FFT在时域紧缩场方向图测量中的应用

离散傅立叶变换(DFT)在信号的谱分析及系统的分析、设计和实现中起着非常重要的作用.其原因之一是计算DFT有很多高效快速的算法.快速傅立叶变换(FFT)算法就是其中之一.利用FFT算法,可以将微波测量中大量的计算简化,缩短了计算机的计算时间.在时域紧缩场测量方向图的过程中,利用FFT进行时域与频域间的转化,使一次仅能测量一个频率点的方向图,扩展到一次可以测量一个频段的方向图,从而大大缩减了测量时间.     

RECENT PROGRESS IN MULTI—BEAM KLYSTRON IN IECAS

Recent research progresses in Multi-Beam Klystron(MBK)in IECAS are briefly introduced in the letter,The S-band MBKs of IECAs have peak power of 120-250kW,average power of 4-9kW,efficiency of 35-45%,gain of 41-46dB.beam voltage of 15-19kV,and weight of 40-45kg.Some key technical problem of MBK are also described and discussed.Among them,improving the design of MBK to botain the required bandwidth,raising beam transmission to increase average power,eliminating oscillation and spray spectrum,overcoming window breakdown caused by magic mode,reducing breakdown times of electron gun,are most important things for the practical MBK.Besides,further research owrk in MBK in IECAS is commented.     

The Digital Gap in Maracaibo city in Venezuela

The Digital Gap has been recognized as one important issue to develop a country. This paper reviews the most important concepts and parameters that take place in the information and communications technologies and Digital Gap matter. Also reports a survey made in Maracaibo, the second largest city of Venezuela in order to determine the access level to such technologies and discuss the government policies in order to reduce the Digital Gap.     

模电教学中的形象思维

阐述了形象思维在认识客观世界时的重要作用,同时以大量的实例说明形象思维在模电课程中的应用,并论述了如何在模电教学中利用形象思维提高教学质量,同时培养学生的形象思维能力。     

我国互联网域名系统的安全问题

域名系统面临的安全威胁和风险不断加大,安全事件增多主要是缺乏有效的监管和相应的更积极的技术手段和措施。因此,转变对互联网非传统安全问题的认识．充分研究域名系统面临的新情况、新问题和新威胁,切实增强保障域名系统安全的责任感和紧迫感,是保证我国互联网稳定发展的前提。     

Recent advancements in surface plasmon polaritons-plasmonics in subwavelength structures in microwave and terahertz regimes

This paper presents a review of recent investigational studies on exciting Surface Plasmon Polaritons (SPPs) in MicroWave (MW) and TeraHertZ (THz) regimes by using subwavelength corrugated patterns on conductive or metal surfaces. This article also describes SPP Microstrip (MS) structures at microwave and terahertz frequencies, and compares their significance with that of conventional MS Transmission Lines (TL), in order to tackle the key challenges of high gain, bandwidth size, compactness, TL losses, and signal integrity in high-end electronic devices. Because they have subwavelength properties, surface plasmon polaritons are gaining attention for their improved performance and ability for miniaturization in high-speed dense circuits. They possess comparably minuscule wavelength compared to incident light (photons). Consequently, they can demonstrate stronger spatial confinement and higher local field intensity at optical frequencies. In addition to engineering spoof SPP waveguides, which are created by engraving grooves and slits on metal surfaces to allow operation on at low frequencies (microwave and terahertz), semiconductors with smaller permittivity values and thus lower free charge carrier concentration have been demonstrated as a potential candidate in plasmonic devices. If necessary, further tuning of semiconductor-based SPP structures is aided by controlling the charge carrier concentration through doping, or by external stimuli such as optical illumination or thermal excitation of charge carriers from valence to conduction bands. This article conclusively covers previously elucidated perspectives on manipulating SSPPs in the MW and THz ranges, and emphasizes how these could steer next-generation plasmonic devices.     

DDN网在惠州市电信业务中的应用

本文介绍了ＤＤＮ的基本结构和作用，分析了ＤＤＮ设备的几个特点，指出了ＤＤＮ在惠州市电信业务中的几种主要的应用，最后还指出了ＤＤＮ设备使用中存在的问题。     

智能通信在楼宇自控系统中的应用

随着计算机技术、控制技术、通信技术及信息技术的飞速发展,人们对生活、办公环境安全性、舒适性的要求日渐增长,智能建筑应运而生。楼宇自动化控制系统是智能建筑的一个重要组成部分。通过结合具体的智能楼宇控制工程项目,在介绍系统概况的基础上,给出了系统的总体设计方案及子系统的监控方案,具有一定的实用价值。     

Advances in millimeter-wave subsystems in Japan

The authors describe the development trends and results of millimeter-wave systems in Japan in such fields as communication, radar, and measurement systems. The applications included are the W-40G waveguide transmission communication system, an automobile traffic control system using the 60-GHz band, a collision avoidance radar system for an automobile, a plasma electron density measuring system, and satellite communication. The authors describe the development of devices such as high-power FET amplifiers, traveling wave tube amplifiers (TWTAs), IMPATT amplifiers, low-noise amplifiers, and monolithic microwave integrated circuit (MMIC) devices used in constructing the millimeter-wave systems     

Advances in Developing Transitions in Microwave Integrated Circuits

Advances in developing transitions in microwave integrated circuits during the last ten years are reviewed. Some typical structures of transition are introduced, Transition structures can be classified into two basic types: one is transition between the same ]rind of transmission lines on different planes of a common substrate, the other transition between different types of transmission lines.Furthermore, future development of transition structures is discussed.     

数字电视中的频域频率同步技术

提出了一种宽带数字电视地面广播（BDB-T）系统的同步解决方案，重点研究了频域中的频率同步部分，通过对各种算法的仿真分析比较，给出易于实现、节省资源的频域频率同步算法并完成了相应的FPGA硬件电路设计，经BDB—T功能样机在实际无线环境中的传输测试，证明了算法及其电路的良好实际工作性能。     

算术运算的VHDL描述方法探讨

针对在VHDL语言教学过程中,如何进行算术运算的VHDL描述问题进行了探讨.文中首先论述了VHDL语言描述算术运算的局限性;重点阐述了加运算、减运算、乘运算、除运算、取模运算、取余运算的VHDL描述方法;由于设计的结果是一个专用的算式电路,不运行任何程序,工作的可靠性和稳定性都优于用CPU设计.     

高职院校DSP技术教学改革实践

文章介绍了高职院校DSP课程的教学改革情况。以培养应用性人才为目标,根据实际情况整合课程体系内容,通过实验教学、项目教学以及创新实践结合提高DSP课程教学成效。特别突出DSP硬件设计调试能力培养,同时兼顾Matlab及C语言软件的熟练应用。在高职院校开设DSP课程,是信息社会的必然需求,同时也给教学过程带来了新的问题与挑战。     

Progress in electrophotography in Western Europe

A review is given of the progress in electrophotographic science and technology in Western Europe during the years 1967 to early 1971. University research work is mainly directed towards two areas: 1) the electrical and physical properties of photoconductors, such as selenium, chalcogenides, oxides, and organic materials; and 2) the sensitization of these photoconductors. Industrial research teams report on the preparation of electrophotographic layers on development and on image evaluation. A bibliography including scientific papers and patents published on this subject during said period completes this review.     

Moisture diffusion in poltimide films in integrated circuits

This paper reports the use of planar aluminum-PI-aluminum capacitors, in which the variation of low frequency dielectric permittivity is shown to be proportional to absorbed moisture, to carry out in-situ studies of moisture uptake and diffusion in PMDA-ODA device-grade polyimide films. It is found that the equilibrium amount of moisture uptake depends on ambient relative humidity in the temperature range 20-80‡C, and that the diffusion kinetics obey a Fickian model with a diffusion coefficient in the range 3-5 x 10^-9 cm² /sec at room temperature. The diffusion coefficient is temperature dependent, with an activation energy of 0.32-0.34 eV, and is weakly dependent on absorbed moisture at fixed temperature. An asymmetry is observed between absorption and desorption kinetics which correlates with the moisture-dependent diffusion coefficient.     

IC业在拐点生存

分析了IC业的众多特点,例如从90nm向65nm、45nm、32nm、22nm等拐点演进的困难,以及ESL、DFM拐点,制造是设计的拐点,FPGA与ASIC之间的拐点等热门问题.     

向列相液晶四波混频的若干问题

对向列相液晶四波混频进行了理论分析,总结了提高向列相液晶四波混频衍射效率的方法,评述了其相位共轭的研究现状和前景.     

WCDMA和TD-SCDMA中HSDPA的比较

高速下行分组接入(HSDPA)技术是针对第三代移动通信系统上、下行链路业务量不平衡的特点提出的,能够大幅提高下行传输速率。在R5版本中WCDMA和TD-SCDMA分别引入了HSDPA。两系统中的HSDPA技术在MAC层、物理层和技术上有一致性,但同时二者在物理层信令参数、物理信道种类、时隙调整、技术和整体性能上存在着一些差异,而差异的产生源于WCDMA和TD-SCDMA系统本身特点的不同。主要阐述了WCDMA和TD-SCDMA HSDPA的异同,并进行分析。     

密码学在计算机系统安全中的作用

计算机系统中信息安全问题一直以来是广大计算机互联网用户备受关注的焦点,在计算机技术和互联网通信技术飞速发展的大背景下,出现越来越多的隐私泄露、、信息曝光、黑客入侵等现象,让人们在使用计算机网络时担惊受怕,而密码学便由此而产生了。本文立足于当前密码学的相关定理,并阐述了密码学的种类及其作用,最后分析了密码学在计算机系统安全中的的实践运用。