A procedure for preparing a cross-sectional transmission electron microscopy (TEM) micrograph of a specific area is outlined. A specific area in a specimen has been very difficult to observe with TEM, because a particular small area cannot be preselected in the conventional specimen preparation technique using mechanical polishing, dimpling and ion milling. The technique in this paper uses a focused ion beam (FIB) to fabricate a cross-sectional specimen at a desired area. The applications of this specimen preparation technique are illustrated for investigations of particles in the process of fabricating devices and degraded aluminum/aluminum vias. The specimen preparation technique using FIB is useful for observing a specific area. This technique is also useful for shortening the time of specimen preparation and observing wide areas of LSI devices.

Directional dry etching of Tantalum is described X-ray lithography absorber patterns. Experiments are carried out using both reactive ion etching in CBrF3-based plasma and electron-cyclotron-resonance ion-stream etching in Cl2-based plasma. Ta absorber patterns with perpendicular sidewalls cannot be obtained by RIE when only CBrF3 gas is used as the etchant. While adding CH4 to CBrF3 effectively improves the undercutting of Ta patterns, it deteriorates etching stability because of the intensive deposition effect of CH4 fractions. By adding an Ar/CH4 mixture gas to CBrF3, it is possible to use RIE to fabricate 0.2-µm Ta absorber patterns with perpendicular sidewalls. ECR ion-stream etching is investigated to obtain high etching selectivity between Ta and SiO2 (etching mask)/SiN (membrane). Adding O2 to the Cl2 etchant improves undercutting without remarkably decreasing etching selectivity. Furthermore, an ECR ion-stream etching method is developed to stably etch Ta absorber patterns finer than 0.2µm. This is successfully applied to X-ray lithography mask fabrication for LSI test devices.

Since carelessness in driving causes a terrible traffic accident, it is an important subject for a vehicle to avoid collision autonomously. Real-time collision detection between a vehicle and obstacles will be a key target for the next-generation car electronics system. In collision detection, a large storage capacity is usually required to store the 3-D information on the obstacles lacated in a workspace. Moreover, high-computational power is essential not only in coordinate transformation but also in matching operation. In the proposed collision detection VLSI processor, the matching operation is drastically accelerated by using a Content-Addressable Memory (CAM) which evaluates the magnitude relationships between an input word and all the stored words in parallel. A new obstacle representation based on a union of rectangular solids is also used to reduce the obstacle memory capacity, so that the collision detection can be parformed only by parallel magnitude comparison. Parallel architecture using several identical processor elements (PEs) is employed to perform the coordinate transformation at high speed based on the COordinate Rotation DIgital Computation (CORDIC) algorithms. The collision detection time becomes 5.2 ms using 20 PEs and five CAMs with a 42-kbit capacity.

This paper presents a method of translating natural language specifications of communication protocols into algebraic specifications. Such a natural language specification specifies action sequences performed by the protocol machine (program). Usually, a sentence implicitly specifies the state of the protocol machine at which the described actions must be performed. The authors propose a method of analyzing the implicitly specified states of the protocol machine taking the OSI session protocol specification (265 sentences) as an example. The method uses the following properties: (a) syntactic properties of a natural language (English in this paper); (b) syntactic properties introduced by the target algebraic specifications, e.g., type constraints; (c) properties specific to the target domain, e.g., properties of data types. This paper also shows the result of applying this method to the main part of the OSI session protocol specification (29 paragraphs, 98 sentences). For 95 sentences, the translation system uniquely determines the states specified implicitly by these sentences, using only (a) and (b) described above. By using (c) in addition, each implicitly specified state in the remaining three sentences is uniquely determined.

Responsive protocols are communication protocols which ensure timely and reliable recovery when error events occur. Protocol synthesis for design of responsive protocols is to derive a protocol specification based on a service specification. In the previous methods, if the service specification includes simultaneous transmission of primitives from a high layer to a low layer through different service access points, then the derived protocol specification includes protocol errors of unspecified reception caused by message collisions. Also, they only includes a recovery function such as retransmission of messages. This is not enough for recovery from abnormal states due to coordination loss. This paper extends a class of derived protocol specifications to include message collisions which usually occur in real communication protocols. Furthermore, this paper proposes a new method for synthesis of a responsive protocal specification derived from a service specification such that the derived protocol specification is free from protocol erros of unspecified receptions caused by message collisions and includes two recovery functions: message retransmission and checkpoint restart functions.

This paper proposes a new scheme for concatenative speech synthesis to improve the speech segment selection procedure. The proposed scheme selects a segment sequence for concatenation by minimizing acoustic distortions between the selected segment and the desired spectrum for the target without the use of heuristics. Four types of distortion, a) the spectral prototypicality of a segment, b) the spectral difference between the source and target contexts, c) the degradation resulting from concatenation of phonemes, and d) the acoustic discontinuity between the concatenated segments, are formulated as acoustic quantities, and used as measures for minimization. A search method for selecting segments from a large speech database is also descrided. In this method, a three-step optimization using dynamic programming is used to minimize the four types of distortion. A perceptual test shows that this proposed segment selection method with minimum distortion criteria produces high quality synthesized speech, and that contextual spectral difference and acoustic discontinuity at the segment boundary are important measures for improving the quality.

This article discusses on PDM (Petri net based Development Methodology) which integrates approaches, modeling methods, design methods and analysis methods in a coherent manner. Although various development techniques based on Petri nets have demonstrated advantages over conventional techniques, those techniques are rather ad hoc and lack an overall picture on entire development process. PDM anticipates to provide a refernce process model to develop distributed systems with various Petri net based development methods. Behavioral properties of distrbuted systems can be an appropriate application domain of PDM.

The fast and highly reliable method reported here uses two techniques to detect all types of defects, such as unsoldered leads, solder bridges, and misalignes leads in the minute solder joints of high density mounted devices. One technique uses external force applied by an air jet that vibrates or shifts unsoldered leads. The vibration and shift is detected as a change in the speckle pattern produced by laser illumination of the solder joints. The other technique uses fluorescence generated by short-wavelength laser illumination. The fluorescence from a printed circuit board produces a silhouette of the solder joint and this image is processed to detect defects. Experimental results show that this inspection method detects all kinds of defects accurately and with a very low false alarm rate.

The characteristics of an open-boundary Cherenkov laser for an electromagnetic wave with a continuous frequency spectrum are numerically analyzed. A given power spectral density for the input wave is found to get concentrated around the frequency where the spatial growth rate is maximum, as it grows along the electron beam. In addition, the frequency for the maximum growth rate is found to shift gradually to higher values. Furthermore, by gradually increasing the permittivity of the dielectric waveguide along it, we can always get the maximum power spectral density at the frequency where the spatial growth rate initially becomes maximum at the input.

In the future, it will be necessary that robot technology or environmental technology has an auditory function of recognizing sound expect for speech. In this letter, we propose a recognition system for the species of birds receiving birdcalls, based on network technology. We show the first step of a recognition system for the species of birds, as an application of a recognition system for environmental sound.

Reactive systems respond to internal or external stimuli and act in an event-driven manner. It is generally difficult to specify a complex reactive systems' behavior using conventional state machine formalism. One reason is that actual reactive systems are usually formed by combining plural state-machince that behave concurretly. This paper presents the State Diagram Matrix (SDM) which is a visual and hierarchical formalism of such a reactive system's behavior. SDM has two concepts. The first is matrix plane description on which 3-dimensional state space is projected. The second is state abstraction for hierarchical state-machine definition. Understandability and reliability of control software was improved as a consequence of adopting SDM for specifying disk-subsystem control requirements. The development support functions of SDM using a workstation are also described.

The paper presents the improvement of out new approach to optimize the process parameter variation, device heat and wire parasitics for analog LSI design by explicitly incorporating various performance estimations into objective functions for placement and routing. To minimize these objective functions, the placement by the simulated annealing method, and maze routing are effectively modified with the perfomance estimation. The improvement results in the excellent performance driven layout for the large size of analog LSIs.

A coherent communication system using squeezed light is one of candidates for a realization of super-reliable systems. In order to design such a system, it is essential to understand and to analyze modulators mathematically. However, quantum noise of squeezed light has a colored spectrum which changes with respect to phase of a local laser. Therefore the optimization of the relationship between signal and quantum noise spectrums is required at a modulator to obtain the ultimate performance of the communication system. In this paper, some ideas of modulators for squeezed light are proposed and their spectrum transformations are given. After the brief summary of squeezed quantum noise, a new concept which originates from the restriction of the local laser phase is applied to it. This concept makes a problem originated from a colored quantum noise spectrum more serious. It results in the optimization problem for the relationship between the quantum noise spectrum and signal power spectrum. The solution of this problem is also given under the restriction of local laser phase. As a result, a general design theory for coherent communication system using the squeezed light is given.

An asynchronous spread spectrum (SS) wireless modem has been implemented using an efficient ZnO-SiO2-Si surface acoustic wave (SAW) convolver. The modem is based on a direct-sequence/frequency-shift-keying (DS/FSK) method for the modulation. The demodulation is carried out asynchronously utilizing the coherent correlation characteristics of the SAW convolver. In order to improve the narrowband interference rejection capability, we propose a new technique based on the reference signal control. A notched-reference-signal circuit and a self-convolution canceler are implemented in the SS modem for the reference signal control. It was found that the antijam capability for narrowband interference is at least -24dB of desired-to-undesired power ratio (D/U); the improvement of the antijam capability is 16dB up as compared with our previous SS modem.

Concatenated coding techniques are applied to slow frequency-hop packet radio communications for channels with partial-band interference. Binary orthogonal signaling (e.g., binary FSK) is employed with noncoherent demodulation. The outer codes are Reed-Solomon codes and the inner codes are convolutional codes. Two concatenated coding schemes are compared. The first employs an interleaver between the outer Reed-Solomon code and the inner convolutional code. The second scheme employs an additional interleaver following the convolutional code. Comparisons are made between the performance of these concatenated coding schemes and the performance of Reed-Solomon codes alone.

An approximate equation of the odd periodic correlation distribution for the family of binary sequences is derived from the exact even periodic correlation distribution. The distribution means the probabilities of correlation values which appear among all the phase-shifted sequences in the family. It is shown that the approximate distribution is almost the same as the computational result of some family such as the Gold sequences with low even periodic correlation magnitudes, or the Kasami sequences, the bent sequences with optimal even periodic correlation properties in the sense of the Welch's lower bound. It is also shown that the odd periodic correlation distribution of the family with optimal periodic correlation properties is not the Gaussian distribution, but that of the family of the Gold sequences with short period seems to be similar to the Gaussian distribution.

The capacity of a cellular direct sequence code division multiple access system is investigated in situations with and without power control for both the reverse link (from mobile to base station) and the forward link (from base station to mobile). The capacity is defined as the number of simultaneous users per cell with a prespecified performance. A theoretical analysis of the effect of imperfect power control on the reverse link capacity is presented using an analytical model. To investigate the reverse link capacity without any form of power control, a general spatial user distribution is developed which is very suitable for analytical study of any multiple access system with the near-far effect problem. The performance of the reverse link of a CDMA system is also evaluated considering the users located in surrounding cells. Finally, the forward link capacity is studied considering multiple cells. Two possible forward power control schemes, namely carrier-to-interference ratio driven and distance driven systems, are discussed.

The effectiveness of error-control coding in a frequency-hop radio system can be increased greatly by the use of side information that is developed in the radio receiver. The transmission of test symbols provides a simple method for the derivation of side information in a slow-frequency-hop receiver. Requirements on the reliability of the side information are presented, and their implications in determining the necessary number of test symbols are described. Other methods for developing side information are reviewed briefly, and applications of side information to routing protocols for frequency-hop packet radio networks are discussed.

In this paper, we propose a spread spectrum pulse position modulation (SS-PPM) system, and describe its basic performances. In direct sequence spread spectrum (DS/SS) systems, pseudo-noise (PN) matched filters are often used as information demodulation devices. In the PN matched filter demodulation systems, for simple structure and low cost of each receiver, it is desired that each demodulator uses only one PN matched filter, and that signals transmitted from each transmitter are binary. In such systems, on-off keying (SS-OOK), binary-phase-shift keying (SS-BPSK) and differential phase-shift keying (SS-DPSK) have been conventionally used. As one of such systems, we propose the SS-PPM system; the SS-PPM system is divided into the following two systems: 1) the SS-PPM system without sequence inversion keying (SIK) of the spreading code (Without SIK for short); 2) the SS-PPM system with SIK of the spreading code (With SIK for short). As a result, we show that under the same bandwidth and the same code length, the data transmission rate of the SS-PPM system is superior to that of the other conventional SS systems, and that under the same band-width, the same code length and the same data transmission rate, the SS-PPM system is superior to the other conventional SS systems on the following points: 1) Single channel bit error rate (BER) (BER characteristics of the SS-PPM system improve with increasing the number of chip slots of the SS-PPM system, and as the number of chip slots increases, it approaches Shannon's limit); 2) Asynchronous CDMA BER; 3) Frequency utilization efficiency. In addition, we also show that With SIK is superior to Without SIK on these points.

A new method of multipath diversity combination is proposed for Direct Sequence Spread Spectrum (DS-SS) mobile communications. In this method, the transmitted signal from the base staion is the sum of a number of the same spread signal, each one delayed and scaled according to the delay and the strength of the multipaths of the transmission channel. As a result the received signal at the mobile unit will already be a Rake combination of the multipath signals. This new method is called Pre-Rake diversity combination because the Rake diversity combination process is performed before transmission By this method the size and complexity of the mobile unit can be minimized, and the unit is made as simple as a non-combining single path receiver. A theoretical examination of the Signal to Noise Ratio (SNR) and the Bit Error Rate (BER) results for the traditional Rake and the Pre-Rake combiners as well as computer simulations show that the performance of the Pre-Rake combiner is equivalent to that of the Rake combiner.