bluuebunny/crossref_metadata_2025_split huggingface dataset:
On routability for channel routing problem
Authors: Shimamoto Takashi , Sakamoto Akio , Ushida Akio 
Published: July 2007

AbstractThe routing requirement in the channel routing problem for automatic wire routing in the interior of LSI is realizable if the constraint graph contains no cycle. Otherwise, the trunks for several appropriate nets must be divided into pieces. In this paper we modify a routing requirement with cyclic conflicts into one without them by dividing trunks into two parts. First we define a directed bipartite graph G to represent the routing requirement. A set of vertices in a strongly connected component in G is called a crowded set. It is shown that a routing requirement is realizable if there exists no crowded set in G. On the other hand, in the presence of a crowded set we define a method of dividing a net n contained in the crowded set into two subnets n' and n'' at some terminal position. If n' and n'' are not contained in any crowded set in the graph modified by division, we say that the division is effective. We then present a necessary and sufficient condition for the existence of effective division. Further, a semi‐effective division is defined to deal with the case where there is no effective division and then the routability for the channel routing problem is discussed.
A design technique for adaptive filter using lattice elements as adaptation modules
Authors: Kumazawa Itsuo , Iijima Taizo 
Published: July 2007

AbstractA lattice filter has several advantageous properties for adaptive applications. The gradual increase of the degree of estimation by the regular repetition of the adaptation module is particularly advantageous for hardware realization. In this paper, this adaptation module is called a lattice element and a method is proposed for the design of adaptive filters using such lattice elements. The efficiency of this method is demonstrated by the derivation of orthogonalizing and biorthogonalizing filters. The operation of these filters is tested by computer simulation and some problems arising at higher‐order filters are pointed out.
Analysis of electromagnetic wave scattered from cylinders buried in the ground
Authors: Tajima Katsusuke , Iiguchis Shin‐Ichi 
Published: July 2007

AbstractThe phenomena of scattering from an object buried in the ground have been analyzed in the case where the frequency is a few kHz. In such cases the displacement current is negligibly small and the scattering object is sufficiently smaller than the wavelength. On the other hand, recently a ground radar using an RF signal of several hundred MHz has been studied. At such high frequencies the scattering body to be detected is located at a relatively shallow depth and has a size of the order of wave‐lengths because the attenuation is significant. For low‐frequency applications Green's function for the structure with a ground surface does not cause numerical problems. For high‐frequency cases the computation time increases significantly. The integrand for Green's function varies substantially depending on the relative locations of the source, scattering object and observation point. In the present paper the computation time is reduced significantly by deformation of the integration path. When both the source and the observation point are close to the ground surface, the maximum value of the scattered wave computed with consideration of the effect of the ground surface is about (1 + R) times that with this effect neglected if R is the reflection coefficient of the ground to air. The effect of higher‐order scattering is found to be small.
Sets of cyclically orthogonal multilevel sequences derived from monomial phase
Authors: Tanada Yoshihiro 
Published: July 2007

AbstractThis paper derives a set of cyclically orthogonal sequences taking real multilevel values and having different waveforms, aiming at the application to the spread‐spectrum multiplex communication. The real cyclic orthogonal sequence is represented by the cosine function with the phase which is an odd function, and the cross‐correlation functions among sequences with the same or different lengths are discussed. By defining the convolution between sequences of the same length, a set of sequences with different waveforms and the same length can be derived. As examples of the set of sequences, the sets with length being prime number or compound number lengths are considered, which are obtained by forming convolutions of sequences with phases being monomial with odd power. Their properties are discussed. In the set of N sequences with the prime number length N, each of (N ‐ 1) sequence takes odd multilevels between 3 and N, and the cross‐correlation function between sequences is 1/√N times the sequence value. By forming the product of such sequences with different prime number lengths, a set of sequences with compound number lengths can be generated, which is a good compromise between the number of multilevels and the absolute maximum value of the cross‐correlation function. N ‐ 1 sequences of prime number lengths generated by the third‐order monomial takes 3 to N multilevels and their cross‐correlation function does not exceed 2/√N in the absolute value.
In‐house wireless optical digital SSMA
Authors: Yamauchi Yukiji , Sato Masashi , Namekawas Toshihiko 
Published: July 2007

AbstractWith the recent development of the office automation, portable in‐house terminals for data communication have attracted attention. For this purpose, wireless transmission by optical link is considered promising, since it does not require the installation of signal lines. The past discussions and experiments, however, considered only the one‐to‐one or one‐to‐many communications, but many‐to‐many, i.e., multiple connections were not considered. This paper aims at the application of the spread‐spectrum system to the wireless optical communication link to realize the multiple connections, and derives the basic theoretical expressions for the receiver characteristics. More precisely, the modulation scheme is selected taking the restriction into consideration, which is inherent to the inhouse wireless optical link. Then, the receiver error rate and the multiple connection characteristics of the proposed modulation scheme have been theoretically derived, providing the basis for the system design. Finally, a qualitative discussion is made on the construction and operation of the synchronous system for the proposed modulation scheme.
Performance analysis of a buffered CSMA/CD system
Authors: Tasaka Shuji , Ishikawa Hiroshi 
Published: July 2007

AbstractMost of the performance analyses of CSMA/CD systems have assumed that each user has a buffer space for only one packet. Using the technique of equilibrium point analysis, this paper analyzes the dynamic behavior of a slotted nonpersistent CSMA/CD system with a finite number of users, each of whom has a finite buffer space for more than one packet. Two schemes of packet transmission are studied: (1) once a user captures the channel, he continuously transmits all of the packets which have been stored in his buffer by the instant of the capture (gating type); and (2)he transmits at most one packet at a time (limiting type). First the gating type is analyzed, and its throughput, its average packet delay and its system stability are evaluated. An approximate probability distribution for the number of packets in the buffer space of a user is derived. On the basis of these analytic results, we study how to select both the buffer size and the rescheduling probability of packets which guarantee the system stability, keep the probability of buffer overflow sufficiently small and at the same time minimize the average packet delay. The two schemes are compared and it is shown that the gating scheme out performs the limiting scheme in terms of average packet delay and the average and variance for the number of packets in a buffer.
Arrangement of sources in the charge simulation method and singularities of solutions of the helmholtz equation. Scattering by a perfectly conducting cylinder of electromagnetic waves radiated from a line source
Authors: Komiyama Akira 
Published: July 2007

AbstractIn the charge simulation method, the scattered wave is represented by a linear combination of electromagnetic waves radiated from fictitious sources which are arranged inside the scattering body. The singularities of the scattered wave are the true sources from which the scattered wave is radiated. Therefore, the arrangement of fictitious sources will be affected by the location of singularities of the exact solution.This paper treats the scattering by a perfectly conducting cylinder of electromagnetic waves radiated from a line source. Singularities of the exact solution are located by a simple method, making use of the comformal mapping. An arrangement of sources taking the location of singularities into consideration is proposed.Numerical calculations of the residual error of the boundary condition are performed for an elliptic cylinder. The results show the effectiveness of the source arrangement. Calculations of the electric field distribution and scattering pattern are done by making use of the arrangement for an elliptic cylinder and a square cylinder. The fundamental properties of the line source scattering are clarified.
Radiation characteristics of reflector antenna with radome at 10∼30 GHz in rainy conditions
Authors: Kondou Manabu , Fukuda Shigeru , Kagoshima Kenichi 
Published: July 2007

AbstractThe increase in radome loss, sidelobe levels, and cross‐polarization level in the rain plays an important role in determining antenna characteristics. These effects have been investigated at 10 GHz ∼ 30 GHz with a reflector antenna having a planar radome, and a new method has been propsoed for deriving the radome loss in which a water‐shedding property of the radome is taken into account. Raindrops on the radome form water streams that flow down onto the surface thereby increasing the loss of the vertical polarization wave. It is also found that the cross‐polarization level generated by a wet radome is less than −40 dB. The sidelobe level is not increased and the paraxial radiation pattern is not changed by a wet radome but it is lowered as a whole. In the present theory, the contact angle of a raindrop surface with a radome surface determines the condition of the wet radome surface and this angle was predicted theoretically by using measured radome loss.
A method for reducing the number of product terms in a symbolic reliability expression
Authors: Higashiyama Youichi , Ariyoshi Hiromu 
Published: July 2007

AbstractAmong methods for deriving a symbolic reliability expression between two specified vertices (s, t) in a network, a treeexpansion method proposed herein generates an expression in summation form with fewer product terms and computes it very fast. The tree‐expansion method has a fundamental operation to enumerate s – t paths {μ1, μ2, …, μm} and generates a rooted tree (reference tree) from subpaths of paths μj (J = 1, 2, …, i – 1) having their initial and terminal vertices on a path μi and then derives a symbolic reliability expression directly from its subtree (implicant tree). This method has a disadvantage in that the number of product terms depends heavily on the order of path generation since the reference tree must be generated according to the order of paths obtained by a depth‐first search. In this paper for each vertex in a network we define its weight as the number of edges in a shortest path from the vertex to t. We show that if we generate paths by a depth‐first search to prefer those edges with terminal vertices having small weights and apply the tree‐expansion method according to the generation order, then we can reduce the number of product terms (this is called the modified tree‐expansion method). Also, we show by computer experiments that the modified tree‐expansion method can reduce the number of product terms and its running time.
Mullis–Roberts–type approximation for continuous–time linear systems
Authors: Nagaoka Hiroshi 
Published: July 2007

AbstractAs lower‐order approximation methods for discrete‐time linear systems, Mullis and Roberts have proposed two methods: the so‐called modified least‐square approximation (MLSA), and the interpolatory approximation (IA). The characteristics of the two methods were investigated considering their relationships. In this paper, a lower‐order approximation method for continuous‐time linear systems is presented in a form corresponding to MLSA, with its property, algorithm and state‐space representation discussed in correspondence with the discrete‐time case. The approximation can also be regarded as corresponding to IA, and thus the proposed method is called the continuous‐time Mullis‐Roberts‐type approximation (CMRA). The latter half of this paper presents a formulation for the limiting case (as sampling time ← 0) from a lower‐order approximation method for discrete‐time systems to one for continuous‐time systems. Thus it is shown that CMRA is obtained as a common limit of MLSA and LA, thereby providing a physical interpretation to the formal correspondence between CMRA and MLSA/IA.
Analysis for loss system with finite sources which require several channels simultaneously
Authors: Miyake Kou 
Published: July 2007

AbstractThis paper analyzes a loss system with finite sources. The idle period of a source forms a renewal process and each customer requires several channels simultaneously. The service time of customers which require the same number of channels exhibit a general independent identical distribution. This is a general traffic model for a subscriber concentration stage in a high‐speed wide‐band communication network. The distributions of the numbers of customers in the system at arbitrary and customer arrival epochs are derived using the supplementary variable technique, where the backward recurrence‐time of call idle period and holding time are chosen as supplementary variables. It is shown that these distributions are determined only by the mean service time and the mean idle period of a source, irrespective of their distributions (robustness). Finally, some traffic characteristics, such as loss probability and circuit occupancy, are evaluated numerically for two‐traffic models and unbalanced input traffic models.
Grounded immittance simulation using single operational amplifier with a finite gain‐bandwidth product
Authors: Ishida Masaru , Ebisutani Keisuke , Fukui Yutaka , Kasai Tamotsu 
Published: July 2007

AbstractMany papers on the active‐RC immittance simulation using operational amplifiers with a finite open‐loop gain have been published. This structure is not suitable for high frequency operation. It has been shown that the active‐R immittance simulator utilizing a finite gain‐bandwidth product give the reliable high frequency performance. However, in the active‐R form, magnification in value of simulated elements has not been considered to date.In this paper, a grounded immittance simulator composed of a single operational amplifier and thirteen passive circuit elements is presented. In order to analyze the driving‐point admittance using the computer, the circuit configuration is simplified such that eight passive elements out of thirteen are removed from the general circuit. Analytical results show that the various immittances can be realized. In particular, we deal with the increase in value of the simulated inductance and the circuit for generating a negative conductance. Furthermore, the effects of the second pole of an operational amplifier on the driving‐point admittance are also discussed. From experimental results, it is seen that both circuits work well in the high frequency range.
A method of measuring shielding effectiveness for conducting materials using a spherical cell
Authors: Hasebe Nozomu , Kobayashi Kazuhiko 
Published: July 2007

AbstractRecently, many conducting plastic shielding materials have been retailed in connection with environmental electromagnetic problems. This paper proposes a method of measuring the shielding effectiveness using a spherical cell as a means of evaluating shielding effectiveness. The shielding effectiveness against electric and magnetic fields can be evaluated by the proposed method. The measured values provide quantitative information for practical shielding because the cell forms a practical shield housing of circuits or parts. It is easy to handle theoretically since we use a spherical shape. Favorable agreement is obtained between the results of theoretical analysis and values of experimental measurements. Gradual decreases of the shielding effectiveness occurred in the high‐frequency region against the electric fields and in the low‐frequency region against the magnetic fields for a material with low electrical conductivity. Sudden large decreases of the shielding effectiveness against the electric and the magnetic fields due to resonant effects were observed when the diameter of the sphere becomes close to the wavelength based on numerical calculations. It was found that in designing shielding housings, careful attention must be given to their dimensions.
Polarization characteristics in UHF‐band mobile radio propagation
Authors: Kaji Masatake 
Published: July 2007

AbstractA propagation study has been conducted for horizontal and vertical polarization inside buildings in residential areas and in business districts with tall buildings. The following findings have been obtained: (i) when half‐wave dipole antennas are used both for transmission and reception, the received power is stronger for transmission and reception in the vertical polarization than for transmission and reception in the horizontal polarization. This phenomenon is due to the difference of the directivity of the dipole antenna; (ii) the cross polarization discrimination (XPD), defined as the ratio of the in‐phase polarization component voltage to that of the orthogonal polarization, correlates with the loss increase from the free space propagation. As the latter is increased, the XPD degrades more; (iii) the XPD degrades more as the propagation distance increases. This is because the attenuation constant of the in‐phase polarization component is larger than that of the orthogonal polarization component; (iv) the XPD of the wave propagation outside is determined by the ratio of the RG wave guided along a road to the BD wave diffracted by the top edge of a building. It degrades more as the BD wave component is increased; and (v) for a distance of less than about 1 km line‐of‐sight, the difference in attenuation by the polarization is negligible.
Detection of objects buried in snow using multifrequency holography
Authors: Sakamoto Yuji , Tajiri Katuhiro , Sawai Takaya , Aoki Yoshinao 
Published: July 2007

AbstractSeveral approaches are being considered for use in the visualization of the interior of snow and ice which are invisible to visible light. The authors have studied this subject with the objective of developing a radar system that detects an object buried in snow. Good transparency of the microwave in snow and the high resolving power of long wavelength holography are used for snow radar. A multifrequency holography has been used for further enhancing the resolving power. Using the snow radar system developed herein, we carried out experiments for detecting three‐dimensional information of objects buried in snow. The relationship of the three‐dimensional positions and the shapes are detected successfully for metal cylinders and mannequins. Also, it is proved that the system is effective for detection of nonmetal objects, such as meat.
Analysis of a DC current detector in a highly accurate DC‐DC converter
Authors: Yamamoto Katsuhiko 
Published: July 2007

AbstractThis paper describes the analysis and design method for a new biased rectifier amplifier (BRAM). The BRAM is driven by a high‐frequency square wave, employs a new self‐biased circuit configuration, and simulates dc detection characteristics using equivalent circuits. Design parameters of the core and operating frequency are studied to obtain a high conversion ratio of 2750. Applying the BRAM to a dc current detector gives a highly accurate, constant current dc‐dc converter.
TV interference from foreign transmitters and the polarization characteristics of Es‐propagation wave
Authors: Watari Shin‐Ichi 
Published: July 2007

AbstractThe ionospheric sporadic‐E (Es) layer has a high electron concentration and is capable of reflecting VHF radiowaves. It shows up mainly in summer in an unpredictable manner. The problem of TV interference by Es propagation waves has become increasingly severe with the increase in TV and FM stations between neighboring countries. Measurements have been made of the polarization characteristics of Es propagation waves in an attempt to find possible techniques to counteract this interference. In the summer of 1985, 1986, and 1987, observations were made of several VHF waves from known transmitting stations using log‐periodic antennas placed horizontally and vertically, and the ratios of horizontally and vertically polarized signals were measured. The results show that Es propagation waves have the same strength between two received signals, independent of propagation direction. Horizontally polarized signals are used in transmitting stations, showing that the polarization is rotated during Es propagation.
Traffic evaluation of channel‐reservation methods to improve the imbalance among internal blocking probabilities on a T‐S‐T network
Authors: Masuda Etsuo 
Published: July 2007

AbstractChannel reservation methods RSC, RBC, and RIC are proposed and studied. These methods handle a mixture of single‐ and multislot calls and improve the imbalance among the internal blocking probabilities of the calls on a T‐S‐T network. They also restrict the connection of lower bit‐rate calls based on the scope of channels (RSC), the number of the channels already being used by the same class of lower bit‐rate calls (RBC), or the number of pairs of primary and secondary T‐switches having the minimum idle channels that are required to connect either class of higher bit‐rate calls (RIC). Simulation results show that these three methods are nearly equal in improving imbalance, and RIC is most desirable because of its robustness in handling a variation of possible traffic mixes.
Performance comparison of two CSMA/CD systems with prioritized retransmission
Authors: Matsumoto Yutaka , Takahashi Yutaka , Hasegawa Toshiharu 
Published: July 2007

AbstractFor efficient processing of various types of traffic in LAN's, the introduction of a priority mechanism is considered to be effective. This paper considers nonpersistent CSMA/CD systems with a new priority mechanism, and derives the throughput and the average response time for each priority class by using the imbedded Markov chain method. The priority structure is achieved by assigning higher exponential retransmission rates to higher priority classes. As for the basis of priority assignment, we analyze two mathematical models: one is terminal‐based and the other is message‐based. Because the models allow feedback of packets, we can apply our results to error‐prone CSMA/CD systems, also. Numerical results show that the simple priority mechanism works effectively, and clarify the differences between the terminal‐based system and the message‐based system.