bluuebunny/crossref_metadata_2025_split huggingface dataset:
Migration method for subsurface radar considering variation of propagation velocity in depth direction
Authors: Ho Gwang‐Su , Kawanaka Akira 
Published: July 2007

AbstractThere are two methods for improving the resolution in the scan axis direction of the subsurface radar, i.e., the F‐K migration method and the phase‐shift method. The resolution can be improved significantly by the F‐K migration method if the propagation velocity of the radio wave in the ground is uniform and by the phase‐shift method if the propagation speed varies in depth and is known. In general, the propagation speed of the radio wave often changes in depth and its distribution is unknown.In this paper, a method is proposed in which the radar image is divided in the depth direction and the propagation time difference up to the divided block is compensated for so that the F‐K migration method is applied to each block. The propagation speed of each block is estimated as the case in which the maximum reflection value of the reconstructed image is the largest after the F‐K migration process is carried out for several candidate values of the propagation speed. By means of this method, the distribution of the propagation speed can be estimated and a reconstructed image with high resolution can be obtained. This reconstructed image is of sufficiently good quality in comparison to the one by the phase‐shift method using the empirical propagation speed distribution. The processing time excluding the propagation speed estimation is reduced to one‐seventh that needed for the phase‐shift method.
A quantitative evaluation for the introduction of quasi‐synchronous transfer mode method on the asynchronous transfer mode network
Authors: Kamiyama Noriaki , Tode Hideki , Yamamoto Miki , Okada Hiromi 
Published: July 2007

AbstractThe quasi‐synchronous transfer mode (Q‐STM) method realizes cell‐loss free and intranetwork delay jitter‐free transmission on asynchronous transfer mode network, by allocating transmitted cell positions. In this paper, some design issues of the Q‐STM method are considered and the applicability of the Q‐STM method is investigated. First, the algorithms of the call setup procedure for Q‐STM are compared. The effect of the number of subframes (NS) is investigated, and the most efficient NS in an assumed environment is obtained. Moreover, the QOS of ATM service class and processing time of a call setup are evaluated. Through these evaluations, we show guidelines for implementing the Q‐STM and the applicability of the Q‐STM.
An effective access control method for high‐speed local area networks and metropolitan area networks
Authors: Morino Hiroaki , Aoki Terumasa , Aida Hitoshi , Saito Tadao 
Published: July 2007

AbstractThis paper proposes an access protocol with a high throughput for the ultrahigh‐speed local area network (LAN) and metropolitan area network (MAN) with the transmission capacity exceeding 100 Mbps. The slottedring configuration is suited to the access method for the ultrahigh‐speed LAN/MAN. Several protocols have been proposed, such as DQDB and ATMR, which, however, have problems in that the throughput in DQDB cannot reach the transmission capacity and the throughput in ATMR decreases when the traffic is nonuniform.In the proposed protocol, the reset signal circulates the ring and the fairness of the access is ensured by limiting the number of slots to be sent by each node by the window size. The number of slots to be sent is not limited if none of the downstream nodes has data to be sent. This helps to realize a high throughput independently of the traffic situation. As the result of performance evaluation, it is verified that the proposed protocol is useful in the following two points: (1) approximately 1.8 times higher throughput is realized compared to the existing protocols when the traffic concentrates to a particular node; and (2) the delay time is suppressed to a low value for burst traffic such as video.
Rapid ambiguity resolution for kinematic gps based on integer constraints
Authors: Wang Dun , Morikawa Hiroyuki , Mizumachi Moriyuki 
Published: July 2007

AbstractThe kinematic GPS is a method in which the positioning with an accuracy of several centimeters is realized using continuous tracking by a mobile user for the phase of the carrier sent from the GPS satellite. In the mobile positioning system based on the carrier phase, there exists a phase bias uncertainty (ambiguity) corresponding to the integer multiple of the wavelength in the phase measurement; and there must be a processing that can resolve the phase ambiguity with a high speed while the user is moving. This paper indicates that an integer constraint exists based on the geometrical positions of the observation point and the satellite as well as the ambiguity and presents a method that can resolve the ambiguity with a high speed by utilizing the integer constraint. In other words, a method is presented that can resolve the ambiguity with high speed by noting the time redundancy contained in the result of measurement and by applying the smoothing along the time axis.
Using a neural network to obtain an output voltage control method in an interconnection inverter
Authors: Tazume Kunitoshi , Aoki Tadahito , Kuwata Yutaka , Nozaki Yousuke 
Published: July 2007

AbstractGenerated power savings result when the harmonic current in the output of an inverter that connects solar cells and fuel cells to ac lines is suppressed. This suppression is done by canceling the harmonic voltage in the ac line by generating the same harmonic voltage in the inverter output. A method to control the output voltage of an interconnection inverter is proposed that uses a neural network that has learned a sample of the ac line voltage, including its harmonic components. Simulation and experimental results show that this method sufficiently suppresses the total harmonic distortion of the inverter output current. It also is shown that this method is adaptable to various types of distortion.
Cost evaluation and architectures for access network using cable systems and radio systems
Authors: Ogawa Keisuke , Segawa Jun 
Published: July 2007

AbstractIn recent years, telecommunications technology has progressed rapidly, resulting in digital intelligent networks and cheap miniaturized terminals with high functionality. The main constraint on the ability to offer various services at inexpensive rates is the ability to economically construct access networks. The cost of constructing access networks can be reduced by using transmission technologies such as optical fiber and radio, multiplexing, and channel assignment, which have recently made remarkable advances. The total cost can be reduced by optimizing the elements of the access system, if it is assumed that these technologies can be attained economically. The cost of underground transmission infrastructures accounts for a large proportion of the total cost, so it is an important factor in trying to reduce access network costs, given the strong preference of the public for underground cables. Furthermore, combining optical fiber systems and radio systems is an effective solution and application of this method from the viewpoint of required frequency bandwidth is considered.
Efficient hybrid image coding scheme for color facsimile
Authors: Katsuno Satoshi , Koike Atsushi , Hatori Yoshinori , Endoh Toshiaki 
Published: July 2007

AbstractThe international standard coding scheme for continuous‐tone still images, JPEG, is not suitable for images that include characters and multicolor areas. When such images are encoded with joint photographic experts group (JPEG), the quality of the decoded images is heavily degraded. A hybrid coding scheme is proposed that combines JPEG and joint bilevel experts group (JBIG) to solve this problem. With this coding scheme, characters and multicolor areas are subtracted from an original image and coded with a JBIG and DPCM coding scheme. The subtracted continuous‐tone areas in this image are coded with a JPEG coding scheme. In this paper, experimental results using several kinds of test images show that the proposed method improves the quality of the decoded image much more than the JPEG coding scheme does.
Input characteristic of tri‐plate aperture array antenna
Authors: Tsukamoto Katsuya , Arai Hiroyuki 
Published: July 2007

AbstractThis paper treats an array antenna excited electro‐magnetically by a feed probe through holes (aperture elements) on the upper conductor as the radiating element in a tri‐plate antenna configuration. The impedance of the feed probe is analyzed by the induced electromotive force (emf) method in the spectral domain with a periodic boundary condition. The results are compared with the measured data. From the numerical results, it is found that an impedance matching between the probe and the radiating elements can be realized by adjusting the probe length and that the resonant condition for the antenna can be determined. Further, it is found that the impedance of the strip line to the feed probe and the impedance of the feed probe determine the input characteristics which become the operating condition of the tri‐plate antenna. The analysis results agree well with the measured data so that the validity of the method is confirmed.
Design and fabrication of 94‐ghz slot array antennas
Authors: Kobayashi Hiroaki , Yasuoka Yoshizumi 
Published: July 2007

AbstractA slot array antenna with parasitic slots was fabricated with the goal of increasing the gain of a slot antenna on a thick dielectric substrate operating in both millimeter and submillimeter wave regions. By using the design values obtained by microwave model experiments, a 94‐GHz millimeter‐wave slot array antenna was fabricated on a fused quartz substrate and the power gain of this antenna was experimentally studied. The fabricated antenna was found to operate as an array antenna at 94 GHz. Its power gain was increased by 5 ˜ 6 dB over that of the single‐slot antenna. This value agreed well with the 5.5‐dB gain improvement derived in the microwave model experiments. Hence, it was confined that the parasitic slots effectively contribute to the gain improvement of the antenna.
Characteristics of orthogonal slow frequency hopping/16‐quadrature amplitude modulation system with an interference immunity decoding method for digital land mobile communications
Authors: Hamaguchi Kiyoshi , Sasaoka Hideichi 
Published: July 2007

AbstractThis characteristics of a slow frequency‐hopping system using 16‐ary quadrature amplitude modulation (SFH/16‐QAM) to provide superior spectral efficiency and high‐quality transmissions in digital land mobile communications is investigated. In this method, highly efficient transmissions are realized with 16‐QAM through fading distortion compensation based on the injection of pilot symbols; but, since 16‐QAM alone provides insufficient immunity to interference, several strategies are required for applications to cellular systems. Here, a new interference immune decoding method is proposed that is based on an improvement in error‐correction methods. In the orthogonal SFH, since mutually different hopping patterns are used for each cell, the interference waveforms from other cells are randomized with respect to the desired waveform. By using this property, the level of the interference superimposed on the desired waveform is detected and estimated from the gaps of inserted periodic slots, and the interference immunity of 16‐QAM with minimum weighted Euclidean distance decoding is improved. Computer simulations of frequency selective fading shows that the proposed method has strengths relative to the near‐far problem and is especially effective for utilization in the cellular system uplink. The introduction of voice activated control is shown to be effective in the downlink. Also, as a result of the frequency diversity realized through SFH, performance degradations due to slow fading are slight.
Measurement of characteristics of reflected signals from buried objects in sandy soil using a cw radar
Authors: Shibata Kouji , Taniguchi Kougaku , Saito Yasunori , Nomura Akio 
Published: July 2007

AbstractThe fundamental characteristics of signals reflected from objects buried in the ground were measured with a CW radar system. In this measurement system, the reflected signals from buried objects are detected synchronously so that the measurement of amplitude and phase of the reflected signals is possible. From the results of measurement, it was found that the reflected power from buried objects is almost proportional to the minus fourth power of the equivalent distance and that the phase variation agrees almost with the result anticipated from Snell's law under a plane wave approximation. From these observations, it is found that the measurement of the reflected signals from buried objects is possible with a CW radar system, and that underground remote sensing also is possible.
Analog coherent optical space communication system using polarization ellipticity angle modulation
Authors: Kuri Toshiaki , Tsukamoto Katsutoshi , Morinaga Norihiko 
Published: July 2007

AbstractIt is expected that analog coherent optical communication systems will become an important system for future space communications, in which an optical carrier is coherently modulated by frequency‐multiplexed radio signals and optically transmitted. In this paper, the fundamental of the analog coherent optical space communication system are investigated, and a new analog optical communication scheme suitable for the space communication is proposed and analyzed. In the proposed analog scheme, the polarization ellipticity angle is selected as the modulation parameter, and the insensitiveness to the phase noise of the high‐power laser and to the polarization axis mismatch are obtained as well as the high detection gain due to the use of a wideband FM signal during the demodulation of the polarization ellipticity angle.
Atm hitless line protection switching method for forced switch commands
Authors: Ohta Hiroshi , Ueda Hiromi 
Published: July 2007

AbstractThis paper proposes a hitless line protection switching method for SDH‐based ATM networks. The proposed method aligns cell streams of side 0 and side 1 using bit comparison of the received cells to realize hitless line switching on forced switching. A cell stream alignment algorithm, which consists of the search process, the confirmation process, and the out‐of‐alignment detection process, is introduced. Evaluation shows that this algorithm provides quick and stable cell stream alignment. The standard line protection switching control method defined in ITU‐T Recommendation G.783 can be incorporated into this method.
Clique packing and dynamic channel assignment in cellular mobile communication systems
Authors: Nakano Keisuke , Sengoku Masakazu , Shinoda Shoji , Abe Takeo 
Published: July 2007

AbstractThis paper discusses the communication traffic characteristics of Dynamic Channel Assignment (DCA) in cellular mobile communication systems. In general, it is difficult theoretically to analyze the communication traffic characteristics of DCA. This paper proposes an approximate method called clique packing, for analyzing the blocking probability performance of an idealized DCA. For calculating the blocking probability of clique packing, an approximate formula is derived which is based on the Erlang B formula and is in a simple form. It is shown that the numerical results of the approximate method agree with computer simulation results.An approximate analytical method for calculation of the blocking rate of practical DCA methods such as the first‐available method also is proposed. To calculate the blocking rate of the practical DCA methods, the simple formula for clique packing is used after modeling the practical DCA methods as clique packing. It is shown that the modeling is appropriate. This modeling enables the blocking rate of the practical DCA methods to be calculated by using the approximate formula for clique packing.
Performance of high‐speed data transfer using an fec method in a multimedia network environment
Authors: Murata Masayuki , Kikuchi Yasutoshi , Miyahara Hideo 
Published: July 2007

AbstractIn the ATM system, all multimedia information, such as voice, picture and data, is divided into packets with the fixed length of 53 bytes, called cells, and the cells are transferred. Intensive studies have been made on the performance of the system, where such multimedia information is multiplexed in the network switch. In the ATM network, the cell loss is not compensated, and it is necessary that the end‐user should recover from the errors in order to realize highly reliable data transfer among computers. As one such approach, the error‐correcting code (FEC) has been considered interesting.From such a viewpoint, this paper evaluates analytically the data transfer performance when FEC is used. When FEC is used, the redundant cell produces an overhead, which may enhance congestion when the traffic in the network is high and deteriorate the performance. Also, from this viewpoint, this paper considers the priority control, where the redundant cells are discarded positively when the network is congested. The effectiveness of the approach is examined, as in the data transfer performance for the case where the video and the data exist together in the traffic, and it is demonstrated that the control parameters in the priority control are especially important in that case.
Effect of incorporating multicast traffic under the heterogeneous load condition in the output buffer‐type asynchronous transfer mode switch
Authors: Tode Hideki , Okada Hiromi , Ikeda Hiromasa 
Published: July 2007

AbstractIn the asynchronous transfer mode (ATM) switch, unbalance with respect to the statistical destination port selection among the output ports can exist. There has been some research on output buffer‐type ATM switching architecture in the case of the point‐to‐point cell arrival, assuming such nonuniform load condition of the output ports. However, the multicast traffic arrival condition, very important in future multimedia networks, has not been considered. Therefore, we evaluate the switch performance of the output buffer‐type architecture in the case of including multicast cells at various ratios among the arrival cells on condition that the total amount of traffic load through all output ports is constant. As a result, it is clarified that exchanging the multicast cells intentionally in the ATM switch leads to the improvement of cell‐loss performance in the output buffers having statistically high selection rate, if the buffers that are offered statistically high load, actually accommodate as many of the multicast cells as possible. From these results, by means of the network control that incorporates the multicast calls at a constant ratio in each ATM switch, it is possible to prevent the excessive load concentration to specific output port having statistically high utilization.
Near‐field measurement method of a phased‐array antenna—measurement of element amplitude and phase for array
Authors: Haryu Ken'ichi , Chiba Isamu , Mano Seiji , Katagi Takashi 
Published: July 2007

AbstractOne of the measurement methods for a phased array is the rotation element field vector (REV) method. With this method, the relative amplitude and phase of the radiated field of each element antenna can be found from only the measurement of the amplitude. Hence, an arbitrary radiation pattern made possible by the tested phased antenna can be realized. To derive the far‐field radiation pattern of a large aperture antenna, the near‐field measurement method is often used. When a phased array realizing various radiation patterns is measured by this method, a prohibitive amount of time is required because the electric field distribution on the plane on which the probe antenna moves differs depending on the excitation phase distribution. Because it is not possible to obtain relative amplitude, the phase of the radiation field of each element antenna necessary for realization of an arbitrary radiation pattern cannot be obtained. When the REV method is applied for near‐field measurement, the direction of the probe antenna seen from each element antenna differs with respect to the reference direction installed on the phased‐array antenna. Therefore, it is necessary to find both the amplitude and the phase of the electric field received by the probe antennas at different locations in order to obtain the relative amplitude and phase of the radiated field of each element antenna in the same direction needed for the radiation pattern synthesis of the far field. In this paper, a phased‐array antenna is used as a probe antenna. The REV method is applied to both this antenna and the phased‐array antenna being tested. A method is presented for finding the relative amplitude and phase of the radiation pattern of each element antenna using only the measurement of the amplitude.
Vehicle‐to‐vehicle communications and ranging system using spread spectrum techniques
Authors: Mizui Kiyoshi , Uchida Masatoshi , Nakagawa Masao 
Published: July 2007

AbstractA vehicle‐to‐vehicle communications and ranging system able to perform communications and ranging simultaneously using spread spectrum techniques is proposed in this paper. In this system, a vehicle (Vehicle‐A) can obtain information on a target vehicle (Vehicle‐B) by spread spectrum demodulation based on information calculated and retransmitted by Vehicle‐B in response to a PN signal transmitted by Vehicle‐A. The distance between Vehicle‐A and Vehicle‐B can be measured accurately by detecting the phase difference of the sent and received PN signals. In addition, Vehicle‐A can measure the distance between the two vehicles only through the waves reflected from the transmitted PN signal (as in the case of conventional spread spectrum radar), even if the target vehicle system is not a system‐loaded vehicle. This system not only prevents accidents but also allows safe driving without delay by communicating vehicle information and operator information and then measuring the distance between two vehicles effectively.Computer simulation results confirmed that the proposed system allows Vehicle‐A to demodulate information from Vehicle‐B and measure the distance between the vehicles simultaneously even when interference signals from vehicles running in the same or opposite direction exist.
Two‐dimensional analysis of AlGaAs/GaAs heterostructure devices
Authors: Yokoyama Kiyoyuki , Tomizawa Masaaki , Yoshii Akira 
Published: July 2007

AbstractA two‐dimensional device simulator HESPER, which can numerically analyze the AlGaAs/GaAs heterostructure devices, has been developed. This program was applied to a heterostructure bipolar transistor and its performance was compared with a homostructure device. As a result, it was shown that the transistor characteristics such as current gain and cutoff‐frequency are improved greatly by the introduction of a heterostructure. In addition, from carrier and potential distributions, the advantage of heterostructure devices was clarified. Moreover, HESPER was applied to a two‐dimensional electron gas FET, and the calculated transconductance values have agreed well with the measured results for different AlGaAs thicknesses. Furthermore, it was also suggested that the increasing mobility in the low electric field region and/or the saturation velocity mobility are effective to realize the high‐speed operation. That is, we can expect more excellent performance of the two‐dimensional electron gas devices at 77 K and/or in velocity overshoot region.