bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation pattern analysis of reflector antennas
Authors: Ando Makoto 
Published: July 2007

AbstractA method is proposed for accurately calculating the radiation pattern of reflector antennas in the entire angular range from the main beam direction to the off axis region. The principle of the method is similar to the physical optics diffraction theory, and consists of the result obtained by conventional physical optics corrected with the contribution from the edge current calculated by the geometrical theory of diffraction. However, the edge current is expressed in a simple form by means of a local coordinate system defined by the peripheral line and the mirror normal at each edge point and of the incident electromagnetic vector components in reference to this coordinate system. Therefore, it is possible to treat an arbitrarily shaped mirror surface and an antenna with a primary radiator using an arbitrary pattern. It is confirmed that the results obtained by the present method approach those obtained by the physical optics method near the main beam and those obtained by the geometrical theory of diffraction at the off axis. Accuracy is tested by applying the present method to the problem of diffraction from a circular disk for which a rigorous solution exists. The present method makes unnecessary the distinction of the use of physical optics (main beam) and the geometrical theory of diffraction (off axis) performed so far, in an empirical manner. It is possible systematically to obtain the pattern near the first‐third side lobes where two methods may be connected.
Linear programming design of IIR digital phase networks
Authors: Sugahara Kazunori 
Published: July 2007

AbstractThis paper demonstrates that the IIR digital phase network can be designed by linear programming. The phase network is used not only to compensate the phase distortion of the signal by the filter, but it is used also in various other problems in communication area. In particular, the network with chirp characteristics is well known. There are IIR and FIR digital phase networks, but it is difficult to design completely flat amplitude characteristics for the latter. The design problem for the IIR digital phase filter has been considered as a nonlinear programming problem. By reducing this problem to that of linear programming, the optimal solution can be obtained, if it exists, without any particular consideration for the convergence of iteration or the initial values. This paper also discusses the order of the digital phase network so designed, and it is shown that the order is determined from the given design specifications. Finally, several design examples are illustrated, indicating that the proposed method is effective.
Speech analysis‐synthesis system and quality of synthesized speech using mel‐cepstrum
Authors: Kitamura Tadashi , Imai Satoshi , Furuichi Chieko , Kobayashi Takao 
Published: July 2007

AbstractThe quality of synthesized speech in the speech analysis‐synthesis system based on the mel‐cepstrum method is described. Mel‐cepstrum is defined as the Fourier coefficients of the log spectrum on a nonlinear frequency scale approximating the mel scale. The true mel‐log spectral envelope is estimated in this system by an improved cepstral method in the analysis part and a mel‐log spectrum approximating filter is used in the synthesis part. The preference score by pair comparison tests is used for subjective evaluation and spectral distortion on a nonlinear frequency scale is used for an objective evaluation. Using this system, 1.7 kbit/s, high‐quality synthesized speech is obtained.
Fast search algorithms for vector quantization in orthogonal transform domain
Authors: Nakaide Hiroshi , Aizawa Kiyoharu , Harashima Hiroshi 
Published: July 2007

AbstractTo realize fast search at vector quantization applied to high‐efficiency coding of signals, we propose a partial distance algorithm and a nearest‐neighbor search algorithm, both in the orthogonal transform domain. These algorithms provide efficient search for signals such as, for example, picture signals which have a concentration in the transform domain power distribution. Further, we propose a nearest‐neighbor search algorithm in orthogonal transform domain with component selection which is effective also for memoryless random information sources with Gaussian distribution.The proposed algorithm is applied to vector quantizers of picture signals, separating‐mean‐normalized vector quantizers, and vector quantizers of memoryless Gaussian sources and its efficiency is demonstrated for these cases. Particularly, in the case of vector quantizers of picture signals, it is shown that the proposed method requires fewer multiplications to determine the optimum reconstructing vector than the conventional tree search algorithm.
Sign structures of 3 × 3 stable matrices and their generalization to higher‐order matrices
Authors: Miyamichi Juichi 
Published: July 2007

AbstractA matrix A is called stable if all its characteristic roots have negative real parts. This paper discusses the stability of sign matrices (matrices for which only the sign of the elements is given) and presents some basic sign patterns of stable matrices. The stability of a matrix and the stability of a system whose interaction matrix coincides with the matrix are related closely and thus the sign pattern consideration is a useful method to study the internal structures of stable systems. We discuss the potential stability (the property that there exists a stable matrix with the sign pattern) and the sign instability (the property that there are no stable matrices with the sign pattern) of sign matrices. A signed digraph is defined for each sign matrix and the connection between its structure and the matrix stability is discussed. Methods to check potential stability and sign instability of sign matrices are given. Through the computer stability check of all 3x3 matrices, the relationships between graph structure and matrix stability are clarified and seven basic sign structures of 3x3 stable matrices are obtained. Finally, based upon these seven basic structures, potentially stable structures of higher‐order matrices are considered. Some stable sign patterns of nxn matrices together with their stability proofs are given.
Analysis of transient response of electromagnetic waves scattered by a perfectly conducting sphere. The cases of back‐ and forward‐scattering
Authors: Hosono Toshio , Yuda Kouhachi , Itoh Akira 
Published: July 2007

AbstractTransient responses of back‐ and forward‐scattering are analyzed by a perfectly conducting sphere. For numerical calculation the numerical inversion of Laplace transform (FILT) developed by Hosono was used. The truncation error for the transient response of the scattered fields was examined by increasing the number of modes of the electromagnetic fields and the number of terms in the FILT method. Based on these results we confirmed that we could control the accuracy of numerical calculation for transient responses of the scattered fields. In this paper the relative error of the results of calculation is maintained less than 2 percent.The results of analysis are shown mainly for far fields. When the incident wave was a half‐sine pulse, we obtained the following results: (1) the creeping wave was confirmed to exist in transient responses of back‐scattering; (2) the transient responses of forward‐scattering observed at a far point had waveforms which were nearly the derivatives of the incident waves; (3) the waveform of the near field was examined in detail to confirm that the result of the foregoing item (2) was not in violation of the causality law.
Null synthesis based on the principle of pattern multiplication
Authors: Inagaki Naoki 
Published: July 2007

AbstractIn this paper we propose a new method for an economical and realizable null synthesis to prevent interference between wireless communication lines and mixing with interfering waves. Existing methods are based on the principle of a subtraction of the directivity of a cancelling beam which has a maximum value along the prescribed null direction from that of the original array. These methods cannot avoid a degradation of the directivity in directions other than the null direction.In this paper we have applied the concept of an array of the arrays. We have synthesized nulls by the array factor of an (M + 1) element array which has M nulls in the directivity of an N element array. In total, we used M + N elements for the array. This method depends on the principle of the products of directivities.As long as the null direction is far removed from the main beam direction, there is, in principle, no degradation of the array directivity. By approximating element weights, we can synthesize nulls by controlling the weights of only terminal 2M elements. Past methods have noted experimentally a possible null synthesis by controlling the weights of the terminal elements.This paper provides clearly for the first time its theoretical reason and limits. We have applied the present analysis method for cases of Taylor directivity for the side‐lobe level ‐30 dB for n = 5 in a linear array with elements placed one‐half wavelength apart. We show calculations in examples for syntheses of cases of one null and two nulls. We found that by synthesizing two symmetric nulls with respect to the main beam, there was almost no degradation of the array directivity.
Near field monitoring system for the dsb d‐vor
Authors: Tanaka Shuichi , Nihei Shiro , Nagaoka Masashi 
Published: July 2007

AbstractOf the VORs providing directional information to aircraft, the new DSB‐type Doppler VOR has recently been employed as the domestic standard. In this system, the required receiving signal is obtained in the far field whereas the received signal is distorted if it is received near the VOR station. On the other hand, when a VOR station is installed, it is difficult to secure a larger area than the present one because the acquisition cost of the land is high and selection of the land becomes even more difficult if the traditional land requirement is modified. Therefore, the receiving antenna for monitoring the operating condition and the performance of the equipment is often installed near the VOR antenna so that the signal can be distorted for accurate monitoring unless an appropriate distance is maintained.This paper studies a method in which the DSB‐type Doppler VOR can be monitored even if the receiving distance is short. The circuit configuration is complicated in the method in which the phase of the carrier being received is forced to follow the phase change of the side band signal. Instead, this paper proposes a method for simplifying the circuit configuration by replacing the carrier wave with a new carrier with an appropriate fixed phase, and an experiment is carried out. It is found that the distortion is reduced significantly and a VOR direction characteristic close to the case for a far field reception even with a short receiving distance is obtained.
Block demodulation method for psk signal by sequential regression estimator
Authors: Ohsawa Tomoki 
Published: July 2007

AbstractThis paper considers the block demodulation method with carrier phase synchronization without preamble, and presents a proposal and evaluation for the new carrier phase synchronization method based on the sequential regression estimator. The block demodulation has a feature in that the traditional way of real‐time demodulation is not adhered to, and the preamble is not required. This improves greatly the throughput especially in a short packet communication.The traditional system is based on the least‐square scheme, noting that the cumulative carrier phase variation between data symbols is represented in a linear form. It has a problem in that the linearity is lost due to noise in deriving the cumulative value for the phase variation, which may greatly deteriorate the demodulation performance.The sequential regression estimator proposed in this paper is based essentially on the least‐square principle. However, the cumulative value is not determined for each time as in the traditional method but the estimation is updated based on the difference between the observed value and the value estimated from the data up to the previous sample. Consequently, the problem in the traditional system essentially is eliminated.Because of this elaboration, the computation in the proposed system is very small compared with traditional systems. It is seen as a result of simulation that the tolerable noise margin for 80 percent synchronizing probability, which has been used as the evaluation criterion, is improved by 11 dB for BPSK.In the satellite packet communications network such as VSAT (very small aperture terminal), the throughput is improved remarkably. Applying the proposed principle to the design of the present link, the time‐ratio, where the burst synchronization error is 1 percent or less in the Ku band, is 0.03 percent. In VSAT, a random access scheme is employed. Considering the burst collision probability of the access, it follows that the burst synchronization error probability of 1 percent does not affect the overall performance, and the proposal in this paper can be considered as sufficiently practical.
Diagnosing hang‐ups and automatic restoration for nodes in networks of ring topology
Authors: Fuwa Yasushi , Nakamura Yatsuka 
Published: July 2007

AbstractThis paper proposes a method to diagnose and restore automatically hang‐ups at the nodes connected into networks of ring topology and afterward reports the place where the hang‐ups occurred to an arbitrary equipment. Various measures have been taken to prevent hang‐ups from occurring at the nodes. These hang‐ups affect the network seriously when they occur, and it is important to determine and restore them immediately.The following method is introduced. Each node sends a mutual checking packet at regular intervals, and each node itself determines whether or not its hang‐up occurs from the result of receiving this packet and restores it. After restoration is completed, the node reports to the equipment connected with an arbitrary node the place where hangups occurred. This method has the following features:

It can be applied generally to networks of ring topology;
little hardware is needed;
diagnosing, restoration and reporting are done at each node. A special‐purpose control system is useless.
Multimedia burst‐type multiplexing based on fuzzy requirement
Authors: Sakai Yoshinori , Su Jing 
Published: July 2007

AbstractIn multimedia communication, the quality requirement from each medium to the network is not a definitive measure but usually contains a fuzziness. This paper represents, by a fuzzy set, the propagation delay of the network that can be tolerated by each medium and discusses the optimal burst multiplexing method for the required quality.First, various kinds of fuzzy quality requirements are examined, and it is shown that the quasi‐optimal quality measure is obtained in common with the control at the network node.Then based on the quasi‐optimal quality measure, two control methods at the network node are proposed: the variable priority and fuzzy priority methods. The performances of these methods are examined by numerical analysis and computer simulation, and the results are compared with those of the traditional control methods.Finally, it is shown that the variable priority method is better when the packet delay at each node can be measured, and the fuzzy priority method is better when it cannot be measured.
A self‐learning control of atm service quality using neural network
Authors: Hiramatsu Atsushi 
Published: July 2007

AbstractStudies of ATM network are conducted aiming at the integrated processing of multimedia. One of the important problems is to find a control method for the ATM network which can meet various types of requirements for the service quality arising from the diversity of sources connected to the network. For such a problem, the traditional approach by exhaustive analysis and simulation that has been used in the circuit switching network has a problem in that a large number of parameters to be considered in the ATM network complicates the control and it is difficult to deal flexibly with the diversity of sources and the change of traffic characteristics due to the new service.The leaky pattern table method is proposed which can realize a highly accurate control by learning from the data with small generation rate. As an example of application of the proposed method, the call admission control in the ATM node is considered. The detailed construction of the control system is discussed, and the proposed system is evaluated by computer simulation using a basic model.From such a viewpoint, this paper applies the neural network which can realize a high‐speed learning of the multiinput/multi‐output nonlinear function by back propagation to obtain the relation between the load in the ATM network and the communication quality by training. This network is used also to effect the learning control to deal flexibly with the change of the environment.
Crosstalk noise and signal‐to‐noise ratio characteristics for digital symmetrical pair cable transmission system in synchronous clock operation
Authors: Wataya Hideo , Ohtake Kohhei 
Published: July 2007

AbstractIn the digital transmission system using a symmetrical pair cable, the following problems arise in the application to the communication network.(1) The transmission distance and the system accommodation rate in the symmetrical pair cable are limited by the crosstalk noise. Consequently, it is necessary to evaluate the crosstalk noise in pulse transmission with synchronized clock frequency and to provide system design based on the evaluation.(2) In the application of digital transmission systems to city links and subscriber loops, a highly efficient system accommodation in the existing cable is required. Then the signal‐to‐noise ratio (SNR) of the system in the multiple crosstalk environment must be evaluated accurately.For the first problem, it is noted that the crosstalk noise is a cyclostationary stochastic process. It is shown that the peak value of the instantaneous noise power, which is an ensemble average over multipairs, gives the worst evaluation of the crosstalk interference to the systems with synchronous clock operation. A new method for noise evaluation is proposed based on the result.For the second problem, a general case is considered. In this case, the crosstalk noise of the cable in SNR evaluation of multiple crosstalk is composed of more than one subpopulation. The principle of SNR distribution is analyzed, and a method of calculation for SNR is proposed based on the average and variance. It is shown that the proposed method of SNR valuation can be used in the design of digital transmission system in a crosstalk environment.
Digital signal transmission characteristics in maritime satellite communications
Authors: Yasuda Yutaka , Ohashi Masayoshi , Sugaya Fumiaki , Okinaka Hideo 
Published: July 2007

AbstractDigital signal transmission will be used widely in the future mobile satellite communication system to realize an efficient operation of the system and to provide diversified service. In the global mobile satellite communication system, such as maritime and aeronautical communications where a wide service area is required, the influence of the multipath fading due to sea surface reflection at low elevation angle on the digital signal transmission characteristics is a particular problem.This paper deals with the application of the digital transmission system to the INMARSAT (International Maritime Satellite Organization), which provides the international maritime satellite communication service. The configuration of the digital maritime satellite communication system, which was developed for experimental purpose, as well as the result of analysis of the digital signal transmission characteristics in the low‐elevation maritime communication experiment, are presented.Based on the result of field experiment, the required power margin for low elevation operation is evaluated, and a means to secure a high‐quality communication is discussed. Thus, a guideline is presented for the digital transmission system design in mobile satellite communication, affected by the sea surface multipath fading.
A distributively controlled homogeneous self‐routing space switch network for large‐capacity cross‐connect systems
Authors: Obara Hitoshi , Uemattu Hitoshi , Okamoto Satoru , Matunaga Haruhiko 
Published: July 2007

AbstractThis paper presents a new construction of the distributively controlled homogeneous self‐routing space switch network, which is composed of single‐kind 2 × 2 unit modules. The feature of the proposed method is that the order is defined among the destination addresses according to their binary representation by the bitwise comparison. The bionic sort is executed based on the order.In the conventional space switch network composed of a single kind of module, the total number of unit modules is of the order of N2 at the minimum, where N is the number of I/0 ports. In the space switch network proposed in this paper, the total number of unit modules is of the order of (N log3 N). The total number of unit modules in the proposed method is equal to that of the conventional method for N ≦ 8 but is less for ′N≧16. When N = 1024, for example, the total number of unit modules in the proposed method is approximately one‐sixth that of the conventional method. Another point is that the processing speed within the 2 × 2 unit module is independent of N, as in the conventional method, and is small. This is advantageous in the high‐speed operation.
Calibration of antenna positions in millimeter wave interferometry
Authors: Morita Koh‐Ichiro , Ishiguro Masato , Kobayashi Hideyuki 
Published: July 2007

AbstractIn a radio interferometer, the error of the antenna position is one of the factors affecting significantly the synthesized map. We have developed a calibration method for the antenna position for the Nobeyama millimeter array. In comparison with the conventional method, the new calibration method has two significant characteristics. First, using the relative phase between reference celestial radio sources, the phase variation of a large time scale due to the atmospheric fluctuation and the receiver variation can be eliminated. Second, by means of the three‐dimensional discrete Fourier transform, one can estimate the antenna position errors without any ambiguity. With this calibration method, the antenna positions of the Nobeyama millimeter array were determined within 0.3 mm rms. As a result, directions of celestial radio sources were measured within 0.1 arcsec.
Two‐dimensional analysis for gain enhancement of dielectric loaded antenna with a ground plane
Authors: Sugio Yoshihiko , Makimoto Toshio , Tsugawa Tetsuo 
Published: July 2007

AbstractA gain enhancement is shown by loading with a dielectric plate of permittivity ϵrfor an antenna with a reflection plate placed parallel in front of the antenna. For an infinitely extended dielectric plate, for simplicity, a two‐dimensional problem with a linear current of a delta‐function type was treated. Fourier analyses and geometrical optics were applied and a detailed examination was made of the radiation characteristics, gain, the generation rate of surface waves and the near fields as functions of the separation distance between the reflection plate and the dielectric plate, thicknesstof the dielectric plate and ϵr. In particular, the radiated beam was directed toward the frontal direction (θ = 0) forh=mλ/2 andtr= (2n‐1)λ/4, (mandnare integers; λ is free space wavelength) for either TE or TM waves. The radiated power was multiplied by a factor of ϵrof the power by the antenna itself. Good agreement was obtained with experimental results.