"猫眼"效应及其应用

本文对“猫眼”效应的研究进展作了综述，介绍了目前存在的几种“猫眼”效应模型，并推导出由于光敏面的离焦引起的发散角。对“猫眼”回波功率和漫反射小目标回波功率之比的物理意义作了解释。最后对“猫眼”效应应用中的一些问题作了讨论。     

基于“猫眼效应”的Nd:YAG激光谐振腔

阐述了“猫眼效应”的基本原理,分析了将“猫眼”目标作为激光谐振腔腔镜,取代普通激光器球面腔镜,获得激光振荡的可能性;计算了“猫眼”目标作为激光腔镜时的等效反射率,指出利用激光在其焦平面的聚焦特性实现激光干扰的新方法。并在实验中得到证实。     

离焦状态下“猫眼”效应的实验研究

“猫眼”目标回波功率是激光主动探测系统的重要指标,可用米评估光电装备“猫眼”效应的强弱,并为探测器的优化设计提供参考。分别建立了正负离焦状态下“猫眼”目标回波功率数学模型,仿真分析了离焦量对“猫眼”目标回波功率的影响,利用搭建的激光主动探测系统及倒置的望远系统,实现了离焦状态下典型“猫眼”效应的实验。理论仿真结果与实验...     

激光主动侦察技术应用

光电设备或光学观瞄设备的光学窗口对入射激光具有较强的反射特性，该特性亦被称为“猫眼”效应．从理论上分析了猫眼效应产生的机理，并将理论计算结果与实验结果进行了比较；论述了基于“猫眼”效应的激光侦察技术原理，最后介绍了该技术的应用．     

光电系统离焦量对其猫眼效应回波功率的影响规律及原因分析

离焦量是决定光电系统猫眼效应回波功率强弱的关键因素。为了分析不同离焦情况对猫眼效应回波功率的影响规律及原因,通过对光电系统猫眼效应几何光学传输模型的分析,推导了包含离焦量的猫眼效应回波功率和等效回波波束球心的表达式,分析了不同离焦情况对回波功率的影响机理,并进行了实验验证。研究结果表明:在离焦情况下,猫眼效应回波波束可以等效为从目标处发出的一束锥状球面波,随着离焦量的增大,该球面波的球心距接收点的距离逐渐增大,因此回波功率逐渐衰减;正离焦时,该等效球面波的球心与接收点位于目标的同侧,负离焦时,球面波的球心与接收点位于目标的异侧,因此,在相同离焦量条件下,负离焦所导致的回波功率衰减程度比正离焦时更大;实验结果验证了这个结论。     

激光照射“猫眼”效应实验研究

通过激光捕获跟踪实验研究,记录到了一系列的“猫眼”效应的回波光斑图像,提出了回波光源模型简明分析表达式,为“猫眼”效应的进一步研究和应用提供了可靠的实验依据.     

光电成像系统“猫眼效应”目标回波特征研究北大核心CSCD

针对基于“猫眼效应”的激光主动探测技术在光电对抗中的广泛应用,对激光主动照明光源波长,被探测光电成像系统“猫眼效应”及探测系统最大探测距离之间的关系进行了分析研究,修正了与入射波长相关的反光指数模型及最大探测距离数学模型,并模拟了入射波长与最大探测距离间的数值关系。为了验证建立的数学模型的正确性,利用已研制的激光主动探测装置,选用焦距可调的光电成像传感器,进行了光电成像系统实焦与虚焦时最大探测距离验证实验,模拟值分别为1445 m与1751 m,实验值分别达到1230 m与1632 m。结果表明:实焦与虚焦时最大探测距离模拟值与实验值有很好的一致性。     

可应用于高效光电对抗的新颖结构激光谐振腔

光电设备具备的猫眼效应可以将入射的光线沿原路反射,基于这一现象,可以将该光学系统作为激光器的一个腔镜构成激光谐振腔。文中计算了猫眼效应光学系统作为激光器腔镜的等效反射率。实验中用灯泵Nd:YAG激光器,角锥棱镜和猫眼光学系统搭建了免调激光谐振腔,获得了激光振荡,激光起振的同时,在猫眼光学系统焦平面不同材质介质上留下烧痕。这种将对方光学系统作为激光器的腔镜,激光起振即摧毁的构成,可应用于光电对抗之中实现高效对抗。     

激光主动侦察技术研究

介绍了“猫眼”效应及激光主动侦察原理,给出了激光主动侦察条件下回波功率计算公式,分析了侦察系统的作用距离,讨论了光学系统离焦量对反射回波的影响,为激光主动侦察问题的深入研究作了有益的探索．     

基于APD的“猫眼”目标主动探测系统信噪比分析

信噪比是表征激光主动探测系统性能的重要指标,通过分析雪崩光电二极管(APD)的噪声来源和离焦“猫眼”目标回波功率,建立了APD探测器的信噪比模型,分析了离焦量、目标距离、激光发散角对APD探测器信噪比的影响,并进行了数值模拟分析,结果表明:离焦量的增大会引起“猫眼”目标回波功率变小,进而使APD探测器信噪比减小;“猫眼...     

High Dynamic Range Design for ΣΔM with Wide Input Ranges

A new design algorithm is introduced to improve the input ranges of Sigma-Delta Modulation (M). Modified digital error correction techniques are proposed and employed to carry out the wide range DAC of a modulator. This design algorithm includes the advantages from both single-bit M and multi-bit M. This paper utilizes a second order lowpass modulator as an explanatory example to demonstrate our design process as well as the performance improvement. The analytical results from a quasilinear model are described to offer a theoretical explanation of the system performance. This algorithm can also be applied to bandpass and MASH architectures.     

汉字输入的新处理技术及“自由”输入法

本文提出以汉字信息库替代扫描表为特点的新的汉字输入内部处理方式。新方式给予人们以“按键自由”和“输入方法选择的自由”。完成的自由输入法,输入汉字可用笔划法,部件法,或每一步都可自由地选择两法之一。自由输入法含大自由,小自由和超自由等多种方法,可适用于专业或非专业人士。     

Optimization and Design of a Low Power Switched Current A/D-ΣΔ-Modulator for Voice Band Applications

This paper presents a third order switched current -modulator. The modulator is optimized at the system level for minimum power consumption by careful design of the noise transfer function. A thorough noise analysis of the cascode type current copiers used to implement the modulator, together with a new methodology for evaluating the nonlinear settling behavior is presented. This leads to a new optimization methodology that minimize the power consumption in switched current circuits for given design parameters. The optimization methodology takes process variations into account. The modulator is implemented in a standard 2.4 m CMOS process only using MOS capacitors. For a power supply of 3.3 V the power consumption is approximately 2.5 mW when operating at a sampling rate of 600 kHz. Under these condition the peak SNR it measured to 74.5 dB with a signal band width of 5.5 kHz. Due to internal clamping in the integrators and proper scaling the modulator shows excellent stability properties. In order to compare the performance of the modulator presented in this paper to other -modulators two figure-of-merits (FOMs) are proposed. From these figure-of-merits it is found that the performance of the modulator presented in this paper is significantely higher than the perforamce of other switched current -modulators reported. Also, the figure-of-merits show that the performance is comparable to the performance of reported switched capacitor -modulators.     

Floor acquisition multiple access (FAMA) in single‐channel wireless networks

The FAMANCS protocol is introduced for wireless LANs and adhoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMANCS (for floor acquisition multiple access with nonpersistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMANCS is based on a threeway handshake between sender and receiver in which the sender uses nonpersistent carrier sensing to transmit a requesttosend (RTS) and the receiver sends a cleartosend (CTS) that lasts much longer than the RTS to serve as a busy tone that forces all hidden nodes to back off long enough to allow a collisionfree data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collisionfree transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMANCS is analyzed for singlechannel networks with and without hidden terminals; the analysis shows that FAMANCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results.     

Testing for Function and Performance: Towards an Integrated Processor Validation Methodology

Microprocessor design teams use a combination of simulation-based and formal verification techniques to validate the pre-silicon models prior to tape-out and chip fabrication. Pseudo-random test case generation to cover the architectural space is still relied upon as the principal means to identify design bugs. However, such methods are limited to functional bugs only. Detection and diagnosis of timing (performance) bugs at the architectural level is largely an expert job. Architects guide the performance team to run manually generated test cases to validate the design from a performance viewpoint. In this paper, we will review some of the new approaches being tried out to automate the generation of performance test cases. We will show how this can be done within the basic framework of current functional validation and testing of pre-silicon processor models. Three categories of reference specifications are used in determining the defect-free pipeline timing behavior associated with generated test cases: (a) axiomatic specifications of intrinsic machine latencies and bandwidths; (b) proven analytical models for simple basic block and loop test cases; and, (c) a stable reference behavioral/functional (pre-RTL) model of the processor under development. We report experimental results obtained in performance validation studies applied to real PowerPC processor development projects.     

The Future Generations of Mobile Communications Based on Broadband Access Methods

The forthcoming mobile communication systems are expected to provide much variety of services from high quality voice to high definition videos through high data rate wireless channels at anywhere in the world. High data rate requires broad frequency bands, and sufficient broadband can be achieved in higher frequency bands such as microwave, Ka-band and millimeter-wave. Broadband wireless channels have to be connected to broadband fixed networks such as the Internet and local area networks. The future generation systems will include not only cellular phones, but also many new types of communication systems such as broadband wireless access systems, millimeter-wave LAN, intelligent transport systems (ITS) and high altitude stratospheric platform station (HAPS) systems. The key words in the future generations of mobile communications are multimedia communications, wireless access to broadband fixed networks and seamless roaming among different systems. This article discusses the future generations mobile communication systems.     

Si抛光片存储中表面起"雾"的研究

存储中Si片起"雾"是Si片存储面临的最大挑战,"雾"缺陷是可见或可印刷的晶体结构,从污染生长而来,已是困扰半导体业界长达10年以上的大问题.半导体制造商们至今还未能提出良好的解决方案.所以研究Si片的"雾"缺陷,并克服"雾"缺陷显得尤为迫切.从实际生产出发,根据实验数据分析和理论推导,建立了一个起"雾"原因基本模型,对引起"雾"缺陷影响因素进行了独立细致的分析,并在这个模型的基础上提出了相对应的有效的解决方案.     

Recursive identification algorithms

Mechanisms for adapting models, filters, decisions, regulators, and so on to changing properties of a system or a signal are of fundamental importance in many modern signal processing and control algorithms. This contribution describes a basic foundation for developing and analyzing such algorithms. Special attention is paid to the rationale behind the different algorithms, thus distinguishing between optimal algorithms and ad hoc algorithms. We also outline the basic approaches to performance analysis of adaptive algorithms.     

Pervasive Home Environments

For decades, technologists have been promising the intelligent house. The vision is usually portrayed as a house filled with technology which will do the dweller's bidding and take all domestic drudgery out of their lives. The truly intelligent house is still some way off, but the emergence of broadband, availability of faster, smaller and ever cheaper computing equipment and a variety of wired and wireless network technologies are enabling technologies that bring this vision closer to reality. These technology trends lead to the concept that computing and other smart devices will become pervasive, fully networked and disappear into the infrastructure of the home. People will carry out their tasks unaware of the complexity of the infrastructure that supports their activities in much the same way as people today use mains electricity.This paper introduces these concepts and discusses the technological challenges to be overcome. We present our vision of the pervasive home environment where inhabitants can focus on tasks rather than the technology: I need to create X and send it to Y rather than I need to use this computer and this application which needs access to service A and resource B. Although this sounds simple, the environment needs to understand who I is, and who or what Y is. Appropriate permissions must be in place and resources allocated, if available. The most appropriate interface for the task and user must be determined.The pervasive, intelligent home will make available new ways to access and share information. It will herald new services, such as care and support of people in the home, entertainment, educational and security services. The final part of the paper discusses the commercial opportunities and challenges which must be met, not least the need for industry to agree on open standards and interfaces.