电子信息工程专业英语翻译清华出版社English for IT and EE-07

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信息科学与电子工程专业英语

Technical EnglishFor Information Science and Electronic Engineering

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信息科学与电子工程专业英语

Unit 7Satellite Communications

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信息科学与电子工程专业英语

Part IApplications of Communications satellite

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New Wordsabbreviate 缩略，简写成 缩略， elliptical orbit 椭圆轨道 submarine 海底的，潜水艇 海底的， analogous 模拟的，类似的 模拟的， constellation 星座图，星罗棋布 星座图， affiliate 会员，分支机构 会员， diameter 直径 headend 数据转发器 transponder 转发器，应答器 转发器， amateur 业余爱好，业余的 业余爱好， geostationary orbit 对地静止轨道 complementary 互补的，补充的 互补的， relay 中继，接力 中继， disturbance 扰动，干扰 扰动， geosynchronous 地球同步的 limelight 众人注目的中心 free-tofree-to-air TV 不加密不收费电视 ambiguous 模糊的，混淆的 模糊的， spacespace-borne repeater 天空转发器 dialup 拨号3

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1A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications. telecommunications. Modern communications satellites use a variety of orbits including geostationary orbits, elliptical orbits, orbits and low (polar and non-polar) Earth orbits. (polar non停留在太空 现代通信卫星使用多种轨道，包括对地 现代通信卫星使用多种轨道， 静止轨道、椭圆形轨道、 静止轨道、椭圆形轨道、低地球轨道 过极地和不过极地)。 (过极地和不过极地)。

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2For fixed (point-to-point) services, communications satellites (point-to-point) provide a technology complementary to that of fiber optic submarine communication cables. They are also used for cables. mobile applications such as communications to ships, vehicles, planes and hand-held terminals, and for TV and radio handbroadcasting, for which application of other technologies, such as cable, is impractical or impossible.1 它们也可用于如船，车辆，飞机和手持终端的移动 它们也可用于如船，车辆， 通信，用于电视和无线电广播，以及应用其它技术， 通信，用于电视和无线电广播，以及应用其它技术， 比如电缆，是不现实或不可能的地方。 比如电缆，是不现实或不可能的地方。5

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3 TelephonyThe first and historically the most important application for communication satellites is in international telephony. Fixedtelephony. Fixedpoint telephones relay calls to an earth station, where they are then transmitted to a geostationary satellite.

固定电话将通话传输到地面站，在那里 固定电话将通话传输到地面站， 再发射到对地静止卫星上

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3An analogous path is then followed on the downlink. In contrast, mobile telephones (to and from ships and airplanes) must be directly connected to equipment to uplink the

signal to the satellite, as well as being able to ensure satellite pointing in the presence of disturbances, such as waves onboard a ship.2 相反，移动电话(船和飞机上接收和发送的) 相反，移动电话(船和飞机上接收和发送的)必 须直接连到设备把信号上传到卫星， 须直接连到设备把信号上传到卫星，又能确保在 有干扰时的卫星指向，如船上的电波干扰。 有干扰时的卫星指向，如船上的电波干扰。7

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4Improvements in submarine communications cables caused a decline in the use of satellites for fixed telephony in the late 20th century. Hand held telephones (cellular phones) used in urban areas do not make use of satellite communications. Instead they have access to a ground based constellation of receiving and retransmitting stations. stations. 海底通信电缆的改进导致了20世纪后期 海底通信电缆的改进导致了20世纪后期 用于固定电话的卫星应用有所下降。 用于固定电话的卫星应用有所下降。 接入地面上用于接收和发射 的星罗棋布的基站群8

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5 Satellite Television and radioTelevision became the main market, its demand for simultaneous delivery of relatively few signals of large bandwidth to many receivers being a more precise match for the capabilities of geosynchronous comsats.3 Two satellite types are used for North American television and radio: Direct Broadcast Satellite (DBS), and Fixed Service Satellite (FSS). 电视成为主要市场，其对相对很少的大带 电视成为主要市场， 宽信号同时传送给很多接收机的要求更好 地匹配了对地静止通信卫星的性能。 地匹配了对地静止通信卫星的性能。9

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6A direct broadcast satellite is a communications satellite that transmits to small DBS satellite dishes (usually 18 to 24 inches in diameter). Direct broadcast satellites generally operate in the upper portion of the microwave Ku band. DBS technology band. is used for DTH-oriented (Direct-To-Home) satellite TV DTH(Direct-To-Home) services. 直播卫星是一种通信卫星，它直接 直播卫星是一种通信卫星， 向小型DBS卫星天线发射 卫星天线发射。 向小型DBS卫星天线发射。

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7Fixed Service Satellites (FSS) use the C band, and the lower band, portions of the Ku bands. They are normally used for broadcast feeds to and from television networks and local affiliate stations, as well as being used for distance learning by schools and universities, business television, videoconferencing, television, videoconferencing, and general commercial telecommunications.4 FSS satellites are also used to distribute national cable channels to the central control units. 它们通常用于向电视网和加盟地方台 units. 馈送或收集广播节目， 馈送或收集广播节目，也用于中小学 和大学的远程教学、商业电视、 和大学的远程教学、商业电视、视频 会议和一般商用通

信。 会议和一般商用通信。11

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8FSS satellites differ from DBS satellites in that they have a lower RF power output than the latter, requiring a much larger dish for reception (3 to 8 feet in diameter for Ku band, and 12 feet on up for C band), as well as using linear band), polarization for each of the transponders’ RF input and transponders’ output (as opposed to circular polarization used by DBS satellites). satellites).5 FSS与DBS的不同之处在于固定业务卫星 FSS与DBS的不同之处在于固定业务卫星 具有更低的射频 …… 此处隐藏：4183字，全部文档内容请下载后查看。喜欢就下载吧 ……