bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large‐capacity optical communication systems
Authors: Nakagawa Kiyoshi 
Published: July 2007

AbstractAlong with widened and diversified social activities, there is an increasing demand for transmission capacity including voice, data, video and yet‐to‐evolve new business and entertainment markets. Studies are performed in ultrahigh‐speed optical modulation/demodulation circuits and transmission characteristics of rare earth doped fiber amplifiers which satisfy the requirements needed in widening the repeater‐span and increasing the transmission speed. It has become possible to realize ultrahigh‐speed 10 Gbit/s transmission systems with the capacity of about 130,000 telephone channels. In these systems, besides the flexibility in their transmission bit rate and new forms of installation, maintenance and operation, it is considered that the new technology will contribute to a great evolution in future optical communication networks and equipment. A prospective on a next‐generation large‐capacity optical communication techniques also is given.
128‐channel, 480‐km optical frequency division multiplexing transmission employing 0.98‐μm pumped erbium‐doped fiber amplifiers and a gain equalizer
Authors: Oda Kazuhiro , Fukutoku Mitsunori , Toba Hiromu , Kitoh Tsutomu 
Published: July 2007

AbstractIn optical frequency division multiplexing (FDM) transmission systems using optical amplifiers, the transmission distance is limited mainly by gain‐tilt of erbiumdoped fiber amplifiers (EDFAs), accumulations of the ASE noise, and crosstalk due to the four‐wave mixing (FWM). Especially when dispersion‐shifted fibers are used, the transmission distance is limited by the decrease of the allowable input level to the fiber due to the FWM. It is shown here that a 0.98‐μm pumped EDFA has a smaller gain‐tilt accumulation and is suitable for optical FDM transmission. Level diagram is designed taking into account the ASE noise and the FWM crosstalk accumulation; the relationship between fiber‐EDFA input level and the receiver sensitivity is investigated. A 128‐channel optical FDM transmission experiment with 10‐GHz spacing was carried out, and it is demonstrated that all channels can be successfully transmitted through 480 km of dispersion‐shifted fiber with a power penalty of less than 1 dB by using a tunable gain equalizer.
20‐gb/s optical transmitter and receiver using sige integrated circuits
Authors: Tezuka Hiroshi , Fukuchi Kiyoshi , Takeuchi Takeshi , Soda Masaaki , Suzaki Tetsuyuki , Hashimoto Takasuke , Sato Fumihiko 
Published: July 2007

AbstractA 20‐Gb/s optical transmitter and a receiver with 3R functions is developed for ultrahigh‐speed optical communication systems for future multimedia communications. Integrated circuits (ICs), such as preamplifiers, differential amplifiers, D‐type flip‐flop (D‐F/F), and selectors with a 20‐Gb/s operating speed have been developed using the SiGe process as key components of the optical transmitter and receiver. A waveguide pinphotodiode with very low capacitance is used to realize a wide bandwidth. A front‐end module with a bandwidth of 16 GHz and a gain of 43 dBQ has been achieved using the preamplifier IC and the waveguide pin‐photodiode (PD). A 20‐Gb/s optical transmitter and a receiver is fabricated using the developed SiGe. ICs, high‐speed optical devices, and a receiver sensitivity of −23 dBm are obtained.
Study of shape control for modular mesh antenna
Authors: Shimizu Masashi 
Published: July 2007

AbstractAs the satellite‐borne antenna becomes larger, the degradation of the electrical performance due to thermal deformation on the orbit becomes more problematic. The necessary reflector surface accuracy is determined by the operating frequency regardless of the antenna aperture size. On the other hand, mesh antennas often are used as a satellite‐borne antenna due to weight‐and‐containing requirement.In comparison to the conventional solid mirrors, the mirror surface deformation is known to be larger for the mesh antennas. Hence, it is necessary to control the mirror surface in order to maintain the performance of the mesh antenna.In this paper, the backprojection procedure to derive the mirror surface shape from the antenna pattern measurement is used for the mirror surface shape sensor. A closed‐loop reflector surface control is proposed in which an ultracompact pulse motor installed in the mirror surface for adjusting the cable length is used as an actuator. Instead of measuring the far‐field pattern on the ground base station, an experimental system is constructed for near‐field measurement with a near‐field scanner.The deformed mode is created intentionally which reflects the results of the thermal deformation analysis on the orbit, and a mirror surface control experiment is carried out. It is demonstrated that, by the proposed method, the mirror surface error can be reduced from 2.0 mm RMS to 0.38 mm RMS and the sidelobe level can be improved by 2.0 dB while the directive error can be corrected.
Multicarrier trellis‐coded eight‐phase shift keying system using frequency hopping
Authors: Okawa Koichi , Sasase Iwao 
Published: July 2007

AbstractA multicarrier trellis‐coded eight‐phase shift keying (8‐PSK) system using a frequency hopping (FH) technique is proposed to improve bit‐error rate (BER) performance in digital land mobile communications. In general, a trellis‐coded modulation (TCM) system is employed with interleaving in multipath fading environment; by contrast, in the proposed system, an FH technique is employed to disperse the influence of successively received weak signals due to multipath fading with small delay, i.e., without interleaving process. The BER performances of the proposed system are investigated by computer simulation. It is found that, although there is no improvement in diversity order by applying the FH technique, there is an improvement in energy efficiency as compared with a multicarrier trellis‐coded 8‐PSK system in a Rayleigh fading channel. It is also found that the performance of the proposed system is not affected by the fade rate of the channels, i.e., the proposed system is effective even under slow fading conditions. It is shown that the performance of the proposed system is affected by the number of hopping frequency; moreover, there is an optimum number of hopping frequency, which depends on the span of dominant error event path of the multiple trellis code employed. Therefore, it is found that the proposed system is effective in the case in which the processing delay time is restricted, such as mobile speech communications.
Analysis of stationary oscillations on josephson circuit
Authors: Kanasugi Akinori , Morisue Mititada 
Published: July 2007

AbstractDue to its strong nonlinearity, computer simulation has been used in most cases to analyze the Josephson circuit. Thus, it is difficult to obtain the general prospect for the solutions and their errors are apt to accumulate. This paper proposed an analytical method to solve the stationary oscillation, produced in such a circuit with any higher harmonic components, and the calculated analytical results show a good agreement with those of computer simulation. A method is proposed to obtain solutions based on the combined concepts of the Fourier analysis and harmonic balance method, assuming in advance that the stationary oscillation solution includes any higher harmonic components. The stationary oscillation solutions produced in the captioned circuit can be analyzed with good results. This method is applicable to the analysis of any nonlinear circuits other than the Josephson circuit.
An evaluation of leakage inductance for toroidal core transformers
Authors: Ueda Yoshinori , Muto Hiromichi , Koshiba Tsuneori 
Published: July 2007

AbstractThe effect of winding configuration on leakage inductance of a toroidal core transformer for electronic pulse‐drive circuits is investigated. Theoretical expressions for the effect of wire diameter, conductor spacing of primary and secondary windings, winding pitch, number of turns and core dimensions are derived. It is found that: (1) winding capacitance can be reduced without increasing the leakage inductance by applying an insulation coating to the core; (2) the leakage inductance is simply proportional to the number of turns; (3) a core of square cross‐section can reduce the ratio of leakage inductance to excitation inductance; (4) leakage inductance decreases with decreasing conductor spacing of the pair wire and with increasing diameter; (5) and the leakage inductance decreases with decreasing winding pitch and, in the case of a dense winding, it is less than that of a sparsely wound coil by as much as a value proportional to log (4/3). The experiments in which the above results were obtained were in good agreement with calculated values.
Distributed index formation of planar microlens
Authors: Chiba Takashi , Oikawa Masahiro , Iga Kenichi , Misawa Shigeyoshi 
Published: July 2007

AbstractFinding the distributed index formation in the fabrication of planar microlens is important in realizing the optimization of the conditions controlling the distribution as it determines the optical properties. The system is modeled under the assumption that the penetration of the metal dopant ions follows the drift‐diffusion equation. Before this equation is solved, the diffusion constant and the mobility of metal ions in a glass substrate are measured. It is found that the diffusion constant is strongly dependent on the ion concentration. Based on these findings, the drift‐diffusion equation is analyzed numerically to find the concentration distribution in the planar microlens. It is found that the thermal diffusion with a strong concentration dependence contributes significantly to the formation of concentration profile without a tail.
Measuring method of active impedance of crystal oscillator circuits
Authors: Toki Masahiro , Tsuzuki Yasuo , Mitsuoka Teruyoshi 
Published: July 2007

AbstractAlthough crystal oscillators are used widely in such electronic devices as communication equipment and measuring apparatus, it is not possible to determine if the circuit oscillates or how the adjustment must be made until the crystal is connected to the circuit. To remedy this situation and to improve the design method for the crystal oscillators, a method has been developed for measuring the two‐terminal impedance of the active circuit seen from the crystal terminal or the equivalent capacitance when negative resistance of a specific value is obtained. In principle, a known resistance is connected in series with the crystal terminal so that negative resistance is cancelled. Then the resultant pure capacitance is measured with a bridge circuit. A measurement system consisting of a bridge circuit which is controlled by a computer has been constructed. Representative oscillator circuits have been measured. It is found that a usable frequency range can be found from the measured frequency characteristics of the excitation current and the equivalent capacitance, and that the static capacitance of the active circuit seen from the crystal terminal can be adjusted to a desired value via an adjusting capacitance.
Multistable circuit using Λ‐shaped negative resistance devices and its application to frequency divider
Authors: Sekine Yoshifumi , Suyama Masatoshi 
Published: July 2007

AbstractNew voltage‐controlled negative resistance devices, Λ‐shaped negative resistance devices, are combined with Zener diodes and resistors to form a unit circuit. These unit circuits are connected in parallel to create circuit configurations that cannot be realized by previous voltage‐controlled negative resistance devices. This circuit exhibits multipeak characteristics and realizes a multistable circuit and a frequency dividerIn previous multipeak characteristics, the current peak increases with the voltage. In the present multipeak characteristics, the current peak can be set independetly. A multistable circuit has been constructed with the present structure, analyzed, and its characteristics found. The voltage of the stable point can be varied independently and the number of stable points can be varied with the gate voltage of the Λ‐shaped three‐terminal negative resistance device. When the multistable circuit is used for construction of a frequencey divider, the reset circuit can also be made simply with the Λ‐shaped negative resistance device. In addition to the 1/n divider, an arbitrary rational ratio divider can be fabricated by addition of a feedback loop.
Basic fuzzy logic circuit formed by using p‐MOS current mirror circuits
Authors: Yamakawa Takeshi , Miki Tsutomu , Ueno Fumio 
Published: July 2007

AbstractModern digital computers have great numerical calculation ability, but processing of fuzzy information is poor in terms of effectiveness and cost. Consequently, hardware systems peculiar to fuzzy information processing are anxiously awaited. This paper proposes a basic fuzzy logic circuit formed by using p‐MOS current mirror circuits, discusses the zero‐error condition and verifies their operations by the semicostom fuzzy logic IC designed in a standard Al‐gate p‐MOS technologyThe distinctive features of the proposed fuzzy logic circuits are:
any fuzzy logic functions can be implemented with one kind of master slice (Bounded‐Difference array);
variations of process parameters affect the electrical characteristics of the logic circuits very little;
the basic logic cell is accurate;
the current mode design facilitates the algebraic sum only by Al‐wiring; and
these fuzzy logic circuits can be useful in binary logic and multiple‐valued logic
The basic fuzzy logic cell described here will be a candidate for a logic circuit of Fuzzy Computer in the near future.
Displacement sensors and displacement signal coding circuits using twisted and bent dual‐core fiber
Authors: Taya Hiroyuki , Noda Ken‐Ichi , Kimuras Tadashi , Seki Yohsuke 
Published: July 2007

AbstractDisplacement and twist sensors are constructed by providing twist and/or bend to the dual‐core optical fiber composed of two parallel single‐mode fibers. A circuit is also presented which can produce the coded signal output for the displacement or twist. More precisely, theoretical analysis is made for the twist sensor, which is obtained by twisting the bent central part of the bothend fixed dual‐core optical fiber, and the displacement sensor, which is obtained by displacing the twisted central part of the both‐end fixed dual‐core optical fiber. It is shown that satisfactory sensitivity and the linearity in input‐output characteristics are realized. Then the basic characteristics are measured experimentally. The change of the phase difference due to the length difference of the two cores with twist and bend were measured. The result is in good agreement with the theory. Then as an application to the digital circuit, the principle is investigated to realized ΔM coding of the signal by vibrating the twisted dual‐core optical fiber in the perpendicular direction. Theoretical and experimental investigations are made on the initial rotation and twist, optical coupling to the fiber and the mechanical strength against shear stress due to twist. This will be the problem in practical applications.
A proposal of various recursive switched capacitor filters using a single OP‐Amp and experimental results
Authors: Kudo Michio , Hayashibes Rinpei 
Published: July 2007

AbstractA simple structure filter design technique which uses a first‐order passive circuit and a switched‐capacitor integrator as a negative feedback element is shown to be applicable to a wide variety of second‐order filters. The circuit features less power consuption, fewer component count and less cost. These features are not offered by switched‐capacitor filter designs proposed to date. Transfer function of the filter is analyzed. High Q‐factor bandpass filter design is developped and Q‐factor within approximately 50 ˜ 60 is obtained in the audio‐frequency region. It is demonstrated that local integration of the circuit can realize double Q‐factor and sensitivities of center frequency and Q‐factor can be decreased within one‐half. Improved low‐pass and high‐pass filter design which preserve the wide‐flat sharp transition response curve is proposed and the desired band‐eliminating filter consisting of the combination of them is also shown. Dynamic range of the input signal amplitude, which would be insufficient in current switched‐capacitor filter designs, is improved to have 60 to 70 dB. The effect of the driving pulse waveform on circuit operation is studied further.
A method for improving convergence in a power semiconductor device analysis program
Authors: Sakai Tatsuo , Shimada Yuuki , Katoh Kuniharu 
Published: July 2007

AbstractA new simulation technique for analyzing power semiconductor devices is presented in this paper. In this technique, quasifermi potentials are used as variables for current continuity equations and the upwind differential scheme is used for discretizing the current continuity equations after linearization according to Gummel's method. With this technique, it is possible to analyze the high bias condition of a device using a relatively rough mesh. A detailed design of breakdown voltage can be created since carrier generation and recombination are taken into account. The efficacy of this technique is confirmed by comparing the simulation results obtained using this new technique to assess the lateral MOSFET model with those obtained using a model reported previously. Analyses of 600 V‐ and 40 V‐ VD‐MOSFET using this new technique are carried out, and it is shown that the new technique is effective for modeling power semiconductor devices.
Fabrication of SiO2‐TiO2 glass planar optical waveguides by soot deposition process
Authors: Yasu Mitsuho , Kawachi Masao , Kobayashi Morio 
Published: July 2007

AbstractThis paper concerns the soot deposition fabrication of SiO2‐TiO2 planar optical waveguides using a starting material of SiO4‐TiO4. Two different methods are investigated: thermal oxidation using a CVD tube and direct flame hydrolysis using a torch. The resulting structures and their optical propagation losses are compared to arrive at the main results of this research as summarized below(1) The flame of hydrolysis process is superior to thermal oxidation CVD both in terms of the optical quality and producibility(2) The flame hydrolysis process permits fabrication of guides with arbitrary distribution of index of refraction for step and graded index, as well as single‐mode guides, and with optical losses of ˜0.1 dB/cmThe SiO2‐TiO2 waveguides achieved through this research, either in their obtained thin‐film structure or with additional microfabrication as necessary, will be valuable in the realization of various optical waveguide circuit functions.
Influence of arc discharge types on contact resistance
Authors: Sawa Koichiro , Asakawa Akira , Uekis Tadao , Miyachi Kunio 
Published: July 2007

AbstractThe state of the breaking contact can be steady arc, showering arc or no‐discharge depending on the circuit condition, even if the same current is cut off. These types of discharge are concerned not only with the wear of the contact, but also with the contact resistance. In this paper, using the automatic measuring instrument for contact resistance developed by the authors, the relation between types of arc discharge and the contact resistance is examined, mostly for the silver and palladium contacts. As a result, it is seen that the silver contact in steady arc condition has a fairly high contact resistance (50 ˜ 100 m Ω) with a large variance. On the other hand, the palladium contact in steady arc condition and the palladium and silver contacts in showering arc condition are relatively stable with low contact resistance. These properties are related to the erosion of contact surface by the arc. It is seen from the observation of surface by SEM that the contact resistance of the silver contact in steady arc is affected greatly by the surface film, while a metallic contact is maintained in the palladium contact. In the showering arc condition, both silver and palladium contacts maintain the metallic contact, with the measured contact resistance being in good agreement with the calculation by the theory of spreading resistance.
High rate preparation of C‐axis oriented aln films by reactive sputtering
Authors: Matsuoka Morito , Naoe Masahiko , Hoshi Yoichi 
Published: July 2007

AbstractHighly oriented AlN film has been formed at a high rate of a Targets Facing Type Sputtering (TFTS) method which has reduced substrate bombardment by various high energy particles. The relation between its crystal structure and the formation condition has been studied in detail. As a result, C‐axis oriented AlN film can be obtained for a wide nitrogen gas pressure range of 0.2 ‐ 10 mtorr at a relative low substrate temperature of around 400°C. In particular, at a low pressure of 0.5 ‐ 2 mtorr, C‐axis oriented film with good surface smoothness can be formed. Also, higher film deposition rate results in improved film orientation, and a good orientation with ΔO50 of 1.9° (σ002 of 0.9°) can be obtained at a rate of 0.6 μm/h even for a thin film of 0.2 μm thickness. Furthermore, it has been found that the orientation degrades with bias application to the substrate, and that a high‐orientation AlN film can be obtained by the TFTS method because of the suppression of substrate bombardment by high‐energy particles. From the forementioned results, to obtain a good quality C‐axis oriented AlN film with good orientation and surface smoothness, the necessity of using a sputtering method, such as the TFTS method, has been shown. In this case, particles with sufficient energy to destroy the film do not bombard the substrate, and sputtering particles themselves reach the substrate with an appropriate energy (several eV).
Realization of multiport D‐R mutator and its application to high‐pass filters
Authors: Ikeda Katsuji , Tomita Yasushi , Ishimoto Hidetaka 
Published: July 2007

AbstractActive RC circuits using gyrators as active elements can be applied to the realization of inductorless filters which inherit the superior transmission characteristics of LC filters. However, equivalent transmission characteristics can also be obtained by the application of D ‐ R mutators that simulate frequency dependent negative conductance defined as Y = s2D. Gyrators can be constructed from operational amplifiers used as voltage‐current transducers or negative impedance converters. In this paper, a multiport D ‐ R mutator is realized in the way that the capacitance takes the place of the resistance of multiport gyrator, which is constructed by negative impedance converter using current conveyors as voltage‐current transducer. It is shown that a multiport D ‐ R mutator obtained in this way can then be applied to the realization of a high‐order, high‐pass filter; the excellent measurement results are also presented. It is shown that the realized high‐pass filter has few passive elements in comparison with those derived using methods based on operational amplifiers, the filter characteristic can be easily tuned by grounded passive elements, and the proposed active elements are particularly efficient for the realization of high‐order, high‐pass filters.