A simple and practically accurate method for studying rectangular dielectric waveguides is proposed. This method can provide good evaluations of propagation constant and field distribution of the waveguides by analyzing improved equivalent guide models. In this paper, it is applied in studying a novel taper-formed waveguides system. The waveguides system was experimentally demonstrated of being advantageous in its lightwave transmission characteristics. Experimentally obtained results exhibited good agreement with the performances predicted by the system numerical analyses using the proposed waveguide study technique.

This paper describes the implementation types of private networks from the viewpoint of equipment and users, and utilization trends from low to high-speed services. Technology trends of private networks from the viewpoint of high-speed and broadband communication, multimedia communication, media access methods and intelligent communication are also examined. A concept for implementing future private networks in the Broadband ISDN (B-ISDN) age, and the major technology and the future efforts to achieve this implementation are discussed. Asynchronous Transfer Mode (ATM) is shown to be the key technology for integrating both various and heavy traffic media communication.

This paper describes theoretical analyses of a new CRV (Code Rule Violation) collision detection method applicable to an optical CSMA/CD LANs. The new method is based on the ideas combining a partial response (1,0, --1) circuit with the basic CRV collision detection method; the ideas are proposed in IEEE 802.3 committee. The circuit configuration of the new method, however, is different from that proposed in IEEE 802.3 committee. First, the paper outlines the basic CRV collision detection method and shows the problem that it can't detect a collision when identical bits are continuously received. Secondly, a practical circuit configuration of the new method is introduced. To realize large optical dynamic range and stability in collision detection, the circuit is designed not to detect CRVs on noisy zero level signals caused by signal negation with partial response circuits. The calculation formulae are then derived for the basic and the new method to determine the CRV rate with and without signal collision. At a bit rate of 10Mb/s, the CRV rate with and without signal collision is then calculated for the basic and the new method. Finally, the calculation results are compared with each other, and it is clarified that the new method is an effective method to increase CRV rate when signal collision occurs.

Codes having order-K spectral density nulls, i.e., codes such that the power spectral density of the encoded sequences and its first 2K-1 derivatives vanish at rational submultiples f of the symbol frequency are investigated. Several necessary and sufficient conditions for a code to have an order-K spectral density null at f are given. A lower bound on the minimum Euclidean distance of a code with an integer alphabet and with an order-K spectral density null also is derived. Canonical diagrams for higher order spectral density nulls and nonzero spectral lines are introduced.

In this letter, the relations between the generalized beams with the different parameters are investigated by using the formula for the Hermite polynomials and that for the generalized Laguerre polynomials. The adjoint functions for the generalized Laguerre-Gaussian beam functions are also derived concretely. It is shown that the generalized beam is represented by a finite number of another generalized beam with the different parameter.

Tohoku University has been constructing the academic information-exchange network TAINS (Tohoku University Academic/All-round/Advanced Information Network System) to link its widely spread campuses and to meet several demands for an intrauniversity network. TAINS, the first network based on OSI, became operational in April 1988. The primary function of TAINS is to connect all the geographically dispersed locations of the university via a high-speed digital network in order to facilitate an easy and efficient interconnection among the various computers, terminals and other scientific equipment. TAINS is constructed as a large-scale local area network of hierarchical structure. In the hierarchical network of TAINS, a backbone network, consisting of two 100 Mbps optical fiber rings, interconnects several small-scale IEEE802.3 networks, each of which span a building or a part of a building. This paper describes the background, the basic design concept and the constitution of TAINS. In TAINS, the inhouse network protocol is OSI-based, and the ring network protocol is based on FDDI. The use of these communication protocols are reviewed and the protocol matching adopted for TAINS is described. Finally, a method for estimating the stable operation of a 2-layer hierarchical network using traffic analysis is given.

The Fourier series expansion method is applied to the problem of EM waves guided by a dielectric grating with periodic surface-relief. The periodic structures of dielectric gratings are divided into two types: (1) surface-relief type and (2) modulated refractive index type. For the modulated dielectric grating, the rigorous solution is obtained using the space-harmonics expansion method, but the usual method cannot be applied to the grating whose dielectric constant distribution has discontinuities. Previously, we pointed out this issue and gave an improved method which can be applied to those problems. This method can also be applied to the surface-relief grating by approximating it as an assembly of stratified thin modulated dielectric gratings. In this paper, numerical analysis is given for gratings with sinusoidal surface and triangular surface for both perpendicular polarization (TE waves) and parallel polarization (TM waves). The validity of our method has been checked by increasing the number of modal expansion terms and the number of multilayers. The results are compared with those obtained by other numerical methods. The differences in the propagation characteristics between the surface-relief grating and the modulated dielectric grating in Bragg region are also discussed.

This paper proposes a new service scheme which multiplexes several independent sub-documents onto the main document in a conventional facsimile broadcasting system. These multiplexed facsimile signals are moreover unified besides the voice channels in television system. The scheme does not increase the amount of facsimile signals, thus, it can save the frequency resources and communication channels. In this system, the main facsimile document is open for common subscribers, but the multiplexed sub-documents are delivered only for the special subscribers who are registered to the broadcasting station for each channel.

It is known that the moments of the cepstrum of a mixed phase signal sequence can be calculated without directly calculating the cepstrum, avoiding the phase unwrapping algorithm and the aliasing error etc. Using this, moments of cepstrum of the minimum phase sequence are calculated from the linear phase sequence without actually calculating the minimum phase sequence.

A major problem in Doppler ultrasound has been the lack of quantitation of the magnitude of the blood velocity vector, particularly in intracardiac flow where the flow direction can't be estimated. This paper derives a new flow-mapping system for visualizing the two-dimensional blood velocity vector. The resultant velocity vector is the projection of the three-dimensional velocity vector on the beam scanning plane.

In this paper a new 16-ary Differentially Encoded Quadrature Amplitude (16-DEQAM) demodulator for medium and high bit rate (from 2 MBit/s to 100 MBit/s) Land Mobile Satellite Communications is proposed and its performance is evaluated. The synchronization and detection digital techniques employed in this system are described. The hardware speed limitations have been overcome effectively with extensive use of look-up tables and concurrent digital signal processing on polar signal representation. The acquisition and Bit Error Rate(BER) performances are evaluated by computer simulation over Additive White Gaussian Noise (AWGN) and Rician fading channel.

Most number-theoretic cryptosystems are constructed based on a modular exponentiation, which requires a large number of processing steps. Therefore, one of the most significant problems in cryptographic research is how to reduce the time needed to carry out a modular exponentiation operation. This paper proposes an improved modular exponentiation algorithm using a new table-look-up method. On executing a modular exponentiation computation, first, it must be decomposed efficiently into a series of modular multiplications. For this decomposition, the Binary method is used in this paper. When the Binary method is so implemented as to process the exponent in the-most-significant-bit-first manner, multiplier M, as well as modulus N, can also be considered as a common constant in 1/3 of the decomposed modular multiplications. Thus, with some additional procedure, one can compute beforehand the residues concerning M and N. This makes it possible to process the multiplication and reduction simultaneously. This algorithm is faster than conventional ones which take into account only that the modulus N can be considered a constant. The effectiveness of the proposed method is investigated with an evaluation model proposed in this paper and evaluated by software implemented on a engineering workstation and on a digital signal processor. The evaluation model indicates that the proposed method reduces the execution time by 17% compared with a conventional table-look-up method, if bit length k of modulus N is sufficiently large. The corresponding figure in the computer simulation is 14% for k=512.

Some properties of the multiplication operator, which performs multiplication between two functions on PL transform domain is discussed. Then we derive an efficient generation algorithm for the multiplication operator. The flow diagram of the generation algorithm is also presented.

A definition of flexibility in PCM multiplexing architectures is given based on the concept of information entropy. New architectures and coding arrangements are proposed based on the idea of flexibility. Binary terms are created to allow for a better description of system parameters.

This paper presents solder paste rheology and its printability. Evaluating rheology of solder paste can help to solve problems in the fine pattern printing of solder paste. To quantify the solder paste rheology, viscosity, thixotropy index and viscosity restoration ratio were measured. For these measurements, six test samples of solder paste were prepared. These characteristics can be measured by changing shear rate of viscometer in several steps. Viscosity of solder paste lowers as shear rate increases. Low shear rate viscosity and high shear rate viscosity were calculated from viscosity and thixotropy indexes. These rheological characteristics are closely related to the printing quality. Printability of the solder pastes was evaluated by experimental procedure with a fine pitch QFP (Quad Flat Package) foot print test pattern. The Taguchi method was used in this printing experiment. Analysis of variance were performed to examine factors influencing printability. Evaluated items of printability were short deposit defect, bridge defect, line width increase ratio and rolling effect. Correlation analysis between rheological characteristics and printability of solder paste was performed. Results give a suggestive theoretical zone for good printing quality, that was figured out on the thixotropy index vs. viscosity plot. Its center point is 1800 [Poise] of viscosity and 0.6 of the thixotropy index. Evaluating rheology of solder paste is important when the printability of solder paste in fine pitch technology is concerned.

Data compaction and data expansion methods for an electron beam direct writing system EBM-130V are described. EBM-130V adopts the raster scan method using a variably shaped line beam. The system does not have an effective hierarchical structure in its data format, because it has only a single deflector. So, an extra virtual layer has been introduced into the EB data format, and an artificial hierarchical data structure is used for data compaction. The compacted data is expanded by an EB control software system. For a 4 Mbit DRAM, the data amount was about 30 MBytes (compaction rate 1/16), the data conversion time was about 12 minutes (reduction rate 1/35), and the data transfer time from the system disk to the pattern data memory was reduced to about 1/5, by using the date compaction method.

A trial definition and position of electronic packaging technology which consists of packaging process technology and packaging assembly technology is shown. Then, evaluation of packaging technology from the system engineer's point of view is discussed. In Japan, the most recent main packaging technology is SMT. But it may be only a passing point to COX. Finally a new concept on ultimate high density packaging is introduced.

We discuss how to design mechanically an information processing system presented with two independent requirements, one of which shows information flow to perform some process and one which prohibits illegal information flow. To do this, we introduce one well-known security model the "Bell and LaPadula model" and formulate this design problem. This problem then becomes a security level assignment problem. We show that the design possibilities and level assignment can be mechanically solved by expressing the inequalities in graph theoretical form and by using an analytical method of graph theory.

The two-dimensional scattering problem of electromagnetic waves by a grating composed of two arbitrarily oriented strips in one period is analyzed by means of the formulation using the mutual field. A formulation is presented for the analysis of multiple scattering by the grating by means of the representation of the scattered field by a grating composed of one strip in one period. The Wiener-Hopf equations to be satisfied by each scattered field and the representation of scattered wave based on the solution to these equation are obtained. Since the width of the strips in the grating is finite, it is difficult to carry out rigorously the decomposition in the solution of the Wiener-Hopf equations. The characteristic of the sampling function is used for expansion of the unknown function into a series so that the Wiener-Hopf equations are reduced to a set of simultaneous equations. For evaluation of the convergence and the errors in the results, the relative error with respect to the extrapolated value and the square error for satisfaction of the boundary condition are numerically computed. From numerical comparison of the present method with other various methods, it is found that the present method provides us accurate results. Some numerical examples on the reflection coefficient are presented for the reflection and transmission gratings.