A data-base for data compression is universal if in its construction no prior knowledge of the source distribution is assumed and is optimal if, when we encode the reference index of the data-base, its encoding rate achieves the optimal encoding rate for any given source: in the noiseless case the entropy rate and in the semifaithful case the rate-distortion function of the source. In the present paper, we construct a universal data-base for all stationary ergodic sources, and prove the optimality of the thus constructed data-base for two typical methods of referring to the data-base: one is a block-shift type reference and the other is a single-shift type reference.

Recent high-speed bipolar technologies based on SICOS (Sidewall Base Contact Structure) transistors are reviewed. Bipolar device structures that include polysilicon are key technologies for improving circuit characteristics. As the characteristics of the upward operated SICOS transistors are close to those of downward transistors, they can easily be applied in memory cells which have near-perfect soft-error-immunity. Newly developed process technologies for making shallow base and emitter junctions to improve circuit performance are also reviewed. Finally, complementary bipolar technology for low-power and high-speed circuits using pnp transistors, and a quasi-drift base transistor structure suitable for below 0.1 µm emitters are discussed.

A quasi-synchronous (QS) code division multiple access (CDMA) system is proposed for mobile communications. In the proposed method, which uses the time division duplex (TDD) mode of transmission, a mobile receiver can measure propagation delay changes. It then accordingly adjusts its transmission time so its signal can arrive at base station synchronously with other mobile units. A simple control unit is used at the mobile unit in order to reduce any error due to the propagation delay changes. The system operates as follows. At the start of a call, a mobile unit is quasi-synchronised through feedback control from the base station. The mobile unit then maintains synchronous status without any further base station feedback. The degree of the quasi-synchronous accuracy is determined by a clock in mobile units. This paper shows performance results based on using a clock rate of ten times faster than the spreading rate. Orthogonal codes are used for spreading the signals. The results demonstrate that the reverse link CDMA multiuser interference is to a great degree removed.

This paper describes, from a system architectural viewpoint, how knowledge-based technologies have been utilized in developing EXLOG (an LSI circuit synthesis system) and SOFTEX (a software synthesis system) inside the authors' projects. Although the system architectures for EXLOG and SOFTEX started from the same production systems, consisting of transformation rules in the middle of the 1980's, both branched off in different directions in the 1990's. Based on experiences with EXLOG and SOFTEX, the differences between LSI and software design models are discussed, and the future directions are indicated for the knowledge-based design system architectures.

The buried oxide nonintegrities, represented as the equivalent fixed oxide charge and interface trap densities at both the upper and lower interface of buried oxide, are evaluated for low-dose and high-dose SIMOX wafers, and their effects on device characteristics are investigated. The equivalent fixied oxide charge and trap densities at the lower interface, which are measured with buried oxide capacitors, are negligibly small in as-fabricated SIMOX wafers. This result enables us to make an analytical model of the parasitic drain/source-to-substrate capacitance in an SOI MOSFET, in which the effect of the depletion layer under the buried oxide is considered. The influence of thinner buried oxide and process-induced fixed oxide charge on the parasitic capacitance is explored with this model. The equivalent fixed oxide charge and trap densities at the upper interface are evaluated by the threshold voltage measurement in an SOI NMOSFET. The principle of this evaluation as well as the experimental technique are described in detail. The oxide charge and trap densities at the upper interface are higher than those at the lower interface for both SIMOX wafers. With a new model of the subthreshold slope based on a two-dimensional potential analysis the influence of the trap at the upper interface is discussed.

Mesa structures have been investigated to optimize a buried-heterostructure (BH) for a GaInAsP/InP surface-emitting (SE) laser regrown by metalorganic chemical vapor deposition (MOCVD), and it has been found that a square mesa top pattern of which the sides are at an angle of 45 to the 011 orientation is suitable. A 1.3-µm GaInAsP/InP square buried heterostructure (SBH) SE laser with this mesa structure has been demonstrated and low-threshold CW oscillation (threshold current Ith=0.45 mA) at 77 K and low-threshold room-temperature pulsed oscillation (Ith=12 mA) have been obtained.

Tracing solution curves of nonlinear equations is an important problem in circuit simulation. In this paper, simple techniques are proposed for improving the computational efficiency of the spherical method, which is a method for tracing solution curves. These techniques are very effective in circuit simulation where solution curves often turn very rapidly. Moreover, they can be easily performed with little computational effort.

This paper proposes novel optical path accommodation design algorithms for networks wherein the number of wavelengths multiplexed into a fiber is restricted. This algorithm optimizes both optical path route and wavelength assignment in VWP/WP networks. It minimizes optical path cross-connect (OPXC) system scale in terms of incoming/outgoing fiber port numbers. A comparison in terms of required OPXC system scale between the WP and VWP schemes is demonstrated for the first time.

A 0.1-µm gate-length GaAs MESFET technology is reported. A 48.3-GHz dynamic-frequency divider, and an amplifier with 20-dB gain and 17.5-GHz bandwidth are successfully fabricated by integrating over-100-GHz-cut-off frequency MESFETs using a new lightly-doped drain structure with a buried p-layer (BP-LDD) device structure.

There are three viewpoints involved in software project management: process management, quality management and cost management. Software projects must be managed on the basis of these three viewpoints. However, in many cases process management, quality management and cost management systems are built separately as individual systems respectively. Construction of software project management systems which these three functions are integrated has been rare. Therefore, in order to construct a system integrating these functions, the authors clarify the significance of integration of application systems. And then the authors unveil the structure of a software project management system that process management system, quality management system and cost management system are integrated by using an object oriented database.

Information systems to support cooperative work among people should be first designed to help humam communication. However, there are few systems based on the analysis of human communication. Standing on this situation, we propose a meeting support system for the participants' understandings by indicating the suitable information about the topic of the scene". Our system provides only useful information by monitoring each statement without complex methods. To show something useful multi-media information for members, we propose the following structure of the meeting on the basis of the analysis of communication. Each statement is classified into two levels, either; a statement about the progress" of the meeting (context-level utterances) or, a statement about objects" (content-level utterances). Further, content-level utterances are classified into two types, position utterances and argument utterances. Using this classification of statements, the proceeding of the meeting is represented as the tree model which is called a context-tree". If the structure of meetings is fixed, it is possible to select only useful information from all shared information for members by analyzing each content-level utterance. The system introduced in this paper shows appropriate multi-media information about the topic of the scene" by using the above model. We have implemented a prototype system based on the above ideas. Moreover, we have mode some experiments to show the effectiveness of this system. Those results show that our method is effective to improve the productivity" of meetings.

One approach to develop software efficiently is to reuse existing software by modifying a part of it. However, modifying software will often introduce unexpected side effects into other parts of it. As a result, it costs much time and care to modify the software. So, in order to modify software efficiently, we have proposed a functional model to represent information about side effects caused by modification and a model based supporting system for modifying software. So far, however, an expert software developer must describe the entire functional model of the target software through the analysis of practical modifying processes. This will be an unnecessary burden on him. Moreover, the larger target software becomes, the harder the model construction becomes. Therefore, an automatic constructing method of the functional model is needed in order to solve this problem. So, this paper considers a method of acquiring useful interaction information by learning from training examples of modification. However, in our application domain, it seems that it is impossible to make complete domain theory and to prepare a large number or training examples in advance. Therefore, our learning method involves an integration of explanation-based learning (EBL) from positive examples of modification generated by the user and Similarity-based learning (SBL) from positive or negative examples generated by the user and the learning system. As a result, our method can acquire valid knowledge about the interaction from not so many examples under incomplete theory. Then, this paper presents a constructing method, in which our proposed learning method is incorporated, of a functional model. Finally, this paper demonstrates construction of the functional model in the domain of an event-driven queueing simulation program according to our learning method.

A high efficiency and low voltage operation GaAs power amplifier module has been developed for the application to 1.5 GHz Japanese digital cellular phones. This paper summarizes the design method to increase efficiency and to reduce adjacent channel leakage power. Operated at a low drain bias voltage of 4.6 V, the power amplifier module delivers an output power of 1.5 W with 46% power-added efficiency and -52 dBs adjacent channel leakage power.

To support high bit rate and high quality indoor radio communication systems, we have to solve intersymbol interference (ISI) problem caused by frequency-selective fading. Recently multi-carrier modulation technique is considered to be one of the effective methods for this problem. In this paper we propose Partial Frequency ARQ (Automatic Repeat reQuest) system which can achieve effective ARQ scheme for multi-carrier packet communication. This system operates partial retransmission of erroneous power faded packets, and it is superior to the traditional ARQ systems. Furthermore two different protocols are examined for this system: Static Carrier Assignment (SCA) and Dynamic Carrier Assignment (DCA). By computer simulation we found that DCA method can achieve better performance than SCA in terms of both throughput and packet transmission delay.

We have developed a planar devic technology consisting of 0.15-µm Au/WSiN-gate GaAs-heterostructure MESFETs (HMESFETs) fabricated by self-aligned ion-implantation. The gate-drain breakdown voltage has been improved to 10 V by using an asymmetric LDD structure, and the maximum oscillation frequency is 190 GHz. Because asymmetric and symmetric FETs can be fabricated simultaneously, this technology is suitable for use in making multi-functional millimeter-wave MMICs.

The most creative tasks in synthesizing pipelined data paths executing software descriptions are determinations of latency and stage of pipeline, operation scheduling and hardware allocation. They are interrelated closely and depend on each other; thus finding its optimal solution has been a hard problem so far. By using simulated annealing methodology, these three tasks can be formulated as a three dimensional placement problem of operations in stage, time step and functional units space. This paper presents an efficient method based on simulated annealing to provide excellent solutions to the problem of not only the determinations of latency and stage of pipeline, operation scheduling and hardware allocation simultaneously, but also the pipelined data path synthesis under the constraints of performance or hardware cost. It is able to find a near optimal latency and stage of pipeline, an operation schedule and a hardware allocation in a reasonable time, while effectively exploring the existing tradeoffs in the design space.

This paper describes modifications to a previously proposed 8-kb/s 4-ms-delay CELP speech coding algorithm with a view to improving the speech quality while maintaining low delay and only moderately increasing complexity. The modifications are intended to improve the effectiveness of interframe pitch lag prediction and the sub-optimality level of the excitation coding to the backward adapted synthesis filter by using delayed decision and joint optimization techniques. Results of subjective listening tests using Japanese speech indicate that the coded speech quality is significantly superior to that of the 8-kb/s VSELP coder which has a 20-ms delay. A method that reduces the computational complexity of closed-loop 3-tap pitch prediction with no perceptible degradation in speech quality is proposed, based on representing the pitch-tap vector as the product of a scalar pitch gain and a normalized shape codevector.

Multifrequency microwave radiometry has been investigated for non-invasive measurement of temperatures in a human body. In this paper, we propose a new temperature profile model function, which is based on thermo-physiological considerations, for use in model fitting method of retrieving a temperature profile from a set of multifrequency radiometric data. The microwave radiometric technique using the new model function was tested by numerical simulations against animal experiment and clinical data reported elsewhere. The results show that the microwave radiometric technique can be used effectively to measure temperature profiles in tissues over a depth range from 0 to about 4.5 cm.

A full confocal Gaussian beam open resonator system that determines the dielectric properties of low-loss materials in the 60-GHz band is developed. To achieve high Q values a quasi-optical coupling method is used to feed the resonator. It is connected to a computer-controlled HP 8510C vector network analyzer for automatic measurement. The frequency variation method is used and the data are processed using the open resonator scalar theory. Results from 96% and 99.5% alumina samples with thicknesses ranging from 0.38 mm to 1 mm, are presented in the V band, with loss tangent values of the order of 100 µ radians. This system should be able to measure substrates as thin as less than 0.1 mm to 0.3 mm, which are the thicknesses of substrates in practical use.

The simulation of a specific absorption rate (SAR) with a temperature distribution becomes more important in the treatment planning for microwave hyperthermia. The simulation technique can also be used to estimate SAR distribution inside human body under hazardous electromagnetic (EM) field circumstances. In the simulation, to use exact permittivity of biological tissues becomes very important to obtain accurate SAR distribution. The permittivity of the medium is very sensitive to the temperature. Therefore, it is considered that the SAR distribution is also very sensitive to the tissue temperature. In this paper, SAR distribution is calculated using FDTD method considering tissue temperature under the electromagnetic (EM) field irradiation. Simulations of temperature distribution are also performed using heat transfer equation. In addition, temperature depending blood flow is taking into account to obtain temperature depending SAR distribution. The results can be used to estimate temperature depending heat generation which can be applied such as microwave hyperthermia treatment.