问与答

问：请问ｄＢｉ、ｄＢｄ、ｄＢ、ｄＢｍ、ｄＢｃ之间的区别。 答：它们都是功率增益的单位,不同之处如下。 ｄＢｉ和ｄＢｄ是功率增益的单位,两者都是相对值,但参考基准不一样。ｄＢｉ的参考基准为全方向性天线;ｄＢｄ的参考基准为偶极子。一般认为 ｄＢｉ和 ｄＢｄ表示同一个增益,用ｄＢｉ表示的值比用ｄＢｄ表示的要大２．１５ｄＢｉ。例如：对于一增益为１６ ｄＢｄ的天线,其增益折算成单位为ｄＢｉ时,则为１８．１５ｄＢｉ（一般忽略小数位,为１８ｄＢｉ）。 ｄＢ也是功率增益的单位,表示一个相对值。当计算Ａ的功率相比于 Ｂ…     

光纤传输设备的对应数据转换

ＣＡＴＶ领域的光纤设备越来越多 ,必须根据技术要求合理搭配使用光纤设备 ,为此提供以下数据对应表 ,供搭配设备与设计线路时参考。利用表 1可以方便地把电平由一种单位化为另一种单位 ,例如要把 10 5ｄＢμＶ化为ｄＢＷ时 ,可用原来的数与表中最后一行第一列数 - 138.75相加 ,得 - 33.75ｄＢＷ ;如把 10 5ｄＢμＶ化为ｄＢｍ时 ,可用原来的数与表中最后一行第二列 - 10 8.75相加 ,得 - 3.75ｄＢｍ。表 1　电平单位换算表原 单 位增 加 值新 单 位ｄＢＷｄＢｍｄＢｍＶｄＢμＶｄＢＷ 0 +30 +78.75 +138.75ｄＢｍ -30 0 +48.75 +10 8.75ｄ…     

光纤线路设计调试经验点滴.

在设计光链路时 ,据有关资料介绍往往都要留 1ｄＢ左右的裕量 ,但根据我们实际测试 ,按照这样来设计 ,各光节点的光功率都要偏高。除光发射机输出功率比标称值偏高 0 .8ｄＢ以外 ,光节点处的光功率为 0ｄＢｍ左右 ,而设计值为 - 2ｄＢｍ 1ｄＢｍ ,裕量为 - 1ｄＢｍ ,这样就偏高 1ｄＢ。分析其原因是 :( 1) 1310ｎｍ光纤含熔接损耗在计算时 ,所取的 0 .4ｄＢ/ｋｍ ,比实际的光纤损耗有一定的裕量 ;( 2 )光分路器附加损耗计算时取 0 .55ｄＢ ,而实际为 0 .2 5ｄＢ ;( 3)“光发”、“光收”、光配线架处光纤活动接头计算时按 0 .5ｄＢ/个取值 …     

AD604超低噪声双通道可变增益放大器

特点在最大增益情况下具有超低输入噪声０．８０ｎＶ／　Ｈｚ,３．０ｐＡ／　Ｈｚ两个独立通道ｄＢ成线性可变增益放大器每个通道可编程绝对增益范围从０ｄＢ～＋４８ｄＢ（前放增益＝＋１４ｄＢ）到＋６ｄＢ～＋５４ｄＢ（前放增益＝＋２０ｄＢ）增益精度：±１．０ｄＢ－３ｄＢ带宽：４０ＭＨｚ输入电阻：３００ｋ可变增益系数：２０ｄＢ／Ｖ～４０ｄＢ／Ｖ增益对温度和电源变化保持稳定单端单极性增益控制在增益控制低端,电源待机可直接驱动Ａ／Ｄ转换器应用超声和声纳时间增益控制高性能自动增益控制（ＡＧＣ）系统信号测量ＡＤ９８０…     

宽带毫米波放大器

Ａｌｐｈａ工业公司增加了 5种封装放大器产品 ,以支持微波传感器和通信应用。ＡＢ0 2 8Ｈ1- 14是一种 2 3～ 30ＧＨｚ高增益放大器 ,增益 36ｄＢ ,输出功率 16ｄＢｍ ,噪声系数为 3ｄＢ。ＡＢ0 381- 14的增益为 30ｄＢ ,输出功率 16ｄＢｍ ,噪声系数为 4ｄＢ。二种放大器都为单电源工作。ＡＢ0 2 8Ｖ1- 14是 2 3～ 30ＧＨｚ的可变增益放大器 ,有效增益为 30ｄＢ ,衰减范围为 30ｄＢ ,输出功率 16ｄＢｍ ,噪声系数为 3ｄＢ。二种低噪声放大器ＡＡ0 2 8Ｎ1- 99和ＡＡ0 38Ｎ1- 99工作频率分别为 2 3～ 30ＧＨｚ ,2 6～ 4 2ＧＨｚ。低频型号…     

浅议有线电视中dBmW与dBμV、dBmV之间的换算

有线电视中的ｄＢｍＷ、ｄＢμＶ、ｄＢｍＶ是常用单位 ,《中国有线电视》2 0 0 0年第 2 0期《有线电视系统中的分贝比与电平》一文中已做了比较系统的概述 ,但对于ｄＢｍＷ与ｄＢμＶ、ｄＢｍＶ之间的换算 ,笔者提出不同的意见 ,望与同行共同讨论。先认识一下ｄＢｍＷ、ｄＢｍＶ、ｄＢμＶ的概念。ｄＢｍＷ是以 1ｍＷ为基准功率 ,则功率Ｐ所对应的电平为 10ｌｇ(Ｐ/1ｍＷ) ;ｄＢｍＶ是在有线电视系统中以 1ｍＶ为基准电压 ,则电压Ｕ所对应的电平为 2 0ｌｇ(Ｕ/1ｍＶ) ;ｄＢμＶ是在有线电视系统中以 1μＶ为基准电压 ,则电压Ｕ所对应的电平…     

dBASE for Windows中文版

ｄＢＡＳＥｆｏｒＷｉｎｄｏｗｓ中文版童爱华十几年来，ｄＢＡＳＥ深受计算机专家及社会各方面用户的喜爱，现在ｄＢＡＳＥ在全世界已拥有７００多万ＰＣ用户，其ＰＣ数据库市场占有率达５５．８％。Ｂｏｒｌａｎｄ公司１９９５年推出的新一代ｄＢＡＳＥ——ｄＢＡＳＥｆ...     

高隔离度偏振无关光环行器

本文报道了一种高隔离度偏振无关的三端口光环行器。该环行器在１．５５μｍ中心波长±２０ｎｍ范围内，插入损耗低于１ｄＢ，隔离度大于４５ｄＢ，偏振相关损耗低于０．２ｄＢ，串音大于５０ｄＢ，回波损耗大于５０ｄＢ。     

电源线氧化引起的一例故障

有一次 ,局里接到用户投诉电话 ,反映该片区有线电视信号弱 ,电视屏幕出现严重的横条、拉丝 (交互调 )现象。经检查 ,某级放大器输入电视信号处的用户图像正常 ,测该级放大器输入电平为 74～ 81ｄＢ ,内部采用 12ｄＢ固定式均衡器。之后测放大器输出电平为 90～ 93ｄＢ ,该放大器采用常熟产的ＧＸＴ - 2 733型外供电放大器 ,其增益值为 34ｄＢ。因局里安装时放大器输出电平一般采纳 98～ 10 2ｄＢ半倾斜式输出 ,于是调整该放大器的增益 10ｄＢ可调式电位器至 0ｄＢ衰减 ,此时输出电平为 94～ 98ｄＢ ,场强仪监视图像画面仍出现交互调现象。…     

实用资料

飞利浦CATV放大模块一览表型号(ＭＨｚ)增益(ｄＢ)斜率(ｄＢ)平坦度(ｄＢ)最大值反射损耗 (输入/输出 )(ｄＢ)最小值三阶组合差拍(ｄＢ)最大值交扰调制(ｄＢ)最大值二级组合差拍(ｄＢ)最大值二阶差拍(ｄＢ)最大值输出电平(ｄＢｍＶ)最小值噪声系数(ｄＢ)最大值总ＤＣ电流消耗(ｍＡ)最大值5-75　反向放大器ＢＧＹ68@1 0ＭＨｚ3 0± 0 .8--0 .2～ 0 .5± 0 .2 2 04频道-684频道-60 --702 5ＭＨｚ5.0 1 3 55-1 2 0反向放大器ＢＧＹ66Ｂ@1 0ＭＨｚ2 5± 0 .5--0 .2～ 0 .5± 0 .2 2 01 4频道-661 4频道-54--70 60 .0@1 2 0ＭＨｚ5.0 1 3 55-2 …     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

A Versatile Mixed-Signal Pin Approach for Cost-Effective Test of Automotive ICs

Integrated circuits (ICs) intended for increasingly sophisticated automotive applications bring unique test demands. Advanced ICs for applications such as highly integrated automatic braking system (ABS) and airbag controllers combine high voltage digital channels, significant VI demands and precise timing capability. Along with continued missioncritical reliability concerns, the trend toward higher voltage operation and increased device integration requires specialized test capabilities able to extend across the wide operating ranges found in automotive applications. Among these capabilities, automotive test requirements increasingly dictate a need for a cost-effective versatile mixed-signal pin electronics with very high data rates reaching up to 50MHz with a voltage swing of-2 V to +28 V.     

Optical vibration and deviation measurement of rotating machine parts

It is of interest to get appropriate information about the dynamic behaviour of rotating machinery parts in service. This paper presents an approach of optical vibration and deviation measurement of such parts. Essential of this method is an image derotator combined with a high speed camera or a laser doppler vibrometer （LDV）.     

社长序言（英文）

正Happy New Year!As we step into a new year,we take a look back at the key feature topics covered in China Communications over the past 12 months and set out our expecta-     

Call for Papers

正Introduction Jointly sponsored by the China Institute of Communications(CIC)and the IEEE Communications Society(IEEE ComSoc)since the year 2013,China Communications,currently,is aiming to gradually realise the transition from journal to magazine content and style.     

INTEGRATION OF OPTICAL AND WIRELESS NETWORKS

正For a long time,optical and wireless systems/net-works are developed in separate communities witha few attempts for in-depth convergence.In fact,it prom-ises many advantages to combine the optical and wire-less technologies in the levels of systems and networks.Recently,both academia and industry have made manyefforts to enter a new phase of development to take op-tical and wireless systems as fully integrated networks.To provide high bandwidth and reliable service for bothfixed and mobile users,a well-designed network must     

Call for Papers—Feature Topic,Vol.12,No.3,2015

正Smart Grid Communications The electric power industry is undergoing profound changes as the industry aims to capture the promise of a smart grid for a sustainable energy future.Enabled by the advanced sensing devices such as Phasor Measurement Units(PMUs),increasingly powerful