bluuebunny/crossref_metadata_2025 huggingface dataset:
Migration method for subsurface radar considering variation of propagation velocity in depth direction
Authors: Ho Gwang‐Su , Kawanaka Akira
Published: July 2007

There 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

The 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

This 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

The 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

Generated 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

In 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

The 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

This 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

A 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

This 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

The 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

It 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

This 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

This 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

In 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

In 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

One 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

A 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

A 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.
Analysis of surface‐acoustic‐wave reflectors on piezoelectric layered substrates and its application to resonators
Authors: Takeuchi Masao , Yamanouchi Kazuhiko
Published: July 2007

This paper discusses the layered substrate with excellent temperature characteristics and a large electromechanical coupling coefficient and its application to the surface‐acoustic‐wave resonator. Assuming that periodic perturbations are given to the free surface of the layer and to the boundary between the piezoelectric substrate and the layer, the reflection characteristics of the grating reflector are analyzed using the mode‐coupling theory and the perturbation theory. The magnitude relation and the superposition of the perturbation on the free surface and the perturbation on the free surface and the perturbation on the boundary of the piezoelectric substrate and the layer, as well as the superposition of the electrical and elastic perturbations are clarified. The dependence of the mode‐coupling coefficient of the mode‐coupling equation on the layer thickness is experimentally verified using SiO2/128°Y ‐ XLiNbO3substrate. It is seen that the experimental result agrees well with the prediction by the theory. Then, a one‐port resonator in 200 MHz band was constructed indicating that there exists a layer thickness, for which the first‐order temperature coefficient of frequency is zero, and a fairly small capacitance ratio (55) is obtained.
A floating track method for complete routing
Authors: Sone Tadashi , Nakabayashi Kiyoshi
Published: July 2007

A “floating track” method is proposed for VLSI routing, which ensures a 100 percent connection ratio. This method automatically provides a connection path on the cells by using a line‐search algorithm and solves the problem of unconnected pin pairs by adding extra wiring tracks. Prevention rules and correction procedures are provided for the wiring shorts and disconnections caused by the track addition. Based on the distribution of the track addition requirement calculated from the location and status of the search line, a fast algorithm is developed for determining the location of the additional tracks. With this algorithm a number of unconnected pin pairs can be connected quickly without a penalty in chip size. The layout result of a 20‐Kgate 4‐layered VLSI confirms the usefulness of this method for designing high‐density multilayered VLSIs.
Reduction of dynamic RAM power dissipation by a multidivided data‐line structure
Authors: Kimura Katsutaka , Hori Ryoichi , Etoh Jun , Kawajiri Yoshiki , Itoh Kiyoo
Published: July 2007

To realize a highly integrated large‐capacity DRAM with megabit size, problems such as low S/N and increase of power dissipation due to the charge‐discharge of data‐lines must be resolved. As a possible step toward the solution, we have already proposed a multidivided data‐line system. The feature of the system is that it controls in common the input‐output information of the multidivided data‐lines by a single decoder‐output control‐line, and a senseamplifier and the common I/O‐line are provided between two adjacent divided data lines. However, a quantitative evaluation of the system has not been made sufficiently. From such a viewpoint, this paper presents a quantitative comparison of the system with other systems mostly from the viewpoint of the power dissipation. As a result, it is seen that the system can reduce the power dissipation to one‐third or less, compared with earlier systems. It is also seen that by introducing the hierarchical I/O‐lines and the interchanged connection of the decoder output‐line and the data line, a high‐speed, low‐noise system can be realized. The usefulness of the system is verified by the design and evaluation of the experimental 1 Mbit DRAM. The performance of the fabricated chip with the area 46 mm2is access time of 90 ns and power dissipation of 295 mW (cycle time 260 ns).
Some aspects of position‐sensitive photodetectors made of amorphous silicon
Authors: Ogita Masami , Kawamura Kazuhiko , Yamada Tsutomu , Yamamoto Tatsuo
Published: July 2007

Position‐sensitive photodetectors detect an illuminated position without using image scanning. A large area detector of dual‐axis tetralateral PSD has been fabricated using amorphous silicon for low cost. The effective area of the device was 9.6 × 9.6 mm2, the detection deviation within 2 mm from the center was 0.3 mm and the pulse response time was around 1.5 ms. The resistive divider layer using Pd and Mo thin films provided good results. The position‐sensitive characteristics were simulated numerically by using Lucovsky's equation and the result was in good agreement with the experimental result. The analytical results lead us to the conclusion that in case of two‐dimensional dual‐axis tetralateral PSD, the nonlinearity in the position coordinate of the measured signal is caused by the introduction of both coordinate components for illuminated position (x0,y0) to each signal potential components at thexoryaxis.
Power‐combining operation of window‐output cylindrical cavity multiple‐device structures
Authors: Nogi Shigeji , Fukui Kiyoshi
Published: July 2007

In a multiple device oscillator having a cylindrical cavity loaded with active devices in a ring‐like manner, a method is proposed in which the power‐combined output is extracted through a window on a side wall of the cavity. This paper reports on an analysis of operation and presents the experimental results. First, a modal analysis has been performed based on a lumped element model. To create a situation in which only the desired output mode (TM020) is stable, a condition of suppressing undesired modes is established for the case where the conductances for suppression of undesired modes are arranged: (A) in the direction of the current of the desired node on the cavity bottom plane; and (B) at the location of the zero electric field of the desired mode. It is shown that suppression of undesired modes is more feasible in the new structure than in the conventional probe output method. Next, corresponding experiments have been carried out for an eight‐element oscillator. It is shown that suppression method (B) can suppress the undesired modes with a lower loss than (A), and that (B) enables power combination of almost 100 percent under the complete suppression of undesired modes. By means of an experiment in which the same structure is used as a reflection amplifier, it is found possible to combine the input power and the available powers of each device. Since the window‐output oscillator/amplifier does not require a probe and is easily fabricated even for millimeter wave applications, it is considered very practical.
Design and evaluation of wafer transfer system for LSI production
Authors: Sakano Susumu , Kuroda Hisao , Asakawa Makoto
Published: July 2007

An automatic wafer transportation system has been developed that is suitable for the LSI fabrication line. Design objectives have been to achieve a flexible wafer routing and flexible line construction ensuring a high degree of cleanliness. The system consists of a computer‐controlled carriage system carrying wafer cassettes on a ceiling track, and standardized interface mechanisms installed on each equipment. This paper describes technical factors involved in the realization of flexible lines, and considers also fundamental track arrangement, carriage characteristics, a wafer‐routing control method, and low dust mechanisms.
Design of low–loss saw filters employing distributed acoustic reflection transducers
Authors: Kodama Toshikazu , Kawabata Hirokazu , Sato Hiroaki , Yasuhara Yoshihiko
Published: July 2007

As a means to reduce the loss in an SAW filter, the IDT (interdigital transducer) called the internal reflection‐type transducer has been studied extensively recently. This IDT is believed to be useful as a filter for video and broadband data transmission since it is simple in structure and has low loss over a broadband while its fabrication process and external circuit are simple. So far, the filter constructed with this IDT has had a large ripple in the passband due to a large spurious reflection. To alleviate this problem, a new distributed acoustic reflection transducer is proposed as an internal reflection type IDT in which suppression of the unwanted spurious reflection is possible over a broad frequency range. Next, the operation mechanism of this IDT is investigated and a first‐order design method is presented. It is pointed out that a low‐loss filter with an insertion loss less than 10 dB and spurious reflection suppressed by more than 45 dB can be realized with this IDT over a broad frequency range.
Analysis of broadside–coupled suspended strip lines with side–wall grooves
Authors: Wang Bai Yi , Yamashita Eikichi , Atsuki Kazuhiko
Published: July 2007

Compared to microstrip lines, suspended strip lines have characteristics of low loss and weak dispersion and are being applied to millimeter‐wave circuits. Suspended strip line structures analyzed in the past have been limited to those which have the same substrate width as that of the outer conductor. However, in many practical cases, the side‐walls of the outer conductor have grooves to support a dielectric substrate. The authors have already proposed a quasi‐TEM wave analysis method based on a variational approach using the spline function for trial functions to estimate the effects of these grooves on the characteristics of single‐conductor suspended strip lines. This paper applies this method to characterize broadside coupled strip lines which are necessary to design millimeter‐wave directional couppiers and filters, and considers the effects of the grooves on characteristic impedance, propagation velocity, and coupling coefficient. The proper selection of spline knots is discussed to attain various characteristic constants with high accuracy.
A placement method based on logic circuit structure information
Authors: Takagi Shigeru , Nakabayashi Kiyoshi , Ishikawa Yuuzou
Published: July 2007

Logic circuits for VLSI have become more and more attractive. This paper presents a new placement method reflecting such logic circuit structural features as signal flow direction and logically repeated structure in the chip layout. The placement steps are as follows. The logic synthesis system synthesizes multilevel Boolean expressions for the function block from their high‐level functional specifications and outputs a relative layout for these Boolean expressions. The Boolean expressions are then mapped into physical gates. Finally, the layout system determines the position of physical gates using the relative layout and the mapping information.
An evaluation of leakage inductance for a flat cable transformer with a circular cross–sectional core
Authors: Ueda Yoshinori , Koshiba Tsuneori
Published: July 2007

We have derived the relationship between the leakage inductance and the winding structure for an electronic transformer with a flat cable wound around a circular cross‐sectional core. It is found that: (1) the leakage inductance of a flat cable transformer with a circular cross‐sectional core is approximately identical to one with a square core cross‐sectional core. Next, the winding configuration of a multilayer winding flat cable transformer is classified into lap winding, turn‐up lap winding and twisted lap winding; (2) the leakage inductance is higher for the lap winding and the turn‐up lap winding than for the one layer winding, but the increase of the equivalent capacitance is minimal for the lap winding; (3) the leakage inductance is even smaller in the twisted lap winding than in the one layer winding; and (4) the leakage inductance per winding length does not increase in the flat cable transformer even if insulators are inserted between layers.

Further, based on the leakage coefficient, the unit leakage constant is defined. It is found that: (5) the circular cross‐section core is superior to the square cross‐sectional core for a wider relative bandwidth and a restricted range of unit leakage constant; and (6) a wider relative bandwidth is more difficult to obtain as the core becomes smaller. These results agree well with experimental findings.
Hi‐bicmos 32‐bit execution unit
Authors: Hotta Takashi , Maejima Hideo , Iwamuar Masahiro , Kuri Kouzaburou , Ueno Masahiro , Masuda Ikurou , Hotta Atuo
Published: July 2007

The applicability of the Hi‐BiCMOS (High Performance Bipolar CMOS) technology to the 32‐bit execution unit has been researched to improve the function and speed of such processors as minicomputers CPUs. The HiBiCMOS technology enables MOS devices with performance comparable to pure CMOS LSIs and bipolar devices with performance comparable to pure bipolar LSIs to be combined on the same substrate. Device integrations comparable to CMOS LSIs have been achieved by the utilization of macrocells composed mainly of MOS circuits. Attempts have been made to speed‐up the macrocells by adding Hi‐BiCMOS circuits.

In this paper, the feedback‐type smallamplitude precharge circuit is proposed and fabricated. This circuit affords precise bus voltage. Also, the carry propagation circuit that uses the bipolar sense amplifier to achieve the machine cycle of 25 ns is proposed. Consequently it is confirmed that the precharge circuit operates two times faster and the carry propagation circuit 3.3 times faster than pure CMOS circuits. Thus, one of the promising candidates for the ultrahigh‐speed one‐chip processors is shown.
Maximum available power gain of microwave‐transistor amplifier under large‐signal operation
Authors: Umeda Hiroyuki , Takahashi Kenichiro , Shiraga Yoshiaki
Published: July 2007

Based on linear small‐signalSparameters, large‐signalSparameters are described in terms of the output of the amplifier. With the use of theseSparameters, the maximum available power gain under the large‐signal operation is discussed. The basic analysis method is based on the power chart representation of the input and output powers proposed by Linvill. The input and output powers are represented as points on two paraboloids. From the graphical relation of this parabola, the unconditional stability condition and the input and output matching condition can be formulated. The gain compression phenomena under the large‐signal operation is investigated. Next, with microwave GaAs MESFET's, the measured results of the large‐signalSparameters are shown, as well as the experimental results of the maximum available power gain by the effective load‐pull method. It is shown thatS21andS22of theSparameters have output power dependences of the quadratic form. It is also found that the theoretical maximum available power gain computed from the linear small‐signalSparameters and the nonlinear coefficient of the output power dependence agrees well with the experimental values measured by the effective load‐pull method.
Distributed fluid sensor using eccentrically cladded fibers
Authors: Yoshikawa Hiroshi , Sugata Akihiko , Watanabe Minoru , Ohno Yutaka
Published: July 2007

To increase the sensitivity of distributed gas or liquid sensors using the evanescent wave of optical fibers, methods such as making the fiber single‐mode and reducing its cladding thickness or removing it completely, can be considered. However, the core of the single‐mode fiber is only a few micrometers in diameter and, therefore, it becomes very difficult to preserve it without the cladding layer. On the other hand, increasing the cladding thickness will reduce its sensitivity. In this paper, the eccentrically cladded fiber is proposed as a means to increase the sensitivity without the need to reduce its diameter. The theoretical analysis and its experimental verification are carried out. As a result, it is shown that if the eccentricity is increased, the sensitivity will not decrease remarkably, even at large cladding diameters. Further, as experimental evidence of liquid detection, optical losses of a few decibels per centimeter were observed by attaching a liquid to the fiber. This indicated the possibility of highly sensitive distributed‐type sensors. Because of the good agreement of theoretically estimated radiation losses of W‐type fibers with experimental results, it is concluded that eccentrically cladded fibers can be designed to exhibit the desired sensing characteristics.
Comparison of characteristics between inverted and normal structure heterojunction bipolar transistors
Authors: Akagi Junko , Yoshida Jiro , Kurata Mamoru
Published: July 2007

The collector‐top heterojunction transistor (C‐top HBT) with inverted structure is expected to operate at a much higher speed than the emitter‐top heterojunction transistor (E‐top HBT) because the former has a smaller base‐collector junction area. In this paper, the merits of the C‐top HBT compared to the E‐top HBT in circuit applications were investigated by the simulation of ring oscillation characteristics, including dependence on fan‐out and interconnect line length, and the divide‐by‐four circuit characteristics. The influences of the emitter, base and collector resistances and the external base capacitance of the HBT's on the switching characteristics, and the divide‐by‐four circuit performance were also investigated. The degree of improvement was evaluated, using results of simulation over HBT's with the reduced base resistance and the external base capacitance.
Structure dependence of the short‐channel effect in GaAs MESFETs. Two‐dimensional device simulation
Authors: Hirose Mayumi , Ikawa Yasuo , Toyoda Nobuyuki
Published: July 2007

The structure dependence of the short‐channel effect in GaAs MESFETs has been investigated using a two‐dimensional device simulator. The short‐channel effect for 1‐μm gate length has been clarified as being due to the decrease in the potential barrier at the substrate region under the channel, especially toward the source. This decrease in the potential barrier increases the current injection into the substrate under the channel, and causes the threshold voltage and a decrease in theKvalue, which is one of the performance criteria of FETs. A structure with a thin source/drain n+layer, an offset structure with a small spacing between the gate electrode and the n+layer, and an LDD structure with an intermediately doped layer between the gate and the n+layer increase the potential barrier effect in the substrate compared to a conventional self‐aligned structure, thereby reducing the short‐channel effect. In addition, the formation of ap‐layer around the n+layer increases further this effect, resulting in an almost short‐channel affect free FET action down to 1–μ gate length.
Magnetically tuned microwave oscillator using the YIG film and its applications
Authors: Tsutsumi Makoto
Published: July 2007

Based on the fact that the magnetostatic mode in a YIG thin film depends on the direction of a dc magnetic field, a frequency‐controllable oscillator is proposed. First, the dispersion and delay characteristics are analyzed theoretically for the magnetostatic wave in a YIG thin film magnetized in an arbitrary angle. Especially the delay characteristics have been analyzed both in terms of the group delay and the phase delay, and correlated with the oscillation frequency. Next, on both sides of a YIG thin film with a thickness of 13.6 μm and a size of 5 × 15 mm2, ten metal strips are evaporated at a pitch of 1 mm. The filtering characteristics of this Bragg reflection filter are then evaluated. Subsequently, this filter and an FET amplifier are combined to form an oscillator for 2 to 4 GHz. Measured results for the oscillation characteristics, output power and spectrum for different magnetic field directions are compared with theoretical results. Finally, as an application of this oscillator, a correlator is proposed and its operation is explained.
Electromagnetic wave absorbing properties of carbon‐rubber doped with ferrite
Authors: Naito Yoshiyuki , Yin Jifang , Mizumoto Tetsuya
Published: July 2007

When ferrites are used for electromagnetic wave absorbers in the VHF and UHF bands we note their excellent properties such as their wider dynamic frequency bandwidth and their thinner thickness than that of lossy dielectric absorbers, which are due to their magnetic losses. However, there exists an upper frequency limit beyond which the frequency bandwidth of ferrite absorbers becomes narrower than that of lossy dielectric absorbers. In this paper we added ferrites to carbon‐rubbers and examined their characteristics as electromagnetic wave absorbers. We found through experiments that the relative bandwidth is widened more than twice by adding ferrites of only relative weight ratio 0.2 to rubber when the relative weight ratio of carbon to rubber is 1.1. Although we made measurements in the frequency range of 5 to 6 GHz, we expect the same effectiveness at higher frequencies.
On–chip multibit–test scheme for VLSI memories
Authors: Hidaka Hideto , Fujishima Kazuyasu , Kumanoya Masaki , Miyatake Hideshi , Dosaka Katsumi , Nishimura Yasumasa , Yoshihara Tsutomu
Published: July 2007

To reduce the time needed for testing VLSI memory chips, an on‐chip multibit‐test (MBT) scheme is proposed. The conditions for the test scheme and the relationship between the test mode and the memory array architecture (data bus structure, redundancy scheme, and so forth) are discussed. When the MBT mode is applied to the 1‐Mbit DRAM, the increase in the chip area and power consumption are minimized, and the test for a 256‐K bit device can be adopted to the memory array operating test. Using this technique, the time required for testing the device is reduced one‐half to one‐third.
Computer—aided estimation of refractive—index profile of optical waveguides from propagation—mode near field pattern
Authors: Sawa Shinnosuke , Ono Kazuo , Norimatsu Naoki , Kakemizu Kouji
Published: July 2007

Several methods have been proposed for estimating the structural parameters of a waveguide from transmission characteristics of the guided mode. In this paper, a simple and effective method is proposed for estimating the index profile in the cross section of the optical waveguide. In this method the measured field distribution of the guided mode and that calculated from the assumed index profile are compared directly and the index profile is sought for which the two field distributions coincide. To confirm the validity of the method, numerical simulations have been carried out for several graded index slab waveguides. Even if the simplest step index profile is assumed as the initial guess of the profile, the index profile of the waveguide can be estimated with practically sufficient accuracy. In this method, no differential process is needed for the measured values nor a high‐degree smoothing operation. Hence, the method is expected to be superior to others in terms of noise tolerance.
Effect of dielectric constant on characteristics of transmission lines formed in multilayer ceramic circuit board
Authors: Hashimoto Kaoru , Niwa Koichi
Published: July 2007

The effects of the dielectric constant on the transmission characteristics of multilayer ceramic circuit boards were examined. Multilayer ceramic circuit boards were fabricated using various kinds of ceramic materials with different dielectric constants, and their characteristic impedances, crosstalk, and propagation delays were measured. Experimental results show that the lower the dielectric constant, the higher the characteristic impedance, with less crosstalk and propagation delay. Based on these results, lowering the dielectric constant of the board material is found to be essential for realizing higher‐density wiring, e.g., the reduction in the dielectric thickness and transmission line spacing in multilayer ceramic circuit boards.