In this letter, we propose an adaptive multiuser receiver using a Hopfield network for code-division multiple-access communications and its performance is compared with that of the other types of multiuser receiver via computer simulation. The proposed adaptive receiver estimates both the signal amplitudes and spreading sequences for all the users using training data.

The coupling response of an external transient electromagnetic field to a transmission line is considered. An experiment has been conducted to verify the line equations for a transmission line excited externally by a transient near field. The model field is generated by a monopole antenna installed in the vicinity of the transmission line and driven by a step waveform. The waveform is analyzed into discrete spectrum components using a Fourier transform. The frequency-domain field components affecting the transmission line are estimated by the moment method, and then the induced frequency-domain voltage at the terminal load is converted into a time-domain voltage using an inverse Fourier transform. Comparison between the measured and the computed values provides verification of the line equations. The coupling mechanism is discussed from the experimental results. It seems equivalently that the transmission line picks up the field, generated at the feed point and the top point of the monopole antenna, at both terminal ends.

Polynomials are called permutation polynomials if they induce bijective functions. This paper investigates algebraic properties of permutation polynomials over a finite field, especially properties associated with permutation cycles. A permutation polynomial has a simple structure but good randomness properties suitable for applications. The cycle structure of permutations are considered to be related to randomness. We investigate the algebraic structure from the viewpoint of randomness. First we show the relationship between polynomials and permutations using a matrix equation. Then, we give a general form of a permutation polynomial corresponding to a product C1C2Ck of pairwise disjoint cycles. Finally, permutation polynomials with fixed points -or with 2, 3 and 4-cycles -and their compositions are given together with distribution of degree of the permutation polynomials.

A calibrating analog-to digital (A/D) converter employing a T-Model neural network is described. The T-Model neural-based A/D converter architecure is presented with particular emphasis on the elimination of local minimum of the Hopfield neural network. Furthermore, a teacher forcing algorithm is presented and used to synthesize the A/D converter and correct errors of the converter due to offset and device mismatch. An experimental A/D converter using standard 5-µm CMOS discrete IC circuits demonstrates high-performance analog-to-digital conversion and calibrating.

This paper describes the characteristics of the radiated magnetic field caused by breaking arcs between a pair of Ag, AgDdO, AgSnO2 or Pd contacts in a DC 50V/1.9-5.0A circuit. For Ag contacts, in an interrupting current less than 3.3A, the radiated magnetic field appears strongly during the metallic phase arc where the smaller the interrupting current is, the more the number of frequency spectra of the radiated magnetic field becomes. In an interrupting current more than 3.3A, the radiated magnetic field appears weakly during the metallic-gaseous transition period. For AgSnO2 and AgCdO contacts, there is a weak radiated magnetic field in the metallic-gaseous transition period and the smaller the interrupting current is, the stronger the maximum intensities of frequency spectra of the radiated magnetic field in the transition period are. For Pd contacts, the maximum intensities of frequency spectra of the radiated magnetic field do not change very much from the beginning to the end of the breaking arc, which do not depend on the interrupting current. From the experimental results, the maximum intensities of frequency spectra of the radiated magnetic fields are found to depend on the contact material. And their distribution depends on the impedance of the circuit containing the contacts that generates the breaking arc.

Based on the test method proposed by Sub-Committee G of the International Special Committee on Radio Interference, most telephone receivers in Japan have insufficient immunity to acoustic noise caused by radio-frequency fields. This is because the modulation depth of the RF signal used is too high to accurately simulate the audio-frequency components of TV video signals. Reducing the modulation depth from 80% to 5% produces a more realistic simulation.

This paper clarified fundamental aspects of both triboelectric processes and electrostatic discharge (ESD) phenomena to the electronic systems. A chance for ESD can occur if a charged metal object (steel piped chair, for example) contacts or collides with another metal objects at moderate speed. At metal-metal ESD event, the metal objects act as a radiation antenna in a very short time (some 100ps, for example) which emanates impulsive electromagnetic fields with unipolarity into the surrounding space. Because of ESD at low-voltage (3kV or less) conditions, the direction of electrons movement at the spark gap is always unidirectional and fixed. The spark gap works as a momentary switch and also as a "diode." The dominant fields radiated from the metal objects are impulsive electric fields or impulsive magnetic fields which depend on the metal object's electrical and geometric conditions. This impulsive electromagnetic fields penetrate electronic systems, causing electromagnetic interference (EMI) such as malfunctions or circuit upset. The difference between EMI actions in high-voltage ESD and low-voltage ESD is experimentally analyzed in terms of energy conversion/consumption. A series of experiments revealed that EMI actions due to the metal-metal ESD are not proportional to the charge voltage nor the discharge current. In order to capture single shot impulsive electromagnetic fields very close to the ESD point (wave source), a short monopole antenna as an ultra broad-band field sensor was devised. As for signal transmissions between the short monopole antenna and the instrument (receiver), micro/millimeter wave techniques were applied. The transmission line's minimum band width DC-18.5GHz is required for time domain measurements of low-voltage ESD.

A new matched-filter (MF) acquisition scheme with adaptive threshold is proposed for a frequency-hopped/spread-spectrum multiple-access (FH/SSMA) system. Detection and false alarm probabilities are derived for combined interference environments. The combined interference consists of partialband noise jamming or tone jamming, multiple access interference (MAI), multipath interference, and thermal noise. We use Gaussian approximation for modeling the MAI and multipath interference. Equal power assumption of the users is employed which is typically used in the SSMA system analysis. In the proposed scheme, MF output is compared to an adaptive threshold determined by the number of jammed frequency slots. It is shown that the proposed adaptive-threshold acquisition scheme achieves higher detection probability and lower false alarm probability than a conventional fixed-threshold scheme for each jammed fractional bandwidth, JSR, the number of multipaths, and the number of users. It is also shown that adaptive threshold achieves faster acquisition and higher packet throughput than fixed threshold in application to FH/SSMA packet radio system.

A new yield prediction model has been developed, which can successfully describe the actual chip fabrication yield. It basically consists of modeling of particles deposited on wafer surface, considering the change in their size and spatial distribution due to the subsequent processing steps and a new concept of virtual line width in pattern layouts. It is confirmed that this yield prediction model serves as an effective navigator for improvement/optimization of fabrication lines such as pointing out the process step/equipments to be modified for yield improvements.

This letter shows that a portable visual stimulator for MEG measurements can be realized using an optical fiber bundle and a CRT display system offering high brightness and high speed raster scanning, and that MEGs with neither magnetic contamination nor jitter can be measured by the stimulator.

Effects of field edge steps on characteristics of MOSFETs with tungsten polycide stacked gate electrodes patterned by KrF excimer laser lithography was studied through an electrical gate length measurement technique. Sheet resistance of the gate electrodes on the field oxide, on the active region and across the field edge steps was determined from the relationship between gate conductance and designed gate linewidth. The sheet resistance of the gate electrode across the field edge steps was larger than that on the flat regions. Effects of field edge steps on gate linewidth variation were evaluated by SEM observations and electrical measurements. Distribution of gate linewidth in a wafer was measured by the MOSFET test structures with the linewidth down to sub-quarter micron. Gate linewidth variation near the field edge steps was found to influence the short channel MOSFET characteristics.

Soft-error immunity of a 1-V operating CMOS memory cell is described. To evaluate the immunity precisely at the supply voltage of 1 V, a multi-threshold CMOS (MTCMOS) memory scheme, which has a peripheral circuit combining low-threshold CMOS logic gates and high-threshold MOSFETs with a virtual supply line, is adopted as a test structure. A 1-kb memory was designed and fabricated with 0.5-µm MTCMOS technology and the soft-error immunity of the memory cells was evaluated. The results of an alpha-particle exposure test and a pulse laser test show that a full-CMOS memory cell has high immunity at 1-V operations.

Threshold voltage shift in high frequency operation of 0.3µm and 0.35µm gate SOI CMOS is experimentally studied, using supply current measurement of inverter chains as test structures. The threshold voltage shift is obtained from the measurement of the leak currents in DC and high frequency condition. For a large supply voltage the electron-hole generation current becomes dominant, resulting in lowered threshold voltage, while the threshold voltage becomes higher than DC case for a low supply voltage. A reasonable relation of the threshold voltage shift and average electric field in the channel is obtained in this study. This method will be useful as a measure of "substrate current" for floating body SOI CMOS.

New series expressing the radiation fields from both axial and circumferential slots on a circular conducting cylinder are derived. These new series converge rapidly even for near fields. This letter includes useful figures showing characteristics of near fields calculated numerically using the new series.

A direct gradient descent learning algorithm of energy function in Hopfield neural networks is proposed. The gradient descent learning is not performed on usual error functions, but the Hopfield energy functions directly. We demonstrate the algorithm by testing it on an analog-to-digital conversion and an associative memory problems.

A novel technique for evaluation of charge build-up in semiconductor wafer processing such as ion implantation, plasma etching and plasma enhanced chemical vapor deposition by using the breakdown of MOS capacitors with charge collecting electrodes (antenna) is proposed. The charge build-up during high beam current ion implantation is successfully evaluated by using this technique. The breakdown sensitivity of a MOS capacitor is improved by using a small area MOS capacitor with a large area antenna electrode. To estimate charge build-up on wafers quantitatively, the best combination of gate oxide thickness, substrate type, MOS capacitor area and antenna ratio should be carefully chosen for individual charge build-up situation. The optimum structured antenna MOS capacitors which relationship between QBD and stressing current density was well characterized give us very simple and quantitative charge build-up evaluation. This technique is very simple and useful to estimate charge build-up as compared with conventional technique by suing EEPROM devices or large area MOS capacitors.

In a (k,n) threshold digital signature scheme, k out of n signers must cooperate to issue a signature. In this paper, we show an efncient (k,n) threshold EIGamal type digital signature scheme with no trusted center. We first present a variant of EIGamal type digital signature scheme which requires only a linear combination of two shared secrets when applied to the (k,n)-threshold scenario. More precisely, it is a variant of Digital Signature Standard (DSS) which was recommended by the U.S. National Institute ofStandard and Technology (NIST). We consider that it is meaningful to develop an efficient (k,n)-threshold digital signature scheme for DSS. The proposed (k,n)-threshold digital signature scheme is proved to be as secure as the proposed variant of DSS against chosen message attack.

The SAR distributions over a homogeneous human model exposed to a near field of a short electric dipole in the resonant frequency region were calculated with the spatial resolution of 1cm3 which approximated 1g tissue by using the FDTD method with the expansion technique. The dependences of the SAR distribution on the distance between the model and the source and on frequency were investigated. It was shown that the large local SAR appeared in the parts of the body nearest to the source when the source was located at 20cm from the body, whereas the local SAR were largest in the narrow sections such as the neck and legs when the source was farther than 80cm from the model. It was also shown that, for the near-field exposure in the resonant frequency region, the profile of the layer averaged SAR distribution along the main axis of the body of the human model depended little on frequency, and that the SAR distribution in the section perpendicular to the main axis of the human body depended on frequency. The maximum local SAR per gram tissue over the whole body model was also determined, showing that the ratios of the maximum local SAR to the whole-body averaged SAR for the near-field exposure were at most several times as large as the corresponding ratio for the far-field exposure, when the small source located farther than 20cm from the surface of the human model.

This paper describes a finite element method to obtain an accurate solution of the scalar Helmholtz equation with field singularities. It is known that the spatial derivatives of the eigenfunction of the scalar Helmholtz equation become infinite under certain conditions. These field singularities under mine the accuracy of the numerical solutions obtained by conventional finite element methods based on piecewise polynomials. In this paper, a regularized eigenfunction is introduced by subtracting the field singularities from the original eigenfunction. The finite element method formulated in terms of the regularized eigenfunction is expected to improve the accuracy and convergence of the numerical solutions. The finite element matrices for the present method can be easily evaluated since they do not involve any singular integrands. Moreover, the Dirichlet-type boundary conditions are explicitly imposed on the variables using a transform matrix while the Neumann-type boundary conditions are implicitly imposed in the functional. The numerical results for three test problems show that the present method clearly improves the accuracy of the numerical solutions.

With the fully depleted ultra-thin-film SOI CMOS, one important issue is controlling the threshold voltage (Vth) while maintaining high speed operation and low power consumption. To control the Vth, applying a bias voltage to the substrate is one of the most practical methods. We suggest a fully depleted ultra-thin-film SOI CMOS with a floating back gate, which is formed at the lower part of the channel field inside the substrate and stores electrons injected into it. This device can eliminate the necessity of an extra circuit or a separate power supply to apply a negative voltage. The silicon wafer direct bonding technique is used to construct this device. With the prototyped devices, we can successfully control the Vth for both the nMOSFET and pMOSFET at around 0.5 V by controlling the quantity of the electric charges injected into the floating back gate.