Process and device modeling for VISI

The appearance of Very Large Scale Integration caused a pronounced interest in concentrating on process and device modeling. The fundamental properties which represent the basis for all device modeling activities are summarized. The sensible use of physical and technological parameters is discussed and the most important physical phenomena which are required to be taken into account are scrutinized. The assumptions necessary for finding a reasonable trade-off between efficiency and effort for a model synthesis are recollected. Methods to bypass limitations induced by these assumptions are pin-pointed. Formulae that are applicable in a simple and easy way for the physical parameters of major importance are presented. The necessity of a careful parameter-selection, based on physical information, is shown. Some glimpses on the numerical solution of the semiconductor equations are given. The discretisation of the partial differential equations with finite differences is outlined. Linearisation methods and algorithms for the solution of large sparse linear systems are sketched. Results of our two dimensional MOSFET model — MINIMOS — are discussed. Much emphasis is laid on the didactic potential of such a complex high order model.     

Design and Experimental investigation of an antenna array based on EBG waveguides

Problems of the design of a centimeter-band antenna array containing a multichannel power divider based on EBG waveguides and helical radiators are considered. The general configuration of such an array is proposed. The properties of this array and the requirements on the array elements are analyzed. Features of the design of two-channel and four-channel elementary power dividers forming the multichannel power divider are studied. The structure and the parameters of these devices are determined. The array input part is designed in the form of a coaxial-to-waveguide transition (CWT) with equal power division. The CWT characteristics obtained with the use of numerical simulation are compared with experimental data. The results of the experimental investigation of a 16-element thinned antenna array in the frequency band 8–10 GHz are presented.     

Analysis of phase noise effects in OFDM modems

The effects of the phase noise (PN) on orthogonal frequency-division multiplex modems are evaluated. Three receivers are studied: a coherent receiver, a common phase error correction receiver (which is a receiver specially designed to combat PN) and a differential receiver. The impact of the PN on the decision signal-to-noise ratio (SNR) of each of these receivers is computed as a function of the PN spectrum. The resulting formulas are extremely simple. The theory is applicable to a wide range of PN models, and unifies and extends previous results on the topic. The conditions under which the decision SNR yields correct symbol error rate predictions are discussed. Simulations are reported that confirm the results.     

多层非线性介质板的电磁反射和传输

本文根据由Volterra泛函级数理论所得到的非线性介质中的色散关系,讨论了单色平面波斜入射多层平板非线性介质的传输问题;导出了反射率和透射率的一级近似公式;对非线性单层和具有周期性的双层介质板进行了数值计算;最后讨论了非线性介质对电波传播特性的影响。     

Surface wave modes of printed circuits on ferrite substrates

Surface waves due to a current source on a grounded ferrite slab are investigated. Electromagnetic fields of the structure are in terms of a continuous plane wave spectrum. The spectrum of each field component is obtained numerically through the exponential-matrix method. The surface waves of the structure are extracted from the continuous spectrum by using the residue theorem and the method of steepest descent. Two types of surface waves are found and their properties are described. The surface wave modes found include dynamic surface wave modes which are closely related to the surface waves of a grounded dielectric slab, and magnetostatic surface wave modes which are related to the solution of Laplace's equation for the magnetic potential     

Micro-automating semiconductor fabrication

Progress in automating very-small-scale mechanical processes is reviewed. The special requirements of microautomation are identified, and three applications are examined. They are positioning, electrical probing, and mechanical probing. The architecture and design of a microautomation system are described. Microsensors and microactuators are discussed. The use of magnetics technology for driving the microautomation system is reported, and a precision workspace for demonstrating a microautomation system is described. Also described are a coarse/fine positioner and a linear transport path capable of moving the fine manipulator from one precision-demanding area to another     

Multiple Dielectric Posts in a Rectangular Waveguide

This paper presents a complete analysis for a system of Iinear, homogeneous, and isotropic dielectric posts in a rectangular waveguide. These posts are assumed uniform along the narrow side of the waveguide, but are otherwise of arbitrary cross section and thickness. The scattering and impedance matrices describing the effect of the posts on the dominant waveguide mode are derived. The latter is then realized as a two-port T-network. A moment procedure is devised and applied to a set of test problems with a wide variety of post configurations to compute the scattering parameters and equivalent network elements. The accuracy and convergence aspects of the numerical solution are also investigated. The branch and network resonances are determined for some post configurations.     

Interaction of Electromagnetic Waves with Cylindrical Plasma

Exact numerical solutions are given for the interaction of a plane, electromagnetic wave with a cylindrical plasma. The incident wave is normal to the plasma axis and both TE and TM polarizations are considered. The electron density profile is represented by a Gaussian curve consistent with flow-field calculations for wakes and jets. Transmitted and scattered amplitudes are evaluated as functions of the polar angle and plasma parameters. The data are compared with previous theoretical and experimental work. [17],[18] Parabolic electron density profiles are also investigated and contrasted with the Gaussian results. The sharp cutoff in a parabolic profile has a significant effect on the electromagnetic interaction. Applications to microwave diagnostics are discussed including a new bistatic method.     

Choosing the best battery for portable equipment

The ways in which a battery can affect the design and performance of a product are discussed, identifying the significant battery characteristics. Two new primary (single-use) batteries and two secondary (rechargeable) batteries that are widely used are described. The issues of cost and safety are examined. Guidelines are given for deciding the size and number of batteries to use in a design     

Performance boundaries for prioritized multiplexing systems

Systems in which many data sources are multiplexed over a single communication channel are considered. Data from all the sources are generated in fixed-length packets and are stored in a common buffer with finite capacity. Packets that overflowed or were removed from the buffer prior to transmission are lost. The system performance measure is the set of packet loss probabilities associated with the sources. Queueing disciplines vary depending on the stringency of prioritization and the utilization of the system resources. The set of all possible performances is characterized as we span the set of all queueing disciplines. Whether a given performance is possible can be deduced. Strategies that achieve the minimum overall loss probability are identified. The extreme disciplines are specified, and their performances are calculable by means of a given algorithm.     

Parameter estimation for a modified Weibull distribution, for progressively type-II censored samples

In this paper, the estimation of parameters based on a progressively Type-II censored sample from a modified Weibull distribution is studied. The likelihood equations, and the maximum likelihood estimators are derived. The estimators based on a least-squares fit of a multiple linear regression on a Weibull probability paper plot are compared with the MLE via Monte Carlo simulations. The observed Fisher information matrix, as well as the asymptotic variance-covariance matrix of the MLE are derived. Approximate confidence intervals for the parameters are constructed based on the s-normal approximation to the asymptotic distribution of MLE, and log-transformed MLE. The coverage probabilities of the individual s-normal-approximation confidence intervals for the parameters are examined numerically. Some recommendations are made from the results of a Monte Carlo simulation study, and a numerical example is presented to illustrate all of the methods of inference developed here.     

Physical limitations of antennas in a lossy medium

The dissipated power and the directivity of antennas in a homogeneous, lossy medium are systematically analyzed in this paper. The antennas are ideal and located inside a lossless sphere. In the lossy space outside the sphere, the electromagnetic fields are expanded in a complete set of vector wave functions. The radiation efficiency, the directivity, and the power gain are defined for antennas in a lossy medium, and the optimal values of these quantities are derived. Simple relations between the maximal number of ports, or channels, an antenna can use and the optimal directivity and gain of the antenna are presented.     

Studies of the focal region of a spherical reflector: Stationary phase evaluation

The geometric optics and polarization properties of a spherical reflector are used to develop an integral representation of its focal region fields. These integrals are evaluated by the extended method of stationary phase for field points off the caustics, on the axial caustic, on the caustic surface, and at the paraxial focus. The contributions to the field at a field point are shown to arise respectively from three ordinary stationary points: a stationary ring and a stationary point at the vertex; an ordinary stationary point and a caustic type stationary point; and a fourth-order stationary point. The resulting formulas are used to compute the value of the focal region fields. The computed results are then compared to measured data.     

Electromagnetic field of a horizontal electric dipole buried in a medium covering one-dimensionally anisotropic medium

The electromagnetic fields of a horizontal electric dipole buried in a medium covering one-dimensionally anisotropic medium are studied. There are three media, one-dimensionally anisotropic medium covered with a dielectric under the air. The electromagnetic field components are complex because of the multiple reflections from the up and down boundaries. The electromagnetic field components between air and one-dimensionally anisotropic medium are given, the trapped surface waves and lateral waves along the dielectric-anisotropic medium boundary are computed. The results have some practical applications in the communication in sea or lake above one-dimensionally anisotropic earth or sediments.     

Outlier-resistant algorithms for detecting a change in a stochasticprocess

Outlier-resistant algorithms that detect a change from a given nominal stationary process to another such process are given. The nominal processes are assumed to be mutually independent and to satisfy some general regularity conditions. The outlier sequences are assumed to be independently and identically distributed and independent of the nominal processes. The proposed algorithms are sequential and consist of uniformly bounded steps. The asymptotic performance of the algorithms is analyzed, both in the absence and the presence of outliers. Breakdown points and influence functions are defined and analyzed. The algorithms are studied in more detail for Gaussian autoregressive nominal processes     

Axilens透镜的设计、加工和实验

给出了一种用Axilens透镜产生线焦的方法。导出了Axilens透镜的面形微分方程及其近似解;对Axilens的衍射特性进行了理论分析和数值计算;分析了面形方程近似解的误差;给出了面形方程的傅里叶级数表达式;实验结果表明,所设计及直接用Taylor Hobson Nanoform 300超精密车床制造的两个Axilens确实形成了所需的线焦。     

Computational and experimental estimation of the autoelectron energy spectrum for multiple-tip cathode matrix made of glassy carbon

The experimental and theoretical studies of the emission characteristics of a multiple-tip cathode matrix made of glassy carbon are discussed. The thermal conditions of microtips are calculated based on the experimental current-voltage characteristics of a cathode matrix and the effective emission cross sections. The dependences between the emitting-center temperature and the autoemission current are found, and the maximum temperatures corresponding to the boundary of the stable autoelectronic emission zone are determined. The distribution functions characterizing the total energy of autoelectrons are calculated allowing for the emitting-center temperatures. The dependences of the Fermi level shift and the autoelectron energy spectrum width on the temperature are revealed.     

Performance of direct-sequence systems with long pseudonoisesequences

A performance analysis of direct-sequence systems with long pseudonoise sequences is presented. The assessment of the symbol error probability in the presence of multiple-access interference is stressed, but other types of interference are also considered for completeness. Both binary and quaternary spreading waveforms are treated. The analysis, which uses a nonstandard Gaussian approximation, makes transparent the answers to a number of technical issues. Approximate error probabilities that are relatively simple computationally are derived. The approximations are accurate to within at least one decibel and, more typically, a few tenths of a decibel     

Complex gradient and Hessian

The gradient and Hessian are often used in analytical and numerical function optimisation complex valued parameter estimation problems. In a number of signal processing applications the function is a real function of complex variables. Then the optimisation is usually carried out with respect to the real and imaginary part of these variables; therefore, the gradient and Hessian concerned are real. The reason for this approach is to avoid difficulties with the definition and interpretation of the gradient and Hessian with respect to the complex variables. Definitions of a complex gradient and Hessian are proposed to solve these difficulties. The proposed and the real gradient and Hessian are fully compatible and are related by simple linear transformations. The results presented are an extension of a result by Brandwood (1983) concerning a complex gradient     

Best short rate 1/2 tailbiting codes for the bit-error ratecriterion

We give a method of finding convolutional codes with minimum bit-error rate (BER) that combines ideas of importance sampling, Monte Carlo integration, and maximum a posteriori probability decoding. The method is applied to rate 1/2 tailbiting convolutional coding, both feedforward and feedback systematic. Tables of BER-minimizing encoders are given for memories 2-5 and tailbiting size 5-40, over a range of good and bad binary symmetric and additive white Gaussian noise channels. The best generators for these cases are in general all different and are not necessarily the generators that optimize distance. The best generators for bad channels are always systematic. The best when the channel quality is known are usually feedforward, but when it is unknown, they are feedback systematic. The best generators in good channels are predicted by a union bound technique