: July 2007

Echo cancellers are used in telephone channels with long propagation delay to prevent speech quality deterioration due to echoes. The circuit structures of conventional methods tend to be redundant to meet the various cases of near‐end delay predicted in a real channel and to correct impedance mismatching at 2/4‐wire transform points. This paper proposes an echo canceller composed of m cascaded echo canceller units. It can accommodate an echo path delay m times the maximum near‐end delay accommodated by a unit circuit. By adapting the size of the circuit unit to VLSI fabrication and choosing the proper value of m, an echo canceller composed of single‐kind units and with little redundancy can be constructed. As a result, miniaturization and economization are achieved. This paper discusses the construction method of a unit circuit, the procedure of cascade connection, the operation principle and its performance. The experimental results are also shown.
Nonstationary analysis by bpes (backward prediction error space)
Authors: Kiryu Tohru , Iijima Taizo
Published: July 2007

This paper describes a method of non‐stationary analysis based on the geometrical orthogonal projection with least‐squares estimation for a linear model. In the past, local stationary analysis and adaptive methods which successively estimate the parameters have been used for this purpose. However, in application to the nonstationarity case as in biomedical signals these methods have the disadvantage that it is difficult to see the physical significance of the parameters. In consideration of this, the present paper defines the backward prediction error space (BPES) consisting of the backward prediction error vector in each dimension and proposes to handle the nonstationarity by expanding the property into the orthogonal states in each dimension. The backward prediction error vectors constitute an orthogonal system in the least‐squares estimation and the reflection coefficient is the parameter directly related to this system. The orthogonality can be interpreted in direct relation to the independence of physical functions. As a measure of the nonstationarity, the angle between the vectors is adopted in the BPES. When the parameters which were optimum in the stationary interval are applied to an arbitrary interval, the angle is an exact expression of the discrepancy due to the nonstationarity. By an example of analysis of biomedical signals it is verified that the angle is useful in evaluation of the nonstationarity, especially of that arising from the change of orders. Thus, it is anticipated that the deterministic nonstationary analysis by BPES will provide new information about biological systems.
Differential companding PCM (DC‐PCM) by removed bit accumulation
Authors: Takahashi Susumu , Tanaka Masanori , Kameda Hiromi , Kanzaki Hiroyuki
Published: July 2007

A new PCM transmission system is proposed. At present, near instantaneous companding is being considered as one of the PCM sound transmission methods for satellite broadcasts. Its quality performance and efficiency, however, are not satisfactory in every respect. The system proposed in the present article combines differential PCM with a near instantaneous companding capability. By combining the advantages of both methods, a very remarkable improvement is achieved in the lower frequency signal band and high transmission efficiency is realized at the same time. It is not enough merely to combine differential PCM with near instantaneous companding because bit removal during compression results in difficulties in transmission or signal restoration. This problem has been solved by the so called removed bit accumulation method. In this way, the two techniques can be united, resulting in a dramatical reduction of quantizing noise. This paper explains the principle of this system, describes its features and performance, based on the results of computer simulation and of measurements made on an experimental equipment, and discusses its operation. Comprehensive subjective tests have also been performed and the results demonstrate that high quality sound transmission is achieved even by an 8‐bit transmission channel. Also, the realization of the equipment is fairly simple.
Length dependence of cutoff wavelength for single‐mode fiber
Authors: Kitayama Yoshinobu , Tanaka Shigeru
Published: July 2007

The effective cutoff wavelength of single‐mode fiber cable cannot be completely determined because the bending loss, which prevents propagation of the second‐order mode, depends upon the bending distribution of the fiber as well as on the length and index profile of the fiber. By measuring the bending loss of the LPn mode of step‐index single‐mode fiber, it is found that the effective cutoff wavelength of reel‐wound fiber shifts to lower wavelengths along the distance. The length dependence is proved by experiment and agrees well with the theory. The length dependence of the cutoff wavelength of optical cable is estimated by experiment and it is established that the effective cutoff wavelength can be prescribed by the microbending profile and, compared with the value given by the conventional bend method of a 2‐m sample, the decrease in effective cutoff wavelength for 1‐m cable is estimated as 0.1 um. If this length dependence is used, it can be applied in long‐distance systems provided a fiber having longer cutoff wavelength and favorable.bending loss characteristics or low dispersion is used.
Tree encoding of images using a nonlinear smoothing filter
Authors: Handa Shiro , Tanaka Hatsukazu
Published: July 2007

The DPCM system is often used for encoding images, but particularly in low‐rate encoding methods, two types of noise of different nature (e.g., overload noise and granular noise) are introduced. In this paper a tree encoding scheme is applied to image signals and a design technique for an encoding filter is shown which is a combination of a least‐mean‐square filter derived from linear prediction theory and a nonlinear smoothing filter. The purpose of this nonlinear filter is to decrease the above‐mentioned noise. Its construction is like that of an adaptive quantizer in which one of the preassigned output levels is selected, keeping in view the previously encoded symbols. The linear smoothing filter used in tree encoding of speech is a special case of this sytem. Moreover, the conditional mean output level for the present encoding symbol matches the output level of the Lloyd‐Max quantizer for the Laplacian density function. The results obtained by applying this scheme to a head and shoulder image having clear boundaries are compared with the results without using a nonlinear smoothing filter and improvement of about 2 dB in SNR is obtained when the encoding rate is 1 bit/pixel.
A proposition of the load‐dispersion routing method in telecommunication networks and its evaluation
Authors: Kawarazaki Masatoshi
Published: July 2007

This paper proposes a load‐dispersion routing method as an improvement over the conventional alternate routing method. In this routing method, a part of the load is offered directly to the second route when the first route is overloaded and the overflow traffic of the rest of the load from the first route is offered to the second route. This is based on the property that the less bursty the offered traffic is, the less loss probability it experiences. It is shown that under this routing method the network throughput can be increased without any notable deterioration of first‐route traffic over the alternate route.

The method of removing one out of K calls is considered and it is shown that the burstiness (peakedness) of dispersed traffic and overflow traffic is reduced. Furthermore, two traffic models used for the evaluation of this method are analyzed. That is, an accurate analysis is made of the overflow characteristics of the M‐Efe/M/S/S model (input to the loss system is Poisson with one out of K cells removed periodically) and the Eg + H2/M/S/S model (input to the loss system is a mixture of generalized‐Erlang and hyper‐exponential inputs).
Study of spurious solutions of finite‐element method in the three‐component magnetic field formulation for dielectric waveguide problems
Authors: Koshiba Masanori , Hayata Kazuya , Suzuki Michio
Published: July 2007

The cause of spurious solutions, which are included in the earlier finite‐element formulation of the three magnetic field components, is discussed. To eliminate these spurious solutions, a new functional is proposed. In the finite‐element analysis using this new functional, earlier spurious solutions do not appear but new ones appear. Reasons are given for these phenomena. The new spurious solutions are equivalent to the TE modes of “hollow” waveguides and their appearance is limited to the “fast‐wave” region. Therefore, if one is interested only in the solutions in the “slow‐wave” region which correspond to the surface‐wave modes of dielectric waveguides, the appearance of new spurious solutions is not a serious problem. The finite‐element program based on the new functional is coincident with that based on a Galerkin procedure. This fact proves the validity of both finite‐element programs.
A state equation approximation for a multi‐input/multi‐output system
Authors: Tomiyama Shigenori , Kojima Norio , Matsuura Takenobu , Shinozaki Toshio
Published: July 2007

This paper discusses the problems associated with the state equation approximation of linear shift invariant systems when a multi‐input/multi‐output system is given. First we present the approximation method to obtain the state equation for the system and then we present a method for stabilizing a rational function which is not physically stable. By iterative application of the approximation method we can always obtain a controllable, observable and physically stable system.

The approximation method presented in this paper first considers a system which has multiple inputs and one output sequence and then makes minimum‐order estimates of the sequences to the desired precision and arranges the output sequences in increasing order. We then approximate the state equations which satisfy the output sequence of lowest order and the multiple input sequences. This is a method of approximating the state equation for the second and subsequent output sequences by effectively employing the state variable already obtained. If at the approximation stage a physically unstable rational function is obtained, one can use the technique of first shifting the pole to form a stable function and then determine the coefficients of the numerator polynomial so as to minimize the squared sum of the errors in the output sequence.
Outer electromagnetic field of helical coaxial line with regard to earth effect
Authors: Suzuki Mitsunori , Chiba Jiro , Hosono Toshio
Published: July 2007

This paper describes theoretically and experimentally the outer electromagnetic field of the two‐layered helical coaxial line which is constructed on the ground. First, the relationships between a transmission constant, material, and the structural parameter of the two‐layered helical coaxial line were formulated. Then the outer electromagnetic field was presented with a coupling impedance defined in each E and H mode. Although the effect of earth conductivity can be expressed with an equivalent current image of the earth, this paper proposes a new approximated formula, which can be applied to a surface wave mode having a large effective wavelength ratio. The H‐mode has a smaller effect due to the earth conductivity compared with the E‐mode. Thus it is obvious that large magnetic permeability of a magnetic core which excites the H‐mode is effective in the enhancement and stabilization of an electromagnetic field. The convergence of an electromagnetic field along a line which is the feature of the two‐layered helical coaxial line and the effectiveness of the approximated formula in this paper, were confirmed by the experiments taken for an externally constructed long line.
Characteristics of quasi‐monomode fibers
Authors: Yamauchi Ryozo , Sugawara Yasuyuki , Murayama Toshiyuki
Published: July 2007

In monomode fiber the attenuation of higher order modes is much larger than that of the dominant mode near the cutoff wavelength. Therefore, in practice, the wavelength region in which only the dominant mode propagates is extended toward the shorter wavelength. A fiber used in the region in which two LP modes can theoretically propagate is called quasi‐monomode fiber. This paper investigates the characteristics of the quasi‐monomode fiber for application to communication channels. The behavior of the two modes near the cutoff wavelength is studied. The transmitted pulse waveforms, the effective cutoff wavelength and microbend loss are investigated. Based on the results, conditions for effectively preventing multimode dispersion are found even when coupling exists between these two modes. These conditions include the difference in loss factors, the coupling coefficient between the two modes and the relation between the fiber junction distance and the transmission distance. A measurement method is proposed for the coupling coefficient. It is shown that coupling of the two modes due to microbends, which are important for cable fabrication, creates increased loss not strongly dependent on the wavelength. Dependence of the effective cutoff wavelength on fiber length is clarified. It is shown that the effective cutoff wavelength of an entire length of cable can be estimated from a short sample.
A 3‐port ferrite resonator circuit using slot line
Authors: Ohwi Koichi , Okada Fumiaki
Published: July 2007

This paper proposes a magnetically tuned 3‐port circuit having simultaneously a resonant characteristic and a nonrecriprocal property. In this circuit, a ferrite resonator is placed on the metal conductor side of a slot line on a dielectric substrate and an additional port is created that couples with the resonator. The S matrix of the circuit is derived. The relation between the electromagnetic field and the external Q of the resonator is found and the electromagnetic field distribution of the slot line is calculated. From the calculated results, it is found that there exists an optimum location for the ferrite loading and that the present circuit can be used in a broadband operation. The frequency characteristic and the nonreciprocity are experimentally confirmed. The present circuit has a simple configuration and can be used for a magnetically tuned oscillator that does not require an isolator to eliminate the effect due to load variation.
A theoretical study of recognition of moving objects by monocular vision
Authors: Maruyama Minoru , Amari Shun‐Ichi
Published: July 2007

It is assumed that a human recognizes the movement and 3D‐structure of an object based on the feature quantities and their changes extracted from the retinal images which are the projection of the three‐dimensional object onto the retina. Human recognition of a moving object works as follows. First, primitive recognition takes place based on the change of feature quantity at the local areas corresponding to each small portion on the retina independently. This is local parallel information processing. Second, attention is shifted to the higher level of recognition which integrates all the local primitive recognition. This paper considers the local linear feature of the object. In other words, we consider the infinitesimal plane of the surface of the three‐dimensional object, and we clarify the transformation of the two‐dimensional image caused by the motion of the object. This transformation depends on both the motion of the object and the three‐dimensional structure. Also, we clarify the law of the transformation of the linear features obtained from the image. Based on the above, we show that recognition of the motion of the object and the three‐dimensional structure is possible without the need for identifying the corresponding points. In addition, we demonstrate the condition which the characteristic functions should satisfy, and the concrete computation methods to obtain the motion and the three‐dimensional structure are given.
Simplicial homotopy method for the solution of nonlinear two‐point boundary value problems
Authors: Yamamura Kiyotaka , Oishi Shin'Ichi , Horiuchi Kazuo
Published: July 2007

Homotopy methods are useful in determining the solution of nonlinear equations from a remote initial point. Numerous studies have been made to apply the methods to the numerical solution of nonlinear two‐point boundary value problems. However, the method has a disadvantage in that the execution speed is degraded greatly with the increase of the dimension of the system of finite difference equations. This paper proposes an efficient numerical method for the solution of nonlinear two‐point boundary value problems, based on the simplicial homotopy method and the decomposition technique. It is shown first that the system of equations to consider can always be reduced to the system of equations with lower dimension, by applying the decomposition technique to the system of finite difference equations. By this technique, the computational complexity of the algorithm can be decreased drastically compared with the traditional methods. Then an efficient mesh refinement strategy is proposed, taking into consideration the accuracy of the simplicial approximation. Finally, the theorems concerning the convergence of the method are presented and verified by numerical examples. The results are compared with those of the traditional methods, indicating the effectiveness of the proposed method.
Space and frequency correlation characteristics of L‐band multipath fading due to sea surface reflection
Authors: Karasawa Yoshio , Shiokawa Takayasu
Published: July 2007

When maritime satellite communication is conducted at low elevation angles, fading due to sea surface reflection becomes a problem. For suppression of the fading, space diversity and frequency diversity may be employed. This paper studies the correlation characteristics of multipath fading due to sea reflection in the spatial and frequency domains in L‐band operation. This is important in investigating the diversity effect. First, from the theoretical model of sea surface reflection, the correlation scattering cross sections of the coherent and incoherent components of the reflected wave are obtained. Next, from numerical calculations, the correlation characteristics are obtained with the antenna elevation angle and the height over the sea as the parameters. It is found that in space diversity good diversity effects can be expected from two antennas‐ separated in the vertical direction by about 40 cm. It is also seen that fading reduction cannot be expected with frequency diversity in the case of narrowband communications such as in maritime satellite communications. The effects of various fading reduction measures in the up and down links are considered.
Design and characteristics of sector/cosecant‐square shaped beam antenna
Authors: Yamada Takashi , Kagoshima Kenichi , Itami Yuji
Published: July 2007

The base station antenna for a subscriber radio system is required to have a beam with sector section in the horizontal plane and cosecant‐square beam in the vertical plane. This paper proposes a method for shaping the reflector surface of the antenna so that it forms the required beam in the two planes and also presents the experimental results for a test antenna. It is shown that adequate characteristics can be obtained by this shaping method even for a single reflector. In this method the central cross‐section curve obtained as a solution of a two‐dimensional problem is used as the initial condition and then the reflector coordinates are successively determined from the conditions of the elevation angle of the ray reflected at the surface. The test antenna is a 90° sector beam antenna with aperture of about 52δ in the vertical plane and about 43δ in the horizontal plane. The experimental results indicate a gain of 23.5 dB at the peak and more than 20 dB within an angle of 1.5° in the vertical plane. The antenna beam realizes a sectoral section in the horizontal plane and a cosecant‐square section in the vertical plane to a level as low as ‐10 dBi. The results demonstrate the effectiveness of the present reflector shaping method.
Steady‐state clock phase behavoir in loosely coupled master‐slave synchronization network
Authors: Kihara Masaml , Makino Masatoshi
Published: July 2007

In the Japanese master‐slave synchronization network, the introduction of the cesium atomic beam frequency standard as the master office oscillator for improving the frequency accuracy, and the introduction of a loosely coupled synchronization network using the digital processing type phase‐locked oscillator to improve the clock reliability, are scheduled. An analysis is made of the clock phase behavior of a multi‐link digital clock supply in the steady state. The influence on the clock phase variation by transmission line jitter and DCS (digital clock supply) temperature dependence is considered. The results are expressed by two‐sample variance ßy2(±) which shows short‐term frequency stability, and then by time interval error (TIE) which shows phase fluctuation in the time domain. The results obtained from numerical calculation give maximum TIE of the distributed clock in the domestic 9‐linked DCS (about 25 μs) and a permissible synchronization network within three links for international digital connections by comparison with the TIE recommended by CCITT.
A solution concept in a cooperative n‐person game based on the complaint differences and its application
Authors: Sakawa Masatoshi
Published: July 2007

This paper proposes a new solution concept, based on the minimization, following the lexicographical order, of the complaint differences among coalitions in a cooperative n‐person game in characteristic function form. Such a solution minimizing the maximum complaint difference can be obtained as the pay‐off vector as the inequality constraints sequentially. A discussion is made on the pay‐off vector, which minimizes in the lexicographical order the complaint differences, taking the characteristics of the coalitions into consideration. Then as a method which can solve the formulated linear programming problem with less computational burden, an algorithm involving the relaxation method is proposed. A computer program was constructed and is applied to the cooperative water resource development program.
Steady state analysis of oscillatory circuits with harmonic components by volterra series
Authors: Ichikawa Satoshi , Shyakuda Yukio
Published: July 2007

Chua and Tang reported a method based on the Volterra series to find the amplitude and frequency of the unknown fundamental wave component of a steady‐state oscillation resembling a sinusoidal wave generated in a self‐starting oscillation circuit. In the present paper, the method is used to find the higher‐order terms so that the harmonic components generated from the term related to the determination of the fundamental component can be found relatively easily. Formulas for the determination of such quantities are derived. Next, this method is used for the analysis of the van der Pol oscillator for which the detailed nature of the solution is available. The validity and the limitation of the application are studied. From the results, it is shown that reasonably accurate solutions can be derived for an oscillation waveform close to a sinusoid as well as a distorted one containing harmonic components. In this method there is no need to derive the differential equation for the oscillator. Insteady, only the algebraic equation found from the circuit diagram must be solved. Finally, this characteristic is used for analysis of an RC phase shift oscillator.
Tracking performance of improved delay‐lock loop
Authors: Hasegawa Takaaki , Nakagawa Masao , Wakabayashi Kunihiko
Published: July 2007

A PN (Pseudonoise) code is often used for ranging systems, measurements or clock transmission, etc. Signal transmission using the PN code is effective even at low SNR. The delay‐lock loop is an effective circuit to detect PN code in such large noise, and is used widely. However, in the discriminator characteristic of conventional DLL, the range where the loop control signal can be gained is extremely narrow. Therefore, if the loop once loses lock for noise or for any reason, a large time is required for resynchronization. To compensate the fault of DLL, this paper proposes the improved DLL (IDLL‐1) with extended range of discriminator characteristic. Tracking performances are evaluated theoretically for a first‐order loop, and experimentally for a second‐order loop. Furthermore, the more improved DLL (IDLL‐2), which consists of IDLL‐1 and simple circuits, is proposed. Performance evaluation is done by experiments and simulations.
Recursive ldentification algorithm based on gradient method with application to adaptive bit detector
Authors: Adachi Shu‐Ichi , Sano Akira
Published: July 2007

Because of its rapid convergence the recursive least squares (RLS) method is one of the most popular approaches to adjusting the coefficients of adaptive digital filters. The RLS method is, however, not always effective in practical applications where finite input‐output data are used because it is based on the matrix inversion lemma. The purpose of this paper is to present a new recursive algorithm to obtain the least square estimate of digital filter coefficient parameters on the basis of a finite number of data up to the present by incorporating a gradient approach in solving the normal equation. Although the proposed method is recursive, since it obtains the least square estimate by batch processing of data, it has batch processing merits which are not found in RLS, such as robustness against colored input and noise and smooth convergence to the real value. A method of automatically adjusting the tracking characteristic to time‐variable parameters is described and the effectiveness of this method is examined for the configuration of the FIR adaptive digital filter and the adaptive configuration of the bit detector.
System theoretical consideration on n‐point padé approximation
Authors: Horiguchi Kazumi , Hamada Nozomu
Published: July 2007

In the field of system modelling, circuit synthesis and filter design, it is very important to approximate a given characteristic function by a rational function of an appropriate order. Padé approximation has been known for a long time and is one of the rational function approximation methods used extensively because of its simplicity. This paper proposes to investigate N‐point Padé approximation which is an extension of Padé approximation, from the system‐theoretic viewpoint. The N‐point Padé approximation is a rational function interpolation including the derivative of arbitrary order and, compared to regular Padé approximation and rational Hermite interpolation, it can cope with more diverse demands. In this paper we discuss the following subjects on rational function approximation of given characteristic function: its explicit form, minimal order realization problem, Nuttall's compact form, its relation to continued fractions, and the numerical efficient iterative algorithm. These are more general discussions, even including regular Padé approximation. Also, we give numerical results of the approximation of a transfer function for continuous and discrete systems as an example of application of N‐point Padé approximation.
The volterra series expansion of functionals defined on the finite‐dimensional vector space and its application to saving of computational effort for volterra kernels
Authors: Watanabe Atsushi
Published: July 2007

The Volterra series can be used as a model for a wide range of nonlinear dynamical systems. However, it requires a large amount of computation to determine its kernel from the observation of the input and output of the system. If the input is a white Gaussian signal, the Volterra series can be represented by an expansion using Wiener's orthogonal series of functionals. In that case, numerous methods have already been proposed to reduce the computational complexity utilizing the white gaussian property of the input signal and the orthogonality of the functional series. These methods cannot be applied, however, to the system receiving general input. This paper considers first the space of all functionals defined on the general set of discrete functions, and constructs the set of base functionals spanning that space systematically from the family of linear funtionals with the orthonormal set as the kernels. Then the functional model for the discrete nonlinear system to be measured is determined as a finite‐dimensional approximation in the previously derived functional space. A method is derived to calculate the approximate Volterra kernel. The relation of the proposed method to the multiple correlation function method, which has been used widely as a standard method to determine the kernels, is discussed. Assuming the white gaussian input, the computational complexities are compared, indicacing that the proposed method is far better in reducing the complexity, especially for kernels of higher dimensions.
A consideration on optimum direct detection optical communication receiver
Authors: Hata Masato , Morinaga Norihiko , Namekawa Toshihiko
Published: July 2007

This paper presents an optimum receiver for direct detection/binary intensity modulation optical communication systems. Here, the signal‐plus‐noise model assumes a signal‐dependent nonstationary Gaussian random process. Moreover, assuming white noise and an ideal low‐pass receiver, the receiver vector is generated by sampling of signals and noise. The likelihood ratio for this receive vector is derived based on the maximum likelihood test to determine the structure of optimum receiver. This paper shows that the optimum receiver has both the usual correlation detection for additive noise in the radio wave region and noise energy detection for the signal shot noise. Next, the error rate of this receiver is derived theoretically and its characteristics are evaluated. As a result, the signal shot noise can be effectively utilized for signal detection by allowing a greater bandwidth for the receiver, elucidating treatment of the shot noise from the standpoint of statistical signal detection theory.
General solution for orthogonal periodic real‐number sequences
Authors: Tanada Yoshihiro
Published: July 2007

This paper shows the general solution for the real‐number periodic sequence with an autocorrelation function with zero side lobe, aiming at the application to the spread‐spectrum communication. The general solution is derived by representing the autocorrelation function by a Fourier series and utilizing the components. The solution contains the phase constant. In other words, the sequence and the phase constant are related through the discrete Fourier transform Under the condition that the seqeunce is real, the phase constant is an odd function. However, when the phase constant takes only the value in {O, π}, the phase constant is an even (= odd) function, and the sequence is an even function. From the general solution, it is shown that N sequences obtained by shifting a sequence of order N are orthogonal. An example of the sequence is shown for the case where the phase constant is fixed as φ k E {0, φ }, φk = 2πk3/N (k = 0, 1, ‥, N ‐ l), and for the case where it is continuous as Phiv;1=‐ φ N‐1= θ. The general solution provides a basis for calculating various kinds of pseudonoise sequences.
Successive approximation vector quantization
Authors: Yamada Yoshio , Tazaki Saburo
Published: July 2007

This paper presents a new “ordering” based suboptimal vector quantization, the successive approximation vector quantization (SAVQ). It is found that the SAVQ algorithm can be reduced to the bit arrangement mapping from vector to scalar followed by the scalar quantization. Therefore the SAVQ requires no calculation of distortion. However, the tree search vector quantization (TSVQ), another suboptimal VQ, does require calculation of distortion. This allows the real time vector quantizer to be implemented with significantly less hardware complexity than TSVQ. For the source with exponential density, the simulation results demonstrate that SAVQ provides the mean‐squared‐error equal to or less than that obtained by TSVQ.