This paper addresses onboard processing architecture employing direct regeneration. The advantage of direct regeneration is its hardware simplicity, even though the bit error rate performance is slightly inferior to that of demodulation-remodulation scheme with coherent detection. The channel filtering schemes as well as achievable capacities are examined by computer simulation. It is found that the system with direct regeneration has advantage in channel capacity and transmit earth station e.i.r.p. for small earth stations. A possible configuration of direct regeneration onboard in future satellite systems is proposed.

Single-mode fibers with intentionally induced periodical residual strains (IIPRS) along the fiber length are proposed for the suppression of the stimulated Brillouin scattering (SBS). A change of the residual strain along a fiber will change the Brillouin frequency shift, resulting in a broadening of the Brillouin gain profile. Such an increase of the line-width of the gain profile will cause a decrease of the gain coefficient which will raise the threshold power of the stimulated Brillouin scattering in optical fibers. Two types of the IIPRS fibers were fabricated. The residual strain of one IIPRS fiber is modified rectangularly while that of the other is changed triangularly. The measured spectra of the SBS are compared with that of a fiber with a constant strain. Using a novel mathematical model presented in this report, the possible improvements of the threshold powers for these two IIPRS fibers over the constant-strain fiber can be assessed through the SBS spectra. Finally, the achieved improvements are confirmed with the experimental results. The estimated improvement of the threshold for the IIPRS fiber with the rectangular profile is 2.9dB while the measured is 2.4dB. In case of the IIPRS fiber with a triangular profile, the improvement of the threshold is 5.4dB by estimation and is 5.1dB by experiment. While the limit of the threshold improvement for rectangular IIPRS fibers is 3dB, the threshold improvement for triangular IIPRS fibers is limited only by the allowable deviation of the tension applied during the drawing of fibers. It is estimated that a 5dB improvement is not difficult to realize.

This paper deals with the theory and design method of an efficient radix-4 divider using carry-propagation-free adders based on redundant binary {-1,0,+1} representation. The usual method of normalizing the divisor in the range [1/2,1) eliminates the advantages of using a higher radix than two, bacause many digits of the partial remainder are required to select the quotient digits. In the radix-4 case, it is shown that it is possible to select the quotient digits to refer to only the four (in the usual normalizing method it is seven) most significant digits of the partial remainder, by scaling the divisor in the range [12/8,13/8). This leads to radix-4 dividers more effective than radix-2 ones. We use the hyperstring graph representation proposed in Ref.(18) for redundant binary adders.

An efficient technique for expressing document image is required as part of a unified approach to document image processing. This paper presents a new method, Minimum Covering Run (MCR), for expressing binary images. The name being adapted from horizontal or vertical run representation. The proposed technique uses some horizontal and vertical runs together to represent binary images in which the total number of representative runs is minimized. Considering the characteristic of above run types precisely, it is shown that horizontal and vertical runs of any binary image could be thought of as partite sets of a bipartite graph. Consequently, the MCR expression that corresponds to the construction of one of the most interesting problems in graphs; i.e., maximum matching, is analogously found by using an algorithm which solves this problem in a corresponding graph. The most efficient algorithm takes at most O(n5/2) computations for solving the problem where n is the sum of cardinalities of both partite sets. However, some patterns in images like tables or line drowings, generally, have a large number of runs representing them which results in a long processing time. Therefore, we provide the Rectangular Segment Analysis (RSA) as a pre-processing to define runs representing such patterns beforehand. We also show that horizontal and vertical covering parts of the proposed expression are able to represent stroke components of characters in document images. As an implementation, an efficient algorithm including arrangement for run data structure of the MCR expression is presented. The experimental results show the possibility of stroke extraction of characters in document images. As an application, some patterns such as tables can be extracted from document images.

This paper studies a method for a parallel implementation of digital half toning technique, which converts continuous tone images into monotone one without losing fidelity of images. A new modified algorithm for half toning is proposed, which is able to be implemented on a rectangular or one dimensional parallel multi-processor array as a part of extensions of space partitioning image processings. The purpose of this paper is primarily to apply space partitioning local image processing technique to nonlinear recursive algorithms. The target is to achieve a fast half toning with high quality. For that propose, local directional error diffusion techniques will be introduced, which enable original recursive error diffusion half toning to be converted into a local processing algorithm without losing its original advantages of producing high quality images. The characteristics of proposed methods will be analyzed and the advantages of our algorithm of high speed processing and high quality will be demonstrated by showing the results of simulations for typical examples.

We report on Brillouin optical-fiber time domain reflectometry (BOTDR) for distributed temperature or strain measurement along a single-mode optical fiber. BOTDR uses Brillouin scattering in optical fibers, whose Brillouin frequency shift increases in proportion to temperature or strain induced in the fiber. This method requires access to only one end of a fiber, as with conventional optical time domain reflectometry (OTDR) which uses Rayleigh scattering in optical fibers. In BOTDR, a coherent optical detection method is used as a backscattered light detection technique. This technique can achieve both high sensitivity and high frequency resolution and easily separate a weak Brillouin line from a strong Rayleigh scattering peak and Fresnel reflected light. Experimental results show the potential for measuring temperature and strain distribution with respective accuracies of 3 or 0.006%, and a spatial resolution of 100m in an 11.57km long fiber.

This letter describes a new input and cross-point buffering matrix switching architecture for high-speed ATM switching systems. The proposed switch has input queuing buffers at each input port, and small size buffers for output port arbitration at each cross-point. These two types of buffers share loads using a simple and high-speed retry algorithm. Hardware size is only half that of conventional cross-point buffering switches. In addition, the switch achieves high-throughput at a condition that the switching speed matches the input and output port speed. This switch is expected to enable the development of high-speed ATM switching systems with each port supporting speeds in excess of 1Gbit/s.

An adaptive algorithm is presented for fuzzy clustering of data. Partitioning is fuzzified by addition of an entropy term to objective functions. The proposed method produces more convex membership functions than those given by the fuzzy c-means algorithm.

The evolution of Multiple-Valued Logic (MVL) circuits has been inexorably tied to the rapid technological changes induced by evolving needs and emerging developments in computing methodologies. Unfortunately for MVL, the numbers of designers of technologies and circuits whose lives are dedicated to the improvement of binary techniques, are large and overwhelming. Correspondingly, technological developments in MVL typically await the appearance of a problem or technique in the larger binary world to motivate and/or make possible some new advance. Such opportunities are inevitably quite transient since each such problem is simultaneously attacked by many others of a more conventional bent, and, as well, each technological change begets yet another, quickly. It is in the sensing of this reality that the present paper is written. Correspondingly, its thrust is two-fold: One target is the possibility of encouraging a leap ahead through modest technological projection. The other is the possibility of identifying application areas that already exist in this unbalanced competition, but which are specially suited to multiple-valued solutions. For example, it has been clear for decades that one such area is that of arithmetic. Correspondingly, we in MVL must strive quickly to concentrate our efforts on applications that exploit such demonstrable strengths. Some such applications are includes here; others are visible historically, many probably remain to be found: Search on!

Low-sensitivity digital filters are required for accurate signal processing. Among many low-sensitivity digital filters, a method using complex allpass circuits is well-known. In this paper, a new synthesis of complex allpass circuits is proposed. The proposed synthesis can be realized more easily either only in the z-domain or in the s-domain than conventional methods. The key concept for the synthesis is based on the factorization of lossless scattering matrices. Complex allpass circuits are interpreted as lossless digital two-port circuits, whose scattering matrices are factored. Furthermore, in the cases of Butterworth, Chebyshev and inverse Chebyshev responses, the explicit formulae for multiplier coefficients are derived, which enable us to synthesize the objective circuits directly from the specifications in the s-domain. Finally design examples verify the effectiveness of the proposed method.

The problem of two-dimensional scattering of electromagnetic waves by a grating with several strips arbitrarily oriented in one period is analyzed by means of the Wiener-Hopf technique together with the formulation using the concept of the mutual field. A formulation for the analysis of multiple scattering from the grating is based on the representation of the scattered field by a grating composed of one strip in one period. The Wiener-Hopf equations and a representation of the scattered wave are obtained. The characteristic of the sampling function is used to expand the unknown function associated with the field on the strip into a series, and then the Wiener-Hopf equations are reduced to a set of simultaneous equations. For evaluation of the convergence and the errors in the numerical results, the relative error with respect to the extrapolated value and the square error for satisfaction of the boundary condition are 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 of the reflection coefficients are presented for the reflection grating and transmission gratings.

In order to evaluate multipath signal strengths reflected by mountain, a fundamental equation is derived for both cases where antenna beams are larger and smaller than a reflecting plane, assuming that reflection consists of absoption and scattering at the mountain surface. Absorption loss at a mountain surface was measured on a model propagation path by using sharp beam antennas to separately pick up the mountain-reflected signal.

The diffraction of a plane electromagnetic wave by a parallel-plate waveguide cavity with a thick planar termination is rigorously analyzed for both the E and the H polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved exactly in a formal sense via the factorization and decomposition procedure. Since the formal solution involves an infinite number of unknowns and branch-cut integrals with unknown integrands, approximation procedures based on rigorous asymptotics are further presented to yield the approximate solution convenient for numerical computations. The scattered field inside and outside the cavity is evaluated by taking the inverse Fourier transform and applying the saddle point method. Representative numerical examples of the monostatic and bistatic radar cross sections are presented for various physical parameters, and the scattering characteristics of the cavity are discussed in detail.

Dynamic performance of ultra-thin SIMOX (Separation by IMplanted OXgen) CMOS circuits has been studied using ring oscillators. A novel concept of current-delay product, along with an equivalent linear resistance of MOSFETs, is applied for deriving effective load capacitance of near 0.1 µm gate CMOS circuits. Calculation results showed quatitative agreement with measurement data. It was found that the gate-fringing capacitance limits the delay time is the case of under 0.2 µm gate-length. The lower bound of power-delay product of SIMOX/SOI is expected as low as 0.2 fJ for the gate length of 0.15 µm at the supply voltage of 1.5 V.

Frequency Selective Screens (FSS) with conductor or complementary aperture array are investigated. The electric current distribution on conductor or the magnetic current distribution on aperture is determined by the moment method in the spectral domain. In addition, the power reflection coefficients are calculated and the scattering properties are considered.

The static characteristics of GaInAs(P)/GaInAsP quantum well laser diodes (QW LDs), with graded-index separate-confinement-heterostructure (GRIN-SCH) grown by metalorganic chemical vapor deposition (MOCVD), have been investigated experimentally in terms of threshold current density, internal waveguide loss, differential quantum efficiency and light output power. Very low threshold current density of 410 A/cm2, high characteristic temperature of 113 K, low internal waveguide loss of 5 cm-1, high differential quantum efficiency of 82% and high light output power of 100 mW were obtained in 1.3 µm GRIN-SCH multiple quantum well (MQW) LDs by optimizing the quantum well structure including confinement layer and cavity design. Excellent uniformity for the threshold current, quantum efficiency and emission wavelength was obtained in all MOCVD grown buried heterostructure GRIN-SCH MQW LDs. Lasing characteristics of 1.5 µm GRIN-SCH MQW LDs are also described.

In this paper, scattering waves by a strip grating with an anisotropic substrate for the incidence of inclined polarization are analyzed, and polarization characteristics of scatterd waves are calculated. For simplicity, the analysis is limitted to the case of normal incidence and a perfectly conducting strip grating is assumed.

An efficient reconstruction algorithm for diffraction tomography based on the modified Newton-Kantorovich method is presented and numerically studies. With the Fréchet derivative obtained for the Helmholtz equation, one can derive an iterative formula for getting an object function, which is a function of refractive index of a scatterer. Setting an initial guess of the object function to zero, the pth estimate of the function is obtained by performing the inverse Fourier transform of its spectrum. Since the spectrum is bandlimited within a low-frequency band, the algorithm does not require usual regularization techniques to circumvent ill-posedness of the problem. For numerical calculation of the direct scattering problem, the moment method and the FFT-CG method are utilized. Computer simulations are made for lossless and homogeneous dielectric circular cylinders of various radii and refractive indices. In the iteration process of image reconstruction, the imaginary part of the object function is set to zero with a priori knowledge of the lossless scatterer. Then the convergence behavior of the algorithm remarkably gets improved. From the simulated results, it is seen that the algorithm provides high-quality reconstructed images even for cases where the first-order Born approximation breaks down. Furthermore, the results demonstrate fast convergence properties of the iterative procedure. In particular, we can successfully reconstruct the cylinder of radius 1 wavelength and refractive index that differs by 10% from the surrounding medium. The proposed algorithm is also effective for an object of larger radius.

This paper proposes a new fault tolerant intercommunication scheme for real-time operations and three new interconnection networks to construct a fault tolerant multi-processor system for pipeline processings. The proposed intercommunication scheme using bank memory switching technique has an advantage to make a fault tolerant pipeline system so that it can detect any failure caused in a processing element of the system. In addition, it can overcome conventional problems caused in interconnection circuits to flow data with one way direction such as a pipeline processing.

This paper describes a programming system, K-NET for the development of control software for flexible manufacturing systems composed of robots, numerically-controlled machines, transfer machines and automatic storage/retrieval systems. K-NET is based on a high-level Petri net which makes it simple to express operational functions such as synchronization, interlock and concurrence in sequence control. Petri net in K-NET is colored one in which tokens have attributes, and timed one which can provide a notion of stochastic time. K-NET provides many kinds of boxes having specific functions, and gates specified the firing condition and the token flow control with IF-THEN rules. On the other hand, procedural language can be also used for information processing. K-NET can support all development stages including general design, detailed design, programming and testing. K-NET has an editor to input control specifications expressed with Petri net; a simulator to verify edited specifications; a generator to convert the net to C source programs for a computer or to ladder diagrams for a programmable controller; a reporter to print control specifications; and a monitor to display controller status in real-time. K-NET has been used in the development of control software for an automated guided vehicle system, and results show a 2/3rds cost-saving over development with conventional methods in which only procedural language is used.