正确答案: A

θ=arctg（H/R）+Am

题目：天线俯仰角的计算公式为：（ ）。

解析：A

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举一反三的答案和解析：

[多选题]根据影响通信的范围、持续时间和性质严重程度，故障分为（）。

一般故障

严重故障

重大故障

解析：BCD

[多选题]【Recently， telecommunication carriers has been building All-IP core networks in order to effectively support various kinds of fixed and mobile broadband services，such as up-and down-loading You tube and SNS（Social Networking Services）with rich video file，as well as broadband mobile Internet services. Such All-IP network is called NGN（Next Generation Network），which guarantees secure authentication and QoS such as the bandwidth and the delay. From the service point of view，convergence of fixed and mobile communications，known as FMC（Fixed Mobile Convergence）is becoming a key increasing new services and expanding the market.】 Form the paragraph above，we can see that（）can be defined as a network that can effectively support various kinds of fixed and mobile broadband services，with guaranteed QoS in terms of（）and etc. And the key to develop new services and gain larger market share should be（）

NGN

social network A．data rate

availability

band width， delay A．mobile communications

All-IP core network

解析：C,D,D

[单选题]7号信令系统中的信令链路控制级对应OSI参考模型的（）。

数据链路层

[单选题]B-ISDN提供的各种业务().

差异很大