Recent progress of high-temperature superconductor Josephson junction technology is reviewed in the light of the future application to digital circuits. Among various types of Josephson junctions so far developed, ramp-edge-type junctions with a barrier layer composed of oxide materials in the vicinity of metal-insulator transition seem to offer a unique opportunity to fulfill all the requirements for digital circuit applications by virtue of their small junction dimensions, overdamped properties and relatively high IcRn product values at the temperature of around 30-40 K. Recently developed interface engineered junctions can be classified as junctions of this type. These junctions also raise an interesting problem in physics concerning the possibility of resonant tunneling of Cooper pairs via localized states in the barrier. From the viewpoint of practical applications, the improvement of the spread of the junction parameters is still a serious challenge to the present fabrication technology. Although interface engineered junctions seem to be most promising in this regard at present, 1σ spread of around 8% in the present fabrication technology is far from satisfactory for the fabrication of large-scale integrated circuits. The detailed understanding of the barrier formation mechanism in the interface engineered junction is indispensable not only for advancing this particular fabrication technology but also for improving other junction technology utilizing ramp-edge structures.

We present a symbolic language emptiness check algorithm based on forward state traversal. A verification property is given by a set of error traces written in ω-regular expression and is manipulated explicitly as a non-deterministic state transition graph. State space of the design model is implicitly traversed along the explicit graph. This method has a large amount of flexibility for controlling state traversal on the property space. It should become a good framework of incremental or approximate verification of ω-regular properties.

This paper clarifies two variable-to-fixed length codes which achieve optimum large deviations performance of empirical compression ratio. One is Lempel-Ziv code with fixed number of phrases, and the other is an arithmetic code with fixed codeword length. It is shown that Lempel-Ziv code is asymptotically optimum in the above sense, for the class of finite-alphabet and finite-state sources, and that the arithmetic code is asymptotically optimum for the class of finite-alphabet unifilar sources.

Recently, optical loss increases have appeared at high temperatures in some of the optical drop cables, introduced for FTTH field experiments. Optical drop cable is installed from homes to aerial facilities, and consists of an optical fiber cable part and a self-supporting wire part. Fiber micro-bending is caused by cable sheath buckling in high temperature environments when the cable is bent with the cable part inside. Moreover, adhesion between the steel reinforcing wires and the cable sheath is effective in preventing this fiber micro-bending, which induces loss increases. This paper also shows the most suitable range of adhesive ability in terms of both practical construction and environment.

In this paper, we propose a preemptive priority handoff scheme for integrated voice/data cellular mobile systems. In our scheme, calls are divided into three different classes: handoff voice calls, originating voice calls, and data calls. In each cell of the system there is a queue only for data calls. Priority is given to handoff voice calls over the other two kinds of calls. That is, the right to preempt the service of data is given to a handoff voice call if on arrival it finds no idle channels. The interrupted data call returns to the queue. The system is modeled by a two-dimensional Markov chain. We apply the Successive Over-Relaxation (SOR) method to obtain the equilibrium state probabilities. Blocking and forced termination probabilities for voice calls are obtained. Moreover, average queue length and average transmission delay of data calls are evaluated. The results are compared with another handoff scheme for integrated voice/data cellular mobile systems where some numbers of channels are reserved for voice handoff calls. It is shown that, when the data traffic is not very light, the new scheme can provide lower blocking probability for originating voice calls, lower forced termination probability for ongoing voice calls, and shorter average queue length and less average transmission delay for data calls.

In this paper, performance degradation of satellite broadcasting receiving antenna systems due to weather conditions is examined by measuring their G/T continuously. We show that an offset parabolic reflector antenna of smaller aperture tends to be less affected by weather conditions.

We have developed an InP-based monolithic optical frequency discriminator consisting of a temperature-insensitive optical filter and dual photodiodes. This integrated device detects the optical frequency deviation of the input light as differential photocurrent from the dual photodiodes, and the photocurrent is fedback to the light source for frequency stabilization through a differential amplifier. The FSR and extinction ratio of the filter are 50 GHz and 20 dB. The total opto-electronic conversion efficiency is 40%. In a frequency stabilization experiment using the developed discriminator, the frequency fluctuation of a DFB laser was reduced to less than 10 MHz.

A problem in image recognition in practical circumstances is that an observed image is often degraded by an imaging system. A conventional method in such a case is first to estimate the parameters of the imaging system and then restore the image before analysis. Here, we propose an alternative approach based on phase invariants in Fourier domain that needs no restoration and is fairly robust against both blur and noise. We show that the image phases in positive region of the Fourier transform of the point spread function (PSF) are blur-invariant provided that the PSF is central symmetric. Under the phase-invariant assumption, a phase correlation function between a standard image and the degraded image is used in developing the recognition algorithm. The effectiveness of this algorithm is demonstrated through experiments using ten classes of figure images from car license plates.

We developed an optical transceiver diode (TRAD) module for bi-directional time-compression-multiplexing (TCM) transmission systems. A wavelength-insensitive structure as a receiver and a low-capacitance configuration in the module provide a high sensitivity. Stable switching of 156 Mbit/s NRZ burst signals between the transmitter and receiver modes is achieved. In addition, it is shown that optical module cost can be further reduced by using passive alignment on a Si bench.

A 1.55-µm hybrid integrated wavelength-converter module was fabricated using a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA) on a planar-lightwave-circuit (PLC) platform. Clear eye opening and penalty-free wavelength conversion were obtained at 2.5-Gb/s modulation with a wide wavelength difference of 46 nm. The module showed good characteristics including low insertion loss (0.1 dB), and high conversion efficiency (-0.2 dB). It also showed stable wavelength conversion for as wide as a 13 temperature range.

We developed an optical transceiver diode (TRAD) module for bi-directional time-compression-multiplexing (TCM) transmission systems. A wavelength-insensitive structure as a receiver and a low-capacitance configuration in the module provide a high sensitivity. Stable switching of 156 Mbit/s NRZ burst signals between the transmitter and receiver modes is achieved. In addition, it is shown that optical module cost can be further reduced by using passive alignment on a Si bench.

A 1.55-µm hybrid integrated wavelength-converter module was fabricated using a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA) on a planar-lightwave-circuit (PLC) platform. Clear eye opening and penalty-free wavelength conversion were obtained at 2.5-Gb/s modulation with a wide wavelength difference of 46 nm. The module showed good characteristics including low insertion loss (0.1 dB), and high conversion efficiency (-0.2 dB). It also showed stable wavelength conversion for as wide as a 13 temperature range.

We have developed an InP-based monolithic optical frequency discriminator consisting of a temperature-insensitive optical filter and dual photodiodes. This integrated device detects the optical frequency deviation of the input light as differential photocurrent from the dual photodiodes, and the photocurrent is fedback to the light source for frequency stabilization through a differential amplifier. The FSR and extinction ratio of the filter are 50 GHz and 20 dB. The total opto-electronic conversion efficiency is 40%. In a frequency stabilization experiment using the developed discriminator, the frequency fluctuation of a DFB laser was reduced to less than 10 MHz.

An access attempt overload control method is proposed for CDMA cellular system to provide good communication quality to mobile stations under the traffic overload condition. Under the normal traffic condition, the effect of access attempts on the interference is negligible. But under the traffic overload condition, the interference due to access attempts could be large and deteriorate the communication quality (or reduce the capacity of a reverse link) if access attempts are not controlled properly. The numerical and simulation results show that our access attempt overload control method can maintain the interference caused by access attempts very low and the capacity of the reverse link is not reduced under the traffic overload condition.

High-temperature superconductor (HTS) receiving filter subsystem for mobile telecommunication base station has been developed. An 11-pole HTS filter using YBa2Cu3O7-δ (YBCO) thin films and a low noise amplifier were cooled to 70 K by a small cryocooler. Total noise figure of this subsystem was measured to be 0.5 dB. Furthermore the effect of using the subsystem in the receiver front-end of Code Division Multiple Access (CDMA) cellular base station was investigated. The transmitting power reduction of handy terminal was estimated to be about 35%.

We propose a novel planar filter design for narrow-band applications. The filter consists of half-wavelength ring resonators with open gaps. This design has three advantages over conventional planar designs: a smaller size despite narrow bandwidth, a sharper skirt response at the passband edge without notch, an excellent out-band attenuation. We demonstrated these advantages by fabricating an 8-poles filter centered at 1.95 GHz with a 5 MHz bandwidth using YBCO films on a 2 inch diameter MgO substrate.

Although there are many multimedia presentation systems on the market, they have some shortcomings and most of them only can work on one single computer, and few of them can work on Web. Thus, in the thesis we develop a network multimedia presentation system to let users easily design the multimedia presentation without restriction on technology or presentation time and place. Our system includes 3 main components: User Interface that includes temporal specification editor, spatial specification editor and multimedia object interface, Presentation Interface and Knowledge Base. There is a dynamic homepage generator in our system and we propose a displaying algorithm based on the Allen's theory, that there exist 13 temporal relationships between two intervals, for synchronizing the media objects.

A method for circular pattern recognition in a binary image and its implementation onto an FPGA are described. The proposed method is based on the template matching method using a modified matching degree. This method is implementable onto an FPGA and can realize a real-time system. The usefulness of the proposed method was confirmed by numerical simulations. The real-time performance was confirmed by experiments on the FPGA designed by using Verilog-HDL CAD tool.

Critical properties of real-time embedded systems must be verified before these systems are deployed as failing to meet these properties may cause considerable property damages and/or human casualties. Although Statechart is one of the most popular languages for modeling behavior of real-time systems, proof systems and analysis tools for Statechart so far are in research and do not fully support the semantics of the original Statechart, or have limited capabilities for proving real-time properties. This paper introduces a toolset ASADAL/PROVER for verifying temporal properties of Statechart extended with justice and compassion properties. ASADAL/PROVER is composed of two subsystems, RTTL-Prover and Model-Checker. The RTTL-Prover converts Statechart specifications into real-time temporal logic (RTTL) formulas of Ostroff, and then checks if the formulas satisfy a temporal property (also in RTTL) using theorem proving techniques. The Model-Checker supports verification of a predefined set of real-time properties using a model checking technique. The RTTL-Prover can support verification of any real-time properties as long as they can be specified in RTTL and, therefore, messages generated by the tool are general and may not be of much help in debugging Statechart specifications. The Model-Checker, however, can provide detailed information for debugging. ASADAL/PROVER has been applied successfully to some experimental systems. One of on-going researches in this project is to apply the symbolic model-checking technique by[3]to support Statecharts with a much larger global-state space. We are also extending the types of temporal properties supported by the Model-Checker.

Template learning has potential application in several areas of Cellular Neural Network research, including texture recognition, pattern detection and so on. In this letter, a recently-developed algorithm called Adaptive Simulated Annealing is investigated for learning CNN templates, as a superior alternative to the Genetic Algorithm.