问题 多项选择题

以下关于天线的水平波瓣、垂直波瓣的说法,正确的是哪些()。

A.在天线的水平面(垂直面)方向图上,相当于主瓣最大点功率增益下降3dB的两点之间所张的角度,定义为天线的水平(垂直)波瓣宽度

B.天线辐射的大部分能量都集中在波瓣宽度内,波瓣宽度的大小反映了天线的辐射集中程度

C.全向天线的水平波瓣宽度为360度,而定向天线的常见水平波瓣宽度有20、30、65、90、105、120、180度等多种

D.天线的垂直波瓣宽度一般在3-80度之间,基站天线采用较多的是5-18度之间的天线

E.天线的增益是和天线的水平和垂直波瓣宽度密切相关,一般来说,波瓣宽度越小,增益越大

答案

参考答案:A, B, C, D, E

完形填空

Are you truly happy? Do you ever know what it means to be happy and what it takes to achieve happiness? __小题1:__. The following are a few tips that I follow to create happiness in my life.

Make a plan for achieving goals that you believe will make you happy. Your moods will very likely increase if you are going after something you value.

Surround yourself with happy people. It is easy to begin to think negatively when you are surrounded by people who think that way. __小题2:_.

When something goes wrong, try to find out a solution instead of being lost in self pity. Truly happy people don’t allow difficulties to affect their mood because they know that with a little thought they can change the situation for better.

_小题3:__. These few minutes will give you the opportunity to focus on the positive things in your life and will lead you to continuous happiness.

_小题4:_. Whether you treat yourself to lunch, take a long, relaxing bath or simply spend a few extra minutes on your appearance, you will be subconsciously (下意识地) putting yourself in a better mood.

Finding the humor in situations can also lead to happiness. Find a way to make light of a situation that would otherwise make you happy.

Keeping healthy is another way to achieve happiness. __小题5:_.

A.What makes one person happy may be very different from what makes someone else happy.

B.On the contrary, if you are around people who are happy, their emotional state will be infectious.

C.Being overweight or not eating nutritious foods can have a negative effect on your mood.

D.These are important questions for anyone who is seeking happiness to ask themselves.E.Spend a few minutes each day thinking about the things that make you happy.

F.There are some tips in life that lead to happiness.

G.It’s also important to take some time each day to do something nice for yourself.

单项选择题