光接收机均衡技术的自适应优化方法

自适应技术是目前光通信研究热点之一的接收机均衡技术的重要组成部分.文章在简要介绍光接收机中常用的均衡处理技术的基础上,总结了应用较多的LMS等多种自适应均衡算法的基本形式,并对目前有关算法在光通信中应用的研究结果及多种的算法改进进行了总结和分析,同时对与其紧密相关的反馈监测信号的选取等问题进行了对比分析.     

A statistical model for extracting geometric sources of transistor performance variation

This paper provides an approach to extracting geometrical variations in nominally identical devices fabricated in close proximity to each other. The method assumes correlations between factors can be neglected. With this assumption, it is shown that geometrical variations are significant, and any study of microscopic variations, such as dopant fluctuations, must first strip away these macroscopic geometrical variations. We assess the gate length L and width W dependence of threshold voltage (V/sub T/) variations. Related geometrical variations, namely corner influences where the source and drain encounter the isolation edges are examined, and incorporated in the model. Results from the model are compared to measurements at small dimensions. The differences provide lower bounds for excess variations other than these geometrical contributions. Our study shows that these other variations account for almost half the total V/sub T/ variance at the smallest device size fabricated, demonstrating the seriousness of these other variations when scaling down devices.     

Managing Murphy's law: engineering a minimum-risk system

The meanings of `risk' and `risk analysis' are examined by the author. The steps to be taken in assessing and quantifying risk are described, and the question of accepting and managing risk is briefly considered. Definitions of terms such as hazard, failure, accident and reliability are given. Two sources of uncertainty, i.e. the laws of chance and human error, are finally discussed using the Piper Alpha explosion as an example     

Classical versus reinforcement learning algorithms for unmanned aerial vehicle network communication and coverage path planning: A systematic literature review

The unmanned aerial vehicle network communication includes all points of interest during the coverage path planning. Coverage path planning in such networks is crucial for many applications, such as surveying, monitoring, and disaster management. Since the coverage path planning belongs to NP-hard issues, researchers in this domain are constantly looking for optimal solutions for this task. The speed, direction, altitude, environmental variations, and obstacles make coverage path planning more difficult. Researchers have proposed numerous algorithms regarding coverage path planning. In this study, we examined and discussed existing state-of-the-art coverage path planning algorithms. We divided the existing techniques into two core categories: Classical and reinforcement learning. The classical algorithms are further divided into subcategories due to the availability of considerable variations in this category. For each algorithm in both types, we examined the issues of mobility, altitude, and characteristics of known and unknown environments. We also discuss the optimality of different algorithms. At the end of each section, we discuss the existing research gaps and provide future insights to overcome those gaps.     

超深亚微米CMOS工艺参数波动的测量电路

分析了超深亚微米工艺参数波动对电路的影响;采用"放大"的思路设计了简单的用于测量超深亚微米工艺门延迟、动态功耗、静态功耗及其波动的电路,并提出了一种用于测量门延迟波动特性曲线的新型电路,该电路采用较短的反相器链可以得到超深亚微米工艺下门延迟波动特性曲线.电路在90nm CMOS工艺下进行了流片制作,得到了90nm CMOS工艺下的单位门延迟波动特性曲线.测得延迟的波动范围为78.6%,动态功耗的波动范围为94.0%,漏电流功耗的波动范围为19.5倍,其中以漏电流功耗的波动性最为严重.     

Determination of progression steps in lattice planning method

The most frequently utilized methods of radio frequency planning are briefly reviewed, and the lattice method (also known as the linear rhombic network method) is examined in detail. Unlike other methods, the lattice planning method offers the possibility of arranging the transmitters according to a mathematical law. The arrangement is such that all the distances between adjacent transmitters are equal and all the channel distances are equal, resulting in equal interference, both in type and level, at each transmitter location. This makes it possible to minimize the interference level during planning     

Deterministic approaches for blind equalization of time-varyingchannels with antenna arrays

In this paper, we study the blind equalization problem of time-varying (TV) systems where the channel variations are too rapid to be tracked with conventional adaptive equalizers. We show that using a finite Fourier basis expansion, a TV antenna array system can be cast into a time-invariant multi-input, multi-output (MIMO) framework. The multiple inputs are related through the bases, thereby allowing blind equalization to be accomplished without the use of higher order statistics. Two deterministic blind equalization approaches are presented: one determines the channels first and then the equalizers, whereas the other estimates the equalizers directly. Related issues such as order determination are addressed briefly. The proposed algorithms are illustrated using simulations     

Investigation of manufacturing variations of planar InP/InGaAs avalanche photodiodes for optical receivers

Planar InP/InGaAs avalanche photodiodes are widely used for high-speed optical receivers in optical fiber communication systems. Even though these avalanche photodiodes offer the excellent characteristics in high-speed operation, the performance metrics are affected by manufacturing parameter variations considerably. In this paper, the effects of manufacturing variations on the device performance are investigated. In order to build a photodiode model, the test structures were fabricated and the measured current-voltage characteristics were compared with the simulated data to verify the model. After the model verification, the variations of the breakdown voltage and punch-through voltage according to the different manufacturing parameters such as multiplication layer width and charge sheet density are examined. Based on the results, the manufacturability of the avalanche photodiodes can be improved by analyzing the manufacturing variations.     

Control and suppression of chaos in flared laser systems: anumerical analysis

Numerical analysis of control and suppression of chaos in flared laser systems is presented. In order to stabilize the chaotic output of such systems, both the periodic perturbation method and the proportional feedback method are examined with good results. Several variations of the proportional feedback method are presented. A certain rule of thumb for tuning the different control algorithms is demonstrated to be fruitful     

Supercomputing-balancing resources

The need for high-speed data communications and mass storage systems for supercomputing is examined. The former could be serious bottlenecks in the not-too-distant future, because their capabilities have not kept up with those of supercomputers themselves. The potential of fiber-optic technologies for meeting data communication requirements is discussed, and research around the world is briefly cited. Trends in mass storage are briefly discussed     

Ionospheric scintillation theory--A mini-review

In this paper we briefly review the theories that are used to interpret ionospheric scintillation data. We have emphasized the full structure of the complex signal, because it is now being directly measured with a number of satellites that carry multifrequency phase-coherent beacons. The data that have been analyzed to date clearly show that large phase variations (greater than one radian) are an omnipresent feature of transionospheric signals.     

Optical and optoelectronic devices for optical fiber transmissionsystems

The present status and research trends in light sources, detectors, and various optical components are described, focusing mainly on those for single-mode fiber systems. Laser-diode and light-emitting-diode sources are described, and their problems and advantages are examined. The features of optical detectors, namely, avalanche and p-i-n photodiodes are discussed. A method of comparing the performance of optical receivers with different detectors, by examining the minimum detectable power at a specified error probability for the received pulses, is presented. Optical components such as optical filters, couplers, dividers, isolators, connectors, and switches are considered briefly. The potential of optoelectronic integrated circuits is discussed     

Observers for flux estimation in induction machines

Flux estimation in induction machines is examined from the viewpoint of observer theory. It is pointed out that estimators presently used in connection with schemes such as field-oriented control are typically real-time simulations of machine equations, without feedback of any corrective prediction error. It is shown that corrective feedback can be used to speed up convergence of the flux estimates. It can also reduce the sensitivity of the estimates to parameter variations     

Digital image forensics

This tutorial explains how photo-response nonuniformity (PRNU) of imaging sensors can be used for a variety of important digital forensic tasks, such as device identification, device linking, recovery of processing history, and detection of digital forgeries. The PRNU is an intrinsic property of all digital imaging sensors due to slight variations among individual pixels in their ability to convert photons to electrons. Consequently, every sensor casts a weak noise-like pattern onto every image it takes. This pattern, which plays the role of a sensor fingerprint, is essentially an unintentional stochastic spread-spectrum watermark that survives processing, such as lossy compression or filtering. This tutorial explains how this fingerprint can be estimated from images taken by the camera and later detected in a given image to establish image origin and integrity. Various forensic tasks are formulated as a two-channel hypothesis testing problem approached using the generalized likelihood ratio test. The performance of the introduced forensic methods is briefly illustrated on examples to give the reader a sense of the performance.     

Intelligent satellites for interactive graphics

The spectrum of remote user stations with local processing ability, ranging from simple "smart" terminals to nearly self-sufficient intelligent systems called satellites, is considered. The emphasis is on the latter category, drawing on the authors' research on intelligent satellites for interactive graphics. The necessity of meeting a "critical intelligence threshold" criterion for the satellite is stressed, and some difficult problems and potential solutions in the division of labor between mainframe and satellite are briefly examined. It is hoped that many of the problems and solutions in satellite graphics apply to other areas such as network or satellite process control, experiment control, and signal processing.     

Coherent scattering diagnostic method on heating waves in J.E.T.

The application of a large angle microwave scattering diagnostic to the J.E.T. plasma in order to detect the penetration of the Lower Hybrid heating waves is examined. Fun damental equations of the coherent scattering are briefly reviewed and the scattered power is described on the basis of a full electromagnetic warm plasma dispersion relation. The choice of the best suited incident wavelength and its consequences on the performances of the scattering experiment (range of measurable n”, refraction effects, spatial resolution, etc.) are considered. The feasibility of such an experiment with the existing sources and technology is also considered.     

How to select tools for microcontroller software

The factors that determine the choice of tools are identified. Symbolic versus source-level debugging, programming language tradeoffs, and assembler features are examined. The use of CASE (computer-aided software engineering) tools is briefly considered     

Time domain electromagnetic simulation for microwave CADapplications

Recent progress in time domain modeling is highlighted. Basic properties of time-domain simulators are reviewed, and techniques for improving computational efficiency are examined. The use of numerical synthesis through time reversal is discussed. The user interface is briefly considered and typical simulation results are given     

Ultrasonic characterization of fractal models

Ultrasonic scattering in inhomogeneous fluid media is examined. Of particular interest are those media having a compressibility that varies on a continuum of spatial scales. It is shown that the internal features of such media can be extracted by an analysis of the forward scattered field. The angular distribution of scattered pressure intensity is found to vary with frequency and compressibility contrast. The scattered field data can be rendered stationary to such variations by an application of a similarity transformation. Examples are given for cases where the spatial variation in the compressibility of the media obeys either a power law or exponential correlation function. When these similarity transformations are applied, an estimate of the characteristic radius of the scatterers and the fractal dimension of the medium can be directly obtained