The quality of polycrystalline silicon films and electrical characteristics of polycrystalline silicon gate metal-oxide-semiconductor (MOS) capacitors were investigated under various processing conditions, including phosphorus doping. The stresses observed in Si films deposited in the amorphous phase show complex behavior during thermal treatment. The stresses in as-deposited Si films are compressive. They change to tensile with annealing at 800, and to compressive after an additional annealing at 900. The kind of charges trapped in the SiO2 film during the negative constant current stress in Polycrystalline silicon gate MOS capacitors differ with the maximum process temperature. The trapped charges of samples annealed at 800 were negative, while those of samples annealed at 900 were positive.

Surface damage to n-type silicon wafers induced by Reactive Ion Etching (RIE) with CF4 gas was evaluated using X-ray photoelectron spectroscopy (XPS) and the current-voltage (I-V) characteristics of Au/n-Si Schottky diodes fabricated on the damaged surface. The reaction products (SiF, SiF2, and SiF3) in the damaged layer were detected by XPS. Assuming the surface damage on a silicon wafer induced by RIE acts as a donor, the donor density was found to be about 21019 cm-3. The distribution of SiF3 and the donor density in the depth direction were almost equal. The thickness of the damaged layer was about 15 nm. These findings suggest that the donor in the damaged layer on a silicon surface induced by RIE may be SiF3.

After the intrinsic pulsed light illumination, a transient negative photoconductivity (TRANP) was observed in silicon doped with gold. The ambient temperature dependence of the TRANP-current was measured and compared with the simulated results obtained by solving rate equations. The temperature dependence of the peak value of the TRANP-current was in agreement with the simulated result. The activation energy of gold acceptor level obtained from the time constant in the recovery process was also consistent with the simulation. It was cleared from this result that the recovery process is dominated by the electron re-emission from gold acceptor level to the conduction band. It was concluded that the occurrence of the TRANP is well explained by using our model proposed before.

The a-Si films deposited on quartz substrates were crystallized by lateral sweep annealing in steep temperature gradient using a gas burner. Random nucleation in amorphous region was effectively suppressed in the temperature gradient, so lateral solid phase epitaxial growth from crystallites generated at the initial stage of lateral sweep annealing spread over 100 µm. Their crystallographic orientations were mostly (100).

In this paper, a new M-estimation technique for the linear prediction analysis of speech is proposed. Since in the conventional linear prediction (CLP) method the obtained estimates are very much affected by the large amplitude residual parts, in the proposed method we use a loss function which assigns large weighting factor for small amplitude residuals and small weighting factor for large amplitude residuals which is for instance caused by the pitch excitations. The loss function is based on the assumption that the residual signal has an independent and identical t-distribution t(α) with α degrees of freedom. The efficiency of this new estimator depends on α. When α=, we get the CLP method. When the proposed method with small α is applied to the problems of estimating the formant frequencies and bandwidths of the synthetic speech by finding the roots of the prediction polynomial, we can achieve a more accurate and a smaller standard deviation (SD) estimate than that with large α. When the signal is very spiky, the proposed method can ahieve more efficient and accurate estimates than that with robust linear prediction (RBLP) method. The loss function is modified in the similar manner as the autocorrelation method. The solution is calculated by the Newton-Raphson iteration technique. The simulation results show that only few iterations are needed to reach a stationary point, the stationary point is always a local minimum and the obtained prediction filter is always minimum phase. Preliminary experiments on the human speech data indicate that the obtained results are insensitive to the placement of the analysis window and a higher spectral resolution than the CLP and RBLP method can be achieved.

It is well known that the multiple-valued signed-digit (SD) arithmetic circuits have the attractive features of compactness and high-speed operation. However, both of these features have yet to be utilized fully. In this paper, we consider the application of a parallel-structure-based VLSI processor. A high-performance parallel-structure-based multiple-valued VLSI processor using the radix-2 SD number system is proposed. Its compactness makes the parallelism high under chip size limitations in comparison with the ordinary binary arithmetic circuits. Moreover, the speed of the single arithmetic module is very high in the SD arithmetic circuits, so that we can take advantage of the high-speed operation in the parallel-structure-based VLSI processor chip. The multiple-valued bidirectional current-mode technology is used not only in high-speed small sized arithmetic circuits, but also in reducing the number of connections in the parallel-structure-based VLSI processor. The proposed processor is specially developed for real-time digital control, where the performance is evaluated by delay time. Performance estimation using SPICE simulators shows that the delay time of proposed processor for matrix operations such as matrix multiplication is greatly reduced in comparison with a conventional binary processor.

Among the many fabrication methods for oxide superconductor films, metal organic chemical vapor deposition (MOCVD) is particularly suitable for industrial application because of its mass productivity and the low growth temperature. Therefore we have studied this technique using the horizontal cold wall furnace type MOCVD method to obtain high quality superconducting films. As the result, we have succeeded in fabricating YBa2Cu3Oy films which have high critical temperatures (over 80 K) under substrate temperatures as low as 700 without post-annealing. But, in the course of our experiments, it was found that the thicknesses of YBa2Cu3Oy films fabricated by MOCVD were not uniform. The cause of this non-uniformity is believed to be that the deposition rate exponentially falls off along the flow direction because of the decrease of the source gas concentration through the reaction. In this paper, this non-uniformity is analytically studied. It is shown that the deposition rate decrease can be controlled with a tapered inner tube, and that these theoretical results are in good agreement with the results of experiment. In addition, it is indicated that the superconducting property of the films has less dependence on substrate position as a result of the tapered inner tube.

The transmission of 8-bit µ-law PCM signals using 16-level weighted QAM over Gaussian channels is examined. The weighting process modifies the positions of the QAM constellation points so that the overall distortion in the recovered information-bearing source signal is reduced. The PCM bits are mapped to the weighted QAM points such that the most significant bits have a lower probability of being in error than the least significant bits. The weighted QAM systems have been optimized for the same energy signal energy per transmitted symbol as for unweighted QAM. Also, the erasure zone is established at the detector, such that if the output falls into the erasure zone, the regenerated sample is replaced by interpolation. The theoretical results indicates that 16-level weighted QAM have a gain of 5dB over unweighted QAM.

Telecommunication services are accomplished by cooperative networks of widely distributed communication processes and service users. Those specifications are often modeled by a set of possible message sequences among cooperating processes and users. The distributed and cooperative nature of telecommunication services results in a wide variety of message sequences and makes it more difficult for service designers to design such telecommunication services. To mitigate the difficulty, we propose a design support system with MSRs (message sequence rules) as design knowledge. The system supports the following two design activities: (1) specification of a typical message sequence that corresponds to a service behavior in a successful case, and (2) specification of incidentally possible message sequences that involve service behaviors in successful and unsuccessful cases. For the former activity, the system interacts with designers and identifies the messages they give with MSRs to understand the context of the message sequence and suggest possible subsequent messages. For the latter activity, the system applies MSRs to the typical message sequence and reasons possible messages from/to relevant processes and users under every state to suggest incidentally possible message sequences. Accordingly, designers may be relieved of investigating a wide variety of service behaviors in successful and unsuccessful cases. The system capability is based on MSRs equivalent to reusable message sequence components. MSRs can be obtained through abstraction of implementation-dependent messages and decomposition of those sequences into temporal relations among messages. The rule acquisition method provides MSRs with the potential to generate a wide variety of message sequences. In order to verify rule applicability, we have experimentally designed three kinds of services and conducted an experimental rule application to those specifications. The experimental evaluation results indicate that applicability is fairly high.

The DSD (Double Soft Decision) concatenated forward error correction scheme is proposed to realize a higher-coding-gain forward error correction system with simple hardware. The novel scheme soft decision decodes inner codes as well as outer codes. In this scheme, likelihood information from an inner Viterbi decoder is used for the decoding of outer codes. Path memory circuit status 1,0 ratio is newly proposed as a measure of likelihood information and it is shown that this method is the most reliable even though it has the simplest hardware among the alternative likelihood information extracting methods. Computer simulation clarifies that the proposed DSD scheme improves Pe performance to one-third that of the conventional hard decision outer decoding.

In this paper we examine the architectural and operational design issues of a practical network management system using the Simple Network Management Protocol (SNMP) in the context of a large-scale OSI-based campus-network TAINS. Various design aspects are examined and the importance of time-management is elicited. In the proposed design, intelligent, time-synchronised agents are deployed to collect information about the network segments to which they are attached. The manager talks to the agents and gathers relevant network information. This information is used by the expert network manager, in conjunction with a network knowledge base (NKB) and a management information knowledge base (MIKB) , to reconstruct the overall network-traffic characteristic, to evaluate the status of the network and to take/suggest some action. This model is particularly useful in networks where some global control, monitoring and management is desired and installing agents on all elements, connected to the network, is impossible. The use of time labels and narrow time windows enables the manager to obtain a reasonably accurate picture of the network status. The introduction of time-labelled composite objects in the Management Information Base (MIB) provides a means of reducing the load of management-related traffic on the network. The MIKB containing a logical description of the behaviour of the managed objects defined in the MIB, drives the expert system and provides the knowledge of general nature that a human expert has about networks. The proposed MIKB concept provides a very convenient schema for building the knowledge base in an expert network management system. Further since the MIKB is MIB-specific, it can be used in network management systems for managing similar MIB's.

A ner trial of statistical evaluation for a nonstationary traffic flow and its traffic noise is proposed as a prediction method of its probability distribution function by considering the temporal change of distribution parameters especially from a structural viewpoint. First, a headway distribution of the nonstationary traffic flow passing through within a road segment is proposed on the basis of an Erlang distribution by reflecting a temporal change of its distribution parameters. Then, an initial phase density concerning with asynchronous counting method and the probability of counting n cars over a long time interval are derived from the above nonstationary expression of headway distribution. Thus, the statistics of noise intensity at an observation point has been predicted by combining the above probabilistic factors and deterministic factors related to noise propagation environment with use of a compound stochastic process model. Finally, te effectivenss of the proposed theory has been confirmed experimentally by applying it to the actual traffic flow on a highway.

This paper proposes a hierarchical Digital Signal Processor (DSP) Code Generator VIRGO for large scale general signal processing algorithms. Hierarchical structured Vectorized Signal Flow Graph (V-SFG) description is used as input specifications. Ths DSP independent optimization procedure for both the program size and the execution time is performed each module by each hierarchically with regard to operation order, memory assignment and register allocation. The efficient code generation is demonstrated by comparing both instruction steps and dynamic steps of a practical ADPCM encoder/decoder with a conventional method.

This paper proposes a high resolution and fast frequency settling PLL synthesizer for frequency hopping radio communication equipment. The proposed synthesizer enables the carrier frequency to be changed within the duration of a burst signal and yields higher frequency resolution than the reference signal frequency. To reduce frequency settling time without degradation of frequency resolution and phase noise, this paper proposes a new phase and frequency preset (PEP) PLL synthesizer which employs a digital phase accumulator to generate high resolution reference signal. Experimental results show that the settling time of a prototype synthesizer is less than 300µs while spurious signals are suppressed by more than 55 dB. In comparison with conventional PLL synthesizers, the frequency settling time is reduced by 80%. Furthermore, the higher frequency resolution than the reference signal is successfully demonstrated. Therefore, the proposed PFP PLL synthesizer with the digital reference signal can achieve the output signal with high frequency resolution less than 1Hz.

It often occurs in an environmental phenomenon in our daily life that a specific signal is partially or completely contaminated by the additional external noise. In this study, a digital filter for estimating a specific signal fluctuating impulsively under the existence of an actual external noise with various kinds of probability distribution forms is proposed in an improved form of already reported digital filter. The effectivenss of the proposed theory is experimentally confirmed by applying it to the estimation of an actual impulsve signal in a room acoustic.

This paper proposes a new design method of variable FIR digital filters. The method uses a multi-dimensional linearphase FIR filter as a prototype. The principle of the proposed method is based on the fact that the crosssectional characteristics of a 2-D filter along with a line vary if the intersection of this line is changed. The filter characteristics can be varied by recalculating all the filter coefficients from proposed equations, which leads to an advantage that the variable range is very wide. Another advantage is that the passband and stopband deviations are completely predetermined in the design procedures and that the passband edge can be accurately settled to a desired frequency while keeping the transition band width unchanged. First the proposed design method is explained and the effect of the transition band of 2-D filters is discussed. Then the calculation cost required in updating the filter coefficients are considered. Finally two design examples are presented and the proposed method is compared with the existing one, which shows the usefulness of our method.

This paper describes on the transmission properties of the superconducting coplanar waveguide on LiNbO3 (LN) substrates, fabricated by YBa2Cu3Oy (YBCO) superconducting films. The films have been prepared by the reactive co-evaporation method and patterned by a wet etching process. The surface resistance of the obtained film was 0.04 Ω at 18 GHz and 77 K. It was confirmed from X-ray diffraction (XRD) that these films were highly oriented to the direction of c-axis without a secondary phase. The microwave transmission properties of these YBCO coplanar waveguides were investigated at frequencies up to 20 GHz and compared with that of the aluminum coplanar waveguide. The characteristic impedances of both coplanar waveguides were designed to be 50 Ω. It was found that the attenuation constants of these samples at 77 K were less than that of the aluminum coplanar waveguide for frequencies below 18 GHz.

Experimental results on the superconducting three-terminal devices Using Bi-system High-Tc Superconductors were reported. The VCJJ (Variabel critical-current-type Josephson junction devices) using the thermal effect (VCJJ) and a dual gate Josephson device of a new current-injection type are described. The basic technology and problems for high-Tc three-terminal devices are briefly discussed.

Fast wavelet transform is presented for realtime processing of wavelet transforms. A processor for the fast wavelet transform is of the frequency sampling structure in architectural level. The fast wavelet transform owes its parallelism both to the frequency sampling structure and parallel tapping of a series of delay elements. Computational burden of the fast transform is hence independent of specific scale values in wavelets and the parallel processing of the fast transform is readily implemented for real-time applications. This point is quite different from the computation of wavelet transforms by convolution. We applied the fast wavelet transform to detecting detonation in a vehicle engine for precise real-time control of ignition advancement. The prototype wavelet for this experiment was the Gaussian wavelet (i.e. Gabor function) which is known to have the least spread both in time and in frequency. The number of complex multiplications needed to compute the fast wavelet transform over 51 scales is 714 in this experiment, which is less than one tenth of that required for the convolution method. Experimental results have shown that detonation is successfully detected from the acoustic vibration signal picked up by a single knock sensor embedded in the outer wall of a V/8 engine and is discriminated from other environmental mechanical vibrations.

A 1/2 frequency divider using resonant-tunneling hot electron transistors (RHETs) has been proposed and demonstrated. The circuit make the best use of negative differential conductance, a feature of RHETs, and contains one half transistors than used in conventional circuits. The RHETs were fabricated using self-aligned InGaAs RHETs and WSiN thin-film resistors on a single chip. The RHETs have an i-InGaAlAs/i-InGaAs collector barrier that improves the current gain at low collector-base voltages. Circuit operation was confirmed at 77 K.