There are so many methods of calculating the cylindrical function Zν(x), but it seems that there is no method of calculating Zν(x) in the region of νx and |ν|»1 with high accuracy. The asymptotic series presented by Watson, et al. are frequently used for the numerical calculation of cylindrical function Zν(x) where νx and |ν|»1. However, the function Bm(εx) included in the m'th term of the asymptotic series is known only for m5. Hence, the asymptotic series can not give sufficiently accurate values of the cylindrical functions. The authors attempt to develop programs for the numerical calculation of the cylindrical functions using this asymptotic series. For this purpose, we must know the function Bm(εx) of arbitrary m. We developed a method of calculating Bm(εx) for arbitrary m, and then succeeded in calculating the cylindrical functions in the region νx with high precision.

Current-voltage characteristics of Cr-doped hydrogenated amorphous silicon-V (Cr/p+a-Si:H/V) analogue memory switching devices have been measured over a wide range of device resistance from several kilo-ohms to several hundred kilo-ohms, and over a temperature range from 13 K to 300 K. Both the bias and temperature dependence of the conductance show similar characteristics to that of metal-insulator heterogeneous materials (i.e. discontinuous or granular metallic films), which are analysed in terms of activated tunnelling mechanism. A modified filamentary structure for the Cr/p+a-Si:H/V switching devices is proposed. The influence of embedded metallic particles on memory switching is analysed and discussed.

Sector antennas provide many advantages such as when combined with a narrow beam antenna, they become particularly effective in achieving high-speed wireless communication systems and they aid in simplifying the structure. These antennas have a drawback in that as the number of sectors increases, the antenna size rapidly increases. Therefore, downsizing the sector antenna has become a major research topic. A promising candidate is utilizing a phased-array type antenna; however, this antenna requires a phase-shifter circuit for beam scanning and generally the feeding circuit for this type of antenna is very complicated. To address these issues, we propose a self-selecting feeding circuit that is controlled by the same control circuit and is operated similarly to the conventional single port n-th throw (SPNT) switch. We fabricated a small cylindrical 12-sector antenna at 19 GHz employing the proposed feeding circuit for verification purposes. Furthermore, this paper clarifies the design method of this feeding circuit where the antenna diameter is 71 mm, and the results clearly show that the gain is more than 12 dBi.

Several subband array methods have been proposed as useful means to perform joint spatio-temporal equalization in digital mobile communications. These methods can be applied to mitigate problems caused by the inter-symbol interference (ISI) and co-channel interference (CCI). The subband array methods proposed so far can be classified into two major schemes: (1) a centralized feedback scheme and (2) a localized feedback scheme. In this paper, we propose subband arrays with partial feedback scheme, which generalize the above two feedback schemes. The main contribution of this paper is to derive the steady-state mean square error (MSE) performance of subband arrays implementing these three different feedback schemes. Unlike the centralized feedback scheme which can be designed to provide the optimum equalization performance, the subband arrays with localized and partial feedback schemes are in general suboptimal. The performance of these two suboptimal feedback schemes depends on the channel characteristics, the filter banks employed, and the number of subbands.

This paper presents a multimedia architecture extension design for a 200-MHz, 1.6-GOPS embedded RISC processor. The datapath architecture of the processor which realizes parallel execution of data transfer and SIMD (single instruction stream multiple data stream) parallel arithmetic operations is designed. Four SIMD parallel 16-bit MAC (multiply-accumulation) instructions are introduced with a symmetric rounding scheme which maximizes the accuracy of the 16-bit accumulation. This parallel 16-bit MAC on a 64-bit datapath is shown to be efficiently utilized for DSP applications such as the correlation and the matrix-vector multiplications in the multimedia RISC processor. By using the parallel MAC instruction with the symmetric rounding scheme, a 2D-IDCT which satisfies the IEEE1180 can be implemented in 202 cycles.

This paper describes the implementation of a proposed image filter into a Discrete-Time Cellular Neural Network (DT-CNN). The three stages that compose the filter are described, showing that the resultant filter is capable of (1) erasing or detecting several concentric shapes simultaneously, (2) thresholding and (3) thinning of gray-scale images. Because the DT-CNN has to fill certain conditions for this filter to be implemented, it becomes a modified version of a DT-CNN. Those conditions are described and also experimental results are clearly shown.

This paper presents a novel image coding scheme based on separate coding of region and residue sources. In a subband image coding scheme, quantization errors in each subimage spread over the reconstructed image and result in a blurring or a boundary artifact. To obtain high compression ratio without considerable degradation, an input image, in our scheme, is separated into region and residue sources which are coded using different coding schemes. The region source is coded by adaptive arithmetic coder. The residue source is coded using multiresolution subimages generated by applying a subband filter. Each block in the subimages is predicted by an affine transformation of blocks in lower resolution subimages. Experimental results show that a high coding efficiency is achieved using the proposed scheme, especially in terms of the subjective visual quality and PSNR at low bit-rate compression.

A self-similar behavior characterizes the traffic in many real-world communication networks. This traffic is traditionally modeled as an ON/OFF discrete-time second-order self-similar random process. The self-similar processes are identified by means of a polynomially decaying trend of the autocovariance function. In this work we concentrate on two criteria to build a chaotic system able to generate self-similar trajectories. The first criterion relates self-similarity with the polynomially decaying trend of the autocovariance function. The second one relates self-similarity with the heavy-tailedness of the distributions of the sojourn times in the ON and/or OFF states. A family of discrete-time chaotic systems is then devised among the countable piecewise affine Pseudo-Markov maps. These maps can be constructed so that the quantization of their trajectories emulates traffic processes with different Hurst parameters and average load. Some simulations are reported showing how, according to the theory, the map design is able to fit those specifications.

Coupling between two slot antennas on an infinite ground plane and radiation patterns on a finite ground plane are calculated. We introduce a parasitic wire between slot antennas to reduce coupling. Two typical cases with a monopole or a half-loop are considered in this paper. Numerical results show that the reduction of 13.9 dB is obtained by adjusting a monopole height to about a quarter wavelength of the operating frequency. Also a properly adjusted parasitic half-loop reduces the coupling coefficient by 24 dB. Radiation patterns of the antennas on a 365 mm 465 mm ground plane at 1.5 GHz are calculated where the diffracted fields are taken into account. It is found that the parasitic elements little affect the antenna patterns around the +z-axis that is perpendicular to the ground plane although the reduction of coupling between slot antennas is obtained.

We derive an efficient and simple analytical expression for estimating maximum simultaneous switching noise (SSN) on ground distribution networks in CMOS systems. In order to estimate maximum SSN voltages, we use α-power law MOS model and Taylor's series approximation. The accuracy of the proposed expression is verified by comparing the results with those of previous researches and HSPICE simulations under the contemporary process parameters and environmental conditions. The proposed method predicts the maximum SSN values more accurately when compared to existing approaches even in most practical cases such that there exist some output drivers not in transition.

In this paper we show that the neuron filter is effective for relaxing the coefficient sensitiveness of the Hopfield neural network for combinatorial optimization problems. Since the parameters in motion equation have a significant influence on the performance of the neural network, many studies have been carried out to support determining the value of the parameters. However, not a few researchers have determined the value of the parameters experimentally yet. We show that the use of the neuron filter is effective for the parameter tuning, particularly for determining their values experimentally through simulations.

We often see reflection phenomenon in our life. For example, through window glass, we can see real objects, but reflection causes virtual objects to appear in front of the glass. Thus, it is sometimes difficult to recognize the real objects. Some works have been proposed to separate these real and virtual objects using an optical property called polarization. However, they have a restriction on one assumption: the angle of incidence. In this paper, we overcome this difficulty using independent component analysis (ICA). We show the efficiency of the proposed method, by experimental results.

Magnetic tunnel junctions (MTJ), i.e., structures consisting of two ferromagnetic layers (FM1 and FM2), separated by a very thin insulator barrier (I), have recently attracted attention for their large tunneling magnetoresistance (TMR) which appears when the magnetization of the ferromagnets of FM1 and FM2 changes their relative orientation from parallel to antiparallel in an applied magnetic field. Using an ultrahigh vacuum magnetron sputtering system, a variety of MTJ structures have been explored. Double Hc magnetic tunnel junction, NiFe/Al2O3/Co and FeCo/Al2O3/Co, were fabricated directly using placement of successive contact mask. The tunnel barrier was prepared by in situ plasma oxidation of thin Al layers sputter deposited. For NiFe/Al2O3/Co junctions, the maximum TMR value reaches 5.0% at room temperature, the switching field can be less than 10 Oe and the relative step width is about 30 Oe. The junction resistance changes from hundreds of ohms to hundreds of kilo-ohms and TMR values decrease monotonously with the increase of applied junction voltage bias. For FeCo/Al2O3/Co junctions, TMR values exceeding 7% were obtained at room temperature. It is surprising that an inverse TMR of 4% was observed in FeCo/Al2O3/Co. The physics governing the spin polarization of tunneling electrons remains unclear. Structures, NiFe/FeMn/NiFe/Al2O3/NiFe, in which one of the FM layers is exchange biased with an antiferromagnetic FeMn layer, were also prepared by patterning using optical lithography techniques. Thus, the junctions exhibit two well-defined magnetic states in which the FM layers are either parallel or antiparallel to one another. TMR values of 16% at room temperature were obtained. The switching field is less than 10 Oe and step width is larger than 30 Oe.

A nonlinear Volterra-series analysis of multiple ion-implanted GaAs FETs is given that relates carrier profile parameters of ion-implantation to nonlinear rf characteristics of a FET. Expressions for nonlinear coefficients of transconductance are derived from drain current-voltage characteristics of a multiple ion-implanted FET. Nonlinear transfer functions (NLTFs) are then obtained using Volterra series approach. Using these NLTFs third-order intermodulation distortion and power gain are explicitly given. A good agreement has been found between the calculation and the measurement for a medium power GaAs FET with a total gate width of 800 µm operated at 10-dB back off, verifying the usefulness of the present analysis.

We propose an effective model that can reproduce the reverse short channel effect (RSCE) of the threshold voltage (Vth) of MOSFETs using a conventional process simulator that solves one equation for each impurity. The proposed model is developed for local modeling which is effective within the limited process conditions. The proposed model involves the physics in which RSCE is due to the pile up of channel dopant at the Si/SiO2 interface. We also report the application to actual device design using our model. The calculation cost is much lower than for a pair diffusion model, and device design in an acceptable turn around time is possible.

This paper shows a comparison between several procedures to represent the Physical Optics (PO) current density into a hybrid Moment-Method-Physical-Optics (MM-PO) code. Some numerical results demonstrate that a set of basis functions suitable for the Method of Moments (MM) may be inappropriate to model the PO currents. A new evaluation of the PO operator is proposed. The radiation can be analytically determined and, since it includes a linear interpolation of the phase, it can be applied over large triangular domains. This allows a drastic reduction of the computational cost, maintaining or even improving the level of accuracy.

Dual FDTS/DF detector is an advanced version of FDTS/DF detector that gives significant performance improvement over FDTS/DF scheme on linear channels, and moreover, in contrast to other dual-detector schemes, it is suitable for various d-constraint coded channels. As recording density increases, channel nonlinearities such as non-linear transition shift (NLTS) and partial erasure (PE) degrade the performance of detectors. In this paper, we use nonlinear channel models to study the BER performance of dual FDTS/DF detector and compare the performances with those of other detectors through bit-by-bit simulations. Simulation results show that the dual FDTS/DF detector is superior in performance compared to FDTS/DF and MDFE detectors even on nonlinear channels, and it gives comparable BER performance with M2DFE (adv.) on nonlinear channels. Results also indicate that the detectors on the d=1 coded channels are more robust to channel nonlinearities compared to those of other detectors (such as PRML family detectors) on the d=0 coded channels.

A high quality speech synthesis technique based on the wavelet subband analysis of speech signals was newly devised for enhancing the naturalness of synthesized voiced consonant speech. The technique reproduces a speech characteristic of voiced consonant speech that shows unvoiced feature remarkably in the high frequency subbands. For mixing appropriately the unvoiced feature into voiced speech, a noise inclusion procedure that employed the discrete wavelet transform was proposed. This paper also describes a developed speech synthesizer that employs several random fractal techniques. These techniques were employed for enhancing especially the naturalness of synthesized purely voiced speech. Three types of fluctuations, (1) pitch period fluctuation, (2) amplitude fluctuation, and (3) waveform fluctuation were treated in the speech synthesizer. In addition, instead of a normal impulse train, a triangular pulse was used as a simple model for the glottal excitation pulse. For the compensation for the degraded frequency characteristic of the triangular pulse that overdecreases than the spectral -6 dB/oct characteristic required for the glottal excitation pulse, the random fractal interpolation technique was applied. In order to evaluate the developed speech synthesis system, psychoacoustic experiments were carried out. The experiments especially focused on how the mixed excitation scheme effectively contributed to enhancing the naturalness of voiced consonant speech. In spite that the proposed techniques were just a little modification for enhancing the conventional LPC (linear predictive coding) speech synthesizer, the subjective evaluation suggested that the system could effectively gain the naturalness of the synthesized speech that tended to degrade in the conventional LPC speech synthesis scheme.

In this paper, we give an algorithm for the node-to-set disjoint paths problem in rotator graphs with its evaluation results. The algorithm is based on recursion and it is divided into cases according to the distribution of destination nodes in classes into which all the nodes in a rotator graph are categorized. The sum of the length of paths obtained and the time complexity of the algorithm are estimated and verified by computer simulation.

Several configurations of millimeter wave Gaussian Beam Antennas (GBAs) are studied in this paper. A GBA is a quasi-planar radiating structure comprising a plano-convex half-wavelength Fabry-Perot (FP) resonator excited by a guided source or by a printed source. Both partially transparent mirrors of the resonator are formed with two-dimensional metal meshes. GBAs have very low side lobes, because of the gaussian distribution of the aperture electric field. They can be efficiently used in Wireless Local Area Networks in the 60 GHz band. After a brief presentation of intrinsic properties of FP cavities illuminated by a plane wave under normal incidence, performances of four passive GBAs are described and compared to theoretical results: the first two configurations concern cavities fed either by a waveguide (GBA#1), or by a pyramidal horn antenna (GBA#2); in the last two ones, the cavities are excited by a linearly polarized microstrip patch antenna (GBA#3), or by a coaxial-probe circularly polarized antenna array (GBA#4). These various examples enable to deduce and to compare typical radiation performances of GBAs, depending on (i) the feeding technique (planar or guided), on (ii) the geometry of the FP resonator (radius of curvature, grid parameters) and on (iii) the polarization (linear or circular). In particular, for a planar primary source, it is shown that the directivity and the efficiency of GBAs are respectively in the range [15.5 dB-23.5 dB] and [20%-50%], if power reflectivities of both mirrors are higher than 96.5% and lower than 99.5%, and if the radius of curvature of the cavity varies between 30λ0 and 1600λ0.