When signal subspace techniques, such as MuSIC, are used to locate a number of incident signals, an exhaustive search of the array manifold has to be carried out. This search involves the evaluation of a single cost function at a number of points which form a grid, resulting in quantization-error effects. In this paper a new algorithm is put forward to overcome the quantization problem. The algorithm uses a number of cost functions, and stages, equal to the number of incident signals. At each stage a new cost function is evaluated in a small number of "special" directions, known as characteristic points. For an N-element array the characteristic points, which can be pre-calculated from the array manifold curvatures, partition the array manifold into N-1 regions. By using a simple gradient algorithm, only a small area of one of these regions is searched at each stage, demonstrating the potential benefits of the proposed approach.

A soft magnetic force microscope (MFM) tip was used to evaluate the magnetic recording characteristics of compositionally separated Co-Cr perpendicular media. Small magnetic bits were recorded on thick (350 nm). and thin (100 nm) films, focusing on the fineness of compositionally separated microstructures. MFM images showed bit marks 230 and 150 nm in diameter, measured at full-width at half maximum (FWHM) for the thick and thin films, respectively. These results verify that the recordable bit size can be decreased by using a thinner film with a finer compositionally separated microstructure. Simulation was used to clarify the relationship between the actual sizes of the recorded bits and the sizes of their MFM images. The recorded bit size was found to closely correspond to the FWHM of the MFM bit images.

Ba ferrite films were deposited epitaxially on ZnO underlayer from targets with composition of BaO-6.5Fe2O3 at substrate temperature of 600 using the facing targets sputtering apparatus. The gas mixture of Ar and Xe of 0.18 Pa and O2 of 0.02 Pa was used as the sputtering gas and the dependences of crystallographic and magnetic characteristics on the partial Xe pressure PXe(0.0-0.18 Pa) were investigated. Films deposited at various PXe were composed of BaM ferrite and spinel crystallites, and the minimum centerline average roughness Ra of 8.3 nm was obtained at PXe of 0.10 Pa. Since saturation 4πMs of 5.1 kG and perpendicular anisotropy constant Ku1 of 4.23105 Jm-3 were larger than those of bulk BaM ferrite of 4.8 kG and 3.30105 Jm-3, respectively, these films appeared promising for use as perpendicular recording media.

Currently, many efforts are underway to design wideband mobile communication system. The system is one of alternative of Future Public Land Mobile Telecommunication Systems (FPLMTS). In this paper, we clarify received signal level characteristics for wideband mobile radio channels in line-of-sight (LOS) microcells. The results from urban-area field experiments, where received signal levels for various receiver bandwidths and power delay profiles were measured, show that the depth of fading of the-received signal decreases as normalized RMS delay spread, defined as the product of receiver bandwidth and RMS delay spread, increases. These results are useful in designing wideband microcell systems for urban areas.

Extremely narrow track width of deep submicron range is examined in perpendicular magnetic recording. Head field distribution of a single-pole head analyzed by 3-dimensional computer simulation results in a sharp gradient, but relatively large cross-sectional area is required to maintain head field strength. Based on this design concept, a lateral single-pole head is described and proved to attain track width of 0.4 µm. In addition, multilevel partial response appropriate to the new multitrack recording system is proposed.

The MUSIC algorithm has proven to be an effective means of estimating parameters of multiple incoherent signals. Furthermore, the forward-backward (FB) spatial smoothing technique has been considered the best preprocessing method to decorrelate coherent signals. In this paper, we propose a novel preprocessing technique based upon ideas associated with the FB and adaptive spatial smoothing techniques and report on its superiority in numerical simulations.

Simplification of the Viterbi algorithm and the error rate performance are presented for a partial response maximum-likelihood (PRML) system employing the PR(1, 1) system as a PR system for (1, 7) run-length limited (RLL) code. The minimum run-length of 1's or O's in the output sequence of the precoder for (1, 7) RLL code is limited to 2. Two kinds of simplified Viterbi algorithms using this run-length constraint are proposed. One algorithm requires the path memory length of only two in the Viterbi detector. The Viterbi detector based on the other algorithm is equivalent to the simple PR(1, 1) system followed by a threshold detector. The bit-error rates of PRML systems with Viterbi detectors based on these algorithms are obtained by computer simulation and their performance is compared with that of conventional PRML systems for (1, 7) RLL code. It is shown that the proposed PRML system exhibits better performance than conventional PRML systems at high recording density.

Computer circumstance have changed drastically, and larger capacity removable media is indispensable. Magneto-optical disk is promising candidate to satisfy computer user's needs. In this report, future perspective of high density magneto-optical recording technology is investigated.

This paper proposed a practical method of program validation for state-based reactive concurrent systems. The proposed method is of particular relevance to plant control systems. Plant control systems can be represented by extended state transition systems (e.g., communicating asynchronous transition systems). Our validation method is based on state space analysis. Since naive state space analysis causes the state explosion problem, techniques to ease state explosion are necessary. One of the most promising techniques is the partial order method. However, these techniques usually require some structural assumptions and they are not always effective for actual control systems. Therefore, we claim integration and harmonization of verification (i.e., state space analysis based on the partial order method) and simulation (i.e., conventional validation technique). In the proposed method, verification is modeled as exhaustive simulation over the state space, and two types of simulation management techniques are introduced. One is logical selection (pruning) based on the partial order method. The other is heuristic selection based on priority (a priori precedence) specified by the user. In order to harmonize verification (logical selection) and conventional simulation (heuristic selection), we propose a new logical selection mechanism (the default priority method). The default priority method which prunes redundant state generation based on default priority is in harmony with heuristic selection based on the user's priority. We have implemented a practical validation tool, Simulation And Verification Environment for Reactive Concurrent Systems (SAVE/RCS), and applied it to chemical plant control systems.

The performance of decision-feedback equalization combined with maximum-likelihood detection (DFE/ML) using the fixed-delay-tree-search/decision feedback (FDTS/DF) algorithm was estimated analytically in terms of the length of the feedback-filter and the depth of the ML-detector. Performance degradation due to error propagation in the feedback-loop and in the ML-detector was taken into account by using a Markov process analysis. It was quantitatively shown that signal-to-noise-ratio (SNR) performance in high-density magnetic recording channels can be improved by combining an ML-detector with a feedback-filter and that the error propagation in the DFE channel can be reduced by using an ML-detector. Finally, it was found that near-optimum performance with regard to channel SNR and error propagation can be achieved, over the channel density range from 2 to 3, by increasing the sum of the feedback-filter length and the ML-detector depth to six bits.

A particulate recording medium with an ultrathin magnetic layer is presented in this paper. This medium consists of a magnetic layer and a nonmagnetic underlayer composed of very fine titanium dioxide powder. When metal powder was employed, we observed the anticipated advantages of decreasing the thickness of the magnetic layer in tapes and diskettes. By reducing the layer thickness to below 0.3 µm we were able to increase the reproduced output at short wavelengths, and improve both the overwrite erasability and the D50. There was also a decrease in the half peak width of an isolated pulse and a peak shift. Tribological advantages were also observed with this medium. When barium ferrite was employed as the magnetic powder, we observed that the modulation noise of thin-layer barium ferrite medium was less than that of a thinlayer MP medium while it generated an output as high as that of the MP medium. The advantages of the barium ferrite medium lie in its two-layer construction. Particulate media will continue to develop as magnetic powder is improved mainly in terms of its size, saturation magnetization, and coercivity.

The dielectric rod waveguides with corrugation consisting of nonintegral-ratio period waves are investigated numerically. The leakage characteristics of HE11-type wave in the waveguide is analyzed by applying Yasuura's method. The complex propagation constants and the far field patterns are presented. The radiation pattern of a fabricated waveguide with corrugation agrees well with the calculated value. The dependence of radiation characteristics on the corrugation form is discussed. It is shown that the leakage directions and the intensity of leaky waves are controlled independently one another. The radiation pattern can be synthesized by choosing the geometric parameters of the corrugation properly.

We propose a new high-performance message router for k-ary n-cube multicomputer systems, called the Tokky router. The router utilizes a small number of queues at the outputs of its communication ports to allow fully adaptive routing, misrouting to prevent deadlocks and randomization to prevent livelock. Uncongeste network performance is improved by the inclusion of the packet expressway. Accurate models are developed to predict the switch and buffer performance of routers for varying radix and dimension and these models can be used in the design of routers for networks other than those investigated here. The simulated performance of the router exceeds that of published results for oblivious routers and is equal to or exceeds those reported for other adaptive routers. These performance predictions are especially encouraging when the simplicity of the control structures required to implement the router are taken into consideration.

The concept of a new visual communication environment is proposed. The proposed system is a shared and interactive multi-user virtual space that consists of a CG-based virtual space structure and video-based objects. Human interface design issues are discussed from the view point of creating a new reality for enhanced communication.

We present a 44 matrix-based analysis of scattering form a two-dimensional rectangular resistive plane gratings placed on an anisotropic dielectric slab. The solution procedure used is formulated by extending the 44 matrix approach. The fields are expanded in terms of two-dimensional Floquet modes. Total fields can be given as sum of primary and secondary fields whose expression are obtained through eigenvalue problem of coupled wave matrix. Unknown currents on resistive patches are determined by applying Galerkin's method to the resistive boundary condition on resistive grating. Results are compared with other numerical examples available in the literature for isotropic cases. Further, numerical calculation are performed in the case of gratings with polar-type anisotropic slab.

In this paper, we propose a register file with data bypassing function. This register file bypasses data using data bypassing units instead of functional units when actual operation in functional units such as ALU is unnecessary. Applying this method to a general purpose microprocessor with benchmark programs, we demonstrate 50% power consumption reduction in functional units. Though length of bus lines increases a little due to an additional hardware in register file, as buses are not driven when data is bypassed, power consumption in bus lines is also reduced by 40% compared with the conventional architecture.

It is important to analyze a tracking or synchronizing process in Spread Spectrum (SS) receiving system. The most common SS tracking system considered here consists of pseudorandom (PN) generator, Lowpass Filter (LPE) and Voltage Controlled Oscillator (VCO). The SS receiver is to track or synchronize its local PN generator to the received PN waveform by VCO. The fundamental equation of the system is known by a second order nonlinear differential equation in terms of phase difference between local PN generator and received PN waveform. The differential equation is nonautonoumous due to PN function of time t with period T. Picking up the gain of VCO as the main parameter in the system we show that the system has bifurcation from the normal oscillation through subharmonic oscillation to finally chaos. In the final case, chaos is confirmed by investigating maximum Liapunov number and both stable and unstable manifolds.

Dynamic Programming based elastic pattern matching method called Branched Reference Rubber String Matching was investigated. As in Rubber String Matching, the reference pattern is represented as a sequence of direction specified vectors and the input pattern as two dimensional dot pattern. In order to improve the coping of topological variations in input pattern, the reference patterns allow partial pattern alternatives and misses. Effect on the recognition time is almost negligible. Experimental results show the effectiveness of the proposed algorithm.

An exact solution of the propagation constant of a cylindrical waveguide has been obtained in the event of the conductivity of the waveguide-composing conductor being finite. The said analysis has been reduced to a problem to solve a transcendental equation concerning an eigenvalue of the individual modes of the in-guide electromagnetic wave, and calculation of Jn-1(z)/Jn(z) by using of Bessel function becomes necessary. With a large conductivity the absolute value of the complex number z becomes excessively large, and none of calculation method with high accuracy has been found with the aid of a computer. This paper has solved the problem by using a continued fraction for the calculation with regard to which a recurrence formula is utilized. With the TE01 wave that has conventionally been used as a millimeter-wave guide, it is cleared that it is sufficient to select the number of the calculation terms of the continued fraction to the extent of approximately 1000 in the accuracy in accordance with this calculation method. It is also cleared that the approximation solution obtained by a method of perturbation coincides with the exact solution for the conductivity σ 102 [S/m].

Coherent and incoherent electromagnetic (EM) waves scattered by many particles are approximately expressed as solutions of integral equations by unconventional multiple scattering method. The particles are randomly displaced from a uniformly ordered distribution, and hence the distribution of particles can change from total uniformity to complete randomness. The approximate expressions of the EM waves are systematically given, independent of the distributions of particles, on the following assumptions. First the particles are identical in material, shape, size and orientation. Second each random displacement of particles from the ordered positions is statistically independent of each other and homogeneous in space. These assumptions may be extended to more general ones but have been used here to make clear the derivation process of the coherent and incoherent EM waves. The approximate expressions of the EM waves are reduced to known ones for both limiting cases: a periodic distribution and a very sparse random distribution. The effective dielectric constant of a random medium containing randomly distributed dielectric spheres can be calculated from the coherent EM wave and compared with those given by conventional methods such as the quasi-crystalline approximation, using the previous results. The comparison indicates the advantage of the method presented here. The present method is expected to be useful for the study of interaction of EM waves with many particles.