bluuebunny/crossref_metadata_2025 huggingface dataset:
Distortion in analog transmission for subsampled picture signals
Authors: Liu Fu‐Sheng , Tanimoto Masayuki
Published: July 2007

In sampled‐value transmission such as TAT where pixel values are transmitted, the transmission characteristics must be equalized so that the transmission distortion caused by the interference between sampled values is reduced below the detectable limit or tolerable limit. This paper considers the situation where the image signal bandwidth compressed by subsampling is to be transmitted by baseband or VSB transmission.

The analysis and computer simulation for the transmission distortion are presented. The relation of the maximum transmission distortion to the deviation of the frequency characteristics or the deviation of resampling timing of the transmission system is examined quantitatively. The detectable limit and the tolerable limit of the distortion, for the case where the distortion spreads by the interpolation, are determined by subjective experiment. Their relation to the compression ratio and interpolation scheme is examined.

The following properties were obtained. The maximum distortions are nearly the same for the transmitted and interpolated pixels, independently of the bandwidth compression ratio and the scheme of compression. The detectable limit and the tolerable limit become smaller with the extent of compression, imposing more severe requirements on the transmission characteristics. The effect of the interpolation scheme is small.
Delay performances of tandem go‐back‐n arq scheme
Authors: Hayashida Yukuo , Sugimachi Nobuyuki , Yoshida Yoshinori
Published: July 2007

The performances (throughput and transmission delay) of the Go‐back‐N ARQ scheme are affected greatly by the bit error rate of the link and the round‐trip propagation delay. This paper discusses the transmission delay of the tandem Go‐back‐N scheme, in which the round‐trip propagation delay can substantially be reduced. First, the generating function for the transmission delay distribution is derived, and then the result is applied to derive the average transmission delay. As a result, it is shown clearly that the performance of the tandem Go‐back‐N ARQ scheme is better than that of the standard Go‐back‐N ARQ scheme.
Mode partition of high‐definition television signals using adaptive subsampling
Authors: Sakurai Naoya , Kishimoto Ryozo
Published: July 2007

In the analog transmission of high‐definition television signal using satellites, the transmission must be performed within a limited band. For this purpose, an adaptive subsampling system is proposed and is used in the highly efficient transmission of the high‐definition television signal. One of the important problems in the adaptive subsampling for improving the picture quality is to partition the picture into as many subsampling modes as possible in an efficient way.

This paper proposes an adaptive subsampling system with four different subsampling modes. The four modes are composed of three modes for the moving part and one mode for the still part. Discussions are made on the partitioning of three modes in the moving part, and the partitioning between moving and still parts. In the mode partitioning in the moving part, a method (histogram method) is proposed where the distortion over the whole picture is reduced, based on the histogram derived from the distortion for each subsampling block to determine the subsampling mode partitioning.

The proposed method is compared with the traditional method by computer simulation, and it is verified that the SN ratio is improved by the proposed method. As to the partitioning between moving and still parts, a control method for the motion detection threshold is proposed, which seeks a balance between the distortions of still and moving parts. The performance of the control method is verified by a computer simulation for the picture data containing a scene change. Finally, the usefulness of the proposed method is verified by a simulation using motion pictures.
Coded continuous phase modulation combined with nonuniform mapping and multi‐h scheme
Authors: Itoh Toshiyuki , Sasase Iwao , Mori Shinsaku
Published: July 2007

The convolutional coding combined with continuous phase modulation (CPM) has been shown as a good tradeoff between coding and bandwidth. This paper proposes the coded CPM with the nonuniform signal constellation and the multi‐h scheme to achieve further coding gains over the conventional uniform mapping single‐h coded CPM. Using the minimum Euclidean distance, the number of merge events up to a certain depth in the state trellis and the average bandwidth as estimated criteria, the performance of the non‐uniform multi‐h coded CPM is analyzed. It is found that the nonuniform multi‐h coded CPM achieves larger Euclidean distance and diminishes the number of merge events without expanding the bandwidth.
Development and performance evaluation of highly efficient retransmission scheme for high‐speed data transfer via satellite
Authors: Nakamura Tsutomu , Sasaki Ryooichi , Fujikura Nobuyuki , Morita Hiroshi
Published: July 2007

Satellite communication has the following problems. The propagation delay is larger than in the terrestrial channel. When the carrier frequency exceeds 10 GHz, the bit‐error rate tends to increase due to the effect of rain and snow, which degrades the transmission efficiency. To cope with such problems, a highly efficient error control protocol has been proposed to prevent the degradation of the transmission efficiency.

This paper describes a new large‐capacity, highly efficient retransmission scheme for satellite communication (extended SREJ scheme), which was devised considering the compatibility to the terrestrial network. The method is based on the SREJ (selective reject) scheme, which is specified in the HDLC (high‐level data link control) protocol, employed widely in terrestrial data transmission. To evaluate quantitatively REJ, SREJ and extended SREJ schemes, a satellite communication control equipment was developed.

The result of the data transmission experiment is described in detail, indicating that the extended SREJ scheme is efficient. Then, through the discussion of practical usefulness, it is shown that the extended SREJ scheme has no problem from the viewpoint of the number of buffers in transmitting and receiving stations. Furthermore, to realize the efficient processing as far as possible, even if the bit‐error rate is higher than 1.0 × 10−4, the extended SREJ/REJ scheme is discussed by combining the proposed scheme with the REJ scheme.
Development of a location system for tv ghost sources and its serviceability
Authors: Miyazawa Hiroshi , Itoh Hironobu
Published: July 2007

A practical system was developed which locates the origin of reception interference (the so‐called ghost interference) by the reflection of a wave incident on a building which is a major factor for electromagnetic interference in television broadcasting. One of the authors has already developed a prototype system in which the location of the ghost source can be detected by measuring the delay time and the direction of arrival of the reflected wave (so‐called ghost wave) with respect to the direct wave at the measurement point. In this method, the ghost wave is separated at each delay time while the measurement antenna is rotated and the receiving pattern of each ghost wave is obtained so that the location of the ghost source is detected.

A system of locating the ghost sources was developed. In this system, a small computer is combined with the PDUR measurement system for measurement and analysis of the ghost wave. As a result, the portability is increased to be useful at the location of the electromagnetic interference by means of size reduction and reduced power consumption. From the examples of measurement of actual ghost interference and the direction‐finding accuracy at the measurement site, the measurement accuracy was studied for the reflection location of the ghost wave in the VHF and UHF broadcasting bands so that the serviceability of the system was confirmed.
An adaptive two‐stage image coding scheme using dpcm and vector quantization
Authors: Itoh Susumu , Naitoh Ichiroh , Kishidas Kouji , Utsunomiya Toshio
Published: July 2007

This paper proposes a two‐stage coding scheme, whereby a reduced image for retrieval is sent at the first stage, as a highly efficient coding scheme for images and other databases. In the first stage, the reduced image is encoded by block adaptive DPCM. In the second stage, the interpolative error component is encoded using adaptive vector quantization. In this scheme the number of quantization levels is easily determined from the standard deviation of the prediction error signals calculated for each subregion and the rate‐distortion characteristic of the scalar or vector quantizers, using the same method for either of the two stages. By designing the quantizers for typical probability distributions of the predictive error signal, a highly versatile coding scheme is realized.

The proposed method has a better overall coding performance than a vector quantizer with the same block size (4 × 4 pixels), which has been designed in an optimal way in the original signal space. Compared with adaptive discrete cosine transform vector quantization [16] and adaptive predictive error vector quantization of the prediction error signals [7], which are also highly versatile, the proposed method exhibits a better characteristic when the coding rate exceeds a certain level. There is little degradation due to the two‐stage coding process. It has also been verified that the proposed method is effective for coding color images.
Routing algorithms of multiple‐destination telecommunication services
Authors: Tanaka Akira , Mizusawa Jun‐Ichi
Published: July 2007

Multiple‐destination telecommunication is one of the new services in circuit switching. The telephone conference service, which is already in practical use in Tokyo 03 area, is an example of such a service. This paper assumes the use of a network control data base, and proposes a routing algorithm which is required in the realization of wide‐area multiple‐destination communication by placing a large number of bifurcations (bridges) in the network. It is required that the algorithm should not only suppress the circuit utilization cost for the determined route but also should determine the route in a sufficiently short time to cope with the immediate call.

Five kinds of algorithms are proposed, including the search of the “minimum‐spanning tree,” which generally is considered as the basic connection configuration for the multiple‐destination communication. The two foregoing items are used as the items for evaluation, and a connection algorithm is presented which is the optimal for the given mumber distribution and the bridge placement. It is shown as a result that there exists an algorithm which is better than the “minimum‐spanning‐tree” search algorithm.
Studies on realization of information retrieval service function by fiber optic broadband distribution system
Authors: Yamagata Jun , Takemoto Kenji
Published: July 2007

As one approach to the realization of post 64 kbit/s ISDN, studies have been made on the optic broadband distribution system, based on the fiber optic transmission by tree (or bus) trunk line and star subscriber line. To realize a more versatile C‐E communication system, however, not only must the service functions such as distribution of multichannel video information, character, still picture and data be provided, but also the information retrieval function with random access such as videotex.

This paper discusses theoretically the realizability of the information retrieval service by the optic broadband distribution system from the viewpoint of whether or not a sufficient number of subscribers can be accommodated.
Post‐detection combining diversity improvement of four‐phase dpsk system in mobile satellite communications
Authors: Hara Shinsuke , Morinaga Norihiko
Published: July 2007

In mobile satellite communications with a wide service area, the largest problems in composing the system are the Rician fading, where the direct wave component and the random time‐varying scattered wave component interfere with each other, as well as the low received power due to the propagation for a long distance.

This paper considers diversity as a means to overcome these problems. The four‐phase DPSK system is considered, and a theoretical analysis is made on the error rate improvement by the post‐detection combining diversity. The characteristic functions of two orthogonal delayed detection outputs of the branches are used in the derivation of the error rate. Three communication systems of satellite/aircraft, satellite/land mobile and satellite/ship are considered as the models. Theoretical expressions are derived to evaluate the improvements. The error rate is also evaluated for the selective diversity. The result is compared with the case of combining diversity, together with the discussion for the difference between the two schemes.
Heating of deep—seated tumors by te wave irradiation
Authors: Ikeda Takuji , Morita Nagayoshi
Published: July 2007

As an applicator for heating deep‐seated tumors in the human body in a non‐invasive manner, a multiapplicator system radiating TE wave is proposed. In addition, it is shown that a hot zone can be formed deeply inside the human body if a method for good adjustment of the amplitude and phase of each applicator element is used. As an actual example, a homogeneous two‐layered cylindrical human body model is used for the cross section of the adrenal‐kidney level. Numerical calculations are carried out for the case where several line sources are placed around this model. It is confirmed that a hot zone is formed near the center. It is also demonstrated that the FD‐TD method is effective for the analysis of the electromagnetic scattering of a TE wave by an inhomogeneous cylindrical model which is the most important in the algorithm in the present method.
Analysis of electromagnetic field distribution in tunnels with partition walls
Authors: Sakai Koichi , Koshiba Masanori
Published: July 2007

A method of formulation based on the boundary element method is provided for the electromagnetic field in a two‐dimensional impedance tunnel with partition walls excited by the fundamental mode. The impedance boundary condition used often for the analysis of the electromagnetic scattering problem from a lossy dielectric and of the wave propagation in a tunnel is based on the characteristic impedance for an infinitely thick medium. Since there is no provision on the transmitted wave behind the dielectric plate, this boundary condition cannot be applied directly if the dielectric plate used is thinner than the skin depth.

This paper derives first a new boundary condition in which the values of the electromagnetic field in the region opposite to the wall surface are considered. In the case of a plane wave (TE wave) incidence on an infinitely wide than dielectric plate, the computed values by the boundary element method with the new boundary condition are compared with the rigorous solutions. It is found that the results agree with each other for both the reflection and transmission coefficients so that the impedance boundary condition introduced here can be used as the boundary condition for a thin dielectric plate. Further, assuming a tunnel with a thin partition wall, we carried out a microwave simulation experiment with a Bakelite plate so that the validity and usefulness of the present method are confirmed.
Tree configuration of n:1 multiconnection nonblocking switching networks
Authors: Tanaka Yoshiaki , Sezaki Kaoru , Akiyama Minoru
Published: July 2007

With the widespread use of broadband communication, the nonblocking N:1 multiconnection switching network is required in video distribution and in other applications. In most of the N:1 multiconnection nonblocking switching networks, some rearrangements or simultaneous origination of multiconnection calls must be assumed. For the switching network which is nonblocking for any N:l multiconnections under no conditions, only a few studies have been made on the three‐stage switching network.

This paper proposes an efficient method of constructing a switching network which can realize arbitrary nonblocking N:1 multi‐connections. First, the construction of a d:1 connection network is shown which serves as the fundamental component of the proposed structure. Then it is shown that by connecting several d:1 connection networks an N:1 multiconnection switching network which can realize arbitrary N:1 connection can be constructed. The number of crosspoints required in the switching network is calculated.
A performance comparison of link level connection schemes in csma/cd networks
Authors: Tasaka Shuji , Hirota Masaya
Published: July 2007

This paper considers the logical link control (LLC) sublayer in the CSMA/CD local area network, and compares analytically the performance of connection‐oriented (CO) and connectionless (CL) protocols. As the medium access protocol, slotted nonpersistent CSMA/CD with a priority assigned to some types of frames is employed. In comparison, the overhead for connection establishment/release in the CO‐LLC protocol, and the receiver‐buffer overflow in the CL‐LLC protocol are especially considered, and the two kinds of protocols are compared.

In the CO‐LLC protocol, a connection is established corresponding to a message. Employing the technique of equilibrium point analysis, the throughput and the average response time of the two kinds of LLC protocols are derived. To compare the performance of the two kinds of protocols, the receiver‐buffer size is kept constant, and the average number of data frames in a message is varied. As a result, it is shown that the CL‐LLC protocol is better than the CO‐LLC protocol when the average number of data frames is sufficiently less than the receiver‐buffer size, but the order is reversed when the average number of data frames is increased.
A new access scheme for pure aloha using capture effect by time‐varying power control
Authors: Mutsuura Kouichi , Okada Hiromi , Tezuka Yoshikazu , Ohtuki Kazuhiro
Published: July 2007

The advent of VSAT (very small aperture terminal) has made it possible to consider a new utilization of satellite communication. This paper proposes a new access protocol v‐ALOHA, which is matched to the characteristics of the packet switching network based on VSAT. p‐ALOHA is used as a means to cope with the requirement for simplification. To complement its disadvantage of low through‐put, a new control scheme is combined based on the new utilization. The performance is improved by the capture effect.

The basic idea of the control scheme is to vary the power with time while transmitting packets. The difference in the transmission‐start time is converted into the power difference and produces the capture effect, thereby improving the performance. Thus, an access protocol is realized which improves the low throughput of p‐ALOHA while preserving its simplicity.

This paper describes the basic idea of this v‐ALOHA and the protocol structure, indicating qualitatively its features. Then the throughput performance is formulated through a quantitative analysis. It is shown from the numerical results for the fixed‐length packet that the performance of the proposed scheme is better than other capture schemes, approaching sufficiently the performance of s‐ALOHA. For the case of the variable‐length packet, there is no slot loss as in s‐ALOHA, and the proposed scheme is shown, using an example, to be better sometimes than s‐ALOHA.
Diffusion approximation for queueing systems with nonexhaustive cyclic service
Authors: Yanagiya Masayuki , Takahashi Haruhisa
Published: July 2007

The nonexhaustive cyclic service queueing system is a performance evaluation model for various communication systems. In this queueing model, a specified maximum number of jobs in the queue, denoted by K, will be served upon the arrival of a server. Although the analysis for K ≥ 2 is difficult, recently Fuhrmann et al. [12] and Everitt [13] have proposed approximations for mean waiting time on the basis of pseudo‐conservation law.

This paper presents an approximation method for deriving the mean waiting time of GI(x)/G/1 system with nonexhaustive cyclic service, using diffusion approximation and an iterative method. Here, [x] denotes the batch arrival. By use of the proposed method, some performance for nonsymmetrical cases with arbitrary K can be evaluated. Here, “nonsymmetrical” means that arrival process and service time distribution at each queue can be different. Numerical results are shown and compared with existing results such as by Fuhrmann et al. [12] and also by computer simulation.
Novel phase‐locked loop with digital control techniques
Authors: Guonai Xu , Mori Shinsaku
Published: July 2007

Recently, a number of digital phase‐locked loops (DPLL) have been studied. In the usual DPLLs, a divider is added to the output so that the discontinuous and sudden variations in the frequency and phase adjustment by digital operations can be averaged and smoothed. Hence, in the usual DPLLs, an internal clock oscillator with its frequency several tens times the input frequency is needed. This requirement places a certain limit in the input frequency by the maximum operating frequency of the digital logic circuit if the DPLL is used for a high input frequency.

This paper proposes a phase‐locked loop (DC‐PLL) in which no divider is used and a clock frequency is almost equal to that of the input signal used for digital control. The free running frequency of the loop is equal to the clock frequency. The waveform of the clock signal is transformed to a saw‐toothed signal and the content of the reversible counter is transformed to a dc signal by a D‐A converter.

These two signals are injected simultaneously to the voltage comparator so that the comparator outputs at the moment the former exceeds the latter. This is the output signal of the system.

By the phase control signal, the content of the reversible counter varies and the output dc level of the D‐A converter also varies. At the same time, the phase of the output signal changes so that the phase control is accomplished. The characteristics of the proposed phase‐locked loop are confirmed to be identical to those of the conventional DPLL in which a divider is used.
Self‐routing benes network distributively controlled by dynamic load balance
Authors: Kishimoto Ryozo , Sakurai Naoya
Published: July 2007

This paper proposes a self‐routing Benes network controlled distributively by dynamic load balancing. This Benes network consists of a distribution network and a routing network. The distribution network is controlled by a proposed method called “Dynamic Load Balance,” where load information is fed back to the input side via each unit switch so that loads at intermediate unit switches are equalized.

The routing network is self‐routed by an output tag. The computer simulation results show that mean time delay vs. throughput characteristic of the proposed dynamic load balance Benes network is superior to those of conventional networks.
Optimum design of a pipelined time slot interchanger with time slot sequence integrity
Authors: Obara Hitoshi , Nakazawa Yutaka
Published: July 2007

The time slot interchanger (TSI) is employed widely in practice as the switch fabric of digital cross‐connect systems or exchange systems in the digital synchronized network. With the increasing need for ISDN with the fundamental rate of 64 kbit/s as the background, it is desired to realize a large‐capacity TSI. This paper discusses the optimum design of the pipelined TSI which has been proposed in the past, aiming at the realization of a large‐capacity TSI.

First, the TSI configuration is proposed which realizes the time slot integrity in multislot connection, which has been a problem in the traditional pipelined TSI. The proposed method corresponds to the traditional TSI using RAM, where the time slot sequence integrity is realized by employing the double‐buffer structure.

Then the optimum design method for the proposed pipelined TSI is presented, where the evaluation measure is the performance index, defined as the product of memory capacity and the operation speed. For comparison based on the defined performance index, the pipelined TSI optimized by the proposed method has several tens to several hundred times better performance than the conventional TSI using RAM or shift registers. Thus, it is demonstrated that the proposed construction is effective in realizing a large‐capacity TSI.
Error rate performance in high‐speed gmsk transmission on mobile satellite channel
Authors: Konishi Ken‐Ichi , Miyagaki Yoshiya
Published: July 2007

In high‐speed digital transmission in mobile satellite and land mobile communications, one of the serious problems is the effect of waveform distortion due to the frequency‐selective fading. This paper considers the GMSK modulation system, which is considered as useful as the modulation scheme for digital mobile communication.

The effect of the waveform distortion produced by the time‐delay spread of the scattered interfering waves in the Nakagami‐Rice fading channel is considered and the bit error rate is calculated theoretically. Numerical examples of bit error rate performance are illustrated. It is shown that the bit error rate is improved when there is an average delay time or a time‐delay spread in the scattered interfering wave, compared with the case without a delay. However, the effect is relatively small.
Focusing properties of fresnel zone‐plate and its application to a helix radiating a circularly polarized wave
Authors: Yamauchi Junji , Honma Shin'Ichi , Honmas Teruaki , Nakano Hisamatsu
Published: July 2007

This paper discusses applications of the Fresnel zone‐plate (FZP) made of metal foil to microwave antennas. First, the focusing effect and the far‐field pattern for the FZP are analyzed using the Kirchhoff‐Huygens diffraction integral. It is found that a phase‐reversing FZP, in which the phase of either its even or odd zones is inverted, has a sharp beam with a low sidelobe level.

On the basis of the fundamental analysis, an antenna syctem in which a reflector‐type FZP fed by a backfire helix is proposed as an application of the phase‐reversing FZP. It is pointed out that a sharp circularly polarized beam with a half‐power beam‐width of 9 deg is obtained when the outermost radius of the FZP is about 4 wavelengths.

Next, the gain variation by the change in the ground plate radius of the axial‐model helical antenna is explained by the Fresnel zone principle, and an axial‐mode helical antenna with a zoned ground plate is proposed. An absolute gain of 12.2 dB is realized by a two‐turn short helix with a zoned ground plate.
An asynchronous correlation receiver for a bus‐type twisted pair LAN
Authors: Member Hideo Kishimoto
Published: July 2007

LANs are used to achieve mutual communication among microcomputers and workstations and their wiring flexibility with terminals is becoming a necessity. However, the wiring flexibility of a bus‐type twisted pair LAN is low because of limited tap connection.

Although the equalization of a transmission line is necessary to improve wiring flexibility, a long sequence of training signals (more than a kilo bit long) must be sent before data transmission. Therefore, the transmission efficiency becomes significantly low in the case of a short data transmission such as in an LAN, and hence the application of conventional equalization techniques becomes difficult. Thus, wiring system technology to improve wiring flexibility becomes important in a private network system.

This paper proposes an asynchronous correlation receiver which improves wiring flexibility for a bus‐type twisted pair LAN by allowing taps. Hence, a received waveform is decoded by pattern matching between the received waveform and the reference waveforms. The reference waveforms are stored in a memory in a prior training period using the multiple sampling method.

Several experiments are carried out and their results revealed that the training time can be shortened (e.g., to 19 bits), the required clock accuracy is well realized by an ordinary crystal oscillator, and the transmission error rate can be made less than 10−6 under the worst transmission condition for a bus‐type LAN.
Tracking accuracy of astronomical objects in the nobeyama millimeter array
Authors: Morita Koh‐Ichiro , Ishiguro Masato , Chikada Yoshihiro , Kanzawa Tomio , Takahashi Toshikazu
Published: July 2007

The authors have developed the tracking control system of astronomical objects in the Nobeyama millimeter array. A system was studied which can accomplish sufficient tracking accuracy for an interferometer, such as delay tracking, phase tracking, and fine delay correction. It was found that the location error of an astronomical object can be made less than 1 percent of the maximum spatial resolution on a synthesized map and the radio intensity degradation less than 0.1 percent if the phase tracking is executed at an interval of about 10 s and the fine delay correction at 1 ‐ 2 s. Further, from the actual observation results, it was confirmed that this system has realized an extremely high tracking accuracy.
Measurement of polarimetric backscattering characteristics of random media
Authors: Kobayashi Osamu , Matsuzaka Yukihiko , Hirosawa Haruto
Published: July 2007

Radar polarimetry is considered a new subject of study in the field of microwave remote sensing. This paper describes a measurement method to obtain polarimetric microwave backscattering characteristics of random media using a power‐measuring type, indoor‐use microwave scatterometer.

In general, the polarimetric backscattering characteristics are measured in the form of scattering matrices. However, in the method here, modified Mueller matrices of random media were obtained by measuring backscattering coefficients for multiple polarizations. For transmitting and receiving polarizations, the horizontal linear, vertical linear, left‐handed circular, right‐handed circular, 45 degrees tilted linear, and 135 degrees tilted linear were combined.

In comparing the measurement method to obtain scattering matrices, the method herein has these features: i) the modified Mueller matrices which represent the back‐scattering characteristics of random media are derived directly; ii) since phase measurement is avoided, the measurement system is simple and the calibration technique becomes stratightforward. In this paper, the measurement method, also with the fabricated scatterometer for the C band and the experimental results for backscatters from the random media composed of needle‐shaped scatters are discussed.
An analysis of the crossed twin delta loop antennas with circular polarization
Authors: Kumon Yasunori , Tsukiji Takehiko
Published: July 2007

In the circularly polarized antenna with two orthogonally placed wire antennas of identical shape, each antenna is fed with a phase difference of 90 degrees. In this paper, a crossed twin delta loop antenna is proposed in which two triangular delta loop antennas of different sizes are placed orthogonally. It is demonstrated in principle that this antenna can work as a circularly polarized antenna without any phase shifter. To make the phase difference of the currents between the orthogonal delta loops 90 degrees, the peripheral length of one of the triangular delta loop antennas is longer that that of another by the length corresponding to the phase delay of 90 degrees of the transmission line (=1/4 wavelength × 2). These orthogonally placed triangular delta loop antennas are fed in parallel with a single source.

In this paper, a circularly polarized orthogonal equilateral triangular delta loop antenna with a reflector is considered. Detailed numerical studies are carried out for the axial ratio of the radiation field and the gain characteristics versus the spacing between the antenna and the reflector. As a result, an optimum shape is found in which the gain is high and the axial ratio of the circular polarization is good. For this structure, the input impedance, current distribution and radiation pattern are computed numerically so that the general characteristics of the present antenna are evaluated. The validity of the theory is confirmed by comparison with experiments.
Performance evaluation of layered communication protocol
Authors: Inai Hiroshi , Yokohira Tokumi , Murata Masayuki , Miyahara Hideo
Published: July 2007

This paper proposes a queueing network model for the layered communication protocol and its approximate analysis method. The performance of the layered communication protocol is evaluated by using the proposed model and analysis.

First, the queueing network model is constructed for the connection‐oriented and connectionless data transmissions between peer layers. In each queueing network model, the transmission delay in the lower layer protocol is represented by an infinite‐servor queue.

The performance model for the layered communication protocol is constructed by piling up each model. Then an approximate analysis is presented for each queueing network model. Based on the relation to be satisfied by the packet transmission delay in each layer and the throughput between adjacent layers, an approximate analysis of the whole model can be executed iteratively.

In numerical examples, the validity of the approximate analysis for the model is shown. The effects of window size, the time‐out period, and receiver buffer size on the transmission delay are discussed.
Fully digitalized transversal equalizer for digital radio systems
Authors: Shirato Tadashi , Matsue Hideaki , Murase Takehiro
Published: July 2007

In digital radio communication employing multilevel modulation, the waveform equalizer is needed to eliminate the waveform distortion generated in the transmission channel or in other components. This paper aims at a highly accurate automatic equalizer which is applicable to the ultramultilevel modulation, such as 256 QAM, and discusses the fully digital realization of the equalizer which has been constructed by analog circuits.

First, the transversal equalizer to be used in 256 QAM is considered, and the relation between the number of taps and the equalizer performance is described theoretically. Then the construction of the fully digital waveform equalizer is proposed based on the digital signal processing techniques. The decision range expanded (DRE) method is proposed, aiming at the maximum utilization of the equalization performance of the waveform equalizer. Finally, the transversal automatic equalizer is implemented on LSI.

As a result of experiment with the clock rate of 12.5 Mbaud and 256 QAM signal, a satisfactory result agreeing with the theoretical investigation is obtained. Especially, it is demonstrated that the DRE method is very useful in constructing the digital waveform equalizer. Thus, a highperformance transversal automatic equalizer is realized, which is applicable to the ultramultilevel modulation system.
Analysis of ferrite absorber considering hysteresis and relaxation characteristics by spatial network method
Authors: Morita Takashi , Yoshida Norinobu , Fukai Ichiro
Published: July 2007

Recently, various microwave absorbers have been studied and developed for electromagnetic interference problems. One of the important materials for absorbers is ferrite in which the high‐frequency magnetization mechanism consists of a superposition of the motion of the magnetic wall and the rotation of the magnetization. Its complex permeability has a frequency dispersion; therefore, it is difficult to develop a rigorous theoretical analysis as an absorber. If a numerical analysis based on a simulation model is possible, the design of the absorber will be expedited.

In this paper, the spatial network method is used for treating the hysteresis characteristics of the shift of the magnetic domain wall and the relaxation characteristics with an absorbing characteristic for the rotation of magnetization. A basic equivalent circuit model is proposed in which both are combined, and then this model is used to analyze the frequency characteristics of the reflection coefficient of a plane wave. The results based only on the basic relaxation model are shown to agree well with the theory. The basic validity of the model is verified by showing that the reflection coefficient is reduced at less than the matching frequency due to the hysteresis loss, and that the matching frequency and the tendency agree with the experimental results by Ishino et al.
Error performance improvement of digital transmission with π/2‐TFSK in the mobile radio environment
Authors: Horikoshi Jun , Kawano Osamu , Kurihara Kazuo
Published: July 2007

To construct a digital mobile radio system, it is necessary to select a modulation scheme to satisfy conditions for the error performance, the occupied bandwidth and the out‐of‐band radiation. It is especially important to develop a modulation scheme with compact spectral characteristics which is affected little by the multipath interference at a high transmission rate.

In this paper, the power spectral density of π/2‐TFSK proposed by one of the authors is obtained first and then the detection ability accounting eye opening of 1‐bit and 2‐bit differential detector is discussed. It is revealed further that the magnitude of the eye opening of RC‐π/2‐TFSK (raised cosine Nyquist filtered π/2‐TFSK) is larger than that of RC‐MSK (raised cosine filtered minimum shift keying) and the applicability to the mobile radio channel is shown. The preferable receiving bandwidth of RC‐π/2‐TFSK is obtained. These are confirmed by the hardware experiments in the laboratory.
Suppression of radar clutter via nonparametric CFAR
Authors: Chikara Sakae , Saji Keiichi , Sekine Matsuo , Musha Toshimitsu
Published: July 2007

In radar signal processing, clutter must be suppressed to discriminate a target. For this purpose statistical properties of clutter have been investigated and an ordinary CFAR (constant false alarm rate) circuit based on clutter statistics works very well. A nonparametric CFAR circuit, however, does not depend on clutter statistics; and this technique was applied to sea clutter suppression in which a ship was detected with good accuracy.
Quality control at the cell level and its characteristics in the ATM network
Authors: Nogami Shinya
Published: July 2007

In the ATM network, information is transmitted by the continuous transmission from node to node of a fixed‐length packet called a “cell.” The requirements of the cell on the traffic characteristics and the network depend on the kind of information source. The information from a video terminal arriving at a node, for example, is bursty, and a severe condition is imposed on the delay. When cells from more than one medium arrive in a mixed way at the network, a certain control mechanism will be needed to satisfy the respective requirements from the cells. On the other hand, this control mechanism should be realized by as simple a structure as possible.

This paper discusses the necessity of the quality control at the cell level and the basic concept in the control for the node handling different kinds of calls. First, the characteristics for the case of a single kind of call source (such as voice, video or data) are analyzed. Then the necessity and usefulness of the control methods when various kinds of calls are mixed and arrive at the node are discussed for different control methods using numerical examples.
Capacity assignment algorithm for packet‐switching network with unreliable links
Authors: Yokohira Tokumi , Sugano Masashi , Nishida Takeshi , Miyahara Hideo
Published: July 2007

In this paper, a link capacity assignment algorithm for a packet switched communication network is presented. This algorithm, called max‐delay‐link algorithm, prevents sharp performance degradation in a network even in case of link failures. An optimal link capacity assignment can be obtained with respect to link cost minimization, subject to the constraint that the average packet network transmission delay does not exceed a predetermined value.

Robust networks against failures can be designed by assigning large capacities to links where overflow traffic and packet delay are expected to increase in case of a failure. Several numerical examples also are shown to examine the effectiveness of the algorithm in comparison with the conventional capacity assignment algorithm where link failures are not taken into account.
A method for transporting sdh signals using existing transmission systems
Authors: Ueda Hiromi
Published: July 2007

This paper discusses a signal transmission method based on the existing digital hierarchical transmission system that transmits signals as defined in the network node interface (NNI) of the new CCITT synchronous digital hierarchy (SDH). The method transmits the information corresponding to two virtual containers (VC‐3s) with the capacity of 28 of 1.5 Mbit/s over existing transmission systems using the fourth digital level, which is the basic unit of operation in the existing network. The fourth digital level signal in Japan has a bandwidth of 97.728 Mbit/s as specified in Rec. G.702. If two VC‐3s are to be contained according to the basic SDH philosophy of NNI, the required transmission capacity is 103.68 Mbit/s. The method that allows two VC‐3s to be transmitted at 97.728 Mbit/s should be considered.

It is shown first that the use of the pointer introduced in SDH is adequate. A pointer scheme with a fourmultiframe structure is proposed, aiming at efficient information transmission. The characteristics of the fourmultiframe‐type pointer are then discussed, and the assignment of the overhead required in the transfer of maintenance/operation information is considered. Based on those discussions, the frame structure for the 97.728 Mbit/s signal is derived, which is the fourth level of the existing digital hierarchy.
Bandwidth assignment control in ATM system
Authors: Kuribayashi Shin‐Ichi
Published: July 2007

ATM (asynchronous transfer mode) system transfers and switches the information from various media such as voice, data, and video in a unified way. Since media with severe requirements for high‐speed transfer or real‐time processing must be handled, there is no flow control function during communication. As a result, a certain bandwidth must be assigned to each call to ensure service quality.

This paper considers first the case where the same bandwidth is shared by several classes with different service requirements. The “flexible processing” system is proposed as a priority processing method where the qualities of other classes are not deteriorated even if there arises an unexpected traffic flow of a particular class. For bandwidth assignment to each call in the same class, the “volume declaration” method is proposed, wherein the user declares the maximum information content (= volume) that can be transferred in the specified time, in addition to the maximum information transfer rate. It is shown that the service quality of the call can be insured by this method.

Then we examine the case in which physically distributed bandwidths are utilized by more than one service quality class, and it is shown that the results of past studies on the multirate circuit switching can be applied, by assuming the forementioned volume declaration method.
Relationship between array excitation distribution and radiation pattern ripple depth
Authors: Kijima Makoto , Yamada Yoshihide
Published: July 2007

To develop a radiation pattern synthesis technique for array antennas, the relationship between the ripple depth of the radiation pattern and the flatness of the array excitation amplitude distribution is clarified analytically. The roots of the representation equation of the radiation pattern are shifted radially from Schelkunoff's unit circle so that the ripple depth is changed. The ripple depth of the radiation pattern and the flatness of the excitation amplitude distribution are expressed by approximate equations in terms of the amount of the shift of the root. If the amount of the shift of the root is eliminated from these two equations, the relationship between the ripple depth and the flatness of the excitation amplitude distribution can be derived.

Approximate equations indicate that the relationship between the two is almost independent of the sidelobe level and is determined mainly by the number of elements. As a numerical example, an asymmetrically shaped pattern is generated for a 20‐element array antenna with an element spacing of 0.5 wavelengths. The approximate equations and the rigorously calculated results are compared for error evaluation. It is confirmed that the approximate equations yield accurate evaluations if the ripple depth is more than 4 dB. Flatter excitation amplitude distributions reduce the influence of fabrication error and the mutual coupling of the elements and thereby improve the accuracy of the excitation coefficients. Useful design data also are obtained.
Energy flux densities of electromagnetic waves
Authors: Tokumaru Shinobu
Published: July 2007

In time‐harmonic electromagnetic fields, the Poynting vector, the cross product of electric field with the complex conjugate of the magnetic field, is well known as an energy flux density vector. Here, a new type of vector is proposed in which the cross products of electric and magnetic fields with their corresponding complex conjugates are taken, and its relationship with the Poynting vector is established as a pair of Max‐wellian‐type equations. Moreover, the usefulness of this vector is demonstrated by the examples of optical theorem, reciprocity theorem and decomposition of radiated power into circularly polarized fields, where it supplements the Poynting vector. This vector, like the Poynting vector, can also be considered as the energy flux density vector of the electromagnetic wave.
Radiation pattern analysis of an antenna mounted on a finite ground plane with a dielectric coating
Authors: Hasebe Nozomu , Takahashi Yoshihiro , Tanioka Noritaka
Published: July 2007

The airborne antenna may be considered to be small since it is mounted on a conductor which is large compared to the wavelength and its radiation pattern has to include the diffracted fields from the conductor. Moreover, thick dielectric coating on the body, which is used as insulating material, causes a serious distortion of the radiation pattern; and this is confirmed through measurements that the effect is quite large.

This paper proposes a method of analysis where the effect of dielectric material on the radiation pattern is estimated analytically using a simple plane conductor model. Analysis is based on the excitation of the surface wave which propagates inside the dielectric sheet and making assumptions about the radiation mechanism, its diffracted field is calculated by the uniform theory of diffraction (UTD) method. The availability of this method of analysis was confirmed by comparing the measured results of this model with the calculated values. From the measured and analytical results, it was confirmed that a large effect is produced in the axially back direction of the rocket due to dielectric coating on the body.