（ ）利用对流层大气的不均匀性对微波的散射作用，可以进行散射

【名词&注释】

移动用户(mobile user)、电磁波(electromagnetic wave)、不均匀性(inhomogeneity)、高频开关电源(high frequency switching power supply)、无线电(radio)、微波通信(microwave communication)、对流层大气(tropospheric)、通信局(communication bureau)、开关电源系统

[单选题]（ ）利用对流层大气^{(tropospheric)}的不均匀性对微波的散射作用，可以进行散射通信，每个接力段可长达数百公里。

A. 长波通信
B. 中波通信
C. 短波通信
D. 微波通信

查看答案&解析查看所有试题

学习资料：

[单选题]移动通信是以移动用户为服务对象的（ ）通信业务。

A. 电磁波
B. 有线电
C. 无线电
D. 卫星

[多选题]【A popular service that has attercted the interest of companies and has home users alike is the sending of voice signals over an IP-based network, such as the Internet. The practice of making telephone calls over the internet has had a number of different names, including packet voice, voice over packet, voice over the internet, internet telephone, and Voice over Ip（Voip）. But it appears the industry has settled on the term”Voice ove IP” in reference to the internet protocol, which controls the transfer of data over the internet. There are currently three ways to deliver VoIp to users, the first technique is found at the corporate level. Many companies are offering VoIP systerms that operate over a local area network. These systems involve a fair amount of equipment, such as VoIP servers, special IP-enabled telephones, and routers that can direct telephone calls. Today a large portion of corporate sites have converted their older internal telephone systems to VoIP systems that opreate over a LAN, thus converging two systems into one. A second common solution is the one often encountered at home. Using existing telephones, a special converter is added between the telephone and a high speed internet（DSL or cable modem）connection. The converter digitizes the voice signal and creates a stream of packets that are then sent over an ip connection.The third technique involves smart cell phones. Never cell technologies are all packet-based, thus requiring a telephone call to be converted to digital packets and sending those packets over IP networks.】From the paragraph above，a popular service that has attracetd the interest of companies and home users,is termed as （） . The data transfer over the Internet is controlled by the （） . At corporate level, many companies have replaced their older internal telephone systerms with （） that oprerate over a local area network.

A. voice over the internet B、voice over packet
B. Voice over IP
C. internet telephony A、packet B、internet protocol
D. industry
E. VoIp servers A、VoIP systems B、IP-enablde telephones
F. VoIP servers
G. routers

[多选题]The maximum data rate of any single wireless link can be described by the shannon’s theorem which is related to the（）in hertz，and the（）on the channel

A. signal frequency
B. bandwidth
C. carrier frequency
D. noise frequency A．signal
E. caeeier
F. noise
G. data signal

[多选题]通信局^{(communication bureau)}（站）所用高频开关电源系统均分负荷的方法有（ ）。

A. 限流并联
B. 限流串联
C. 主从均流
D. 自动平均均流

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