A hybrid integrated optical module composed of a silica-based planar lightwave circuit (PLC), a laser diode with an integrated monitor-photodiode, and a pin-photodiode is fabricated for use in high-performance, compact and cost-effective fiber optic subscriber systems. Its applicability to a wavelength-division-multiplex (WDM) system with a 1.3-µm bi-directional signal and a 1.5-µm one-way signal is demonstrated. The PLC was fabricated by a combination of flame hydrolysis deposition (FHD) and reactive ion etching (RIE), and it simultaneously achieved 1.3-µm/1.5-µm multi/demultiplexing and 1.3-µm Y-branching functions. The optical module exhibited insertion losses of 4.1dB at 1.31µm (including a Y-branch circuit loss of 3dB) and 0.5dB at 1.53µm. An optical output power of more than -4dBm was obtained from the optical module and the crosstalk was sufficiently low at less than -20dB between wavelengths of 1.3µm and 1.5µm. Temperature cycle tests on the optical module showed reliable and stable operation with an optical power fluctuation of less than 0.3dB for 500 cycles.

This letter considers a subclass of t-symmetric error correcting/all unidirectional error detecting (t-SyEC/AUED) codes in which the information is represented in an m-out-of-k coded form, which thus can be regarded as virtually systematic for practical purposes. For t3, previous researchers proposed methods for constructing codes of this subclass which are either optimal or of asymptotically optimal order. This letter proposes a new method for constructing, for any values of t, m and k, codes that are either optimal or of asymptotically optimal order. The redundancy of the obtained code is of the order tlog2k bits when mt.

In case of the system identification problem, such as an echo canceller, estimated impulse response obtained by the frequency-domain adaptive filter based on the circular convolution has estimation error because the unknown system is based on the linear convolution in the time domain. In this correspondence, we consider a sufficient condition to reduce the estimation error.

In this paper, we propose a method to simulate the curve surface of the initial height in the movement of the electronic wire bonder using the experimental data. For given measured data (xk, yk, zk (k=1, 2, , m)), we propose an algebraic surface of n-th degree as a methematical model of the initial height surface. The AIC method is a method of evaluating the goodness of a given model. The maximum likelihood model is selected by comparing with the AIC value of each model for n=0, 1, 2, 3, , 11. Useing this model, the initial raise position of the electronic wire bonder can be controlled by computer programing and can make the movement of wire bonder full-automatic. As a resurt, the well-arranged wiring and reliable contacting can be obtained.

Runlength-limited block codes are investigated. These codes are useful for storing data in storage devices. Since most devices are not noiselss, the codes are often required to have some error-control capability. We consider runlength-limited codes that can correct or detect unidirectional byte errors. Some constructions of such codes are presented.

Silicon nitride (SiNx) films have been deposited at lower substrate temperatures (500) by direct (without mercury-sensitization) photo-chemical vapor deposition (photo-CVD) using SiH4 and NH3 with a low-pressure mercury lamp. Films deposited at around 350 have a polymeric structure such as (Si(NH)2)n. Films deposited at 500 were close to stoichiometric Si3N4 with a slight amount of hydrogen. The refractive index and the dielectric constant of films deposited at 500 became almost equal to the values of thermally synthesized Si3N4. The resistivity was as high as 51016 Ωcm. The minimum density of interface states in Al/SiNx/Si MIS (metal-insulator-semiconductor) diodes was estimated to be 91010 cm-2eV-1 by a quasi-static capacitance-voltage measurement. For SiNx films deposited at 300, the density of interface states, which was in the order of 1011 cm-2eV-1 as deposited, decreased by a rapid thermal anneal after the deposition. For Al/SiNx/InP MIS diodes, it was 31011 cm-2eV-1 by high-frequency capacitance-voltage measurements. Direct photo-CVD for SiNx films is promising for low-temperature formation of a gate insulator.

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.

The wave distribution functions (WDFs) have been reconstructed by means of the maximum entropy inversion to the observed spectral matrix composed of the auto- and cross-power spectra among the three field components (Bx, By and Ez) in which the exactly right-handed circular polarization is taken in the integration kernels. The purpose of this paper is to investigate the properties of wave distribution functions reconstructed for wave sources whose central polarization is somewhat deviated from right-handed circular and to study (1) the WDF's by using the right-handed circular polarization in the kernels, (2) the effect of larger deviations for the polarization of elementary plane waves consituting the wave source, (3) the WDF's based on the elliptical polarization kernels and (4) the effect of limiting the number of eigenvalues. It is then found that changing the polarization model in the integration kernels would be helpful in finding out the polarization of the actually observed signals.

The authors design a simple feed system for a planar slotted waveguide array. A waveguide π-junction with negligible reflection is cascaded to compose a multiple-way power divider. The frequency characteristics of the power divided to each port and the reflection at the feed point are discussed and high performances are predicted. The maximum number of cascaded junctions in this system can be determined in terms of a desired frequency bandwidth and allowable deviation in divided power.

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.

This paper describes the structure and properties of superconductive small antennas with thin-film matching circuits. These circuits make it possible to realize small antennas, 38 mm20 mm16 mm in size. This is one quarter the length of our previously reported ceramic antennas. The actual gain of this antennas was -4.5 dBi at 470 MHz. This value is 5.5 dB higher than that of Cu antennas with exactly the same structure.

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.

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.

In this letter, we consider a magnetic or optical recording system employing a concatenated code that consists of a runlength-limited (d, k) block code as an inner code and a byte-error-correcting code as an outer code. (d, k) means that any two consecutive ones in the code bit stream are separated by at least d zeros and by at most k zeros. The minimum separation d and the maximum separation k are imposed in order to reduce intersymbol interference and extract clock control from the received bit stream, respectively. This letter recommends to use as the outer code a unidirectional-byte-error-correcting code instead of an ordinary byte-error-correcting code. If we devise the mapping of the code symbols of the outer code onto the codewords of the inner code, we may improve the error performance. Examples of the mappings are described.

Syntax-directed editors have several advantages in editing programs because programming is guided by the syntax and free from syntax errors. Nevertheless, they are less popular than text editiors. One of the reason is that they force a priori specified editing structures on the user and do not allow him to use his own structure. ACE (Algorithmically Customizable syntax-directed Editor) provides a solution for this problem by using a technique of machine learning; ACE has a special function of customizing the grammar algorithmically and interactively based on the learning method for grammars from examples and queries. The grammar used in the editor is customized through interaction with the user so that the user can edit his program in a more familiar structure. The customizing function has been implemented based on the methods for learning of context-free grammars from structural examples, for which the correctness and the efficiency are proved formally. This guarantees the soundness and the efficiency of customization. Furthermore, ACE can be used as an algorithmic and interactive tool to design grammars, which is required for several purposes such as compiler design and pretty-printer design.

In this paper, subband image coding with symmetric biorthogonal wavelet filters is studied. In order to implement the symmetric biorthogonal wavelet basis, we use the Laplacian Pyramid Model (LPM) and the trigonometric polynomial solution method. These symmetric biorthogonal wavelet basis are used to form filters in each subband. Also coefficients of the filter are optimized with respect to the coding efficiency. From this optimization, we show that the values of a in the LPM generating kernel have the best coding efficiency in the range of 0.7 to 0.75. We also present an optimal bit allocation method based on considerations of the reconstruction filter characteristics. The step size of each subband uniform quantizer is determined by using this bit allocation method. The coding efficiency of the symmetric biorthogonal wavelet filter is compared with those of other filters: QMF, SSKF and Orthonormal wavelet filter. Simulation results demonstrate that the symmetric biorthogonal wavelet filter is useful as a basic means for image analysis/synthesis filters and can give better coding efficiency than other filters.

We have developed an advanced tool for dimensioning circuit-switched networks, called CNEP (Circuit-Switched Network Evaluation Program) , for effective design of digital networks. CNEP features a high-reliability network structure (node dispersion, double homing, etc) , both-way circuit operation, and circuit modularity (or big module size), all of which are critical for digital networks. CNEP also solves other dimensioning problems such as the cost difference between existing and newly installed circuits, and handles multi-hour traffic conditions, dynamic routing, and multiple-switching-unit nodes. Operations Research techniques are applied to produce exact and heuristic algorithms for these problems. Algorithms with good time-performance trade-off characteristics are chosen for CNEP.

For the development of a practical device simulation, it is necessary to solve the large sparse linear equations with a high speed computation of direct solution method. The use of parallel computation methods to solve the linear equations can reduce the CPU time greatly. The Multi Step Diakoptics (MSD) algorithm, is proposed as one of these parallel computation methods with direct solution, which is based on Diakoptics, that is, a tearing-based parallel computation method for sparse linear equations. We have applied the MSD algorithm to device simulation. This letter describes the partition and connection schedules in the MSD algorithm. The evaluation of this algorithm is done using a massively parallel computer with distributed memory (AP1000).

A new CMOS neuron circuit suitable for VLSI implementation of artificial neural networks is proposed. A cross-coupled current comparator structure is adopted to obtain large differential neuron signals for high-speed multi-input/multi-output neuron operations. In addition, the shape of the output function of the proposed neuron circuit can be modified by simply varying the value of the auxiliary current sources. To estimate the performance of the proposed circuit as an element in a neural network, a 15-bit associative memory based on the Hopfield neural network was designed. The performances of a single 7-input neuron and of the 15-neuron associative memory are confirmed by SPICE simulations.

Plasmaless etching using ClF3 gas has been investigated on nitride films with different composition. For the sputter deposited and thermally grown silicon nitride films containing no hydrogen, the etch rate increases and the activation energy decreases with increase of the composition ratio of silicon to nitrogen between 0.75 and 1.3. This fact indicates that the etching is likely to proceed through the reaction between Si and ClF3. The native oxide on the silicon-nitride films can also be removed with ClF3 gas. Ultra-violet light irradiation from a low pressure mercury lamp remarkably accelerates the removal of the native oxide and the etch rate of the thermally grown silicon-nitride films. For the plasma deposited films, the etch rate is strongly accelerate with increasing hydrogen content in the films, but the activation energy hardly depends on the bounded hydrogen in the films, consistent with the results for Si etching.