北交《天线与电波传播》在线作业二

adminhan

微波炉中不能使用金属容器，这主要是因为（ ）<br><br>
A:金属易生锈，弄脏炉体<br><br>
B:金属容易导电，造成漏电事故<br><br>
C:微波能在金属中产生强大的电流，损坏微波炉<br><br>
D:金属易传热 ，使炉体温度过高<br><br>

亥姆霍兹定理说明：一个矢量场由它的（） 和 （）唯一确定。<br><br>
A:旋度 散度<br><br>
B:散度 旋度&nbsp;<br><br>
C:散度 光度<br><br>
D:光度 散度<br><br>

真空中所有的电磁波都具有相同的（ ）<br><br>
A:频率<br><br>
B:波长<br><br>
C:波速<br><br>
D:能量<br><br>

沿 x 方向传播的 TE波必有 （）<br><br>
A:<img class="kfformula" src="data:image/png;base64,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" data-latex="{H}_{z}=0"><br><br>
B:<img class="kfformula" src="data:image/png;base64,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" data-latex="{H}_{x}=0">
C:<img class="kfformula" src="data:image/png;base64,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" data-latex="{E}_{z}=0">
D:<img class="kfformula" src="data:image/png;base64,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" data-latex="{E}_{x}=0">

在正弦电磁场中，位移电流与该处电场的方向一致，其相位（）<br><br>
A:与电场相同<br><br>
B:与电场相反<br><br>
C:超前电场90°<br><br>
D:滞后电场 90°<br><br>

关于电磁理论，下列说法正确的是（ ）<br><br>
A:在电场的周围空间一定产生磁场<br><br>
B:任何变化的电场周围空间一定产生变化的磁场
C:均匀变化的电场在周围空间产生变化的磁场<br><br>
D:振荡的电场在周围空间产生变化的振荡磁场<br><br>

关于电磁波的传播，以下说法正确的是（ ）<br><br>
A:只能在真空中传播<br><br>
B:在水中不能传播<br><br>
C:可以在很多介质中传播<br><br>
D:只能在空气中传播<br><br>

调谐电路中可变电容器的动片从完全旋入到完全旋出仍接收不到某较高频率电台发出的电信号，要收到该电台的信号，应该怎么办？（ ）<br><br>
A:增加调谐电路线圈的匝数<br><br>
B:加大电源电压<br><br>
C:减少调谐电路线圈的匝数<br><br>
D:减小电源电压<br><br>

<img class="kfformula" src="data:image/png;base64,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" data-latex="E={E}_{0}(2{e}_{x}+j{e}_{y}）">是（）
A:左旋圆极化<br><br>
B:左旋椭圆极化
C:右旋圆极化<br><br>
D:&nbsp;右旋椭圆极化<br><br>

自由空间中，天线的远区电场与磁场的比为（&nbsp;）<br><br>
A:120π<br><br>
B:π/120&nbsp;<br><br>
C:1/(120π)<br><br>
D:μ0<br><br>

调幅波的英文简称是 AM，按照使用频率范围的不同又可分为（）&nbsp;<br><br>
A:中长波<br><br>
B:长波<br><br>
C:中波<br><br>
D:短波<br><br>

高频信号种类有（）<br><br>
A:超低频<br><br>
B:极低频<br><br>
C:甚低频<br><br>
D:超高频<br><br>

相控阵天线由三个部分组成（）<br><br>
A:馈电网络<br><br>
B:波束控制器<br><br>
C:天线阵<br><br>
D:振元<br><br>

相控阵天线由三个部分组成（）<br><br>
A:馈电网络<br><br>
B:波束控制器<br><br>
C:天线阵<br><br>
D:振元<br><br>

长波传输的特点是（）<br><br>
A:距离300km以内主要靠地波&nbsp;<br><br>
B:用长波通信时，在接收点的场强稳定<br><br>
C:表面波衰减慢，对其他收信台干扰大<br><br>
D:作为通信广播不多<br><br>

机械波和电磁波都能发生（）现象<br><br>
A:反射&nbsp;<br><br>
B:折射&nbsp;<br><br>
C:干涉<br><br>
D:衍射<br><br>

相位偏移对辐射场的主要影响（ ）<br><br>
A:最大辐射方向偏移<br><br>
B:主瓣变窄<br><br>
C:方向系数增加<br><br>
D:零点模糊<br><br>

理想媒质中，均匀平面波的波长由下列哪些因素决定？<br><br>
A:频率<br><br>
B:媒质的介电常数<br><br>
C:相素<br><br>
D:相位<br><br>

天线电参数有（ ）<br><br>
A:方向函数<br><br>
B:增益<br><br>
C:天线效率<br><br>
D:输入阻抗<br><br>

天线的研究方法有（）<br><br>
A:解析法<br><br>
B:数值法<br><br>
C:公式法<br><br>
D:理论法<br><br>

电磁波不能产生干涉、衍射现象。<br><br>
A:对
B:错

灵敏度是衡量接收机对微弱信号接收能力的重要参数。<br><br>
A:对
B:错

发射机的谐波或杂散辐射在接收有用信号的通带内造成的干扰，称为带外干扰。<br><br>
A:对
B:错

调幅波的英文简称是 AM，按照使用频率范围的不同又可分为长波、中波、短波，相对应的英文简称为 LW、MW、SW。<br><br>
A:对
B:错

产生无线电波必须先产生高频电磁振荡，就是产生“载波” ，然后把欲传递的信息加上去， 这个过程的无线电俗语叫做 “解调”。<br><br>
A:对
B:错

LC 回路中电容器极板上的电荷量随时间的变化关系如下图所示，下列说法是否正确。<br><img src="http://file.open.com.cn/ueditorupload/image/2019/04/21/6369147799529780062719201.png" title="图片1.png" alt="图片1.png"><br>在 t1 时刻，电路中的磁场能最小 （ ）<br><br>
A:对
B:错

&nbsp;电磁污染，又称频谱污染或电噪音污染。它是以电磁场的场力为特性， 并和电噪音的性质、 功率密度及频率等因素密切相关。<br><br>
A:对
B:错

机械波和电磁波都能发生反射、折射、干涉和衍射现象。<br><br>
A:对
B:错

&nbsp;Electromagnetic Interference （EMI） 的中文意思是电磁干扰。<br><br>
A:对
B:错

&nbsp;电磁污染，又称频谱污染或电噪音污染。它是以电磁场的场力为特性， 并和电噪音的性质、 功率密度及频率等因素密切相关。<br><br>
A:对
B:错