《通信与电子信息科技英语》课件unit 11.ppt

1、Microwave Radio TransmissionNew words and phrases 1 propagation n.传播 propagation path传播路径2 waveguide n.波导 rectangular waveguide 矩形波导circular waveguide 圆波导3 couple v.耦合,连接coupling loss连接损耗,耦合损耗4 comprehension n.理解5 encounter v.遇到,碰到6 radiated adj.辐射的 radiated power 辐射功率radiated wave 辐射波7 beam n.波束8 l

2、ineofsight n.视线 line of sight transmission视距传输9 clearance n.间隙，距离10 spherical adj.球面的11 watt n.瓦特12 concentrated adj.集中的concentrationn.集中Microwave Radio Transmission13 axis n.轴14 regroup v.重组,重编15 dissipation n.耗散,消耗 power dissipation功率耗散,功率消耗16 reflection n.反射17 unobstructed adj.没有障碍的,畅通无阻的18 proje

3、ction n.投影19 reinforcement n.增援,加强20 refraction n.折光,折射21 substantially adv.充分地22 remedy vt.补救,修补23 dielectric n.电介质,绝缘体24 permittivity n.介电常数,电容率 dielectric permittivity介电常数25 markedadj.明显的,显著的markedlyadv.显著地,明显地26 scattering n.散射Microwave Radio Transmission27 vulnerable adj.易受攻击的28 versatile adj.通

4、用的,万能的29 rugged adj.不规则的30 parabolic adj.抛物线的，像抛物线的 parabolic antenna 抛物面天线31 characteristic n.特性,特征32 deflect v.(使)偏斜,(使)偏转33 resistance n.抵抗力34 polarization n.极化(作用)35 discrimination n.辨别,识别力 cross polarization discrimination 交叉极化鉴别度36 repeater n.中继器,(又称)转发器(RP)repeater system转发系统37 configuration

5、n.配置,构造38 emanate vi.散发,发出,放射39 electromagnetic adj.电磁的electromagnetic field电磁场40 transverse adj.横向的,横断的Microwave Radio Transmission41 attenuation n.衰减42 bronze n.青铜；adj.青铜色的43 guide n.波导,引导 44 uniformity n.均匀性(度)45 homogeneity n.均匀性;同质性,一致性46 twist n.扭曲,盘旋47 irregularity n.不规则,无规律48 discontinuity n

6、.不连续(pl.discontinuities)49 ferrite n.铁氧体magnetic ferrite磁性铁氧体50 isolator n.隔离器,绝缘子51 impedance n.阻抗 impedance matching阻抗匹配52 klystron n.速调管(极超短波用电子管)53 oscillator n.振荡器 klystron oscillator速调管振荡器Microwave Radio Transmission1 path loss 路径损耗2 antenna pattern 天线方向图3 ground reflected wave 地面反射波4 free spa

7、ce 自由空间 free space loss 自由空间损耗5 point source 点源6 transmitting antenna 发射天线7 receiving antenna 接收天线8 inverse square law 平方反比律,反平方律 9 effective area 有效面积10 account for 说明,解决11 hornreflector 喇叭反射器12 grazing angle 入射余角Microwave Radio Transmission13 clear up 了结；结束；变缓和14 phase reversal 反相,倒相,逆相位15 superhi

8、gh frequency 超高频16 longhaul system 长途系统17 side lobe(sidelobe)旁瓣18 antenna tower 天线塔19 half power beam width 半功率波束宽度20 coaxial probe 同轴探针21 be closely associated with 与密切相关22 under development 正在研制中，正在发展中23 crosssectional dimension 横断面尺寸，横截面尺寸 cross section横截面24 be parallel to 与平行Microwave Radio Tran

9、smission25 propagation mode 传播模式26 cutoff wavelength 截止波长27 dominant mode 主模28 tower base 塔底座29 traveling wave 行波30 wire line 金属线31 coaxial cable 同轴电缆32 all the same 仍然33 interfere with 干扰34 traveling wave tube 行波管Microwave Radio Transmission Microwave radio transmission media include propagation pa

10、ths,antennas,and the waveguides used to couple the transmitters and receivers to the antennas.Comprehension of radio propagation and the path losses encountered,antenna patterns and efficiencies,and waveguide transmission characteristics are essential to an understanding of these media.For microwave

11、 transmission,portions of the 2 to 40 GHz spectrum are made available by the Federal Communications Commission for fixed,commoncarrier service.This range corresponds to wavelengths of 150 to 7.5 mm respectively where it is practicable to direct the Propagation Paths The principal propagation paths i

12、n the microwave range are the direct(free space)wave and the ground reflected wave as illustrated in Fig.11-1.If the antennas are located to provide a lineofsight path with adequate clearance,the path loss for a large percentage of the time approximates the free space loss.This loss obeys the invers

13、e square law.Microwave Radio Transmission Line-of-Sight TransmissionImagine a radiated wave expanding as a spherical surface from a point source.The power density,in terms of power per square unit of that surface at distance d from the source radiating power pT watts,is the radiated power divided by

14、 the spherical surface at that distance,or pT/4d2.If that radiated power is now concentrated in a narrow beam by means of a suitable antenna and accurately aimed at a receiving antenna,the latter receives many times the energy it received before the beam was concentrated.The actual power it receives

15、 before concentration is pR=pTAR/4d2Exercises.Please translate the following words and phrases into Chinese.1.frequency spectrum 2.radiating power3.propagation path4.beam 5.adjacent channel6.frequency band7.sidelobe8.propagation mode9.magnetic ferrites10.klystron oscillator11.TE mode12.TM mode13.gra

16、zing angle14.antenna tower频谱频谱发射功率发射功率传播路径传播路径波束波束邻道邻道频带频带旁瓣旁瓣传播模式传播模式磁性铁氧体磁性铁氧体速调管振荡器速调管振荡器横电模横电模(transverse electric mode)横磁模横磁模(transverse magnetic mode)入射余角入射余角天线塔天线塔Exercises.Please translate the following words and phrases into English.1.路径损耗2.截止波长 3.自由空间4.横截面5.主模 6.连接（耦合）损耗7.圆波导8.抛物面天线 path l

17、osscutoff wavelengthfree spacecross sectiondominant modecoupling losscircular waveguideparabolic antennasExercises9.视距路径10.超高频11.喇叭反射器12.电磁场13.行波14.同轴探针15.接收天线16.发射天线17.阻抗匹配18.矩形波导 lineofsight pathsuperhigh frequencyhorn reflectorelectromagnetic fieldtraveling wavescoaxial probereceiving antennatran

18、smitting antennaimpedance matchingrectangular waveguideExercises.Fill in the blanks with the missing word(s).1.If the antennas are located to provide a lineofsight path with adequate clearance,the path loss for a large percentage of the time approximates the free space loss.2.These factors may be re

19、grouped so that the transmitting and receiving antenna gains are in the same form.3.The effective areas,AT and AR,are smaller than the physical areas because of power dissipation and reflections in the antennas.4.The phase relationship depends on the wavelength,the difference in length between the t

20、wo paths,and whether or not the grazing angle at the projectionissmall enough to cause a phase reversal at the reflection.5.In the TE mode,the electric field is transverse to the axis of the guides and the magnetic field is parallel at the axis.6.Reflection losses can be caused by bends or twists th

21、at are not gradual enoug or by improper terminations to the sending or receiving end.Exercises7.The magnets are placed outside the waveguides to produce magnetic fields in the ferrites which are placed inside.8.These devices,called isolators,prevent energy reflected from transmitting antennas or dis

22、continuities in the waveguides from interfering with the operation of components such as klystron oscillators or traveling wave tube amplifiers.9.Imagine a radiated wave expanding as a spherical surface from a point source.10.If that radiated power is now concentrated in a narrow beam by means of a

23、suitable antenna and accurately aimed at a receiving antenna,the latter receives many times the energy it received before the beam was (is,was)concentrated.11.Note that the antenna gains are frequency dependent(dependent,dependence)and that the free space path loss is (be,is,one,was)both distance an

24、d frequency dependent.12.Waves taking a longer path can arrive at the receiving antenna in any phase relationship with the direct wave.Exercises.Answer the following questions according to the text.1.What do microwave radio transmission media include?Microwave radio transmission media include propag

25、ation paths,antennas,and the waveguides used to couple the transmitters and receivers to the antennas.2.What are the chief propagation paths in the microwave range?The chief propagation paths in the microwave range are the direct(free space)wave and the ground reflected wave.3.Please calculate the p

26、ower density at distance d from a point source which has radiating power pT watts.The actual power is PR=(pT/4d2).4.Tell the kinds of beams radiated from an antenna.The beam include the main beam and minor beams.Exercises5.The narrower the beam,the better the antenna.Is it correct?Why?It is not corr

27、ect.The narrower the beam,the greater the gain,but too narrow a beam may be deflected from its target by unusual stresses on the antenna tower6.How many kinds of fading are discussed in this article and what are they?There are two kinds of fading discussed in this article.They are slowfading and fas

28、t fading.7.How many major modes of propagation are there in a waveguide?What are their characteristics?The major modes of propagation are the transverse electric(TE)modes and the transverse magnetic(TM)modes.In the TE mode,the electric field is transverse to the axis of the guides and the magnetic field is parallel to the axis.In the TM modes,the reverse is true.Exercises8.How can we effectively limit transmission to only one direction in a waveguide?Waveguides can be made effectively to limit transmission to only one direction by means of accurately placed magnetic ferrites and magnets.