《专业英语词汇》PPT课件.ppt

,专业英语,aerial adj. 天线的 n.天线 e. m. wave 电磁波 convey vt.传递 the morse code 莫尔斯电码 in a controlled way 有控制的 bang n.响声 Quality of Service 服务质量 Service Status 服务状态,Float Type 浮点型（数据） s.s.b=single sideband 单边带 reinsert n.重插入 take place 发生 allow for 考虑到，允许 multiply v. 乘， 扩大 Intersymbol Interference 码间干扰 Auxiliary Equipment 辅助设备,in the case of 在情况下 foresight n.远见 look like 看起来象 prone (to) adj.易于的 Payphone 付费电话 Payload 负荷 payloadpointers 负荷指针 Appendix 附录,Coverage 覆盖 Coverage Area 覆盖范围,覆盖区,有效区 Interference 干扰 Preliminary Design 概要设计,初步设计 Jam-to-signal ratio 干扰信号比 Interferer diversity 干扰源分集 Interference-Adaptive System 干扰自适应系统,感应电荷 Inductive charge 高保真度音响 High Fidelity 高层兼容性 High Layer Compatibility 高电位差 High potential difference 高频 High Frequency （HF） 高增益天线 High gain antenna 高增益功放板 High gain Power Amplifier board 告警面板 Alarm panel,告警模块 Alarm module 格式转换 Format Conversion 隔行扫描 Interlace Scanning 个人编码 Personal Number 个人识别码 Personal Identity Number 工程手册 Engineering Manual 工具软件 Tool Software 个人通信网，专用通信网 Personal Communications Network,工业水平尺 Industrial horizontal ruler 工作波长 Working wavelength 工作单元 working unit 功率分配结构 Distributed Power Architecture 公用密钥,公开密钥 Public key 供参考 For reference 共享内存 Shared Memory 共享资源 Shared Resource,规程 Procedure 规定容限,可接受容限 Tolerance 规范和描述语言 Specification & Description Language SDL 规则脉冲激励长期预测 Regular Pulse Excited Long-Term Prediction 硅钢片 Silicon Steel Sheet 硅谷 Silicon Valley 硅控整流器 Silicon Control Rectifier,骨干网 Backbone Network 固定比特率 Constant Bit Rate 固定卫星业务 Fixed Satellite Services 固定信道分配 Fixed Channel Allocation 固态继电器 Solid-state Relay 故障,错误 fault, error，failure, Bug 故障定位 Fault locating 故障申告受理 Fault Complaint Handling,光探测器 Photodetector 光开关 Optical Switch 光缆 Fiber Optic Cable 光连接器 Fiber Connectors 光滤波器 Optical Filters 光敏电阻 Optical Resistor 光耦合器 Optical Couplers 光收发模块 Optical Transceivers,光通道 Optical channel 光网络单元 Optical Network Unit 光无源器件 Optical Passive Devices 光纤 Optical Fiber/Optic fiber 光纤包层 Cladding of Fiber 国标 National Standard 国际电信联盟 International Telecommunications Union 国内长途号码 National Toll Number,If a transmitting aerial radiates a constant amplitude e. m. wave it conveys little information to the receiver.,transmit 发射，传播 aerial 天线 radiate 辐射 constant 常量，不变的 amplitude 振幅 e.m. wave=electromagnetic wave 电磁波 convey 传达 receiver 接收者，接收机,The simplest way of sending information is to switch the transmitter on and off so that a series of dots and dashes are transmitted -the morse code for example. This is a very common method of communicating between ships at sea , but it does require the operator to read the code .,switch on (off ) 开（关） a series of 一连串的 morse code 莫尔斯电码 operator 话务员,Any process of superimposing some pattern on the continuous e. m. wave which allows information to be carried is called modulation. We say the carrier wave is modulated. To modulate a carrier wave all we need to do is to vary a property of the wave in a controlled way.,superimpose 迭加 modulation 调制 carrier wave 载波 property 特性，性质 in a controlled way 有控制地,Thus, if we vary its amplitude we produce amplitude modulation(a.m.), if we vary its frequency we produce frequency modulation(f. m.), and if we vary its phase we have phase modulation.(p. m).,vary 改变 amplitude 振幅 amplitude modulation(a.m.) 调幅 frequency 频率 frequency modulation(f.m.) 调频 phase 相位 phase modulation(p.m.) 调相,Generally, interferencefrom lighting or electrical machines-produces amplitude disturbances on an e. m. wave passing by .干扰是在光电产品中,伴随着电磁波的传播而产生幅度的干扰 Because the amplitude of f. m. carrier is not carrying information，调频载波幅度并不承载信息such interference has very little effect on the received signal.This is not the case with an a. m. carrier , 但是调幅载波就不一样了，where all such bangs and crackle are detected at the receiver as information.,interference 干扰 amplitude disturbance 振幅波动 received signal 接收信号 bang 巨响 crackle 劈啪响,On the other hand the bandwidth of the a.m. carrier is much less than that of the f. m. carrier as we shall now show.下面将给出例子,on the other hand 另一方面 bandwidth 带宽 much less 少得多,If we modulate a 100kHz carrier with a 1kHz signal， it might be expected that although the carrier amplitude would miss and fall in step with the amplitude of the 1kHz signal the carrier frequency would remain at 100kHz. 尽管载波幅度回损失和下降到与一致,但其频率仍有期望保持在In fact two new frequency components can be detected in the modulated carrier; they are 101kHz and 99 kHz.,in step with 与同步 remain 保持 component 成分 modulated carrier 调制波,Thus a carrier of frequency fc , amplitude modulated with a signal of frequency fs 当一个载波频率为 信号频率为的幅度信号调制包含三个频率contains frequencies fc, fc+fs, fc-fs. The last two are called sidebands. Fig.5.1 is the frequency spectrum of an a. m. carrier .,sideband 边带 frequency spectrum 频谱 a.m. carrier 调幅载波,Fig. 5.1 The carrier and sidebands of an a.m. signal,The carrier componentremains at constant amplitude and is not conveying information (except about its own frequency).载波的成分保持在一个固定的幅度且并不传播信息 It represents wasted transmitter power. Sometimes it is not radiated没有辐射 -then we have a suppressed carrier a.m. transmission.抑制Sometimes only the carrier and one sideband are radiated, sometimes only one sideband (s.s.b=single s.b.).,represent 表明 wasted 浪费，消耗 suppress 抑制 transmission 传输,If less than the full a.m. carrier完全振幅调制载波 is transmitted the receiver needs to be more complicated to receive it,接收非常复杂 because basically the carrier must be reinserted at the receiver before detection can take place. 在检波前要重新再植 入一个载波,less than 小于 complicated 复杂的 reinsert 重新插入 detection 检波,In a. m. the full bandwidth在振幅调制里一个完全的带宽 is from fc-fs to fc+fs, i.e. 2fs so that for a speech transmission where voice frequencies extend up to 3kHz -we should need 6kHz of bandwidth; for music 30kHz needed.,bandwidth 带宽 i.e. 也就是 speech transmission 音频传输 extend up to 增加到,Transmitters should be spaces apart in frequency to allow for these bandwidth requirements. There are international agreements about frequencies but they are not observed by all countries.,transmitter 发射机 space apart 空间分离 allow for 虑及，考虑到 bandwidth requirement 带宽要求 international agreement 国际协议 observe 遵守,For the mathematically inclined it is easy to show that the sinusoidal modulation of the amplitude of a sinusoidal wave-form results in the production of sum and difference frequencies.,inclined 倾向 sinusoidal modulation 正弦调制 sinusoidal wave-form 正弦波形 result in 导致，体现,Suppose we have an un-modulated carrier (fc) of the form a=Asin(2fct) where a is the instantaneous amplitude and A is the maximum amplitude, often simply referred to as the amplitude of the carrier. Now let us modulate A sinusoidally at a frequency fs, and write.,suppose 假设 un-modulated 未调制 instantaneous amplitude 瞬时值 maximum amplitude 最大值 sinusoidally 正弦地,a=A1+ksin(2fst)sin(2fct) k is a constant multiplying out we get a=A sin(2fc t)+Aksin(2fs t)sin(2fct) =Asin(2fst)+AK/2cos(2(fc-fs)t)- cos(2(fc+fs)t) = carrier+AK/2lower sideband -upper sideband,multiply out 乘 lower sideband 下边带 upper sideband 上边带,When k is 1 we have 100% modulation, for the two sidebands each of amplitude A/2 can combine to make the total amplitude vary from zero to 2A.,“for” 引导原因状语从句； “When k is 1 ” 是时间状语从句； “each of amplitude A/2 ” 则是后置定语，修饰“sideband”。,In the case of f. m. a mathematical analysis of the modulated carrier is more difficult than for a.m. and would involve us in Bessel functions.,mathematical analysis 数学分析 modulated carrier （已）调制载波 Bessel functions 贝塞尔方程 involve in 涉及,Bessel was a nineteenth century mathematician who had the foresight to solve the very equations we need for f. m. So we can go straight to the end o