电子与通信技术专业英语Unit 3 lesson 16

1、PART1 GPS is the Global Positioning System. GPS uses satellite technology to enable a terrestrial terminal to determine its position on the Earth in latitude and longitude. GPS receivers do this by measuring the signals from three or more satellites simultan- eously and determining their position us

2、ing the timing of these signals（Fig.16-1）. Lesson 16Global Positioning System (GPS)TextNew wordNotesExercisesTranslationVocabulary Fig.16-1 Global Positioning System (GPS)PART1Lesson 16Global Positioning System (GPS)GPS operates using trilateration. Trilatera- tion is the process of determining the

3、position of an unknown point by measuring the lengths of the sides of an imaginary triangle between the unknown point and two or more known points.In the GPS system, the two known points are provided by two GPS satellites. These satellites constantly transmit an identifying signal. The GPS receiver

4、measures the distance to each GPS satellite by measuring the time each signal took to travel between the GPS satellite and the GPS receiver.The GPS system is divided into three segments:The Space Segment The Control Segment The User SegmentTextNew wordNotesExercisesTranslationVocabulary PART1Lesson

5、16Global Positioning System (GPS) GPS uses twenty-one operational satellites, with an additional three satellites in orbit as redundant backup. GPS uses NAVSTAR satellites manufactured by Rockwell International.Each NAVSTAR satellite is approximately 5 meters wide (with solar panels extended) and we

6、ighs approximately 900kg. GPS satellites orbit the earth at an altitude of approximately 20,200km. Each GPS satellite has an orbital period of 11 hours and 58 minutes. This means that each GPS satellite orbits the Earth twice each day. These twenty-four satellites orbit in six orbital planes, or pat

7、hs. This means that four GPS satellites operate in each orbital plane. Each of these six orbital planes is spaced sixty degrees apart. All of these orbital planes are inclined fifty-five degrees from the Equator. In order for GPS tracking to work, it is necessary to have both access to the Global Po

8、sitioning System and have a GPS receiver (Fig.16-2). The GPS receiver is able to receiveTextNew wordNotesExercisesTranslationVocabulary PART1Lesson 16Global Positioning System (GPS)TextNew wordNotesExercisesTranslationVocabulary Fig.16-2 GPS ReceiverPART1Lesson 16Global Positioning System (GPS)signa

9、ls that are transmitted by GPS satellites orbiting orerhead. Once these satellite transmissions are received by the GPS receiver, location and other information such as speed and direction can be calculated. The receiver contains a mathematical model to account for these influences, and the satellit

10、es also broadcast some related information which helps the receiver in estimating the correct speed of propagation. Certain delay sources, such as the ionosphere, affect the speed of radio waves based on their frequencies; dual frequency receivers can actually measure the effects on the signals. In

11、order to measure the time delay between satellite and receiver, the satellite sends a repeating 1,023 bit long pseudo random sequence; the receiver constructs an identical sequence and shifts it until the two sequences match. Different satellites use different sequences, which lets them all broadcas

12、t on the sameTextNew wordNotesExercisesTranslationVocabulary PART1Lesson 16Global Positioning System (GPS)frequencies while still allowing receivers to distinguish between satellites. This is an application of Code Division Multiple Access, CDMA. There are two frequencies in use: 1575.42 MHz (referr

13、ed to as L1), and 1227.60 MHz (L2). The L1 signal carries a publicly usable coarse-acquisition (C/A) code as well as an encrypted P(Y) code. The L2 signal usually carries only the P(Y) code.TextNew wordNotesExercisesTranslationVocabulary PART2New words and phrases:terrestrial tirestril adj.地球的，地上的la

14、titude ltitju:d n. 纬度longitude lnditju:d n. 经度trilateration ,trailtrein n.【测】三边测量（术）redundant ridndnt adj. 多余的segment semnt n. 段；部分orbit :bit n. & v. 轨道，常轨，绕轨道而行delay dilei n. & v. 耽搁，延迟ionosphere ain,sfi n. 电离层pseudo psju:du adj. 假的，冒充的sequence si:kwns n. 序列，继起的事，顺序multiple mltipl adj. 多样的，多重的acces

15、s kses n. 通路，进入，使用之权encrypt inkript v. 加密，将译成密码TextNew wordNotesExercisesTranslationVocabulary PART3Notes:1latitude and longitude 经纬度如：One used to represent a unit of measurement, such as feet or minutes in latitude and longitude.用来代表某一测量单位，如经度或纬度上的英尺或分。如：Nothing make the earth seem so spacious as t

16、o have friend at a distance; they make latitude and longitude. 没有一件事情比得上有朋在远方更使这地球显得如此广大的了；他们构成纬度，也构成经度。如：GPS is the Global Positioning System. GPS uses satellite technology to enable a terrestrial terminal to determine its position on the Earth in latitude and longitude.GPS是全球卫星定位系统。GPS使用卫星技术，能使地面终

17、端确定它在地球上的经度和纬度。 2simultaneously adv. 同时地（联立地）如：That cannot be simultaneously true; mutually exclusive. 互相矛盾的不能同时成立的；互斥的TextNew wordNotesExercisesTranslationVocabulary PART3如：A group of three bits or three pulses, usually in sequence on one wire or simultaneously on three wires.三个二进制位或三个脉冲组成的一种组，通常按时

18、间顺序出现在一根导线上或同时出现在三根导线上。如：GPS receivers do this by measuring the signals from three or more satellites simultaneously and determining their position using the timing of these signals.GPS接收器同时测量来自三个或三个以上的卫星的信号，并通过这些信号的传播时间来确定位置。3NAVSTAR satellites 导航卫星4Rockwell International 罗克韦尔国际集团如：GPS uses NAVSTAR

19、 satellites manufactured by Rockwell International. 全球定位系统采用由罗克韦尔国际制造的导航卫星。5equator 名词1.（地球或天球的）赤道2.（平分球形物体的面的）圆。如：the celestial equator 天球赤道the earths equator 地球赤道the magnetic equator 地磁赤道如：All of these orbital planes are inclined fifty-five degrees from the equator.所有这些轨道面都偏离赤道倾斜55度。Notes:TextNew

20、wordNotesExercisesTranslationVocabulary PART4Exercises:1.Write T (True) or F (False) beside the following statements about the text.a. GPS uses computer technology to enable a terrestrial terminal to determine its position on the Earth. b. GPS receivers do this by measuring the signals from only one

21、 satellites simultaneously and determining their position using the timing of these signals.c. Trilateration is the process of determining the position of an unknown point by measuring the temperature of the sides of an imaginary triangle between the unknown point and two or more known points.d. Eac

22、h NAVSTAR satellite is approximately 50 meters wide and weighs approximately 90kg.e. In order for GPS tracking to work, it is necessary to have access to the Global Positioning System but have a GPS receiverf. In the GPS system, the two known points are provided by one GPS satellites.g. The GPS rece

23、iver is able to receive signals that are transmitted by stars orbiting over head.h. Even these satellite transmissions are received by the GPS receiver, location and other information such as speed and direction can not be calculated.TextNew wordNotesExercisesTranslationVocabulary PART4Exercises:2.

24、Match the following terms to appropriate definition or expression.a. GPS. 1. Space, Control and User Segmentb. CDMA. 2. Code Division Multiple Accessc. orbital period of 11 hours and 58 minute3. Global Positioning Systemd. GPS system is divided into 4. orbits the Earth twice each day3. Fill in the m

25、issing words according to the text.a. In order to measure the time delay between _ and _, the satellite sends a repeating 1,023 bit long pseudo random sequence; the receiver constructs an identical sequence and shifts it until the_ match.b. These satellites constantly transmit an identifying _.c. Th

26、e GPS receiver measures the _ to each GPS satellite by measuring the time each signal took to travel between the _ and the GPS receiver.d. GPS uses _operational satellites, with an additional _ in orbit as redundant backup.TextNew wordNotesExercisesTranslationVocabulary PART4Exercises:4. Translate t

27、he following paragraph into Chinese. The receiver contains a mathematical model to account for these influences, and the satellites also broadcast some related information which helps the receiver in estimating the correct speed of propagation. Certain delay sources, such as the ionosphere, affect t

28、he speed of radio waves based on their frequencies, dual frequency receivers can actually measure the effects on the signals.TextNew wordNotesExercisesTranslationVocabulary PART5Translation第16课 全球定位系统（GPS） GPS是全球卫星定位系统。GPS使用卫星技术，能使地面终端确定它在地球上的经度和纬度的位置。 接收器同时测量来自三个或三个以上的卫星的信号，并通过这些信号的传播时间来确定位置（图16-1）。 GPS的工作使用三边测量法。三边测量是指在未知点两侧有两个或