《微波通信的介绍-The introduction of microwave communication专业英语作业(2009111222梅亚敏).doc》由会员分享，可在线阅读，更多相关《微波通信的介绍-The introduction of microwave communication专业英语作业(2009111222梅亚敏).doc（7页珍藏版）》请在三一文库上搜索。
1、The introduction of microwave communicationMicrowave communication is the transmission of signals via radio using a series of microwave towers. Microwave communication is known as a form of line of sight communication, because there must be nothing obstructing the transmission of data between these
2、towers for signals to be properly sent and received.It is the use of wavelength in 0.1 millimeter to 1 m between the electromagnetic wave, Microwave Communication. Microwave communication dont need solid medium, when between two points line range when barrier-free can use microwave transmission. Usi
3、ng microwave communication advantages of large capacity, good quality and can spread to far distance, so is the national network is a kind of important means of communication, and is widely used in all kinds of special network.introductionChina microwave communication widely used L, S, C, X the freq
4、uency band, K frequency band is still in the development of application. Because microwave frequency is extremely high, wavelength and very short, and its in the air and light wave propagation characteristics similar, also is straight forward, meets the barrier was reflex or was blocked, so microwav
5、e communication main way is stadia communication, more than stadia later need relaying. Generally speaking, the result of the earth and the influence and space transmission loss, every 50 km or so, you need to set relay station, will wave amplification forward and extension. This kind of communicati
6、on mode, also known as microwave relay communication or say microwave relay communication. Long distance microwave communication mains may pass through dozens of times and then spread to thousands of kilometers can still keep high communication quality.Brief developmentThe development of microwave i
7、s with the development of wireless communication are inseparable. Microwave Communication Technology was Developed in the 1940sThe technology used for microwave communication was developed in the early 1940s by Western Union. The first microwave message was sent in 1945 from towers located in New Yo
8、rk and Philadelphia. Following this successful attempt, microwave communication became the most commonly used data transmission method for telecommunications service providers. In 1901 MaKeNi USES 800 KHZ medium wave signal from Britain to North America Newfoundland world first trans-atlantic radio
9、communications test, and create a new era of human wireless communication. Wireless communication at the initial stage, people use the long sweep medium wave to communication. In the early 1920 s people found the short-wave communication, until the 1960 s, the rise of satellite communication, it has
10、 always been the main international long distance communication means, and current emergency and military communication is still important.Microwave communication is the product of 20th century 50 s. Because of its communication of large capacity and investment cost province (accounts for about one
11、5 of the cable investment, high construction speed, strong ability to fight the advantages and achieve rapid development. In the 1940 s to 50 s produced transmission band wider, performance is stable microwave communication, become long and large capacity ground main wireless transmission main means
12、, analog FM transmission capacity up to 2700 road, also can simultaneously transmit high quality color television, and then gradually into the medium capacity and large capacity digital microwave transmission. Since the early 80 s, with the frequency selective fading dispersion of digital microwave
13、transmission interrupt influence and found a series of adaptive fading against technology and high state modulation and detection technology development, make the digital microwave transmission produced a revolutionary change. Special should point out is the 80 s to the 90 s of the development of a
14、set of high-speed multi-mode adaptive coded modulation demodulation technology and signal processing and signal detection technology rapid development, to todays satellite communications, mobile communications, digital HDTV transmission, general high speed wire/wireless access, and high quality magn
15、etic recording and many other fields of signal design and signal processing applications, played an important role.(2)The introduction of digital microwaveDigital microwave communication utilizes more advanced, more reliable technology. It is much easier to find equipment to support this transmissio
16、n method because it is the newer form of microwave communication. Because it has a higher bandwidth, it also allows you to transmit more data using more verbose protocols. The increased speeds will also decrease the time it takes to poll your microwave site equipment. This more reliable format provi
17、des for more reliable reporting with advanced communication equipment, while also allowing you to bring in your LAN connection when it becomes available at the site.Whether you utilize a digital or analog microwave communication method, it is imperative that you monitor your mission-critical microwa
18、ve communication equipment. You need to know 100% for certain that you data transmission equipment is online. Dont let your customers be the first to inform you of a network outage. Deploy a microwave network alarm monitoring system to instantly notify you of microwave communication failures.One ver
19、y important characteristic of digital microwave radio transmission is its immunity to noise. Noise refers to unwanted electromagnetic waveforms that corrupt a message signal. Noise is inevitable in electrical communications systems. In order to transmit an electrical signal over a long distance it i
20、s necessary to boost the signal level at intervals along the transmission path; this is the job of a device called a repeater. Microwave radio offers several advantages over cable-based transmission. Microwave radio is simpler, faster, more feasible and more flexible to implement than cable systems.
21、 Because there is no buried cable involved, microwave systems do not require right-of-way, and they are not susceptible to cable cuts. New markets and applications continue to emerge for wireless communications. Future wireless communications markets will include rapid growth of PCS/PCN (Personal Co
22、mmunications Networks) and ESMR (Enhanced Specialized Mobile Radio) networks, as well as higher bandwidth applications that support video and data in large local area and wide area networks. Other potential applications include the use of microwave as the last mile connection into rural communities.
23、 The future may also bring the convergence of telecommunications, computers, and other markets, to satisfy user demands for rapid, interactive exchange of information.The main featuresMicrowave communication has good performance of disaster relief, flood, storm, earthquake and other natural disaster
24、s, microwave communication generally are not affected. But the air microwave transmission, susceptible to interference, in the same microwave circuit cannot use the same frequency in the same direction, therefore microwave circuit must be in radio management department under the strict management of
25、 construction. In addition because microwave rectilinear propagation characteristics, in the direction of the beam waves, there can be tall buildings block, so the urban planning departments should consider the city space microwave channel planning, make from high-rise block and influence communicat
26、ion.(3)The main equipmentMicrowave station equipment including antenna, transceiver, modulator, multiplexing equipment and power supply equipment, automatic control equipment, etc. In order to put the wave together become beam, send to the distance, typically use the parabolic antenna, the focusing
27、effect can greatly increase the transmission distance. Multiple transceiver can common use a antenna and does not interfere with each other, Chinas active microwave system in the same frequency band the same direction can have six accept six hair work together at the same time, also can receive eigh
28、t eight hair also work to increase the overall capacity of microwave circuit. Multiplexing equipment have the branch of analog and digital. Analog microwave system each transceiver can work in 60 road, road 960, 1800 road or road 2700 communication, can be used for different capacity grades of micro
29、wave circuit. Digital microwave system USES digital multiplexing equipment to 30 road telephone by time division multiplexing principle component a group, which can form a second group of 120 road, three group of 480 road, four group of 1920 road, and after digital modulator modulation in emission m
30、achine, at the receiving end by digital demodulator reduction into multiple phone. The latest microwave communication equipment, its digital series standard and optical fiber communication synchronous digital series (SDH) completely consistent, called SDH microwave. This kind of microwave equipment
31、in an electric road, eight beam wave can simultaneously transmit thirty thousand multiple digital telephone circuit (2.4 Gbit/s).characteristicsMicrowave basic properties usually appears as penetration, reflection, absorption three characteristics. For glass, plastic and porcelain, microwave is almo
32、st through and not be absorbed. For water and food, etc will absorb microwave and make their own fever. But to metal stuff, can reflex microwave.A, penetrabilityMicrowave radiation heating than other used for electromagnetic wave, such as infrared and far infrared ray and short wavelength, so it has
33、 better penetrability. Microwave penetration medium, due to the dielectric loss caused by the medium temperature rise, make the dielectric material internal and external almost at the same time, heating temperature, form body heat source condition, greatly reducing the conventional heating of the he
34、at conduction time, and the conditions for dielectric loss factor and medium temperature was negatively correlated relations, material inside and outside heating uniform.Second, the selective heatingMaterial absorb microwave ability, mainly by its dielectric loss factor to decide. Dielectric loss fa
35、ctor of substance in microwave absorption ability is strong, on the contrary, dielectric loss factor small material absorb microwave ability also weak. Because each material loss factor existence difference, microwave heating will show the characteristics of the selective heating. Material is differ
36、ent, the heat generated by the different effects. Water molecules of polar molecules, dielectric constant is bigger, the dielectric loss factor is very big also, the microwave has strong absorption ability. And protein, carbohydrates and the dielectric constant of relatively small, the microwave abs
37、orption ability much smaller than water. So, for food, it how much water content of microwave heating effect affected.Three, thermal inertia smallMicrowave to dielectric material is instantaneous heating temperature, energy consumption is low. On the other hand, the microwave output power can be adj
38、usted at any time, medium temperature rise but no inert change, there is no heat phenomenon, extremely helpful for automatic control and continuous production needs.(4)Development situationChinas successful development point to more microwave communication system, which adopts full center to the ant
39、enna emit, around 50 km within, can have more than one point place subscriber station, from the user station to ceding multiple phone respectively connected to each user to use. The overall capacity has 100 lines, 500 lines and 1000 line and so on the different capacity equipment, each user can dist
40、ribute station dozen or dozens of phone users, when necessary, can also through the relay station extend to hundreds of kilometers away users. This kind of point-to-multipoint microwave communication system for the city suburb, the county to the rural villages and towns or coastal islands of users,
41、to the dispersion of the residential areas is also very share, more economic.Microwave communication and tropospheric scatter communication, meteor trail communication and so on, is the use of upper atmosphere of nonuniformity or meteors over a trace of wave scattering effect and achieve more than s
42、tadia communication, these systems in China, less application.Foreign developed countries of the microwave relay communication in long distance communication network and the proportion of as high as 50% above. According to statistics the United States for 66%, Japan is 50%, 54% French. Our country s
43、ince 1956 from east Germany introduced first set of microwave communication equipment since, after imitation and spontaneous development process, has made great achievements, in the 1976 tangshan earthquake, in between Beijing and tianjin coaxial cable all fracture, six microwave channel all safe. T
44、he ninety s of the middle and lower Yangtze river of extreme flood, microwave communication once again shows its great power. In todays world of communication revolution, microwave communication is still the most the prospects of development is one of the means of communication. Microwave is also ea
45、sy to move if there is a change in a network .Cellular carriers often face aggressive schedules to provide service for customers and to generate immediate revenue. In order to turn up their networks, cellular carriers need to connect their cell sites to switching stations. To make this connection, t
46、hey usually choose microwave, because it is reliable and can be commissioned within a day. Many businesses use microwave in their private networks because its the fastest way for them to install digital communications. Microwave offers businesses a low cost, high security alternative to traditional
47、communications systems. Public transport organizations, railroads and other public utilities are major users of microwave. These companies use microwave to carry control and monitoring information to and from power substations, pumping stations, and switching stations.Long Distance Carrier Connectio
48、nsA significant part of the cost of a long distance telephone call is in thhe local connection to a long distance carrier. Microwave radio links the end user to the long distance carrier, reducing the cost of this connection. In areas where long distance service is available but there are no local l
49、ines, microwave can provide the last mile connection. Natural disasters can wreak havoc on a telephone network. Microwave is often used to restore communications while transmission equipment damaged by earthquakes, floods, hurricanes or other natural disasters is being repaired. Business typesMicrowave communication because of its wide frequency band, large capacity, can be used in a variety of telecom business transfer, such as telephone, telegram, data, f